"larry moe 'n curly" wrote in message
ups.com...
I have a Conext (by APC) model CNB-325 battery backup power supply (not
a real UPS) that shows funny voltages when the power cord is
disconnected.

Backup supply plugged into AC outlet;

hot-neutral: 120 VAC
hot-ground: 120 VAC
neutral-ground: 0.7 VAC

Backup supply unplugged from AC outlet, computer used as load:

hot-neutral: 115 VAC
hot-ground: 58 VAC
neutral-ground: 58 VAC

Backup supply unplugged form AC outlet, no load:

hot-neutral: 115 VAC
hot-ground: 19 VAC
neutral-ground: 60 VAC

A different model Conext, model CNB-300, behaved similarly, only the
no-load voltage on battery power was 90 VAC neutral-ground and 40 VAC
hot-ground.

I didn't get such wierd voltages on battery operation with a much older
APC BK-300 (much larger battery, all-metal case); hot-neutral and
hot-ground both measured 118 VAC, neutral-ground was slightly under 1
VAC.

I measured with both a Fluke 73 digital meter (true RMP) and an analog
meter with 10K/volt sensitivity. The analog meter gave very different
voltages with each backup supply running off battery, but I assume it
was caused by the AC not being a real sine wave.


the chances are when its not conected to an ac suply the output is floating
with respect to ground, so any voltages relative to gnd are due to leakage,
with a load conected there is more balanced leakage.

Colin =^.^=