My UPS,Zebronics ZEB-U725 UPS is not working when there is no main supply. If I switch it on when there is no main supply, momentarily voltage comes on its out put socket (Which can be seen by a volt meter only) then shuts down, even when load is not connected. I checked the battery voltage. It is about 11V. When I switch on the UPS the battery voltage comes slightly down ie it comes down to about 10.5V, then returns to 11V as the UPS shuts down. Please suggest solutions.