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Technical manual

X3.3

Low maintenance high performance batteries

XHP

April 2007

1. Introduction 3

2. Electrochemistry of Ni-Cd batteries 4

3. Construction features of the XHPbattery 53.1 Positive plate 53.2 Negative plate 53.3 Plate tab 53.4 Separator 53.5 Terminal pillars 53.6 Electrolyte 53.7 Vent system 63.8 Cell container 6

4. Operating features 74.1 Capacity 74.2 Cell voltage 74.3 Internal resistance 74.4 Effect of temperature on performance 74.5 Short-circuit values 84.6 Open circuit loss 84.7 Cycling 84.8 Effect of temperature on lifetime 94.9 Water consumption and gas evolution 10

5. Battery sizing principles in standbyapplications 115.1 The voltage window 115.2 Discharge profile 115.3 Temperature 115.4 State of charge or recharge time 115.5 Ageing 115.6 Floating effect 125.7 Number of cells in a battery 12

6. Battery charging 136.1 Constant voltage charging methods 136.2 Charge acceptance 136.3 Charge efficiency 146.4 Temperature effects 14

7. Special operating factors 157.1 Electrical abuse 157.2 Mechanical abuse 15

8. Installation and operatinginstructions 168.1 Receiving the shipment 168.2 Storage 168.3 Installation 168.4 Commissioning 188.5 Charging in service 188.6 Topping-up 198.7 Periodic maintenance 198.8 Changing electrolyte 19

9. Maintaining the XHP in service 209.1 Cleanliness/mechanical 209.2 Water replenishment 219.3 Capacity check 219.4 Recommended maintenance procedure 21

10. Disposal and recycling 22

Contents

XHP Range

3 XHP TECHNICAL MANUAL

Alcad XHP is specified where reliable standby poweris not just a preference but where it is essential forsafety and total peace of mind. This battery providessolutions for crucial engine starting applications, costeffective UPS installations and reliable emergencyback-up systems.

Where today’s high technology digital systems,computer-controlled processes and telecommunicationsstations must maintain hard-won positions in acompetitive market, Alcad XHP is your reliablepartner.

Alcad XHP range of nickel-cadmium batteries isdesigned and built to withstand physical andelectrical abuses. The batteries’ sintered/pbe plateconfiguration, immersed in a generous reservoir ofelectrolyte, delivers optimum performance, ensureslong life and high energy efficiency. Continuousoperation without risk of sudden failure is a featureof XHP’s Ni-Cd technology. The XHP can operate innormal operating temperature from – 20ºC to +50ºC,(– 4˚F to +122˚F) and accepts extreme temperaturefrom – 50ºC to +70ºC (–58˚F to +158˚F).

XHP can deliver repeated high discharges so that,even when partly discharged, it is ideal for enginestarting duties. For UPS installations, XHP will deliverhigh power within a narrow voltage window, andbecause of its unique electrochemistry and robustbuild, it will require only minimal maintenance for theduration of its 20 plus years’ life. XHP batteries canbe stored for many years before use, eradicatingproblems of stock control or availability.

The XHP range provides you with the reliability andperformance you need today, with the comfort of alow life-cost and ultra-low maintenance requirementfor more than 20 years ahead.

This manual details construction, installation andoperation principles for your Alcad XHP battery.Alcad experts are always available to offer practicaladvice to ensure you achieve optimum performancefrom your battery.

1 Introduction


discharge2 NiOOH + 2H2O + Cd 2 Ni(OH)2 + Cd(OH)2

charge

2 Electrochemistry of Ni-Cd batteries

The charge/discharge reaction is as follows :

The nickel-cadmium battery uses nickel hydroxide asthe active material for the positive plate, cadmiumhydroxide for the negative plate.

The electrolyte is an aqueous solution of potassiumhydroxide containing small quantities of lithiumhydroxide to improve cycle life and high temperatureoperation. The electrolyte is only used for iontransfer; it is not chemically changed or degradedduring the charge/discharge cycle. In the case of thelead acid battery, the positive and negative activematerials chemically react with the sulphuric acidelectrolyte with a resulting ageing process.

The support structure of both plates is steel. This isunaffected by the electrochemistry and retains itscharacteristics throughout the life of the cell. In thecase of the lead acid battery, the basic structure ofboth plates is lead and lead oxide which play a partin the electrochemistry of the process and arenaturally corroded during the life of the battery.

During discharge the trivalent nickel hydroxide isreduced to divalent nickel hydroxide and thecadmium at the negative plate forms cadmiumhydroxide.

On charge, the reverse reaction takes place until thecell potential rises to a level where hydrogen isevolved at the negative plate and oxygen at thepositive plate which results in water loss.

