battery maintenance

8/6/2019 Battery Maintenance

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FACILITIES INSTRUCTIONS,STANDARDS, AND TECHNIQUES

VOLUME 3-6

STORAGE BATTERYMAINTENANCE AND PRINCIPLES

Internet version of This Manual Created

June, 1998

HYDROELECTRIC RESEARCH AND

TECHNICAL SERVICES GROUP

The Appearance of the Internet Version of ThisManual May Differ from the Original but the Content does not

UNITED STATES DEPARTMENT OF THE INTERIORBUREAU OF RECLAMATION

DENVER, COLORADO


2/83

TABLE OF CONTENTSSection Page

Flooded, wet cell, lead-acid battery maintenance schedule (last updated 12/31/97) . . . . . . . . . . . . . . . . 11 Condensed instru ctions: lead-acid batteries (last upd ated 12/31/97) . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.2 Battery charging and spec ific gravity t emperature cor rect ion . . . . . . . . . . . . . . . . . . . . 21.3 Voltage readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41.4 Specific gravity readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.5 Temperature readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61.6 Connection resistance readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61.7 Visual inspections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81.8 Battery care . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81.9 Chargers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81.10 Records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91.11 Battery troubles sum mar ized . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1.12 Recommended actions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 1.13 Cell replacemen t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

2 Lead-acid batter y principles (last upd ated 12/31/97) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.2 Full charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.3 Appearance of normal cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.4 Chemical changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.5 Internal self-discharge and effect of impurities on floating voltage . . . . . . . . . . . . . . . 13 2.6 Temperature characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.7 Proper amount of charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.8 High-rate overch arging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.9 Low-rate overch arging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.10 Undercharging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.11 Over discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.12 Sedimentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.13 Replacement water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.14 Water replacem en t rate for lead-an tim on y cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.15 Water replacem en t rate for lead-calciu m cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2.16 Water replacemen t for lead-seleniu m cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2.17 Adjustin g specific gravity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2.18 Hydrometer readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2.19 Constan t voltage char ging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 2.20 Battery life for differen t types an d services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 2.21 Cleanliness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 2.22 In ternal shorts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 2.23 Normal sulfate and over sulfation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2.24 Elimination of over sulfation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2.25 Water treatment for over sulfation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

3 Battery testing (last upd ated 12/31/97) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 3.1 Acceptan ce testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 3.2 Capacity tests to determine replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

4 Optional instru ctions lead-calcium batte ries (last upd ated 12/31/97) . . . . . . . . . . . . . . . . . . . . . . . . 22 4.1 Float charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 4.2 In itial charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

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TABLE OF CONTENTSCCCONTINUED

Section Page

4.3 Voltage readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224.4 Specific gravity readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234.5 Heavy discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234.6 Water replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Valve regulated lead-acid battery (gel cell) maintenance schedule (last updated 12/31/97) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

5 Condensed in struc tionsvalve regulated lead-acid batteries (gel cells) (last upda ted 12/31/97) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255.2 Float charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255.3 Equalizing charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265.4 Charger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265.5 Battery main tenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265.6 Visual inspections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265.7 Voltage readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275.8 Temperature readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275.9 Connection resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285.10 In ternal resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285.11 Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Vented n icke l cadmium ba ttery main tenance schedule ( last updated 12/31/97) . . . . . . . . . . . . . . . . . . 316 Ven ted n icke l cad miu m batter y pr in ciples ( last u pd ate d 12/31/97) . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2

6.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326.2 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326.3 Chemical reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326.4 Upon installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336.5 Charging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336.6 Voltage readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346.7 Temperature readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356.8 Visual inspections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356.9 Battery discharge testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356.10 Electrolyte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366.11 Electrolyte level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376.12 Specific gravity readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376.13 Electrolyte renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386.14 General care . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396.15 Battery records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396.16 Wall card records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

7 Batter ies for microwave and VHF radio equipment ( last updated 12/31/97) . . . . . . . . . . . . . . . . . . . 397.1 Lead-acid batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397.2 Nickel-cadmium batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

8 Battery safety (last updated 12/31/97) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 408.1 Explosive hazard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 408.2 Electrolyte hazard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

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8.3 Flame arresters purpose and cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Section Page

8.4 Ventilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 8.5 Battery rooms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 8.6 Safety mee tings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

9 Battery charging equipment (last updated 12/31/97) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 9.1 Motor-generator sets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 9.2 Static rectifier char gers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

10 Replacement storage battery sizing (last updated 12/31/97) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 11 Standards (last updated 12/31/97) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

TABLES

Table

1 Flooded, wet cell, lead-acid battery main tenance schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Comm on voltage ran ges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 3 Valve regulated lead-acid battery main tenance schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 4 Vented nickel cadmium battery maintenan ce schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

FIGURES

Figure

1 Water consu mpt ion for lead-acid battery sizes and types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 2 Placement of meter probes for connection resistance measurem ents . . . . . . . . . . . . . . . . . . . . . 73 Percent capacity of batteries with pasted and plante type plates for various

discharge rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 4 Effect of concentr ation of electrolyte on cell capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 5 Final voltage at various rates after char ge is fully completed . . . . . . . . . . . . . . . . . . . . . . . . . . 71 6 Per cen t local action in 1.280 electr olyte versus specific gravity of elect rolyte . . . . . . . . . . . . . . 73 7 Approximate variation of local action in lead-acid storage cells with changes in

specific gravity of electrolyte an d ch anges in tem peratu re . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 8 Approximate variation of capacity with tem peratu re in lead-acid chloride-

accumulator type storage cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 9 Typical rech arge cur ves at constan t voltages following 100-percent discharges . . . . . . . . . . . . 77

10 Voltage probe placemen t for nickel-cadmium cells with different type conn ectors . . . . . . . . . 79

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TABLE OF CONTENTSCCCONTINUED

REPORT FORMS

Form Page

POM-133A Flooded lead-acid battery maintenance report (last updated 12/31/97) . . . . . . . . . . . . 51POM-133B Valve regulated lead-acid battery main ten ance report (last updated

12/31/97) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 POM-133C Nickel-cadmium bat tery maintenance report ( last updated 12/31/97) . . . . . . . . . . . . . 55 POM-134A Flooded lead acid batter conn ection resistance annu al report

(last updated 12/31/97) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 POM-134B Valve regulated lead-acid battery conn ection and intern al resistance

annual report (last updated 12/31/97) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59POM-157 Lead-acid storage ba tt ery data ( last updated 12/31/97) . . . . . . . . . . . . . . . . . . . . . 61 POM-159 Nickel cadmium storage bat tery data ( last updated 12/31/97) . . . . . . . . . . . . . . . . 63

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TABLE 1. - FLOODED, WET CELL, LEAD-ACID BATTERY

MAINTENANCE SCHEDULE

1

Mainten anc e New Battery Shift Monthly 3-Month Ann ual 5-Year

Visual Also See 1.10C &D Flame

Inspection Arresters

See 1.7 See 8.3

Battery Float Panel Meter Battery Terminals Compare Panel

Voltage Float Voltage with Digital Mete r to Digital

See 1.3 See 1.3A Voltmete r Voltmete r

Cell Float All Cells Pilot Cells All Cells

Voltages with Digital with Digital with Digital

See 1.3 Voltmete r Voltmete r Voltmete r

Spe cific Gravity All Cells Pilot Cells 10 Per cen t of All Cells

Readings all Cells

See 1.4

Temperature Pilot Cells 10 Percent of

Read ings All Cells

See 1.5

Conn ection All All Conn ections

Resistance Connections

See 1.6

Battery Testing Accepta nce Yearly Capac ity Capac ity

See 3.0 Te st After Tests if 5-Year Dischar ge

1 week Test < 90 Percent Test

Check Safety Wash Equipment;

Equipm ent Protective Clothing;

See 1.7 & 8.0 Fire Extinguisher s,

Etc.

See section 1.11H for sur face charge phen omenon (initial voltage drop u nder load).


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1. CONDENSED INSTRUCTIONS: LEAD-ACID BATTERIES

E1.1 PURPOS11. PURPOSE

The purpose of this section is to outline the duties and responsibilities for

routine operation and care of vent ed lead-acid batteries. Section 2 contains

detailed information on lead-acid battery principles.

