[RE-wrenches] Passive Battery Venting

Ray Walters ray at solarray.com
Tue Oct 28 19:06:09 PDT 2014


That's an interesting idea, but all the failed designs they illustrate 
don't show the way we usually do it.  We don't even bother with an 
inlet, as most battery boxes have enough gap around the door to provide 
intake air, then the exhaust comes off the top with several feet of rise 
to prevent back drafting.  If its in any space that H2s may be a problem 
(living space), we always add a Zephyr Power vent which has a back draft 
preventer.  Even if the Zephyr fails, there will still be passive air 
flow up the pipe past the fan.
I see 4 problems with their setup:
1) Large Copper pipe is really expensive, and steel is hard to work with 
and fittings are expensive.
2) Metal pipe is not only thermally conductive, its also electrically 
conductive.  I try to avoid unnecessary conductors in the battery box.
3)  Metal pipe will corrode when exposed to H2S and battery acid. That's 
why we always use plastic.
4) Their suggested pipe size (1" outside pipe) are way too small to 
provide venting for any more than a couple of golf cart batteries.

Basically, heat exchanger = good idea, but their version = not.

As for the battery pass through connectors: they seem to be adding 
unnecessary connections, and would also prevent using conduit. I'd guess 
they're not UL listed, so that whole idea is also code compliant.  Duct 
seal will prevent the H2S from going up the conduit into the DC load center.

They're trying to seal the box too much; the only time you could 
actually have an explosive build up of H2S is if you sealed every gap on 
the battery box.  I think its easier and safer to keep the gaps, and if 
your venting fails, at least it won't blow up or over heat.

R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760

On 10/28/2014 4:28 PM, Drake wrote:
> Hello Wrenches,
>
> A client wants to use a passive battery venting method with a heat 
> exchanger to the outside for his bank of Full River AGM batteries. 
> Below is a link to one site that recommends this method. Has anyone 
> used this method?
>
> http://www.bdbatteries.com/hydrogenventing.php 
> <http://www.bdbatteries.com/hydrogenventing.php>
>
> My main concern for about the batteries is that they not get cold and 
> lose capacity during the short days when storage is most needed.
>
> He would also like to connect the terminals inside the box to a pass 
> through jumper http://www.bdbatteries.com/lugs.php?id=269 
> <http://www.bdbatteries.com/lugs.php?id=269> and then run the cables, 
> without conduit, to the inverter. As far as I know, conduit is always 
> required on the battery cables even if fuses are used in the battery 
> box. Has anything changed?
>
> Thanks,
>
> Drake
>
> Drake Chamberlin
> /Athens Electric LLC
> OH License 44810
> CO License 3773
> NABCEP Certified Solar PV
> 740-448-7328
> /http://athens-electric.com/
>
>
>
>
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