Unlike the lead acid battery there is little change inthe electrolyte density during charge and discharge.This allows large reserves of electrolyte to be usedwithout inconvenience to the electrochemistry ofthe couple.

Thus, through its electrochemistry, the nickel-cadmium battery has a more stable behaviour thanthe lead acid battery so giving it a longer life,superior characteristics and a greater resistanceagainst abusive conditions.

Nickel-cadmium cells have a nominal voltageof 1.2 V.


3.1 Positive plateThe positive plate used in the cell is of the sinteredtype. This is obtained by chemical impregnation ofnickel hydroxide into a porous nickel structure, whichis obtained by sintering nickel powder into a thin,perforated, nickel-plated strip.

3.2 Negative plateThe negative electrode is a plastic-bonded cadmiumelectrode, produced with a continuous process. Thisinvolves blending together the active material, binderand additives, continuously spreading this onto aperforated nickel-plated steel substrate, drying and,finally, passing the coated band through rollers fordimensioning.

3.3 Plate tabThe electrodes are seam welded to the plate tabs soproducing a continuous interface between the twocomponents. This ensures high current transfer andmaximum strength. The plate tab material is nickel-plated steel and the plate tab thickness is chosen toensure a satisfactory current carrying capabilityconsistent with the application.

3.4 SeparatorThe separator consists of a sandwich of micro-porouspolymer and non-woven felt which maintains anoptimised distance between the electrodes. Theseparator system has been developed to give anoptimum balance between performance, reliabilityand long life.

3.5 Terminal pillarsThe material used for the terminal pillars (copper orsteel) and the number of terminals per cell arechosen as a function of the intended application.The terminal pillars are nickel-plated.

3.6 ElectrolyteThe electrolyte used in the sintered/pbe range, whichis a solution of potassium hydroxide and lithiumhydroxide, is optimised to give the best combinationof performance, life, energy efficiency and a widetemperature range.

The concentration of the standard electrolyte is suchas to allow the cell to be operated down totemperature extremes as low as –20°C (– 4˚F) and ashigh as +50°C (+122˚F). This allows the very hightemperature fluctuation found in certain regions tobe accommodated.

For very low temperatures a special high densityelectrolyte can be used.

It is an important consideration of the sintered/pberange, and indeed all nickel-cadmium batteries, thatthe electrolyte concentration does not change duringcharge and discharge. It retains its ability to transferions between the cell plates, irrespective of thecharge level.

In most applications, the electrolyte will retain itseffectiveness for the life of the battery and will neverneed replacing.

The electrode material is less reactive with thealkaline electrolyte (nickel-cadmium secondarybatteries) than with acid electrolytes (lead acidsecondary batteries). Furthermore, during chargingand discharging in alkaline batteries the electrolyteworks mainly as a carrier of oxygen or hydroxyl ionsfrom one electrode to the other, hence thecomposition or the concentration of the electrolytedoes not change noticeably.

In the charge/discharge reaction of the nickel-cadmium battery, the potassium hydroxide is notmentioned in the reaction formula. A small amountof water is produced during the charging procedure(and consumed during the discharge). The amount isnot enough to make it possible to detect if thebattery is charged or discharged by measuring thedensity of the electrolyte.

Once the battery has been filled with the correctelectrolyte at the battery factory, there is no needto check the electrolyte density periodically. Thedensity of the electrolyte in the battery eitherincreases or decreases as the electrolyte level dropsbecause of water electrolysis or evaporation or risesat topping-up.

Interpretation of density measurements is difficultand could be misleading.

3 Construction features of the XHP battery


3.7 Vent systemThe XHP is fitted with a special flame-arresting flip-top vent to give an effective and safe venting system.

3.8 Cell containerThe XHP range is available in polypropylene or inflame retardant polyamid (nylon).

Separator

Large electrolytereserve withvisible levels

Sintered positiveelectrode

Bayonet flame-arrester vent plug

Plastic-bondednegative electrode

Container

Alcad cells fulfil allrequirements specifiedby IEC 60623


F

4.1 CapacityThe XHP electrical capacity is rated in ampere-hours(Ah) and is the quantity of electricity at +20°C (+68˚F)which it can supply for a 5 hour discharge to 1.0 Vafter being fully charged at 7.5 hours at 0.2 C5 A.This figure is in agreement with the IEC 60623standard.

According to the IEC 60623 (Edition 4), 0.2 C5 A isalso expressed as 0.2 It A. The reference test current(It) is expressed as:

Cn Ah1 h

where:Cn is the rated capacity declared by the

manufacturer in ampere-hours (Ah),and

n is the time base in hours (h) for which therated capacity is declared.

