Battery enclosures and NEC [RE-wrenches]

Ray Walters walters at taosnet.com
Tue Oct 9 09:13:43 PDT 2007


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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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