Hello.
There is an UPS that stopped working when no one's around, when we checked it later, we found it would not power on. The 12v battery is only 4v, but the wall socket is supplying power.
We didn't find anything burn or wrong after took it apart, but it must be broken somewhere, otherwise the battery would not be drained to that low even if the wall power was out.
We don't have a spare battery now, but would a healthy UPS turn on without a good battery(but with wall power only)?
Also what will be the most possible reason for it to broken?
Thanks.