APC Back-UPS CS 500VA UPS System "pl 500" Questions

...500 UPS is of 220 VAC. But when its battery takes over on power outage, it outputs only 165 - 170 VAC. Battery is new. Resetting has not worked. May be some component has weakened or failed. Help ...

...500 VA home inverter (electric power generator-MOSFET based) does not show any (mains ) light indicator even when main supply is on. when switched to battery(mains off) it does no show battery ...