I have a small 750VA UPS which i use to safely shut down computer.The backup is about 5-8 minutes.We are having power shortage and thinking of battery backup but not much cash for inverters.My question is that do my UPS support those large battery(cars and bigger one like 120amp etc,don't have knowledge sorry).How much amp of battery do my UPS support?I calculated my computers' power consumption and it's around 230watt(with 9800GT,not sure)+36Watt monitor.So can i only get battery or my UPS too weak and need inverter?