4.2 Cell voltageThe cell voltage of nickel-cadmium cells results fromthe electrochemical potentials of the nickel and thecadmium active materials in the presence of thepotassium hydroxide electrolyte. The nominal voltagefor this electrochemical couple is 1.2 V.

4.3 Internal resistanceThe internal resistance of a cell varies with the typeof service and the state of charge and is, therefore,difficult to define and measure accurately.

The most practical value for normal applications isthe discharge voltage response to a change indischarge current.

Figure 1 –Temperaturede-rating factor fordifferent ratedischarge

It A =

The typical internal resistance of an XHP cell whenmeasured at normal temperature is 40 mΩ per Ahcapacity. For example, the internal resistance ofXHP 150 is given by:

= 0.27 mΩ

The above figure is for fully charged cells.

For lower states of charge, the values increase.

For cells 50% discharged, the internal resistance isabout 20% higher, and when 90% discharged it isabout 80% higher. The internal resistance of a fullydischarged cell has very little meaning.

Reducing the temperature also increases the internalresistance and, at 0°C (+32˚F), the internal resistanceis about 15% higher.

4.4 Effect of temperature onperformanceVariations in ambient temperature affect theperformance of XHP and this is allowed for in thebattery engineering.

Low temperature operation has the effect ofreducing the performance but the highertemperature characteristics are similar to those atnormal temperatures. The effect of temperature ismore marked at higher rates of discharge.

The factors which are required in sizing a battery tocompensate for temperature variations are given in agraphical form in Figure 1 for an operatingtemperature range of –20°Cto + 40°C(– 4˚F to +104˚F).

For use at temperatures outside this range contactAlcad for advice.

4 Operating features

40150


Figure 2 – Capacity loss on open circuit stand

4.5 Short-circuit valuesThe minimum short-circuit value for the XHP cell is30 times the ampere-hour capacity.

An approximate calculation of the short-circuitcurrent for a given cell is 1.8 x cell discharge currentto 0.65 V for 1 s.

The XHP battery is designed to withstand a short-circuit current of this magnitude for many minuteswithout damage.

4.6 Open circuit lossThe state of charge of XHP on open circuit standslowly decreases with time due to self-discharge.In practice, this decrease is relatively rapid during thefirst two weeks but then stabilises to about 2% permonth at +20°C (+68˚F).

The self-discharge characteristics of a nickel-cadmiumcell are affected by the temperature. At lowtemperatures the charge retention is better than atnormal temperature and so the open circuit loss isreduced. However, the self-discharge is significantlyincreased at higher temperatures.

The open circuit loss for the XHP cell for a range oftemperatures is shown in Figure 2.

4.7 CyclingThe XHP range is designed to withstand the widerange of cycling behaviour encountered in stationaryapplications. This can vary from low depth ofdischarges to discharges of up to 100% and thenumber of cycles that the product will be able toprovide will depend on the depth of dischargerequired.

The less deeply a battery is cycled, the greater thenumber of cycles it is capable of performing beforeit is unable to achieve the minimum design limit.A shallow cycle will give many tens of thousands ofoperations, whereas a deep cycle will give feweroperations.


Figure 4 –Effect oftemperatureon lifetime

Figure 3 –Typical cycle lifeversus depth ofdischarge

However, the reduction in lifetime with increasingtemperature is very much lower for the nickel-cadmium battery than the lead acid battery.

The reduction in lifetime for the nickel-cadmiumbattery and, for comparison, a high quality lead acidbattery is shown graphically in Figure 4. The valuesfor the lead acid battery are as supplied by theindustry and found in IEEE documentation.

Figure 3 gives typical values for the effect of depthof discharge on the available cycle life, and it is clearthat when sizing the battery for a cycling application,the number and depth of cycles have an importantconsequence on the predicted life of the system.

4.8 Effect of temperature on lifetimeThe XHP range is designed as a twenty year lifeproduct but, as with every battery system,increasing temperature reduces the expected life.


In general terms, for every 9°C (16.2˚F) increase intemperature over the normal operating temperatureof +25°C (+77˚F), the reduction in service life for anickel-cadmium battery will be 20%, and for a leadacid battery will be 50%. In high temperaturesituations, therefore, special consideration must begiven to dimensioning the nickel-cadmium battery.Under the same conditions, the lead acid battery isnot a practical proposition, due to its very shortlifetime. The valve-regulated lead acid battery (VRLA),for example, which has a lifetime of about 7 yearsunder good conditions, has this reduced to less than1 year, if used at +50°C (+122˚F).

4.9 Water consumptionand gas evolution

During charging, more ampere-hours are supplied tothe battery than the capacity available for discharge.These additional ampere-hours must be provided toreturn the battery to the fully charged state and,since they are not all retained by the cell and do notall contribute directly to the chemical changes to theactive materials in the plates, they must be dissipatedin some way. This surplus charge, or overcharge,breaks down the water content of the electrolyteinto oxygen and hydrogen, and pure distilled waterhas to be added to replace this loss.

