Battery enclosures and NEC [RE-wrenches]

[John Raynes]

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Thanks all for the great feedback to my earlier questions.

One additional question I have about "site-built" fiberglass or HDPE 
liners fabricated from sheet stock:  By definition, there are gaps 
between the bottom deck and the side lips.  What's the best 
acid-resistant caulk material to use to seal those interfaces?

We've looked at the pre-fab spill containment trays from time to time, 
our problem is that it costs at least as much and perhaps even more to 
ship than the item itself costs, and there's so many variations on 
battery sizes, orientations, etc.  That same rule about buying pre-fab 
also applies to battery boxes unless they can be broken down for 
shipping.  We're 10 hours drive from the nearest full line solar 
distributor, 3 hours from the nearest freight depot so we rarely pick 
up anything ourselves, and all freight is interlined.

I hear Jeff's comments about moving to commercially built boxes 
someday, but they add significant expense, even without the shipping 
costs.  I would hope for a compromise solution where construction 
techniques and materials are more fully specified for all important 
details, such as acid resistance, flame retardancy, strength, back 
draft protection, no access without a tool, etc.

We build our enclosures out of 3/4 plywood for the deck, 1/2 OSB sides 
and top, with 1-1/2 to 2 inches of foam all around.  We rip framing 
lumber into appropriate sizes for strength and fastening support on all 
edges.  I try to avoid site built wherever possible, so I have a basic 
design that breaks down into  6 or 7 flat pieces for transport to site. 
  If I can pre-build at the shop things always turns out better.  That 
pretty much applies to everything we do.

John Raynes
RE Solar
Torrey UT


At 10:37 AM 10/4/2007 -0700, you 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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