[RE-wrenches] Passive Battery Venting

William Miller william at millersolar.com
Fri Oct 31 13:43:31 PDT 2014


You would smell it. 

Miller Solar

> On Oct 31, 2014, at 1:20 PM, Phil Forest <pforest at southmountain.com> wrote:
> 
> Drake,
> Please explain what might happen if something went wrong with one battery, when they are not vented to outside. How would we know it?  Thank you. 
> 
> 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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