( )

( )

)(

Figure 5 –Water replenishmentintervals at1.41 V/cell

Water loss is associated with the current used forovercharging. A battery which is constantly cycled,i.e. is charged and discharged on a regular basis,will consume more water than a battery onstandby operation.

In theory, the quantity of water used can be foundby the Faradic equation that each ampere-hour ofovercharge breaks down 0.366 cm3 of water.However, in practice, the water usage will be lessthan this as the overcharge current is also needed tosupport self-discharge of the electrodes.

The overcharge current is a function of both voltageand temperature and so both have an influence onthe consumption of water.

Figure 5 gives typical water consumption valuesover a range of temperature at floating voltage of1.41 V/cell.

The gas evolution is a function of the amount ofwater electrolysed into hydrogen and oxygen and ispredominantly given off at the end of the chargingperiod. The battery gives off no gas during a normaldischarge.

The electrolysis of 1 cm3 of water produces1865 cm3 of gas mixture and this gas mixture is inthe proportion of 2/3 hydrogen and 1/3 oxygen.Thus the electrolysis of 1cm3 of water produces1243 cm3 of hydrogen.


There are a number of methods which are used tosize nickel-cadmium batteries for standby floatingapplications. These include the IEEE 1115 method ofthe Institute of Electrical and Electronics Engineers.This method is approved and recommended by Alcadfor the sizing of nickel-cadmium batteries. Sizingmethods must take into account multiple discharges,temperature de-rating, performance after floatingand the voltage window available for the battery. Allmethods have to use methods of approximation andsome do this more successfully than others.

A significant advantage of the nickel-cadmiumbattery compared to a lead acid battery is that itcan be fully discharged without any inconveniencein terms of life or recharge. Thus, to obtain thesmallest and least costly battery, it is an advantageto discharge the battery to the lowest practicalvalue in order to obtain the maximum energy fromthe battery.

The principle sizing parameters which are ofinterest are:

5.1 The voltage windowThis is the maximum voltage and the minimumvoltage at the battery terminals acceptable for thesystem. In battery terms, the maximum voltage givesthe voltage which is available to charge the battery,and the minimum voltage gives the lowest voltageacceptable to the system to which the battery canbe discharged. In discharging the nickel-cadmiumbattery, the cell voltage should be taken as low aspossible in order to find the most economic andefficient battery.

5.2 Discharge profileThis is the electrical performance required from thebattery for the application. It may be expressed interms of amperes for a certain duration, or it may beexpressed in terms of power, in watts or kW, for acertain duration. The requirement may be simply onedischarge or many discharges of a complex nature.

5.3 TemperatureThe maximum and minimum temperatures and thenormal ambient temperature will have an influenceon the sizing of the battery. The performance of abattery decreases with decreasing temperature andsizing at a low temperature increases the battery size.Temperature de-rating curves are produced for all celltypes to allow the performance to be recalculated.

5.4 State of charge or recharge timeSome applications may require that the battery shallgive a full duty cycle after a certain time followingthe previous discharge. The factors used for this willdepend on the depth of discharge, the rate ofdischarge, and the charge voltage and current.A requirement for a high state of charge does notjustify a high charge voltage if the result is a highend of discharge voltage.

5.5 AgeingSome customers require a value to be added toallow for the ageing of the battery over its lifetime.This may be a value required by the customer, forexample 10%, or it may be a requirement from thecustomer that a value is used which will ensure theservice of the battery during its lifetime. The value tobe used will depend on the discharge rate of thebattery and the conditions under which thedischarge is carried out.

5 Battery sizing principles in standby applications


5.6 Floating effectWhen a nickel-cadmium cell is maintained at a fixedfloating voltage over a period of time, there is adecrease in the voltage level of the discharge curve.This effect begins after one week and reaches itsmaximum in about 3 months. It can only beeliminated by a full discharge/charge cycle, and itcannot be eliminated by a boost charge. It istherefore necessary to take this into account in anycalculations concerning batteries in floatapplications. This is used in the IEEE sizing methodand the published data for XHP.

5.7 Number of cells in a batteryAs mentioned earlier, due to the voltage windowavailable, the charge voltage and the end ofdischarge voltage have to be chosen to give the bestcompromise between charging time and final end ofdischarge voltage.

If the difference in published performance for a cellfor the same time of discharge but to different endvoltages is examined, it is clear that there is asignificant improvement in performance as the endof discharge voltage is reduced.

As the charge voltage and the end of dischargevoltage are linked by the voltage window, it is anadvantage to use the lowest charge voltagepossible in order to obtain the lowest end ofdischarge voltage.

