UPS not working off battery

[Anonymous user]

Hi All,

Trying to get an old UPS back from the dead.  It's a SUA750RMI2U.  The problem is essentially it won't run off the battery.  On original batteries, with the unit plugged into the mains, running Powerchute via USB the unit detects the battery.  I can view the battery output voltage, charge level, ect, but as soon as I try to run a test it switches to battery and back to mains instantly, sometime displaying the battery disconnected error afterwards.

With the mains unplugged from the unit, I can't fully power on the unit but it does display the battery level so it must be able to get some sort of power from the battery.  Interestingly, I initially charged the unit until Powerchute was displaying 100% then tried a test.  The unit's battery LEDs dropped right down to 2 out of 5 lit and powerchute reports ~25%

I've tried replacing the batteries with some ones out of an old 1000.  they're of a slightly higher amperage (7.2 compared to 7) than the originals, but still 12v, and the unit just showed the battery disconnected LED constantly.  The 1000 contained 4 batteries, the 750 only has 2, so I've tried both sets out of the 1000 with the same results.

Tried "Brain deading" the unit several times, and checked the voltages on all the batteries and the end of the battery cable with 2 batteries plugged in and all checks out.  So what dyou guys think?  6 dead batteries or one dead UPS?

Cheers all

[BillP · Accepted solution]

Have you at any point seen any or all of the front panel LEDs flashing? I know you mentioned you've seen the flashing replace battery LED (which is what I am assuming is the "battery disconnected" error - and when you see that is it just flashing or do you hear a chirp too?

Based on my own expertise and my colleague's, our gut says the batteries are likely the cause if you haven't seen any other strange behavior. You noted you took batteries out of the "old" 1000 - how old were those? If so, the batteries very well could be too old.

[Anonymous user]

Hi Angela,

Many thanks for the reply

I do recall seeing all the lights randomly flashing at one point, like the unit was having a fit, however I think a cold start sorted that.  The light I was talking about before was the battery disconnected light, my apologies.  it flashes and produces a beep every 2 or so seconds.

I couldn't say how old the batteries are exactly, before my time, however I've been with the company about 3 years so at least that old, and I know they've had zero maintenance in that time.  There's no date stamp on them, just a code on the top "UUL4805" which google finds nothing for.

I'll try a systematic approach of every combination of batteries just to rule out it being some of the batteries that are bad.  Getting the sameish voltage reading off them all though, little over 12v

EDIT:

Should have tried that earlier!  Silly.  2 of the 4 7.2A are working fine, so it seems, other two give the pre-reported results.  Test ran successfully, doing a calibration just now.  Looks like I've just gained a UPS for my non-essential equipment!  

Thanks again

[BillP]

You're welcome. Glad you got a set working at least!

[Anonymous user]

My APC SURT 5000 having battery not connected message. The battery was just replaced 3 months and 6 months ago after same message appear. Manual self test was ok after each replaced. Measure the charging voltage, it reads 110V on each cartridge. May I know what wrong with the message?