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

[R Ray Walters]

I'll agree with you, Dana, although I think setting the batteries in the ground will help in more of the cases. 
Battery optimum temperature is actually lower than the standard test temp of 25C (77F).
When you overlay the graph showing increased cycle life of batteries at lower temps with the capacity vs temp graph, optimum battery temp is actually around 55 - 60 dg F. 
(Cycle life is increased by around 15%, while capacity is reduced by only about 5%)
The ideal then, would have the batteries in contact with the core earth temp of 57F.
This means also, that floor heating (at around 100F) could possibly overheat the batteries in direct contact. 
In cold climates, I think an adjacent unheated space, that picks up some stray building heat would be optimum. (basement, garage on shared wall with house, adjacent outdoor closet, battery box in earth)
Also, you only need the Average room temp to be 57F, it could get much colder at night for a few hours)
After moving my system indoors for better cold weather performance, and then back outdoors after 2 years because of the hydrogen sulfide smell and inverter buzzing, I've suffered first hand with this tough decision.

On venting: its easy to prevent the explosive build up of gases, but its much tougher to prevent the hydrogen sulfide from permeating into the living space when EQing. (H2S can be deadly)
I've never had an indoor system I was completely happy with, BTW, even with Zephyr power vents.

On insulating: if we insulate, we only insulate the bottom and the sides up to the height of the fluid level. (that's the core thermal mass) Venting occurs at the top of the battery only, with the air space inside the top of the battery acting as somewhat of a thermal break.

R. Walters
ray at solarray.com
Solar Engineer




On Dec 14, 2010, at 11:46 AM, Dana wrote:

> Nathan –
>  
> I think the thread here is it totally depends on your situation. I am sticking my neck out here but what the heck.
> After 23 years at this is what I do.
>  
> Long winter and cool summer night – probably insulate as keeping warm is to your benefit with a higher winter temp. If it is in a heated space I never insulate.
>  
> Hot summer and mild winter – You could probably go either way insulate or not. Or insulate for winter and remove in summer. This is a big expense if you were to hire it out [for a homeowner].
>  
> Mild year round – why bother to insulate.
>  
> Long hot summers Mild winter  - Sink it in the ground if it would help reduce summer temps?
>  
> Ok let me have it.
>  
> Dana Orzel
> Great Solar Works, Inc
> E - dana at solarwork.com
> V - 970.626.5253
> F - 970.626.4140
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>  
> "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 Nathan Jones
> Sent: Tuesday, December 14, 2010 11:36 AM
> To: RE-wrenches
> Subject: Re: [RE-wrenches] To insulate a battery bank DEPENDS on a lot of factors.
>  
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