General APC SU/SUA1500 behavior question

[BillP]

Hi Everyone,

I have some basic UPS questions - I'm hoping people in the forums here can set me straight. I have about 200 APC UPS units - 75% of them are SU/SUA1500s so let's assume this is the only model I'm referring to.

We track UPS health via NMC /SNMP but every now and then we'll miss a bad battery and a UPS will fail. I'm assuming we have a bad battery, and then when the self-test runs it kills the battery and the UPS unit shuts down. When we swap the battery the APC powers back up just fine. Is this by design? A dead/missing battery during a self test means the UPS should power off?

Why doesn't the APC switch to bypass mode whenever possible? Even if the battery is completely dead but there is commercial power, shouldn't the UPS provide pass-through power? If it's supposed to this isn't what I'm seeing. Is bypass mode only if the UPS is overloaded, has an internal fault, or if I'm hot swapping a battery?

We have redundancy UPS units/power supplies on our server setups but for network equipment it's always a point of failure.

Thanks!
Mike

[BillP]

hi mike,

that particular model does not have an autobypass. generally any of the Smart UPS RT have at a minimum an automatic bypass or even a manual bypass. larger UPSs, such as Symmetra single phase and all three phase units have a bypass as well.

the self test is supposed to put the UPS on battery every so often in order to measure the voltage drop against an internal table. if it is out of range, then it illuminates the replace battery LED. ideally, yes, it should try to warn you and tell you to replaced the battery based on this test about a month ahead of time before its totally "toast." i think for different reasons such as battery environment, heat, unforseen failures, this does not happen and you see the behavior that you mentioned. i am not sure of the granular detail of what causes this but it does happen once in a while. this particular unit does not have a bypass so rarely it can drop the load during a self test or power outage where the battery is faulty.

how old are the batteries that you see this on? i hope it'd only happen on older batteries of 3+ years because if its happening sooner, there may be an environmental issue causing the batteries to not last as long as they should.

one other thing, that particular model uses a line interactive UPS topology which means the inverter is not always online providing output to the load so if there is another issue with the transfer to battery, the load may see a slight 2-6ms delay (most modern power supplies can handle a 15-20ms transfer no problem) and cause this type of issue too.

hope that helps.

[BillP]

Appreciate all your info!

It's definately a battery age issue, I actually have about 200 APCs that I'm monitoring with NMCs but about another 200 or so that aren't monitored whatsoever (lucky to get a visual inspection!).

Looking at my procurement system here at work, I have these two models that are the right size for my wiring closets:
APC Smart-UPS 1000VA LCD 120V
APC Smart-UPS 2200VA LCD 120V

The docs don't seem to indicate these have bypass either - so if these newer models have a failed battery that goes undetected by my team, will they still eventually power down like the scenario I'm having right now? I assume neither of these has online inverters either?

What's the lowest end APC that supports auto bypass when a failed battery has been sitting for a long period of time? Just curious, I don't think it makes sense in my situation as my infrastructure is so spread out.

Thanks for your help!

[BillP · Accepted solution]

Doesn't the self-test put a load on the battery? I was theorizing failing (at least) two self-tests in a row was causing the issue. If a battery is completely dead (0v) and a self-test runs, won't the UPS shut down when it transfers over during the test?