[RE-wrenches] Passive Battery Venting

Fri Oct 31 13:16:47 PDT 2014

Drake,
Please explain what might happen if something went wrong with one battery, and the 

Phil Forest
South Mountain Company

> On Oct 31, 2014, at 8:42 AM, Drake <drake.chamberlin at redwoodalliance.org> wrote:
> 
> One big advantage of not venting AGM batteries to the outside is that when something goes wrong you will know it. A well vented system could have one bad battery ruin the entire pack before the problem was detected.
> 
> 
> At 08:12 AM 10/30/2014, you wrote:
> 
>> To do it totally passive you will need a long (tall) pipe up the side of the
>> building, probably painted a dark color to have the sun help warm the tube
>> to help encourage it to vent up, not draw into the building. Put a 180 on
>> the top to keep the rain out and a screen to keep out the bugs.
>> 
>> With outside venting the batteries will just draw in room temperature air,
>> if the room is 70 the battery min temp will be 70. If they are in a basement
>> they will naturally draw in outside air, run the vent as high as you can to
>> help prevent that. If you are using a Classic use the relay to turn the fan
>> on and off at a specific battery voltage. Use a brushless fan and a voltage
>> powered relay if no other choice. Do not put the relay in the battery box!
>> Sealed batteries do need to be vented. I have seen them gas when things go
>> wrong, not pleasant.
>> 
>> I wouldn't do it without a fan for LA batteries but it would work for
>> sealed. If the home has a makeup air system or huge exhaust system all bets
>> are off.
>> 
>> Just some thoughts,
>> 
>> Bob Ellison
>> 
>> -----Original Message-----
>> From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On
>> Behalf Of Drake
>> Sent: Wednesday, October 29, 2014 8:19 PM
>> To: RE-wrenches
>> Subject: Re: [RE-wrenches] Passive Battery Venting
>> 
>> Hi Daniel,
>> 
>> I typically vent them the way you do, which will allow any small amount of
>> hydrogen out. The customer is absolutely adamant about venting these to the
>> outside. I will cooperate so long as his method doesn't compromise the
>> system through cooling the batteries unnecessarily in the dead of winter.
>> 
>> He is a lawyer and came to the conclusion of the need for venting to the
>> outside from reading the NEC which says that sealed batteries "require the
>> same amount of ventilation" as liquid lead acid batteries. The code also
>> says to vent appropriate to battery technology, so the code says two
>> conflicting things. On the other hand, it doesn't say that liquid
>> electrolyte batteries need to be vented to the outside. They will sure stink
>> if you vent them to the inside.
>> 
>> Drake
>> 
>> At 09:54 AM 10/29/2014, you wrote:
>> >I just re-read the original post Drake. These are AGM batteries. Do you
>> have
>> >a "belt, suspenders,...then a rocket pack" type of client here?
>> >
>> >We typically vent our AGM boxes with small louver vents top and bottom to
>> >allow the batteries to ventilate for cooling purposes, not H2 concerns.
>> >
>> >With Regards,
>> >
>> >Daniel Young,
>> >NABCEP Certified PV Installation ProfessionalTM: Cert #031508-90
>> >NABCEP Certified Solar Heating InstallerTM: Cert #SH031409-13
>> >
>> >-----Original Message-----
>> >From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On
>> >Behalf Of Ray Walters
>> >Sent: Tuesday, October 28, 2014 11:12 PM
>> >To: RE-wrenches
>> >Subject: Re: [RE-wrenches] Passive Battery Venting
>> >
>> >That's why we usually have the batteries in a garage, basement, or out
>> >building that is not open to the living space.
>> >I've seen some cases of very well sealed and insulated enclosures allowing
>> >batteries to over heat, and also build up a lot of acid damaged
>> connections.
>> >Boxes I've seen with more air space and less sealing don't get this build
>> >up, but you're correct: they do occasionally allow H2S into the surrounding
>> >area.
>> >
>> >R.Ray Walters
>> >CTO, Solarray, Inc
>> >Nabcep Certified PV Installer,
>> >Licensed Master Electrician
>> >Solar Design Engineer
>> >303 505-8760
>> >
>> >On 10/28/2014 8:10 PM, Jerry Shafer wrote:
>> > >
>> > > We do what we can to seal the enclosure so if or when a battery fails
>> > > and really gasses off the two vents on the same wall regardless of
>> > > wind direction will vent the gas. If it is not sealed then the gas can
>> > > travel through out the area this is not advised.
>> > >
>> > >
>> >
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