Guys does Capacity of UPS increase if we add 2 batteries? Currently i am using UPS Nirantar UPS-621V, which has a capacity of 360W. This is not enough for my current setup. When the light goes it immediately shuts down without giving any backup not even a second. There is no problem with the ups battery, when i connect a table fan to it it works perfectly. My question is can i add another battery to it so that i can increase the capacity? I have a extra 12V7AH battery. After doing some research it turns out that 2 battery can be added to the ups in parallel to increase the capacity. Has anyone done this modification before? Will it be safe to do this or will there be any damage to the UPS or the pc?