Battery enclosures and NEC [RE-wrenches]

Matt Tritt solarone at charter.net
Tue Oct 9 18:54:19 PDT 2007 

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Remember back in the old days when batteries had the cell connections 
located on top of the case where you can see them? Maybe battery makers 
could return to this (good) old practice but make those lead straps as 
replaceable, fuseable links.

As far as crumbly plywood goes, or OSB for that matter, try coating the 
inside of the box with casting resin. Not to be too redundant, it used 
to be SOP for us to build the bottom as a spill proof tray using glass 
cloth and resin, and to resin the entire interior of the box while we 
were at it. Our usual design was to have a hinged top mounted at about 
20 degrees with the front at least 6" higher than the top of the 
batteries, and I have never seen any degradation of the interior of this 
type of box - even after many years in service.

Matt T

Ray Walters wrote:

>
>
> Boy lots of great points in this thread!
> Tight boxes do have too much acid, battery rooms are better. I had  
> very tight boxes on an Electric Vehicle with the worst corrosion  
> problems ever. Huge battery banks in dedicated rooms have had very  
> little terminal corrosion.
> insulation is only good if the ambient temp is going below 50, it can  
> actually cause batteries to overheat in a warm room with a high  
> charging current. The heat generated is greater than you think. At  
> higher charge rates, your charging efficiency goes way down, and most  
> of that wasted energy  is transferred into battery heat.
> Plywood detoriates horribly in an acid rich environment. We still use  
> it some for lack of a better material. (environmentally its a bad  
> choice too, they use old growth trees for Plywood production)
> We started using Greenlee job boxes for batteries. They fit 12 golf  
> cart batteries perfectly. They are powder coated, we insulate the  
> inside as much for acid protection as cold. They look better than  
> anything we have used before.
> We set them in the ground about a foot to get the batteries closer to  
> ground temperature, as many of our systems are stand alone with no  
> heating source for miles. Batteries don't need to be at room temp,  
> they actually have their best combination of cycle life and capacity  
> at about 55 to 60 deg F. Higher temps have more capacity but at a  
> reduction of cycle life.
> We have had inspection issues related to location of the battery  
> room/ box near the heating equipment (concern was explosion). Once I  
> explained that hydrogen does not accumulate like propane, but is  
> actually very difficult to contain, our inspector relaxed and  
> admitted there was nothing in the code to actually enforce that  
> restriction.
> UL enclosures Jeff? Don't we need UL batteries first? Battery safety  
> has been the silent elephant in the room that this list has had to  
> ignore while we discuss much more mundane safety issues.
> I think we should have batteries with integral fuses that would blow  
> when a Wrench drops a wrench. All those expensive breakers for solar  
> arrays that are inherently current limited, while batteries with  
> surge capabilities of thousands of amps are left unprotected until  
> the middle of the load center.....
>
> Ray
>
>
>
> On Oct 4, 2007, at 11:37 AM, Jeff Yago wrote:
>
>>
>> We started out building tight battery boxes for all our projects  
>> which included a lock hasp on the cover door, but finally switched  
>> over to battery "rooms".
>>
>> We now work with the builder or architect on new construction to  
>> include a long and narrow room dedicated for only the batteries,  
>> with the inverter on a the outside wall surface for this room. The  
>> room is constructed of heavier fire-rated green-board drywall on  the 
>> interior walls and ceiling, a concrete floor with floor drain,  and a 
>> DC in line exhaust fan located at the highest point and  powered from 
>> the inverter. We also add a fire extinguisher and  safety signage on 
>> the access door which is locked.
>>
>> When we switched away from battery boxes, all our past battery and  
>> battery cable corrosion problems dis-appeared. The tight battery  
>> boxes were providing an very acid-rich environment that would  
>> destroy battery cables in less than 3 years, not to mention the  
>> piles of corrosion we had to clean off each year. Now when I check  
>> on an older battery room system, you could eat off the floor and  the 
>> battery terminals are as clean as they day they were installed.
>>
>> I think the days of site-built battery boxes are numbered, most  
>> likely when the NEC takes a look at the safety issues of many  poorly 
>> constructed site built boxes that are out there now. It  would not 
>> surprise me if battery boxes will someday need to be  commercially 
>> made and tested to some kind of UL listing that  addresses proper 
>> venting, door safety, drains, door seals, fire- rated materials, 
>> explosive containment, and include a certification  label on the 
>> cover. Just my 2 cents.....
>>
>> Jeff Yago,
>> NABCEP Certified
>> DTI Solar
>>
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>
> R. Walters
> Solarray.com
> NABCEP # 04170442   
>
>
>
>
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