The Back UPS outputs a stepped approximated wave when on battery which is a square wave versus a round pure sine wave. The voltage will read lower when on battery because of this unless you use a True RMS voltmeter . Reading 165 volts on battery is normal when checking the output with a regular voltmeter. Most computer loads can accept a stepped approximated wave form; however, linear loads such as the fan typically need a pure sine wave output on battery. Our Smart-UPS and higher units output a pure sine wave .

So the Back UPS output is stepped approximation to a sine wave, average meter would read 165 VAC , True RMS meter would read 230VAC.
If you are not having true RMS meter than please Get the UPS to the APC nearest service center we would be able to demonstrate at our service center.

Released for: Schneider Electric India