Brand new Back-UPS models report very wrong runtime

[Anonymous user]

I bought a BE550G-UK and followed the setup instructions by letting it charge 24 hours before use.

Testing it out, everything seems to work fine and the actual battery runtime is in spec, but the runtime reported by the UPS is way out (lower by a factor of 2 to 4 usually). This leads to the obvious problem that I cannot properly program PC shutdown according to runtime left. For example: a constant load running on battery that gives an actual runtime of 120 mins (measured by the clock) begins with a reported runtime of 30 mins... this falls so that after 20 mins it reports 10 minutes runtime remaining... but then the reported runtime falls very slowly, taking 30 minutes to drop from 10 minutes from 9 mins... this goes on till eventually the battery runs out after an actual total of 120 mins. Another example: if actual runtime is 40 minutes, the reported runtime begins at about 20 minutes. And even with no load at all, but monitoring via USB connection, the reported runtime begins at about 38 minutes and drops rapidly at first.

- I tried different devices, they all report the same runtime from the UPS (Powerchute on PC, USB HID on NAS)

- I performed a manual calibration, following the instructions to the letter from https://www.apc.com/us/en/faqs/FA284198/ but it didn't help.

- I tried a brain dead reset (disconnect battery, press power for 10 seconds, reconnect battery) but this also didn't help.

Next, the shop sent me a brand new BE700G-UK... this time I charged it for 24 hours (while switched off and nothing plugged in) then immediately performed a manual calibration before anything else... but it is doing exactly the same thing.