1.21.2 BATTE RY CHARGING AND SPECIFIC GRAVITY TEMPERATURE CORRE CTIONBATTERY CHARGING AND SPECIFIC GRAVITY TEMPERATURE CORRECTION

A.A. Initial Fresh en ing Char geInitial Freshening Charge

To establish a reference, give each new battery, or reinstalled battery stored

for more than 3 mon ths, an initial freshening charge. Use the equalizing

voltage given by the manufacturer for the type cell, but do not exceed the

maximum voltage of othe r loads conn ected to the charger. Apply th is charge

un til each cell gasses freely and equally and specific gravity (sp.gr.) stops

rising. Just before the en d of the initial charge, record th e voltage of eachcell. About 20 m inutes after th e end of the charge, record the specific

gravity of each cell, corrected to 77 EF. For every 3 EF above 77EF, add one

point (0.001) to the reading. For every 3 EF below 77EF, subtract one point

(0.001) from the reading. Use form POM-133A for these records and keep

them for the life of the battery.

ell.CPilot.1A.1 Pilot Cell.After the initial char ge or to begin a yearly cycle, ch oose a pilot

cell from on e of the lowest specific gravity an d lowest voltage cells. Th is cell

is used as a representa tive for readings, for one year. Each year a new pilot

cell is chosen.

eB. Float Cha rg.B F loa t Ch ar ge

Charge batteries continu ously at the float voltage r ecomm ended by the

manufacturer . Monthlyy take the voltage across the overall battery terminalswith an accurate digital mete r and compare t his reading with the ch arger

and bus voltmete rs. If needed, adjust the charger float voltage based on th e

digital mete r. Adjust the char ger an d/or bus voltmete rs to agree with th edigital meter if needed.

A battery is said to float when charging voltage is slightly greater than the

open circu it voltage of the battery. Floating current required to keep lead-

calcium cells at full charge is about one-four th to one-third t hat of lead-an timony cells, but lead-calcium cells usually mu st be floated a t a slight ly

higher voltage. Lead-selen ium cells require float voltages slight ly above

those of lead-calcium.

The oper ation of a batt ery by float m eth od is based on overa ll voltage applied

to the battery term inals. The voltmeter used m ust be very accurate. An

inaccurate meter can result in either over or u ndercharge and resulting

problems, which redu ce life an d service of the battery. See section 1.3.

Rev.12/31/97 2


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C. C. Equ alizing Char geEqu alizing Ch argeThe purpose of the equalizing charge is to ensure that every plate in every

cell is brought with certainty to a state of full charge by a slight overch arge.

Do not perform equalizing charges on a routine basis. If one of the conditions belowoccurs, apply an equalizing charge at th e voltage r ecommended by the

man ufacturer for th e type of cell. Ensure t hat a ll cell levels are at the high

level mark before beginning the charge.

1. Following heavy discharge.2. If specific gravity (corrected for temperature) of any cell is more than 10

points (0.010) below the full charge value wh ile on float.

3. If the voltage of any cell is more th an 0.04 volt below the average cellvoltage when the battery is on float.

4. If the level in any cell or cells falls at or n ear the m inimu m fill line a lotof distilled water mu st be added to restore th e level to the maximum fill

line. If this condition occurs, an equalizing charge mu st be performed to

restore specific gravity.

5. If too little rep lacemen t water is being added, typically indicatingundercharging (see fig. 1 for typical water consumption).

Terminate the equalizing charge when all conditions below are met:

1. Every cell gasses freely and equally.2. The specific gravity of all low cells has stopped rising, determined by two

specific gravity readings measured over the last one-eighth of the

charging period.

3. The voltage difference between the highest and lowest cells is no greaterthan at the initial charge.

Failure to give equalizing charges when needed leads to problems. The

ampere-hou r capacity of weak cells greatly decreases. Dur ing discharge,

these cells will be exhausted well ahead of good cells and then become over

discharged (see section 2.11) or over su lfated; th e plates m ay buckle, andgrids may crack. Cont inued discharge may reverse the polarity, making

positive plates out of the n egatives an d vice versa, which will destroy the

cells.

If one section of the battery runs warmer than the r est, these cells have a

higher rate of intern al self-discharge, and capacity gradually falls below the

others. Hen ce, a battery mu st be located so that sun shine or space heater s

do not affect a portion of the battery, which would mask internal self

Rev.12/31/97 3


9/83

discharge temperature increases.

Rev.12/31/97 4


10/83

D.D. Unatten ded StationsUnattended Stations

The equalizing charge may be term inated au tomatically by a timer. Use the

man ufacture rs recommen ded charge time for the cell type. Set the timer to

switch off the equalizing charge and to reconnect the float charge. In th e

event that th e m anu facturer does not provide a recommen ded charge time,

3 days (72 hou rs) may be used as the charge time.

A "check charge" for batteries at unattended locations may be used to determine ifequalization is necessary. With a "check char ge, the batter y is placed on

charge at th e equ alizing rate. After allowing 15 or 20 m inutes for the rate to

stabilize, the voltages of individual cells are measured . If the highest an d

lowest ce ll voltages (while on charge at the equ alizing rate) d iffer by no

more th an 0.04 volt, the battery does not require equalizing. The battery

shou ld be equalized if the voltage differences exceed 0 .04 volt. Use a digital

me ter accur ate to 0.01 volt. The test described above is effective in

determining equality of cell charge. However, the test cannot be substituted

for a hydrometer in determining state of charge. All cells must be within 5F,the r eason is described in paragraph 2.6, and the temperature mu st not

be below 55 F.

1.31.3 . VOLTAGE READINGSVOLTAGE READINGS

Voltage readings should be taken in accordance with the following

instructions. NNote: Accurate voltmeters are critical for extending batter y life.Provide a digital voltmeter accurate to 0.01 volt re served on ly for sta tion

battery duty and calibrate it or send it out for calibration at least once a year.

This voltmete r m ust be treated with extra care; do not use a shop m eter or

electrician s genera l-use meter for batte ry voltages.

A.A. Each Shift (Attended Stations) or DuringEach Shift (Attended Stations) or During Routine In spections (Unatten ded Stations)Routine Inspections (Un attended Stations)

Check the voltmeter on the control panel to determine if the battery is being

charged at th e proper voltage. Adjust the battery charging voltage if

necessary.

B.B. When Taps Are ChangedWhen Taps Are Changed

Check the voltage on th e control panel when taps are ch anged on power or

station-service tran sform ers. Adjust the battery charging voltage if

necessary.

C.C. Dur ing Equ alizing Char geDur ing Equalizing Ch arge

Just before term inating the equalizing charge, measure the voltages of the

highest voltage ce ll and th e lowest voltage cell of the battery to the nearest 0.01volt with an accu rate digital voltmeter. The equalizing charge should be

continued if the voltage differen ce between the two cells is more than that

recorded for th e initial char ge.

Rev.12/31/97 5


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D.D. Mon t h lyMonthly

With the charger in service, check the overall float voltage across the battery

term inals with an accurate digital mete r an d record on form POM-133A.

E.E. MonthlyMonthly

Che ck the pilot cell float voltage with an accu rate digital voltmeter an d

record on form POM-133A.

F.F. QuarterlyQuarterly

Check the float voltage on a ll individual cells to the nearest 0.01 volt with an

accu rate digital voltmeter. Take the se readings as rapidly as possible and

record them on form POM-133A. At the en d of the year ly cycle, use these

readings to determ ine th e pilot cells for the n ext year.

1.41.4 SPECIFIC GRAVITY READINGSSPECIFIC GRAVITY READINGS

Specific gravity readings of vented lead-acid batteries must be taken in

accordance with the following instructions. Note: All specific gravity read ingsmu st be corrected to 77EF before recording (see 2.18). Do not attem pt to

take an y specific gravity reading after add ing water to a cell. The electrolyte

takes several hou rs to mix after water is added.

A.A. MonthlyMonthly

Take th e specific gravity reading of the pilot cell and record it on form POM

133A.

B.B. QuarterlyQuarterly

Take specific gravity readings of 10 percent of the total number of cells and

record them on form POM-133A. Rotate these cells so that r eadings are

taken on differen t cells each quarter.

C.C. AnnuallyAnnually

Take specific gravity readings of every cell and r ecord them on form POM

133A.

D.D. After Equa lizing Ch argeAfter Equalizing Charge

About 15 minutes after heavy gassing stops, take th e specific gravity readings

of every cell and record th em on form POM-133A. If two cells with the

lowest specific gravity (ch ecked over the last one-eighth of the charging

period) have n ot stopped rising, continue the equalizing charge.

