[RE-wrenches] Battery Venting (WAS Passive Battery Venting)

Sun Nov 2 15:14:11 PST 2014

I have had poor luck with the Zephyr fan lasting. Maybe the newer units are
improved.

Years ago I settled on a Radio Shack 3" fan that has given me good lifetimes
and draws under the relay limit in the controllers. I usually mount it in a
PVC 6 x 6 box as high in the battery box as I can get it. Then run the 2" as
high as I can. If backdrafts are a worry (does not seem to be an issue with
a tall pipe) use a s+d flapper valve, mounted vertically.  

Bob Ellison

From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On
Behalf Of Drake
Sent: Sunday, November 02, 2014 12:08 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Battery Venting (WAS Passive Battery Venting)

Allan,

That was my plan when he insisted on venting to the outside. 

I use the Zephyr Power Vent for liquid lead acid batteries. When replaced
the liquid electrolyte batteries in our backup system with AGM, we turned
off the Zephyr and took the door off the battery box. I showed it to the
client. I think when you use the word hydrogen to many people they think of
the Hindenberg disaster. 

Has New Mexico ever come to conclusions concerning venting sealed batteries
to the outside, or is it still in limbo?

Thanks,

Drake

At 11:39 AM 11/2/2014, you wrote:

Drake,
My suggestion is that to achieve the client's wishes as well as your own
cooling concerns, you include a Zephyr Power Vent in a 2" PVC vent stack to
the outside. Let the charge controller's voltage-actuated auxiliary setting
power the vent (it's OK to do so directly on Outback and Midnite
controllers, and I believe all other major ones as well). As these are
sealed batteries,they won't gas significantly under normal charge voltages.
Set the turn-on voltage at the gassing voltage, or thereabouts depending on
your determination. This will be above (or below but near) normal charge
voltage, and will cause the Power Vent to turn on only under abnormal
conditions. The Power Vent also has a backdraft damper built in (which is
why it must be oriented vertically) so will prevent excessive convective
heat loss when not running.

This won't address the possibility of one cell failing and gassing, as the
string voltage determines turn-on. However, as others have pointed out, that
may be of benefit: if one cell fails you'll still be able to smell it and
address the problem.
Allan

Allan Sindelar
allan at sindelarsolar.com
NABCEP Certified PV Installation Professional
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder (Retired), Positive Energy, Inc.
505 780-2738 cell

On 10/29/2014 6:19 PM, Drake wrote:

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
<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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