The number of cells in the battery is determined bythe maximum voltage available in the voltagewindow, i.e. the charge voltage.

6.1 Constant voltage charging methodsBatteries in stationary applications are normally chargedby a constant voltage float system and this can be twotypes: the two-rate type where there is an initial constantvoltage charge followed by a lower floating voltage, or asingle rate floating voltage.

The single voltage charger is necessarily acompromise between a voltage high enough to givean acceptable charge time and low enough to give alow water usage. However it does give a simplercharging system and accepts a smaller voltagewindow than the two-rate charger.

The two-rate charger has an initial high voltage stage tocharge the battery followed by a lower voltagemaintenance charge. This allows the battery to becharged quickly, and yet, have a low water consumptiondue to the low voltage maintenance level.

For float applications, the values used for XHPrange for single and two-rate charge systems are:

– Single rate charge: 1.41 ± 0.01 V/cell at +20°C (+68˚F)

– Dual rate charge:

High rate: 1.45 ± 0.01 V/cell at +20°C (+68˚F)

Float charge: 1.40 ± 0.01 V/cell at +20°C (+68˚F)

In case of frequent cycling, the recommended chargevoltages are:

– Single rate charge: 1.45 - 1.55 V/cell at +20°C (+68˚F)

– Dual rate charge:

High rate: 1.45 - 1.60 V/cell at +20°C (+68˚F)Float charge: 1.40 ± 0.01 V/cell at +20°C (+68˚F)

To minimise the water usage, it is important to use a lowcharge voltage, and so the minimum voltage for thesingle level and the two level charge voltage is thenormally recommended value. This also helps within avoltage window to obtain the lowest, and mosteffective, end of discharge voltage.

6.2 Charge acceptanceA discharged cell will take a certain time to achieve a fullstate of charge.

Figure 6 gives the capacity available for typical chargingvoltages recommended for the XHP range during thefirst 24 hours of charge from a fully discharged state.

This graph gives the recharge time for a current limit of0.2 C5 A. Clearly, if a lower value for the current is used,e.g. 0.1 C5 A, then the battery will take longer to charge.

If a higher current is used then it will charge morerapidly. This is not in general a pro rata relationship dueto the limited charging voltage.

If the application has a particular recharge timerequirement then this must be taken into account whencalculating the battery.

Figure 6 –Available capacityfor typical chargingvoltages

6 Battery charging



6.3 Charge efficiencyThe charge efficiency of the battery is dependenton the state of charge of the battery and thetemperature. For much of its charge profile, it isrecharged at a high level of efficiency.

In general, at states of charge less than 80% thecharge efficiency remains high, but as the batteryapproaches a fully charged condition, the chargingefficiency falls off. This is illustrated graphically inFigure 7.

6.4 Temperature effectsAs the temperature increases, the electrochemicalbehaviour becomes more active, and so for the samefloating voltage, the current increases. As thetemperature is reduced then the reverse occurs.Increasing the current increases the water loss, andreducing the current creates the risk that the cell will notbe sufficiently charged. For standby application, it isnormally not required to compensate the chargingvoltage with the temperature. However if waterconsumption is of main concern, temperature

compensation should be used if the battery is operatingat high temperature such as +35ºC (+95ºF). At lowtemperature (


7.1 Electrical abuseRipple effects

The nickel-cadmium battery is tolerant to high rippleand will accept ripple currents of up to 0.2 C5 A Ieff.In fact, the only effect of a high ripple current is thatof increased water usage. Thus, in general, anycommercially available charger or generator can beused for commissioning or maintenance charging ofthe XHP. This contrasts with the VRLA battery whererelatively small ripple currents can cause batteryoverheating, and will reduce life and performance.

Over-discharge

If more than the designed capacity is taken out of abattery then it becomes deep-discharged andreversed. This is considered to be an abuse situationfor a battery and should be avoided.

In the case of lead acid batteries this will lead tofailure of the battery and is unacceptable.

The XHP battery is designed to make recovery fromthis situation possible.

Overcharge

In the case of the XHP battery with its generouselectrolyte reserve, a small degree of overcharge overa short period will not significantly alter themaintenance period. In the case of excessiveovercharge, water replenishment is required, butthere will be no significant effect on the life ofthe battery.

7.2 Mechanical abuseShock load

The XHP battery concept has been tested to bothIEC 68-2-29 (bump tests at 5 g, 10 g and 25 g)and IEC 77 (shock test 3 g), where g = acceleration.

Vibration resistance

The XHP battery concept has been tested to IEC 77for 2 hours at 1g, where g = acceleration.

External corrosion

All external metal components are nickel-plated orstainless steel, protected by a neutral vaseline, andthen protected by a rigid plastic cover.