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1.51.5 TEMPE RATURE READINGSTEMPE RATURE READINGS

All cells of a battery should be at the sam e am bient temper ature. Heat

sources such as sun light, portable heate rs, etc. mu st be blocked so they do

not raise the tem peratu re of individual cells. Record the room ambient

temperature before cell temperatures are taken.

Note: An accu rate infrared (IR) cam era m ay be used for tem peratu res;however, the camera calibration mu st be checked at least once each year. If

possible, take the an nu al temperatu re readings of the cells just after cam era

calibration. If the temper ature spread of the cells exceeds 5 F (i.e., upper

rows are warmer) th e room ven tilation m ay be inadequa te.

A.A. MonthlyMonthly

Record the pilot cell temperatures on form POM-133A.


Record temperatu re r eadings of 10 percen t of all the ce lls; rotate the subject

cells each quar ter.


If an accurate IR camera is available, take the tem peratu re of the battery

conn ections du ring a load or discharge test, i.e., while cur ren t is flowing. If

one or more of the connections are loose or dirty, the ir temperatu res will be

higher than the other connections.

1.61.6 CONNECTION RESIS TANCE READINGSCONNECTION RESISTANCE READINGS

A.A. After In sta llationAfter In stallation

Using an accurate micro-ohm meter, record the resistance of each

connection on form POM-134A. The readings should be on the order of a

few micro-ohm s (less than 100). Record the r eadings as a baseline on form

POM-134A. For additional informa tion see IEEE 450-1995Maintenance,Testing , and Replacement of Vented Lead-acid Batteries, Annex D and F. See belowfor detailed instructions.

B.B. AnnuallyAnnually

Repeat resistance ch ecks of the connections ch ecked in step A above an d

compare values. If any conne ction resistance has increased more than 20

percen t, clean, apply no-ox grease, retorque the connections, an d retest.

Fill out both as foun d and as left colum ns on form POM-134A.

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C.C. Recomm en ded Method For Taking Ann ual Micro-Ohm met er Readings Across BatteryRecomm en ded Meth od For Taking Ann ua l Micro-Ohm me ter Read ings Across Batter y

ConnectionsConnections

Figure 2. - Placement of meter probes for connection resistance measurements.

Caution: Never place probes across a cell or cells (between positive an dnegative posts), with th e mete r set on ohms. The m eter m ay be destroyedand arcing may occur at the battery.

1. Make sure the battery is on float charge before beginning the readings.Obtain an accurate digital micro-ohmm eter, an d set it to the lowest scale.

2. On cell No. 1 take the first reading between the connector lug and thefirst post (see fig. 2). This reading will be the resistance between the

post and connect or lug and will be about one-half the m iddle readings.

Record a ll readings on form POM-134A.

3. Take the second reading between opposite polarityposts (not connectors) ofcells No. 1 and No. 2. Following readings will be between positive an dnegative posts of adjacent cells. These middle readings will include the resistance of two connections (one on each post) and the intercelllead(see fig. 2). These readings will be about double the first and last.

4. Take the rem aining middle readings as in step 4, proceeding from cell tocell.

5. Take the last reading between the last post on the last cell and theconnector lug as shown.

6. If high resistance is found , take readings from each post to its conn ectorto determ ine which of the two connections is bad. Mark this and all

high-resistance connec tions for later repair.

7. After readings are complete, disconnect the charger and loads from th ebattery. Caution: do not remove or make connections while current is flowing.Clean problem conn ections, re torque to man ufacturers specifications,

and apply no-ox grease. Retest the repaired connections and record the

resistance in the as-left column on form POM-134A.

Rev.12/31/97 8


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1.71.7 VISUAL INSP ECTIONSVISUAL INSPECTIONS

Visual inspections are made to assess the general condition of the battery,

battery room, and safety equipmen t. See below and section 1.10 and r ecord

on form 133-A.

A.A. MonthlyMonthly

Check for gene ral cleanliness of the battery, moun ting rack, and battery

room. Check for electrolyte leaks and cracks in cells, and take corrective

action if any are found. Check for corrosion at terminals, conn ectors, racks,

and cabinets. Check the ambient tem peratu re and make sure ventilation

devices (fans and ven ts) are operable. Check all the electrolyte levels and

correct if necessary.

Check for availability and con dition of all safety equipmen t, gloves, apr ons,

face shields, etc. (see sect ion 8). Check for a full gallon of labeled

neut ralizing solution, an d operability of eyewash sta tion or portable eyewashequipmen t. Check for operation an d cleanliness of body wash station.

Check for a class C fire extinguisher an d check that it h as been inspected

and tested according to schedu le. Check for availability of insu lated tools

and uten sils so short circuits can be avoided. Check the hydrometer for

cleanliness an d cracking of rubber parts.

1.81.8 BATTERY CAREBATTERY CARE

A.A. Adjustm en t of Specific GravityAdjustm en t of Specific Gravity

Do not add or remove acid in any cell except when following instructions in

paragraph 2.17.

B.B. TemperatureTemperature

Never intentionally allow electrolyte temperature to exceed 100 EF.

C.C. CleanlinessCleanliness

Keep th e battery room or cabinet clean and well ven tilated. Keep cells,

especially the tops, clean, dry, and free of electrolyte and corrosion residue.

D.D. Spilled Electr olyteSpilled Elect rolyte

At each batter y room or cabinet, provide a labeled gallon jar of solut ion

consisting of 1 poun d baking soda to 1 gallon of water . Neu tralize spilled

electrolyte with soda solut ion, rinse with water, an d wipe dry. Do not allow

any solut ion to enter the cells. Keep vent plugs tight and gas ven ts open.

Any missing or worn ven t plug gaskets shou ld be rep laced.

1.91.9 CHARGERSCHARGERS

Rev.12/31/97 9


15/83

Chargers serve two important fun ctions. The m ain function is to provide d

c station power and to keep the battery charged. The second fun ction is to

be able to replace the battery if the need arises. Two main types available

are silicon-controlled rect ifier (SCR) an d ferro-resonan t. The two types

differ greatly. SCR chargers consist of a tran sform er with an SCR bridge

and filtering. All cont rol and protection in these chargers is electron ic.

These chargers are usually the cheapest type because the manufacturer can

buy SCRs and electronics off the she lf. Ferro-resonan t cha rgers uses a

tran sformer specifically designed for each application. When extreme

conditions occur, th ese tran sformers satu rate and limit, by design, th e

maximum cu rren t and voltage. Additional electronics are not needed. This

feature m akes the char gers more du rable and depen dable in a power plant

environm ent . The ferro-resonan t type charger is ther efore recommended.

Chargers norm ally are bought and operated in pairs to shar e the load. Both

chargers operating, with all safety featu res activated on both , will less likely

have a double failure than if one is operating and one is in stan d-by mode.

In an emergency, a cha rger on standby trying to power u p and assume theduties of a failed charger may exceed its current or voltage limits before

safety circuits are enabled. The r esult may be two failed char gers. The best

way to avoid this problem is to opera te both chargers in para llel at all times,

each supplying half the load.

The size of the chargers is very important to the life and service of the

battery. The chargers mu st have enough capacity to easily gas the battery

un der ch arging conditions. Chargers with too little capacity redu ce battery

life. A smaller charger, though cheaper initially, can be the m ost expensive

on a long term basis.

A.A. Ever y Sh iftEvery Sh ift

Check the panel voltmeter to see if the correct float voltage is being used for

charging.


Check each charger by turning off one , then the other, and see if each

charger will carry the total load.


Check the accu racy of the charger panel voltmeter with the digital mete r.

1.101.10 RECORDSRECORDS

Post a battery data card form POM-157 in a conspicuous location n ear th e

battery, and keep accu mu lated forms in a perm anent file.

Loss of capacity over time is shown by a gradu al change in specific gravity of

Rev.12/31/97 10


16/83

the ce lls. Keeping accurate records in th e battery room is important.

Comparison can be made easily between cu rren t and ear lier readings. A

copy of forms POM-133A and POM-134A are included in the forms sect ion

and are available from Reclamations Technical Service Cen ter in Den ver.

Four POM-133A quarterly reports and one POM-134A connection

resistance report ar e requ ired for a 60-cell battery each year. Special care is

necessary to protect data sheets. Keep cur ren t records on clip boards or in a

log book near the battery and transfer th em to a perman ent file at the en d of

the year.

