if everything else is working fine the go for only battery and go for EXIDE, I have 3 UPS's and in all I am using only EXIDE battery and its working fine for me . . .
I had a Microtek 650VA single Battery UPS and encountered the same problem. I changed it to a double battery 1KVA UPS and the problem was solved. Root cause of the problem was defunct circuitry. As my 650VA was in warranty so I had to spend just a few hundreds bucks for replacement -cum-upgrade.
AT my Uncles company they have an APC Online one which they got for Second Hand . Although the price is a bit high the UPS does give them at least 1 Hour of support on their system.
As far as the above UPS are concerned the maximum time you might get is 10 minutes and thats after being optimistic. My system with a 600 VA Ups gives me probably 3 minutes max. I've so far had a good experience with APC and V-Guard .
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