Perhaps he wishes to run the UPS off a car battery instead of the intended SLA.
Doubt the charging circuit would work on the car battery, and the UPS would still have the same wattage rating...
true the charger wont be able to handle a car battery bse i need to use 100Ah battery.secondly the oscillator i feel needs to be changed inorder to handle in our case 50HZ since most euipement is 5ohz and lastly the FETS i believe need to be changed.