Rev.12/31/97 11


17/83

1.111.11 BATTERY TROUBLES SU MMARIZEDBATTERY TROUBLES SUMMARIZED

A.A. Lack of GassingLack of GassingLack of gassing while on charge may indicate an internal short between

plates, i.e., the cell discha rges internally as fast as it is being charged.

B.B. Specific Gravity or VoltageSpecific Gravity or Voltage

Specific gravity or voltage of a ce ll lower than othe r ce lls is an indication of

excessive inte rnal losses an d m ay result from con sistent un derch arging.

C.C. ColorColor

Color or appearan ce of plates or sedimen t differen t from other cells is

addressed below:

1. Patches of white lead sulfate on either the positive or negative plates:caused by standing idle or un derch arging for extended periods.2. Antimony deposit dark-slate patches on negative plates (usually near the

term inal): caused by charging at too high a rate or an aged cell nearing

the en d of its service life.

3. Top layer of sedimen t white: caused by underchar ging.4. Lumpy brown sediment: caused by overcharging.5. All white sediment n o visible layers: caused by overcharging after

prolonged low float voltage.

6. Large flaking on th e inte rplate collector bar : caused by being on floatcharge for extended periods at insufficient float voltage without

equalizing charging being performed.

D. D. Plate Problem sPlate Problem sIf any checks below are excessive, capacity tests must be run to determine if

individual cells or th e en tire battery should be replaced. See section 3.

1.

Cracks on the edges of the positive plate grids.

2. Light-colored sulfating spots on edges of plates below cracks men tionedin check No. 1 above.

3. Excessive sedimen t in th e bottom of the case.4. Mossing or treeing on the tops of negative plates.

Rev.12/31/97 12


18/83

E.E . Wat erWater

1. Cell uses excessive water (ch eck fig. 1 for typical water consu mpt ion):caused by excess charging rates, h igh operating temperatu res, or leaking

cell.

2. Cell requires very little water: cau sed by insufficient ch arging.FF . Buckling of Plate sBuckling of Plate sBuckling of positive plates ind icates excessive su lfation caused by

un derch arging or excessive temper ature. See sections 2.10, 2.22, and 2.23.

GG. Failure to Su pply Rated Ampe re-Hou r LoadsFailure to Su pply Rated Ampe re-Hou r LoadsFailure to supply rated ampere hours indicates dischar ged condition,

excessive su lfation, or loss of active material from positive plates. Cells may

be worn out or act ive ma ter ial may be gone from positive plates. See sec tion3 for testing.

H.H. Surface Charge Phen omenonSurface Charge PhenomenonWhen a battery has been on float charge for a long time and is put u nde r

load with the ch argers off, the voltage will drop rapidly. Th is drop is caused

by plugging of some of the pores on the surface of the plates, which part ially

blocks the tran sfer of ions. The voltage may drop below the low-voltage

alarm and trip settings. After th is initial drop, the voltage will usually

increase to a level above the low-voltage alarm an d trip settings. The battery

will then operate normally until its capacity is exhausted.

If the battery is exercised (partially discharged) on a routine basis, the

voltage dip can be reduced or eliminated. Turning off both chargers and

allowing the battery to take the load for at least 15 minutes exercises the

battery. The first few times th is procedure is performed, disconnect th e low

voltage trip relay to prevent an inadverten t trip. The first time th e battery is

exercised, th e procedu re should be performed several times in succession

un til the voltage drop stays above th e alarm setting. Always give th e

chargers time t o reduce ch arging cur ren t to float value before tu rn ing off the

chargers again for the next cycle.

Each battery has its own cha racteristics, and th e frequen cy of exercisingshould be adjusted so that the voltage drop does not cause the low voltage

alarm. Start at a m onthly cycle and experiment with increasing the time

between exercises. The proper time between exercises exists when the

voltage dr op is just above th e alarm relay setting.

1.121.12 RECOMMENDED ACTIONSRECOMMENDED ACTIONS

If any cells seem to be in trouble, the whole battery shou ld be given an

Rev.12/31/97 13


19/83

equalizing charge, and then specific gravity readings should be taken on all

cells. Ifall cells gas evenly and specific gravity ofevery cell is normal, all thebattery needed was the cha rge. Otherwise, all low gravities shou ld be

recorded, an d an extra thorough charge, as described in section 1.2C should

be given. The t emper ature of all cells should be compared by ther mometer

or IR camera with th e rest of the cells. Sulfated cells will run hot en ough to

cau se dam age if not corr ected. Any cells that still will not gas with the extra

charging should be investigated for impu rities an d inspected for inte rnal

short circu its. See section 3 for testing.

Additional informa tion may be obtained from IEEE Standard 450-

1995Maintenance, Testing, and Replacement of Vented Lead-Acid Batteries. If thisstandard does not help solve a problem, record the voltage of each cell and

the specific gravity of 10 per cen t of all the cells. Also, record the electr olyte

temperature an d the ambient temperature, then contact the battery

manufacturer for assistance.

1.131.13 CELL REPLACEMEN TCELL REPLACEMENT

A faulty cell may be replaced by one in good condition of the same make,

type, rat ing, and approximate age. A new cell shou ld not be insta lled in

series with older ce lls except as a last resort. A battery may be operated

without severa l cells by proper adjustm en t of float and equalizing voltages,

provided discharge capacity requ iremen ts can be met.

2. LEAD-ACID BATTERY PRINCIPLES

2.12.1 PURPOSEPURPOSE

This section describes th e pr inciples of lead-acid battery care an d h ow to

determ ine if the care is adequate and correct. The most importan t part of

battery care is a proper charging program . Keeping and comparing accura te

records of physical conditions and m easured data assists in determ ining

whether the charging program is correct. Correct charging is critical for

long battery life and reliability of service.

The following discussion describes cell conditions with both proper and

improper operation and mainten ance . These principles do not take

preceden ce over the man ufacture r's instructions, but provide explana tions

and details.

2.22.2 FULL CHARGEFULL CHARGE

Knowing when a ce ll is fully charged is importan t. A cell is fully charged

when , charging at the equ alizing rate, the ce ll is gassing, specific gravity has

stopped r ising, and specific gravity rem ains constan t for two successive

readings. Hydromete r readings must be corrected for any changes in cell

temperatu re that have occur red between readings. These two readings

should be taken dur ing the last one-eighth of the charging period.

Rev.12/31/97 14


20/83

2.32.3 APPE ARANCE OF NORMAL CELLSAPPEARANCE OF NORMAL CE LLS

Edges of positive plates do not give much in formation. Edges of negative

plates should be uniformly gray; they should be examined with a non

metallic flash light for sparkling from lead su lfate crystals. Correc t float

charging will cau se no lead sulfate crystals. See sect ion 1.10 for more

informa tion on cell appearan ce.

Rev.12/31/97 15


21/83

No visible change occurs when the ce ll is discharged a normal amount. If

the charging program is correct, sediment accumulates very slowly and

should never be white or lumpy. The ch arging program may require

chan ges to produce a very scanty, fine , dark-brown sediment . The electrolyteshould be at th e m arked level, midway between top of the case an d top of

the plates.

2.42.4 CHEMICAL CHANGESCHEMICAL CH ANGES

A fully charged ce ll has brown lead peroxide on positive plates and gray

sponge lead on n egative plates.

On discharge, electric current converts active materials of positive and

negative plates to norm al lead su lfate an d u ses up su lfuric acid to

man ufacture lead sulfate. This process leaves the acid weak at the en d of

the d ischarge. Lead sulfate is white in color but cann ot be seen on plates

un less the cell is over-discharged, which produ ces over sulfation. This

condition makes the plates first lighter in color and finally mott led white inpatches or white all over.

Charging the cell reverses this process, converting lead sulfate in the plates

to lead peroxide an d sponge lead and producing sulfur ic acid, which restores

the specific gravity to norm al. Chemical reac tions in a storage cell are :

Battery Discharged Battery Char ged

(+ plate) (- plate) (solutio (+ plate) (- plate) (solution)

n

PbSO4 PbSO4 2H 2O PbO2 + Pb 2H2 SO 4+ + +

(lead sulfate) (lead sulfate) (water) (lead peroxide) (lead) (sulfuric acid)

As the charge nears completion little lead sulfate remains to convert to lead.

The charging curren t begins to separate water into oxygen and hydrogen,

which bubbles to the top of the electrolyte and forms a mixture of very

explosive gases.

Quan tity of ampere-hou rs available from a cell decreases with an increasing

rate of discharge. Available ampere-hou rs are m uch less at rapid rates ofdischarge (see fig. 3). The amper e h ours also decrease for cells with weaker

specific gravity (see fig. 4).

