Smart-UPS not holding charge level

[Anonymous user]

Hi.

I've got a Smart-UPS 750 (DLA750I) which has an issue maintaining charge. I changed the battery pack, but issue persists. Here's what happens:

1. Installing new batteries. UPS starts recharging up to 100%.
2. It steadily reports 100%.
3. Next scheduled self-test it beeps due to batteries being discharged (and sometimes also causes a power cut on equipment attached to it)
4. Starts recharging up to 100%. This repeats.

If I let it charge up and leave it for a day, it will report 100%. I run a self-test, and it'll then report the battery charge to 20% (or whatever, depending on load). It'll then charge back up to 100% and then let them drain (without changing the reported charge level).

So basically, the only way to have the batteries "topped up" is to run the self test repeatedly. Anyone else come across this issue and if so, is there a way to fix it?

[Malvineous_apc]

Yes this happens when the batteries are almost dead.  If your batteries are new you'll have to return them for replacement as it means before you bought them they were sitting on a shelf for so long they went flat and were damaged and now can no longer hold a charge properly.

[Anonymous user]

That was my initial thought as well. However, If I do a self-test, let it charge back up to 100% and then cut the power, the equipment I have connected stays on battery power for the expected amount of time. So it would seem the batteries are able to hold a charge. I've changed packs twice.

[Malvineous_apc · Accepted solution]

What happens if you charge the batteries to 100% then unplug them, and a day or two later, plug them back in and then run off battery?  If the batteries are in good condition then they will still run for the expected run time, but if you have one or more bad batteries in the pack, they'll lose their charge even when they are unplugged for that day.

Bad batteries will often work well just after they have charged, but they can't hold the charge for very long and will go flat even if they are unplugged and not being used.  A good battery will be able to be unplugged even for a few weeks without losing much in the way of a charge.