Battery Ventilation

D. Nowicki, PE, P. Eng. 10/15

Agenda

Will discuss: • General concepts• Basic ventilation requirements as it relates

to hazardous classification of an area

Will not be discussing life safety, toxicity, corrosive, separation, handling, disposal, OSHA, etc.This is not intended or to be used as a detailed design method.

Uses

• Uninterruptable Power Supply (UPS) Systems

• Energy storage systems for solar arrays

• Battery in your car• Fork truck charging

stations/battery storage• PDC switchgear UPS systems

Basis of Types

IEEE Standard 1635

Vented (flooded) lead –acid (VLA)

• Typically “Unsealed” batteries• Gases produced are vented to

atmosphere.

Examples

• Flooded• Older style• Caps on the cells

Valve-regulated lead-acid (VRLA)

• Typically “Sealed” batteries• Normal conditions - gases are recycled• Abnormal conditions - gases are

vented

VRLA Typical Examples

• Maintenance free • AGM – Absorbent Glass Mat• Gel type• Newer style, generally used

Nickel – Cadmium (NiCd)

• Typically smaller rechargeable type batteries

• Larger ventilated wet cell batteries• Ventilated type batteries.

Standards

• IEEE/ASHRAE Std© 1635 - 2012 Guide for the Ventilation and Thermal Management of Batteries for Stationary Applications

• NFPA© 1: Fire Code• Industry Specifics recommended

Practices• Such as API© RP 500

IEEE 1635

“Buildings or portions thereof containing battery systems should not be classified as hazardous locations as long as they meet the minimum requirements for natural or forced ventilation and other safety features normally recommended by installation standards or guidelines for battery systems.”

Ventilation

• Purpose is to Remove • Heat• Remove gases

• Two methods• Natural• Mechanical

Natural Ventilation System

• Low air intake opening and a high exhaust opening

• Hydrogen• Heat

IEEE 1635• Values for current, hydrogen release, and heat

generation should be obtained from the manufacturer.

• Table 1 through Table 5 upper bound estimations for gas and heat production.

• Tables are based on conditions such as• Standby/float, equalization charging,

discharge, bulk charge, initial charge, Failure modes (thermal runaway, cell reversal)

IEEE 1635 Flammable Gas Removal

Refers to the LEL and UEL for hydrogen gas rates for removal.

Gassing equations

• Determines upper and lower limits of gas production

• Depends on type, material, room temperature, altitude, temperature, conditions, mode….

• NFPA 1 and the IFC suggest calculating gassing rates for ventilation purposes at boost voltages.

Fire Code Default

• Most fire codes specify that if gas generation from lead-acid batteries is not calculated, the ventilation system must be designed to provide air exchange of 1 cfm per square foot of floor area.