7 Special operating factors


Important recommendations

� Never allow an exposed flame or spark nearthe battery, particularly while charging.

� Never smoke while performing any operationon the battery.

� For protection, wear rubber gloves, longsleeves, and appropriate splash goggles orface shield.

� The electrolyte is harmful to skin and eyes. Inthe event of contact with skin or eyes, washimmediately with plenty of water. If eyes areaffected, flush with water, and obtainimmediate medical attention.

� Remove all rings, watches and other itemswith metal parts before working on thebattery.

� Use insulated tools.

� Avoid static electricity and take measures forprotection against electric shocks.

� Discharge any possible static electricity fromclothing and/or tools by touching an earth -connected part “ground” before working onthe battery.

8.1 Receiving the shipmentUnpack the battery immediately upon arrival. Do notoverturn the package. Transport seals are locatedunder the cover of the vent plug.

The battery is normally shipped filled, discharged andready for installation.

The battery must never be charged with theplastic transport seals in place as this can causepermanent damage.

8.2 StorageStore the battery indoors in a dry, clean and cool(0°C to +30°C/+32°F to +86°F) location.

� Do not store in unopened packing crates. Thelid and the packing material on top of thecells must be removed.

� Make sure that the transport seals remain inplace during storage.

� Do not store in direct sunlight or exposed toexcessive heat.

� A battery delivered discharged and filled may bestored for many years before it is installed.

� A battery delivered exceptionally 80% charged(for starting application) must not be stored formore than 3 months (including transport).

8.3 Installation8.3.1 Location

Install the battery in a dry and clean room. Avoiddirect sunlight, strong daylight and heat.

The battery will give the best performances andmaximum service life when the ambient temperatureis between +10°C to +30°C (+50°F to +86°F).

The batteries can be fitted on to stands, floor-mounted or fitted into cabinets.

Local standards or codes normally define themounting arrangements of batteries, and thesemust be followed if applicable. However, if this isnot the case, the following comments should beused as a guide.

When mounting the battery, it is desirable tomaintain an easy access to all cells; they should besituated in a readily available position.

Distances between stands, and between stands andwalls, should be sufficient to give good access to thebattery.

The overall weight of the battery must be consideredand the load bearing on the floor taken into accountin the selection of the battery accommodation.

If the battery is enclosed in a cabinet or other suchenclosed space, it is important to provide sufficientspace to disperse the gases given off during charging,and also to minimise condensation.

8 Installation and operating instructions


It is recommended that at least 200 mm be allowedabove cell tops, to ensure easy access duringinspection and water replenishment, and thatenough space is allowed between cabinet walls andthe battery to avoid any risk of short-circuits. Flip-topvents may be turned through 180° to achieve themost convenient position for water replenishment.

8.3.2 Ventilation

Note that special regulations for ventilationmay be valid in your area depending on theapplication.

When the battery is housed in a cubicle or enclosedcompartment, it is necessary to provide adequateventilation.

During the last part of high-rate charging, the batteryis emitting gases (oxygen and hydrogen mixture).

If it is required to establish that the ventilation of thebattery room is adequate, then it is necessary tocalculate the rate of evolution of hydrogen to ensurethat the concentration of hydrogen gas in the roomis kept within safe limits.

The theoretical safe limit for hydrogen concentrationis 4%. However, some standards call for more severelevels than this, and levels as low as 1% aresometimes required.

To calculate the ventilation requirements of a batteryroom, the following method can be used:

1 Ah of overcharge breaks down 0.366 cm3 ofwater, and 1 cm3 of water produces 1.865 litres ofgas in the proportion 2/3 hydrogen and 1/3 oxygen.Thus 1 Ah of overcharge produces 0.42 litres ofhydrogen.

Therefore, the volume of hydrogen evolved from abattery per hour

= number of cells x charge current x 0.42 litresor= number of cells x charge current x 0.00042 m3

The volume of hydrogen found by this calculation canbe expressed as a percentage of the total volume ofthe battery room, and from this, the number of airchanges required to keep the concentration ofhydrogen below a certain level can be calculated.

In practice, a typical figure for natural roomventilation is about 2.5 air changes per hour, and so,in this case, it would not be necessary to introduceany forced ventilation.

In a floating situation, the current flowing is verymuch lower than when the cell is being charged,and the gas evolution is minimal; it may becalculated in the same way using typical floatingcurrents.

8.3.3 Mounting

Verify that cells are correctly interconnected with theappropriate polarity. The battery connection to loadshould be with nickel-plated cable lugs.Recommended torques for connecting nuts are:

• M 10 = 10 ± 2 N.m• M 12 = 15 ± 2 N.m

The connectors and terminal nuts should becorrosion-protected by coating with a film of neutralvaseline.