2.52.5 INTE RNAL SELF-DISCHARGE AND EFF ECT OF IMPURITIE S ON FLOATINGINTERNAL SELF-DISCHARGE AND EFFECT OF IMPURITIES ON FLOATING

VOLTAGEVOLTAGE

Lead-calcium and lead-selenium cells have th e advantage of low internal

losses, which rem ain constan t for the life of the cell. Lead-selen ium cells

Rev.12/31/97 16


22/83

contain little antimony and do not have antimony migration like lead-

an timony cells.

Fully charged lead-antimony cells discharge internally by an action between

active mater ial and th e grid. Impu rities may hasten this action and m ay

result in visible or invisible changes on the plates depending on the types of

impurities presen t. No metals should be put into the electrolyte at any time, except acadmium test electrode. Impur ities may prevent a proper floating voltage fromkeeping up th e charge and m ay prevent an equalizing charge from

equalizing voltage, so a higher floating voltage m ay be requ ired.

The ra te of self-discharge is decreased by using a lower specific gravity. The

rate increases as the cell temperatu re rises, as may be seen on th e cur ves of

figures 5 and 6. The charge will not be lost if a small charging curren t, just

equal to the self-discharge rate, is given to the ce ll. Th is charge is known as

a tr ickle charge an d is usu ally made a little larger t han necessary so as to

gradually restore losses caused by small loads connected to the battery.

Self-discha rge increases with age to perhaps five times the initial rate. This

process is believed to be caused by the antimony being deposited on the

negative plate in a form th at behaves as an impu rity. Many batteries use

calcium instead of antimony as the alloying material, which redu ces the

intern al dischar ge as indicated on figure 7.

2.62.6 TEMPE RATURE CHARACTERISTICSTEMPE RATURE CHARACTERISTICS

Operating tem pera ture grea tly affects performan ce of storage cells. Capacity

is greatly reduced when cold, as shown by figure 8. The self-discharge rate

is increased at warm tem peratu res, as shown by figure 7. The tem peratu re

at which the electrolyte will freeze an d bur st cells is lowered a s specificgravity rises. Little dan ger of freezing exists if the battery is kept well

charged.

If charging cu rrent is kept constant , charging voltage will rise to a final value

and is one indication th at full char ge has been reach ed. This final voltage

increasesgreatly as the cell gets colder, as shown by figure 5. For th is reason,do not try to term inate an equalizing charge by a re lay that operates at a

constan t voltage. This procedur e would only work correctly for one

tem peratu re. Relays are available where operat ing voltage varies with

temperatu re. This charge control mu st be subject to the same am bien t

temperature as the battery.

If charging voltage is held constant, final charging current increases with

temperatu re, as also shown in figure 5. This condition is needed to offset

the incr easing intern al self-discharge current. The constant voltage char ge

meth od automatically keeps the cu rren t at the value the battery needs for

replacing both the self discharge and load discharges.

2.72.7 PROPER AMOUNT OF CHARGEPROPE R AMOUNT OF CHARGE

Rev.12/31/97 17


23/83

If cells of either lead-antimony or lead-calcium are undercharged, service willbe poor and battery life short . Ifovercharged, service with eithe r cell type willbe good, but excessive overcharging will shorten life. Proper charging,

means slight overcharging to cause the least possible sedimentation and a minimum ofheavy gassing. This condition requ ires very little makeup water . Noperceptible sedimentation or buckling of plates occurs during charge at high

or low rates if cells are not a llowed to gas vigorously. Sedim en tation star ts

with gassing and is proportional to the total amoun t of gas liberated. Lead-

selen ium cells do not have th e grid growth or the lead-antimony cell

problems. Typical curves of recharge times after 100-percent dischar ge at

the 8-hour rate ar e shown in figure 9.

2.82.8 HIGH -RATE OVERCH ARGINGHIGH-RATE OVERCHARGING

After a battery is fully charged, continuation of charging current at a high

rate dam ages positive plates. Violen t gassing takes place, bu bbles form in

the interior of the active m aterial, and th e re sulting pressure forces bubbles

through the porous active mater ial. The active mater ial restrains thebubbles sufficiently so that many particles of plate material are broken out.

These particles rise with the bubbles and result in a m uddy red or brown

color of the electrolyte. Some of this fine sedimen t settles on n egative plates

where it short circuits. The sedimen t is converted to gray sponge lead and

results in a growth of moss-like sediment deposited on top edges of the

negative plates. This deposit indicates that high-ra te overcha rging

previously occur red . The battery will overh eat on susta ined heavy charge

rates. The t emper ature of the cells should never inten tionally be allowed to

exceed 100 F.

2.92.9 LOW-RATE OVERCHARGINGLOW-RATE OVERCHARGING

At lower rates of overcharge, bubbling is reduced and sediment falls to the

bottom of the cell. Overcharging at a very slow rate disturbs electrolyte so

little th at fine brown sedime nt falls in a vertical line, forming tiny ridges on

top of the sedimen t. Ridged sedimen t is a good indication that th e recen t

overcharging was not at h igh rates. Obviously, overch arging shou ld be kept

at a m inimum , and r idges should be small.

2.102.10 UNDERCHARGINGUNDERCHARGING

If the battery gets too little charging, unconverted sulfate remains on the

plates too long and harden s. The longer plates stay in less-than-full-chargecondition, th e harder the sulfate becomes an d the m ore difficult it is to

reconvert. When n ew, the sulfate is easily converted back to soft active

mate rials by a n ormal ch arge, but a long overch arge is required to rem ove it

after becoming hard. Sulfate accumu lates un noticed, a little on each

charge, if charging is not en ough to eliminate all the sulfate. This residue

build-up con tinues un til a substantial portion of ampere -hour capacity is

lost. The rem edy is to increase charging to give a slight overcharge. Thisprocedure m ust be pu t into practice while the battery is new and followed

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for the life of the battery (see also paragraph 1.2CEqualizing Charge).

Prolonged undercharging also leads to large flaking on the interplate

collector bar .

Sulfate build-up caused by undercharging is the most common cause of buckling plates andcracked grids. Sulfate takes up more room than the original material and strains the plates outof shape. The pressure of expanding active m aterial can break separators an dcause short circuits.

A badly sulfated cell shou ld be trea ted as descr ibed in sect ion 2.24. If

charged at too low a rate, the harden ed sulfate is thrown out of plates and

settles in white ridges on the cell bottom. At higher rates, the gassing

distributes the sedimen t evenly without ridges. An over sulfated ce ll has

high intern al resistance and requ ires extra voltage across the ce ll, which

also causes them to develop higher temper atures on charge. Buckled or

cracked plates cannot be r epaired by rem oval of sulfate but may be used as

long as they retain satisfactory ampere-hou r capacity. See sect ion 3 for

capacity testing.

2.112.11 OVER DISCH ARGEOVER DISCHARGE

The plates suffer greatly when over discharged. Voltage per cell should not beallowed to drop below 1.75 volts. Specific gravity should n ot be allowed todecrease below the limit given by the man ufacturer, which is differen t for

various types and sizes of cells. Asnormal discharge proceeds, activematerials are converted to normal lead sulfate, which requires only slightly

more space th an active mate rials. Over discharge form s more lead sulfate inthe pores of the active ma terial than th ey are able to hold. This process may

expand and bend or buckle plates or crack grids. In some instances,

sufficient pressure is created to crack or puncture separators.

2.122.12 SEDIMENTATIONSEDIMENTATION

The history of each cell is shown by the sedimentation because successive

layers are laid down in colored strata .. These layers can be seen edgewise

against the inside of the case. Layers of fine, dar k gray show periods of

excessive charging (cu rrent too high or char ge too long). Lum py gray layers

indicate times the battery was over discharged. These layers are gene rally

covered by a layer of white sulfate from the following charge. A consider able

am oun t of sedimen t an d slivers will be foun d initially in Gould processed

plate batter ies. This condition is a norm al result of the forming process.Some additional sediment and slivers will be dislodged in shipment and will

accum ulate at th e bottom of the case of these batteries during the first few

equalizing charges. With this exception, a perfectly charged battery should

have noth ing but fine brown sediment, free from lum ps and as scanty as

possible. If some experim en ting is done with th e cha rging program , slight

un derch arging may result in a white sulfate layer. This layer indicates that

the charging should be slightly increased.

