[RE-wrenches] To insulate a battery bank DEPENDS on a lot of factors.

[R Ray Walters]

One AHJ actually got me on this with sealed batteries. I've blown the seal out overcharging a sealed battery too, so this is a real possibility. The venting requirements are not near as stringent though as for a flooded cell. Article 480 says we need to prevent the build up of explosive gases, which isn't very hard considering how hard it is to contain hydrogen. I demonstrated to the AHJ that the steel enclosure had a 1/4" gap x 12' of edge around the door (36 sq in) which is more venting than a 6" diam PVC pipe.
I also showed that hydrogen does not become explosive until you reach over a 4% hydrogen to air mixture, so you have to consider the volume of the battery box as well.
He accepted all of this, which was good, because the battery box was set into the ground (for thermal stabilization) and would have been very hard to change.
(He still made me change one PVC elbow to Schedule 80, what a stickler!)

R. Walters
ray at solarray.com
Solar Engineer




On Dec 14, 2010, at 8:47 AM, Dana wrote:

> Interesting in that our AHJ are not up to speed on this. Sealed is sealed to them and now I know too.
>  
> Thanks
>  
> Dana Orzel
> Great Solar Works, Inc
> E - dana at solarwork.com
> V - 970.626.5253
> F - 970.626.4140
> C - 970.209.4076
> web - www.solarwork.com
>  
> "Responsible Technologies for Responsible People since 1988"
> Do not ever belive anything, but seriously trust through action.
>  
> From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Exeltech
> Sent: Tuesday, December 14, 2010 5:54 AM
> To: RE-wrenches
> Subject: Re: [RE-wrenches] To insulate a battery bank DEPENDS on a lot of factors.
>  
> If sealed batteries are inadvertently overcharged, H2 and O may be created at a rate beyond which the two gasses can be recombined within the cells.  In this case, internal seals may open to prevent excessive pressure from accumulating and turning the battery into an explosion hazard.  Venting of the enclosure is needed for the same reason.  Though sealed batteries are less likely to require venting - it's a necessary safety precaution.
> 
> Dan
> 
> 
> --- On Mon, 12/13/10, jay peltz <jay at asis.com> wrote:
> 
> From: jay peltz <jay at asis.com>
> Subject: Re: [RE-wrenches] To insulate a battery bank DEPENDS on a lot of factors.
> To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
> Date: Monday, December 13, 2010, 6:30 PM
> 
> Hi Dana,
>  
> The manufacturers that I've read, do say they should be in a vented enclosure.
> But your point is taken,
>  
> thanks,
>  
> jay
>  
>  
> On Dec 13, 2010, at 8:32 AM, Dana wrote:
> 
> 
> Sealed batteries do not require a vent , therefore no air passage – less influence of ambient exterior temps to the bank. Perhaps on a small bank this would have an influence.
> On a large bank in a low usage scenario, IE: second home with no one home, the system may be full by 10AM and the fan runs for most of the day inducing cool air.
>  
> Granted most systems have a present [physically] home owner. I have many systems that float for a good part of the winter, awaiting the arrival of either the owner for a week or spring.
>  
> Dana Orzel
> Great Solar Works, Inc
> E - dana at solarwork.com
> V - 970.626.5253
> F - 970.626.4140
> C - 970.209.4076
> web - www.solarwork.com
>  
> "Responsible Technologies for Responsible People since 1988"
> Do not ever belive anything, but seriously trust through action.
>  
> From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of jay peltz
> Sent: Sunday, December 12, 2010 4:49 PM
> To: RE-wrenches
> Subject: Re: [RE-wrenches] To insulate a battery bank DEPENDS on a lot of factors.
>  
> HI Dana,
>  
> I'm curious about why you differentiate sealed vs. flooded batteries?
>  
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