At 01:14 PM 4/30/2009, Hasan A. Khan wrote: >Hi all, > >I recently purchased a used APC SmartUPS 2200VA UPS at a dirt cheap >price. I was thinking I would replace them with ordinary wet cell >automotive batteries because they are really >cheap. Couple of things: 1) Should work just fine in terms of charging. Gel-cells are WAY more fussy than flooded batteries about charge techniques. 2) Modern automotive batteries aren't designed for frequent deep-discharge cycles. They will tolerate some deep discharge operation but not as often as RV or marine batteries. That said: how often do you expect the batteries to operate until they are dead? If that's not often, then no problem. Occasional testing is definitely NOT a problem. 3) Make sure the battery terminals can't be touched. There is a significant chance that the batteries are connected directly to the incoming power line. Plastic battery cases with lids would help there, along with appropriate warning labels. Keep in mind that you are trying to protect people other than yourself from harm. 4) Try to get batteries with removable vent caps - both so that you can keep the battery filled as well as for hydrometer testing. Purchase a battery hydrometer and learn how to read and interpret it. Mark the hydrometer reading on the battery when it is new and fully-charged so that you have something to compare to in a few years time. Go for it! I suspect that you will be quite happy with the results. dwayne -- Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist