Need help with UPS capacity planning

[BillP]

I have SUA1400RM2 Smart-UPS with AP9617 management card. It was running for years at around 40% capacity but I recently added a storage unit to the rack and now its at 60%. However, I started getting notification from management card like this:

Critical - UPS: The battery power is too low to support the load; if power fails, the UPS will be shut down immediately.

As far as I understand there is enough capacity in my UPS to to sustain the load but why it is complaining then?

[voidstar_apc]

You have enough power capacity to sustain the load, but the runtime, or the amount of time the UPS can operate on battery under that load, has dropped below the configured minimum runtime setting.

In the shutdown settings on your AP9617 network management card, there's a low battery duration setting. During a power failure, when the runtime provided by your UPS drops below this setting, the NMC card will start a shutdown and tell any PCNS agents connected to the NMC to start shutting down. That gives them enough time to safely shut down your computers before the UPS battery dies.

When power is okay and the NMC detects that you have insufficient runtime, it alerts you with that message. You have a few options: reduce the load on the UPS, reduce the low battery duration (thus giving any attached PCNS agents less time to shutdown), add more battery capacity (such as by replacing the battery if it would provide enough runtime).

[BillP · Accepted solution]

Thanks voidstar, what you say makes sense. I checked my configuration and my low battery settings are 2 minutes, so I guess it means my battery degraded to about half of its original capacity. The battery is 3 years old so I would assume that this is normal rate of degradation for this kind of batteries (I wouldn't risk running capacity test on it at this time, been there before :-). Thanks again.