UPS, testing model APC Back-UPS RS 500VA HD

Trying out my UPS, BR500 I UPS , capable of 300 watt load It was broken, a bad capistor, because a resistor was to hot right next to it. (Output 500 VA, 300W) Needs power to supply key equipment? This gadget converts the voltage from 12 volt DC (lead battery) to 230 VAC. Good thing when the "blackouts" hits, no current that is. The voltage is sufficient as long as the 12 volt battery has anything left to give. You will have time to shut down safely, etc.