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2.132.13 REPLACEMENT WATERREPLACEMEN T WATER

As batteries are charged, a small quantity of water in the electrolyte is

broken down in to hydrogen and oxygen by the charging curren t. The gases

are dissipated th rough open ings in ven t plugs. As this process takes place,

electrolyte level gradually lowers u nt il distilled water mu st be added .

Comm ercially available "dem ineralized" water has been found by test to be

equal or super ior to commercial or "in plant" distilled water . Referen ces

throughout this bulletin to "distilled water" do not preclude the use of

"dem ineralized water. Do not add water in excess of the maximu m level

mark. Never store distilled water in a meta llic container. Use glass, plastic,

or rubber containers.

Water consu mption of batteries is indicated on figure 1. Take an average of

the am oun t of water added over several month s and compare with the

amounts given on figure 1.

2.142.14 WATER REPLACEMEN T RATE FORWATER REPLACEMENT RATE FOR LEAD-ANTIMONY CELLSLEAD-ANTIMONY CELLS

Lead-an timony cells begin the ir lives with low water consumption, which

increases as m uch as five times toward th e en d of their lives (see fig. 1).

Capped ce lls evaporate very little water, and loss is caused by gassing an d is

proportiona l to the amount of charge the battery rece ives. Heavy gassing

requ ires frequent additions of distilled water. The water should be added

just before or a t the beginn ing of a ch arge so tha t gassing will en sure

thorough mixing before specific gravity readings are taken . Proper charging

minimizes distilled water replacement by limiting the amount of gas

gene rated to a small quan tity. This method is mu ch easier than

overcharging and having to refill cells frequ en tly. It also exten ds the life of

the battery.

2.152.15 WATER REPLACEMEN T RATE FORWATER REPLACEMENT RATE FOR LEAD-CALCIUM CE LLSLEAD-CALCIUM CELLS

Frequ ent additions of distilled water in small amoun ts are not desirable.

Water add itions two or thr ee times a year will probably be sufficient a t most

installations. The electrolyte in all cells shou ld be maint ained within 1/4

inch below the high level mark. Calcium ce lls, becau se of greater pu rity of

their components, require only about one tenth the water needed by

equivalent size an timony cells. This low requirem ent r emains constant

dur ing the entire battery life. See figure 1 for water consum ption r ate.

2.162.16 WATER REPLACEMENT FOR LEAD-SELEN IUM CELLSWATER REPLACEMEN T FOR LEAD-SELENIUM CELLS

Water r eplacemen t should only be necessary every 12 to 18 mon ths if the

battery is not subjected to many dischar ges. If several discharges are

experienced, water replacement should be performed as with the lead-

calcium cells in paragraph 2 .15 above. Water consumption is low

throughout the life of these cells.

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2.172.17 ADJUSTING SPECIFIC GRAVITYADJUSTING SPECIFIC GRAVITY

Specific gravity should nevernever be adjusted un til the gravity is definitelyestablished to be wrong. Before adjusting for low gravity, make su re th at th e

gravity can not be raised by equalizing (see 1.2 C). Continue th e charge

un til the specific gravity shows no rise, an d th en charge for 3 more hour s.

Hydrometer readings must be taken as indicated in 2.18 below. Never make agravity adjustment on a cell that does not gas on charge. Remove some electrolytefrom the cell and replace it with pure, 1.300-gravity sulfuric acid, which

consists of 30-percen t concen trated acid and 70-percent distilled water by

volum e. Recharge un til all cells gas for an hou r. Repeat the procedu re if

the gravity is still not norm al. To lower the gravity, rep lace some of theelectrolyte with distilled water .

2.182.18 HYDROMETE R READINGSHYDROMETER READINGS

Provide two hydrometers of high accuracy and sensitivity and check them

against each other frequen tly. The h ydrometer s should be replaced every 2to 3 years. The hydrometer must be held vert ically for accu rate specific

gravity readings. Do not take readings after adding water (or acid) un til the

electrolyte h as had time to m ix thoroughly (not less than 1 hour when

gassing or 2 days if not gassing for an timony cells, an d severa l weeks for

calcium cells in floating service). Use a long nozzle syringe and take

samples several inch es down to minimize errors. Bubbles in the elect rolyte

cause err ors, and r eadings should not be taken sooner th an 15 m inutes after

gassing has stopped.

Specific gravity of electrolyte mu st be correcte d for temperature. Subtract

one point (0.001) from the specific gravity reading for each 3 EF the

temperatu re is below 77 F, and add one point (0 .001) for each 3 EF thetemperatu re is above 77 F. The r ecomm ended specific gravity spread

between all cells is 0.010.

2.192.19 CON STANT VOLTAGE CH ARGINGCONSTANT VOLTAGE CHARGING

Constant voltage ch arging is the preferred meth od because of extended

service life. If charging equ ipmen t is suitable for a continuou sly floating

charge at a constant voltage, the proper floating voltage should be chosen

from the manufactu rer s data. If the voltage is given for a single cell,

mu ltiply th is voltage by the n um ber of cells in the batte ry.

2.202.20 BATTE RY LIFE FOR DIFF ERENTBATTERY LIFE FOR DIFFERENT TYPES AND SERVICESTYPES AND SERVICES

The life of various types of cells can vary markedly. Valve regulated lead-

acid cells have the shortest life. Formed plates of the P lante or Manchex

type on light du ty and floating charge have a longer life, u sually 14 to 18

years. Pasted p late Plante cells may be expected to last in excess of 25 year s

on float ch arge. Form ed plate ce lls, if cycle cha rged, usu ally last only about

9 years. Lead-calcium cells on constan t float charge typically last 12 to 15

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years. Lead-selen ium cells have a longer life expectation than lead-calcium

or lead-an timony. A batter y is considered worn ou t when it fails to deliver

80 percen t of its original capacity.

2.212.21 CLEANLINESSCLEANLINESS

Battery connections m ust be clean , bright, and free of corrosion for th e

battery to perform. Corrosion tha t is not clean ed off terminals per iodically

will spread in to areas between posts and connectors. Th is condition will

develop into a h igh re sistance connection an d cause h eating and wasted

capacity. The battery and su rroun ding parts should be kept clean, dry, and

free of acid. Su lfur ic acid absorbs moisture, and spilled electrolyte will not

dry up. If electrolyte is spilled or sprayed ou t of the cells on ch arge,

ne ut ralize with a solution of baking soda (1 poun d of soda to 1 gallon of

water), then rinse with distilled water and dry with a soft cloth. A labeled jarof soda solution at least one gallon, must be kept in the battery room. Care should betaken to prevent th e solut ion from getting into the cells. Make sure ven t

plugs are open, flame arresters an d dust caps are in place, and allcomponen ts are in good condition.

2.222.22 INTERNAL SHORTSINTERNAL SHORTS

A short circuit th rough a separ ator may be caused by:

1. Insufficient ch arging causes mater ial in the plates to become mostly leadsulfate. The lead su lfate expan ds and , if the grid does not crack to relieve

the strain, the plate will become distorted. This condition is commonly

known as buckling. The buckling is most pronounced at th e four corn ers

of the positive plates, where sh orts are most likely to occur .

2. Impurities in the solution cau sed by using contaminated water or dirtyutensils.

3. Excessive overcharging causes th e grid specific gravity to be partiallyconverted to lead peroxide, which redu ces mech anical strength and

allows positive an d n egative plate contact.

A short in a cell can be detected by falling specific gravity and falling cell

voltage. In some cases, an oran ge discoloration occur s at the point of the

short . If a shor t is long standing, disin tegration of the positive plate will

occur a t the point of contact with the negative because of the conversion ofpositive plate mater ial to negative.

2.232.23 NORMAL SULFATE AND OVER SULFATIONNORMAL SU LFATE AND OVER SULFATION

During discharge of a battery, "normal" sulfate is formed, which is required

to produce cu rrent . If charging is neglected, the sulfate fills the pores of the

plates and m akes the active mater ial dense and ha rd. This condition is

referr ed to as "over sulfated."

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Normal lead sulfate formed on discharge is in a form th at a charge will

easily recon vert . When a batter y is "over sulfated," plates are less porous

than norm al and absorb a charge with difficulty. With this condition, an

ordinary charge will not reconvert all the sulfate to sulfuric acid and specific

gravity remains below norm al. Active mater ial of "over su lfated" negative

plates is light in color and either h ard an d den se or granular an d gritty and

easily disint egrated . The negative plates requ ire the prolonged charge

necessary to restore an "over su lfated" battery. An individual cell may

become "over su lfated" by extern al groun ding, by an inter na l short, or by

drying out because of failure to add water. Over sulfation may also be caused

by prolonged low float charging.

