[RE-wrenches] battery venting

[Jeff Yago]

Jeffrey,

 

We installed many battery banks in basements for both backup and off-grid systems and in the past few years we have gone to battery “rooms” that were designed for this type use.  These rooms include fire-rated interior drywall construction, an exterior window, a low intake vent louver and a high exhaust louver, fire extinguisher, sealed light fixture, and concrete floor and floor drain.   Our earlier systems had battery boxes that were sealed and had a 2” PVC vent pipe.  Although this size vent seems to work OK, we had lots of problems with the outside air being pulled back into the sealed  battery boxes due to wind pressure acting on the home, causing a lower pressure inside.   This of course is not the way this was intended to work!   Also we quickly learned that you need good insect screening.

 

Although there is always a danger of a hydrogen gas explosion when dealing with lead-acid batteries,  please remember this is near impossible unless the hydrogen gets concentrated, so you want to avoid battery locations in confined areas having limited ventilation.  Also, a healthy battery bank does not give off hydrogen gasses when powering loads or during the large initial bulk charging process.   Typically the most potential for hydrogen gas generation is during the final “top-off” charge or with a poorly maintained battery bank that has low fluid level.   These days we include an in-line PVC mounted 48 VDC vent fan controlled by the aux. relay included on almost all battery based inverters, which is programmed to start when the battery voltage indicates the battery charge is raising.  

 

Jeff Yago

DTI Solar Inc.

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