Hasan A. Khan wrote:

> I recently purchased a used APC SmartUPS 2200VA UPS at a dirt cheap 
> price.  It was cheap because its batteries were near the end of their 
> life.  Replacing the batteries with the same kind of dry cell lead acid 
> is prohibitively expensive here.  I was thinking I would replace them 
> with ordinary wet cell automotive batteries because they are really 
> cheap.  These wet batteries are not the maintenance-free type and they 
> won't obviously fit in the casing.  I will have to keep them watered but 
> that's ok by me.
> 
> My concerns are: is there a charging cycle difference between the two 
> types of batteries?  Will the charger in the UPS work OK?  Any danger of 
> batteries getting burnt or exploding?  I did some search on Google and I 
> could only learn that UPS batteries are deep cycle while automotive 
> batteries are not.  Will that have any negative effect on the UPS?  Any 
> help is appreciated.

Hi Hasan,

Sealed lead-acid batteries are more fussy than liquid electrolyte types.
So I think you should have no problem electrically using wet cells.
Automotive batteries can take fewer deep discharge cycles, but unless
you frequently run the UPS flat I see no problem with lifespan.

But please be aware that if you mount the batteries externally, unsafe
voltage will probably be on one or both of the terminals, 240 volts is
quite possibly connected to one terminal depending on where ground is
referenced.

Being "wet" cells the surface of the batteries may also have high
voltage that can cause accellerated corrosion to anything they are in
contact with. Putting them in battery boxes is a good idea. Or at least
"non flammable" picnic coolers or plastic storage tubs. :)

Cheerful regards,

Bob
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