APC Smart-UPS SUA2200XL acting weird

[carloscbj89]

I have a Smart-UPS SUA2200XL which was acquired in 2009. About a month ago the bad battery alarm and red light came up. I took out the batteries and found two out of four that were not charging more than 9V while the other two stay at 13.24V steady. The two working 12V batteries are 18ah and I purchased two 12V 20ah. The 2ah difference shouldn't be a problem it just means the other two 12V batteries would last longer. So I installed the two new batteries and the UPS seems to work fine. I let it run and charge for 24 hours, the battery light shows full charge on the UPS and as soon as I do a self-test using the powerchute business web app, the battery light drops to one light of charge and the replace battery light comes up. I removed all four batteries and check their voltage and all four are registering 12.84V steady. I left the batteries out for 24 hours and still holding the same voltage value. I don't know how I can determine whether this UPS is broken or if the batteries are bad. I don't know what else to do, the event log in the web app shows replace battery logs

Any suggestions? Thank you!

[sokoloff]

Do a load test on the batteries. Get a 12V lamp with a decent brightness (minimum brake light, but better an old halogen headlamp) and put it on each battery in isolation as a load. Test the voltage on the battery while the load is on it.

[Bratster]

I'm pretty sure that UPS has the batteries set up for 48 volts DC. So all four batteries are in series.

It is highly likely that the two batteries left over from the original batch, that you thought were good since the voltage was okay, are actually very much dead.

but they happen to be just barely good enough that they will float at the correct voltage, and everything looks okay until you put a load on it.


whenever you have a battery bank setup of multiple batteries in series, it is best to replace all of them at the same time so they are the same age and same capacity.





Sent from my Pixel 2 XL using Tapatalk

[carloscbj89]

Thank you both for your suggestions. I took the two batteries from the old batch and attached them to a powerwheels I have at home. Even though both batteries show 13.34V as soon as I connected them to the powerwheels and tried to turn on the motor, the batteries dropped to 0V. I connected the other two new batteries and the powerwheels ran fine with no issues dropping to 11V. So it's definitely the batteries that are not providing any electrical energy, even though they seem to hold 13.34V they are dead. Now I gotta spend more money and buy two new batteries.