2.242.24 ELIMINATION OF OVER SULFATIONELIMINATION OF OVER SULFATION

A battery or ce ll that is "over sulfated" shou ld be ch arged fu lly in the regular

way un til specific gravity stops rising. Then one of the weakest ce lls should

be dischar ged th rough a load resistor at the n ormal 8-hour discharge rate to

a final voltage of 1.75 volts. The batte ry is not over sulfated if therepresen tative cell gives normal capacity, that is, about 100 pe rcen t ra ted

capacity for a fairly new battery or down to 80 percent of initial rated

capacity for a battery nearing the end of its expected life.

If the above capacity is not obtained, possible over sulfation shou ld be

treated as follows:

1. In cases where one or more individual cells have become "over sulfated"and the rest of the battery is in good condition, these cells should be

treated separately after rem oving them from th e circuit.

2. Recharge the removed cells at half the 8-hou r discharge rate. Recordhydrometer readings and tem peratu re at regular intervals (3 to 5 hour s)

during the charge to determine if rising specific gravity has peaked.

Maintain constant electrolyte level by adding water after each reading.

Do not add water before taking readings.

3. Continue the charge, recording the readings un til no furth er specificgravity rise has occurred in any cell for 10 hour s. If the temper ature

reach es 100 F, reduce the cu rren t or temporarily interru pt the ch arge so

as not to exceed this temperatu re. When the specific gravity has reach ed

maximum , terminate th e char ge an d record the hydrometer reading of

each cell.

4. The cells must be replaced if they again fail the capacity check in 2.24.

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2.252.25 WATER TREATMENT FOR OVER SULFATIONWATER TREATMENT FOR OVER SULFATION

In cases of emergency such as plant power loss or loss of both chargers, a

long discharge to the point of over-discharge may make the batte ry difficult

to recover. Over sulfation may have occurred su ch th at prolonged charging

set forth in section 2.24 m ay not recover th e battery.

The water trea tmen t should only be attempted in an emergency as a lastlastresort after p rolonged charges will not restore the specific gravity.

The pr inciple is to reduce th e specific gravity in steps by removing a portion

of the electrolyte and replacing it with distilled water, then charging the

battery after each step. As the specific gravity is reduced and the ch arge is

applied, th e su lfate is dissolved from th e plate s by lower specific gravity

electrolyte at each step. The e lectrolyte becomes more an d more like pur e

water, making it easier for th e su lfate t o tran sfer off the plates into th e

electrolyte. Once th e sulphates have been dissolved an d rem oved, the

process is reversed to bring the electr olyte back to norm al specific gravity.

The steps are as follows:

1. Redu ce th e specific gravity to about 1 .050 to 1.100 by rem oving some ofthe electrolyte an d replacing it with distilled water.

2. Charge the battery at the equalizing rate until the specific gravity of thepilot cell stops rising for two consecu tive readings. However, do not

charge longer than 48 hour s before the n ext step.

3. Again reduce the specific gravity as in step 1 above and repeat the chargein step 2.

4. Repeat th e above steps u ntil the maximum specific gravity obtained at theend of a charge is less than 1.150.

5. Reverse the above process by removing some of the weakened electrolyteand replacing it with 1.300 specific gravity acid. The amoun t to be

replaced is about the sam e as that in step 1 above. Do not try to speed up

the process by replacing more of electrolyte th an that rem oved in steps 1

through 4.

6.

Charge the battery as in step 2 above, ch ecking the specific gravity of 10percen t of the cells.

7. Repeat steps 5 an d 6, increasing the specific gravity un til it is just be lownormal opera ting value. Record th e specific gravity of all the cells on th e

last step.

8. Place the battery back under n ormal float charge an d service.

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9. After 1 month un der n ormal service, the battery should be given a

capacity test to see if the battery must be replaced (see section 3.2).

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3. BATTERY TESTING

The purpose of this section is to describe recom men ded testing procedures

and intervals. Inform ation herein con sists of guidelines on ly and is not

intended to replace manu facturers recomm endations. Follow

man ufacture rs informa tion if a conflict between these guidelines and

man ufacturers information is en countered.

3.13.1 ACCEP TANCE TES TINGACCEPTANCE TESTING

Acceptance testing should be performed n o sooner t han 1 week after th e

battery has had its initial freshening charge (see section 1.2 A). This test

may be done a t the factory before shipping if specified. This test should be

at least a 3-hour d ischarge test an d should provide at least 90 percen t of

rated capacity. An 8-hou r discharge test for acceptance is preferred , and 90

percen t of rated capacity should be required.

3.23.2 CAPACITY TES TS TO DETERMINE REPLACEMEN TCAPACITY TESTS TO DE TERMINE REPLACEMEN T

To establish whether a battery is nearing the end of its useful life, load test

the en tire battery as out lined below at 5-year intervals. This test shou ld be

repeated ann ually if the capacity has dr opped below 90 percent.

A.A. After th e batte ry has been fully charged by equalizing, retu rn it to floatservice for at least 72 h ours, but less than 30 days before pe rforming the

test.

B.B. Check all battery conn ections with a m icro-ohmm eter to en sureconnections are clean an d low resistance. An IR camer a may be used

just after the discharge test has begun to check the connections.

Temperatu re will be higher on poor conn ections. If poor conn ections are

foun d, stop the te st and repair the conn ections before continu ing.

C. C. Record the specific gravity and voltage of each cell just prior to th e test.D. D. Record the tem peratu re of the electrolyte of 10 percen t or more of the

cells (an IR camera may be used an d the tem peratu re of cell cases may

be recorded) to establish an average temperatur e.

E. Record the batte ry term inal float voltage. Use an accu rate digitalvoltmeter.

F.F. Take precau tions t o ensu re that a battery failure will not jeopardize otherequipmen t. Discharge the battery through a suitable resistor and an

amm eter for 3 hour s at rated 3-hou r discharge curren t. Leave the

charger in normal float operation and record each cell voltage every half-

hour during discharge. Watch closely dur ing the last hour an d time the

exact end point accu rately. After ambient tem peratu re correction to

77F, if the minimum voltage of 1.75 in any cell is reached before 3 hours

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has elapsed, the test should be stopped and the amper e-hours discharge

should be computed. Capacity can be de term ined by referring to figure

3. Testing should be done each year if the capacity is less than 90

percen t of the original rating. The entire battery should be replaced as

soon as possible after capacity drops below 80 percen t of original. The

battery cann ot be relied u pon in an emergency if it has deter iorated

below 80-percent capacity.

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4. OPTIONAL INSTRUCTIONS LEAD-CALCIUM BATTERIES

4.14.1 FLOAT CHARGEFLOAT CHARGE

For a typical, 60-cell, lead-calcium battery floated a t 2.17 volts per cell and

equalized at 2.33 volts per cell, the normal voltage range would be 130.2 to

139.8 volts. At many locations, the h ighe r voltage can not be tolerated for

the 6 or more days required for equalizing, particularly where the battery is

a source of power for electronic equipmen t. Lead-calcium batteries do notrequire equalizing if floated between 2.2 an d 2.25 volts per cell. Th is voltagewould give a 60-ce ll battery a voltage between 132 an d 135 volts. Lead-

calcium batteries have a d istinct advantage when constant voltage is

desirable. To match the battery voltage to the rated voltage of the

equipmen t served, the n um ber of cells should be selected to provide

optimu m voltage when floated to eliminate the equalizing charge. This

procedure should be considered when replacing batteries. The table below

lists some common voltage ranges.

Table 2. - Comm on voltage ranges.

Nu mb Voltage Range

er (volts)

of

Cells

12 26.4 to 27.0

23* 50.6 to 51.75

24 52.8 to 54.0

58* 127.6 to 130.5

59* 129.8 to 132.75

60 132.0 to 135.0

116* 225.2 to 261.0

120 264.0 to 270.0

* The low battery alarm m ust be ca librated to r eflect th e lower n um ber of cells.

4.24.2 INITIAL CHARGEINITIAL CHARGE

An initial charge is not required because the battery will charge properly at

the above voltages. After abou t 2 weeks, initial cell voltages and specific

gravity readings shou ld be recorded on form POM-133A. Increase the

voltage to 2.33 to 2.38 volts per cell (connected equipment permitting) if the

initial charge mu st be completed sooner .