Remove the transport seals and close the vents.

Example:

A battery of 98 cells, type XHP 70 on a two step, twotier stand, is placed in a room of dimensions 2 m x2 m x 3 m. The charging system is capable ofcharging at 0.1 C5 and so the charging current is7 Amperes. The volume of hydrogen evolved perhour in this, the worst, case is:

98 x 7 x 0.00042 m3 = 0.29 m3

The total volume of the room is

2 x 2 x 3 = 12 m3

Approximate volume of battery and stand does notexceed 1m3, and so, the volume of free air in theroom is 1 m3. Therefore, the concentration ofhydrogen gas after charging for 1 hour at fullgassing potential at 0.1 C5 will be:

0.2911

Thus, to maintain a maximum concentration of 3%(for example), the air in the room will need changing:

2.6 3

= 2.6 %

= around 1 time per hour


8.3.4 Electrolyte

The electrolyte to be used is: E4.

When checking the electrolyte levels, a fluctuation inlevel between cells is not abnormal and is due to thedifferent amounts of gas held in the separator of eachcell. The level should be at least 15 mm above theminimum mark and there is normally no need toadjust it.

When the cells are charged, the electrolyte level canbe above the high level mark.

8.4 CommissioningVerify that the ventilation is adequateduring this operation.

� For filled and discharged cells stored up to 1 year,a commissioning charge is normally not requiredand the cells are ready for immediate use. If fullperformances are necessary immediately, acommissioning charge is recommended asmentioned in the section below.

� For cells stored more than 1 year, a commissioningcharge is necessary:

• constant current charge is preferable: 8 h at 0.2 C5 A.

When the charger maximum voltage setting is toolow to supply constant current charging, divide thebattery into two parts to be charged individually.

• constant potential charge: 1.50 V/cell minimum.

Charging time: 24 h if the charging current is limitedto 0.2 C5 A, 48 h if the charging current is limited to0.1 C5 A.

Please note: if cells have been stored in chargedconditions for more than 3 months (includingtransport), or if cells have been stored for a fewyears or show difficulties in recoveringperformance, constant current charging becomesnecessary and the following values arerecommended:

a) 15 h charge at 0.2 C5 A

b) discharge at 0.2 C5 A down to 1.0 V/cell

c) 8h charge at 0.2 C5 A

d) the battery is ready for use.

8.5 Charging in serviceAt continuous parallel operation, the battery is oncontinuous charge and has only occasionaldischarges.

Recommended charging voltage(+20°C to +25°C/+68°F to +77°F):

� for dual charge level:

• Float level: 1.40 ± 0.01 V/cell• High level: 1.45 ± 0.01 V/cell

� for single charge level:

• 1.41 ± 0.01 V/cell

In case of frequent deep discharges (cycling), thecharging voltage values should be increased.See section 6.1.

For use at temperature outside +10°C to +30°C(+50°F to +86°F), the correcting factor for chargevoltage is – 2 mV/°C/cell (–1.1 mV/°F/ cell).


8.6 Topping-upNo electrolyte level measurement is necessary if youuse an Alcad filling-pistol, which allows the correctlevel to be obtained by a simple nozzle setting. Seenozzle lengths in Installation and OperatingInstruction sheet.

If a filling-pistol is not available, the electrolyte levelcan be checked by transparence or measured in thecase of flame retardant containers. Insert atransparent glass or plastic tube (alkali resistant,5 to 6 mm in diameter) vertically into the cell ventuntil it touches the top of the plates. Close the topend of the tube by putting a finger on it and removethe tube from the cell.

The height of the liquid in the tube indicates theelectrolyte level above the plates.

Level (mm)high low

XHP 11 25 5

XHP/F 16 to XHP/F 52 55 5

XHP/F 60 to XHP/F 80 70 5

XHP/F 90 to XHP/F 190 65 5

XHP/F 220 to XHP/F 320 55 5

� Keep the battery clean using only water. Do notuse a wire brush or solvents of any kind. Vent capscan be rinsed in clean water if necessary.

� Check visually the electrolyte level. Never let thelevel fall below the minimum level mark. Use onlydistilled or deionized water to top-up. Experiencewill tell the time interval between topping-up.Note:Once the battery has been filled with the correctelectrolyte at the battery factory, there is no needto check the electrolyte density periodically.Interpretation of density measurements is difficultand could be misleading.

� Check every two years that all connectors aretight. The connectors and terminal nuts should becorrosion-protected by coating with neutralvaseline.

� Check the charging voltage. It is important thatthe recommended charging voltage remainsunchanged. The charger should be checked atleast once a year. High water consumption of thebattery is usually caused by improper voltagesetting of the charger.

