Smart UPS 750: Log says "Battery disconnected"

[Anonymous user]

Hi,

I run this UPS at home where it is connected to a Windows 2008 R2 box via USB. The UPS is 1 years old, and the load is typically 25%. Temps are always ok. I usually get 30+ mins of runtime on battery.

Yesterday at night I found the UPS offline. I checked the logs and learnt there was a brief power outage. Normally that is reported as a pair of entries: "Power Failed" and "Power Restores". Instead, I found this:

Seems that shortly after the power failure, the UPS reported a "Battery Disconnected" condition and commenced shutdown. Moreover, it did not turn on by itself after power was restored (which it is configured to do) and just stayed offline until I came home and hit the switch. Any idea what could cause that?

[Anonymous user · Accepted solution]

I wonder if you might possibly have a loose/weak electrical connection between the battery module and the UPS, or internal to the battery module ? Is this a Rack mount 750 or a tower ("brick") style ? Either way I believe it likely has two 12 volt cells in series, connected together with .250 faston (tab) type wiring interconnects and there is one fuse in series usually...if any of the wiring connections between all these bits are loose they may not be able to handle the current draw and not support the load - if this happens when power fails the ups may see this as a "not connected" battery or weak battery and promptly shut itself down...