4.34.3 VOLTAGE READINGSVOLTAGE READINGS

A.A. Each Sh ift (Atten ded Stations) or Dur ing Routine Inspections (Unat ten ded Stations)Each Shift (Attended Stations) or During Routine Inspections (Unattended Stations)

Check the ch arger panel voltmete r to determ ine if the battery is being

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floated at the proper voltage. Adjust the battery charging voltage when

nece ssary, and check when the power or station-service transformer taps are

changed.

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B.B. Mon t hlyMonthly

Check voltage across the battery terminals with an accurate digital voltmeter

and adjust the panel voltmeter if necessary. Record pilot cell voltages to the

nea rest 0.01 volt, measured with an accur ate digital voltmete r, on form

POM-133A. Batte ry is fun ction ing norm ally if all cells are above 2.14 volts.

C.C. QuarterlyQuarterly

Check voltages across all ind ividual cells and r ecord them on POM-133A.

4.44.4 SPECIFIC GRAVITY READINGSSPECIFIC GRAVITY READINGS

A.A. Month ly (Atten ded Stations) or During Routine Inspections(Un atten ded Stations)Monthly (Attended Stations) or During Routine Inspections(Unattended Stations)

Read th e specific gravity of the pilot cell. For accu rate readings, hold the

hydrometer vertically and use a long nozzle syringe about one-third down

from the top. Record th e pilot cell specific gravity, correc ted fortemperatu re, on form POM-133A.

B.B. Quar te rlyQuarterly

Read the specific gravity of 10 percent all cells and record, corrected for

temperatu re, on form POM-133A.


Read the specific gravity of 100 percen t of the ce lls, correc ted for

temperatu re, and record on form POM-133A.

4.54.5 HEAVY DIS CH ARGEHEAVY DIS CH ARGE

The battery should be recharged as quickly as possible following a h eavy

dischar ge. This rech arge can be done by raising the charging voltage to the

maximum allowed by other circu it components but n ot greater than the

ran ge of 2.33 to 2.38 volts per cell. The battery should be retu rned to

norm al voltage after the capacity been restored.

4.64.6 WATER REPLACEMEN TWATER REPLACEMENT

Add water only when the water level approach es th e low level mar k or priorto an equ alizing charge. This step shou ld be needed every 2 or 3 year s with

a proper charging program .

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TABLE 3. - VALVE REGULATED LEAD-ACID BATTERY (GEL CELL)

MAINTENANCE SCHEDULE

31

Mainten anc e New Battery Shift Monthly 3-Month 6-Month Ann ual

Visual General

Inspection Inspection

See 5.6

Batter y Float Pane l Meter Battery Float Voltage

Voltage Float with Digital Voltmeter

See 5.7 Voltage

Cell Float All Cells Pilot Cells All Cells

Voltage with Digital with Digital with Digital

See 5.7 Voltmeter Voltmeter Voltmete r

Tem perat ure All All

Readings Cells Cells

See 5.8

Conne ction All 25 Perce nt All

Resistance Conne ctions of All Conne ctions

See 5.9 Connections

In ter na l All All

Resistance Cells CellsSee 5.10

Battery Accept anc e Capacity Test 6

Testing Capacity mont hs if 1-year

See 5.11 Testing test < 90 percent

Safety Wash Equipment

Equipment Protective Clothing

See 5.6 & 8.0 Fire Extinguisher , etc.


37/83

5. CONDENSED INSTRUCTIONSCC

VALVE REGULATED LEAD-ACID BATTERIES (GEL CELLS)

5.15.1 GENERALGENERAL

Valve regulated lead-acid batteries (VRLA) are u sually manu factured inmu lti-cell blocks, (called modules) rathe r than single cells. The cases are

often made of ABS plastic material and do not permit visual inspection of

plates or electrolyte levels. They are called starved electrolyte or absorbed

electrolyte cells and operate u nder a positive pressure . The h ydrogen and

oxygen ar e not expelled but recombined. Cells are sealed and requ ire no

water addition or specific gravity readings. These ce lls are typically lead

calcium pasted-plate type cells with the electrolyte retained in gel or

fiberglass mats.

These batteries are normally used for emergency lighting,

telecommunications, and other u ninter rupted power supply (UPS) service.

They are best applied where long slow dischar ges are n eeded. Heavy shortdischarges required for breaker operations are n ot recomm ended for th is

type batter y. The life has been foun d to be only 18 mon ths to 10 years in

actual service.

These cells are not flooded and do not effectively dissipate heat. Thischar acteristic can lead to therm al runaway if ambient an d battery

temperatu res are n ot carefully controlled (see 5.2 below). Cases have

occurred in which the battery has burst into flame . Maintaining the cells as

close as possible t o 77 EF is imperative. Ambient tem peratu re should bemaintained as close as possible to 72 EF. Air circu lation must be sufficient

to eliminat e any ambient temperatu re differences. The maximu m cell

temperatu re spread (h ottest to coldest cell) should not exceed 5 EF, and the

hottest cell should not be more than 5EF above am bient. Colder

temperatures reduce capacity, and higher temperatures greatly reduce service life.About 50 pe rcent of the service life will be lost for every 15 EF above 77EF.

Do not allow sun light or other h eat sources to raise the temperatu re of

individual cells. These cells are not recommended for station service because of thesecharacteristicscharacteristics.

VRLA modu les/cells are typically shipped fully charged and do not require

initial charge.

5.25.2 FLOAT CHARGEFLOAT CHARGE

VRLA cells are typically floated at 2.25 to 2.30 volts depending on the

manufactu rer . Correct battery float voltage is critical for valve-regulated

cells. The float voltage mu st be within the m anu facturers recommended

limits compen sated for temperatu re. See the man ufacture rs literatu re for

temperature compensation of float voltages.

When VRLA cells are operated on float at normal full charge, no net

Rev.12/31/97 32


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chem ical reaction occur s and almost all the overcharge energy results in

heat generation. If the en vironmen t is such that th e heat produced can be

dissipated, no therm al runaway problem occur s. If the r ate of hea t

gene rated exceeds the dissipated rate, the battery temperatu re rises and

more cu rren t is requ ired to maintain the float voltage. The additional

current results in more heat generation, which raises the battery

temperatu re furth er, and the cycle is repeated. Ther mal runaway and

destruc tion of the battery result. Elevated am bient temperature (above 72F)

or cell and/or charger malfunction will aggravate this condition.

Ven tilation an d tem pera ture con trol is critical for VRLA cells, and th e

battery should reach t hermal equilibrium at no more than 5F above

ambient for the hottest cell.

As cells approach fu ll cha rge, battery voltage rises to approach the ch arger

output voltage, and charging curren t decreases. The battery is fully charged

when the ch arging curren t has n ot changed more than 10 percen t for more

than 3 hou rs. If the charging voltage has been set h ighe r than float voltage

to redu ce th e ch arging time, redu ce th e ch arging voltage to n ormal floatvalue after th e ch arging cur ren t has stabilized. Caution: Never exceed themaximum charging voltage recommended by the manufacturer.

5.35.3 EQUALIZING CHARGEEQUALIZING CHARGE

Equ alizing charge is not n orma lly per form ed on VRLA cells. An equa lizing

charge m ay be n ecessary if a low float voltage is indicated or if a fast

rech arge is needed. The battery man ufacture r should be consulted before

proceeding if an equalizing charge is needed. The exact voltages and charge

times indicated by the man ufacture r m ust be followed ca refully.

5.45.4 CHARGERCHARGER

A VRLA cell char ger mu st have at least two capabilities: (1) extra e lectrical

filtering to protect the cells from AC ripple, which may lead to thermal run

away, and (2) temperatu re compensation to prevent therm al run-away. Do

not try to charge these cells with a charger designed for afloodedlead-acidcells.

5.55.5 BATTE RY MAINTEN ANCEBATTERY MAINTENANCE

The regimen described below is strongly recommen ded to maximize

performance an d life expectancy. See man ufacture rs data and IEEE 1188-1996Recommended Practice for Maintenance, Testing, and Replacement of Valve-RegulatedLead-Acid (VRLA) Batteries for Stationary Application for further information.

5.65.6 VISUAL INSPECTIONSVISUAL INSPECTIONS

Visual inspections are made to assess the general condition of the battery,

moun ting rack and battery room, and safety equipmen t.

Rev.12/31/97 33


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A.A. MonthlyMonthly

Check for gene ra

battery maintenance

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