8.8 Changing electrolyteDue to the sintered electrode plastic-bondedtechnology, it is not necessary to change theelectrolyte during the lifetime of the cell.

8.7 Periodic maintenance


In a correctly designed standby application, XHPrequires the minimum of attention. However,it isgood practice with any system to carry out aninspection at least once a year, or at therecommended water replenishment interval period,to ensure that the charger, the battery and theauxiliary electronics are all functioning correctly.

When this inspection has been done, it isrecommended that certain procedures should becarried out to ensure that the battery is maintainedin a good state.

9.1 Cleanliness/mechanicalCells must be kept clean and dry at all times, as dustand damp cause current leakage. Terminals andconnectors should be kept clean, and any spillageduring maintenance should be wiped off with aclean cloth. The battery can be cleaned, using water.Do not use a wire brush or a solvent of any kind.Vent caps can be rinsed in clean water, if necessary.

Check that the flame-arresting vents are tightly fittedand that there are no deposits on the vent cap.

Terminals should be checked for tightness, and theterminals and connectors should be corrosion-protected by coating with a thin layer of neutralgrease or anti-corrosion oil.

9 Maintaining the XHP in service


Yearly

check charge voltage settings

check cell voltages

check float current of the battery

Every 2 years

clean cell lids and battery area

check torque values

protect terminal nuts and terminals with neutral vaseline

Every 5 years or as required

capacity check

As required

replenish with water according to defined period

(depend on float voltage, cycles and temperature)

9.2 Water replenishmentCheck the electrolyte level. Never let the level fallbelow the lower MIN mark. Use only approveddistilled or deionized water to replenish. Do notoverfill the cells.

Excessive consumption of water indicates operationat too high a voltage or too high a temperature.Negligible consumption of water, with batteries oncontinuous low current or float charge, could indicateunder-charging. A reasonable consumption of wateris the best indication that a battery is being operatedunder the correct conditions. Any marked change inthe rate of water consumption should be investigatedimmediately. The water replenishment interval can becalculated as described in section 4.9. However, it isrecommended that, initially, electrolyte levels shouldbe monitored monthly to determine the frequency ofwater topping-up required for a particularinstallation.

Alcad has a full range of topping-up equipmentavailable to aid this operation.

9.3 Capacity checkElectrical battery testing is not part of normal routinemaintenance, as the battery is required to give theback-up function and cannot be easily taken out ofservice.

However, if a capacity test of the battery is needed,the following procedure should be followed:

a) Charge of 7.5 h at 0.2 C5 A

b) Discharge the battery at the rate of 0.2 C5 A to afinal average voltage of 1.0 V/cell (i.e. 92 V for a92 cell battery)

c) Charge of 7.5 h at the same rate used in a)

d) Discharge at the same rate used in a), measuringand recording current, voltage and time every quarterhour. This should be continued until a final averagevoltage of 1.0 V/cell is reached. The overall state ofthe battery can then be seen, and if individual cellmeasurements are taken, the state of each cell canbe observed.

9.4 Recommended maintenanceprocedure

In order to obtain the best from your battery, thefollowing maintenance procedure is recommended:

It is also recommended that a maintenance record bekept which should include a record of the temperatureof the battery room.


In a world where autonomous sources of electricpower are ever more in demand, Alcad batteriesprovide an environmentally responsible answer tothese needs. Environmental management lies at thecore of Alcad’s business and we take care to controlevery stage of a battery’s life-cycle in terms ofpotential impact. Environmental protection is our toppriority, from design and production through end-of-life collection, disposal and recycling.

Our respect for the environment is complemented byan equal respect for our customers. We aim togenerate confidence in our products, not only from afunctional standpoint, but also in terms of theenvironmental safeguards that are built into theirlife-cycle. The simple and unique nature of thebattery components make them readily recyclableand this process safeguards valuable naturalresources for future generations.

In partnership with collection agencies worldwide,Alcad organises retrieval from pre-collection pointsand the recycling of spent Alcad batteries.Information about Alcad’s collection network can befound on our web site:

www.alcad.com

Ni-Cd batteries must not be discarded as harmlesswaste and should be treated carefully in accordancewith local and national regulations. Your Alcadrepresentative can assist with further information onthese regulations and with the overall recyclingprocedure.

10 Disposal and recycling

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Alcad Limited

SwedenTelephone: +46 491 68 100Facsimile: +46 491 68 110

Alcad Sales Offices

United KingdomTelephone: +44 1279 772 555Facsimile: +44 1279 420 696

Middle EastTelephone: +357 25 871 816Facsimile: +357 25 343 542

AsiaTelephone: +65 6 7484 486Facsimile: +65 6 7484 639

USATelephone: +1 203 234 8333Facsimile: +1 203 234 8255

www.alcad.com

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