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Replace Battery LED Flashing on an "SUA" or "SUM" Smart-UPS

Article available in these languages: Spanish


The replace battery indicator is flashing.

Product Line:



All SUA and SUM models, All Serial Numbers


The replace battery indicator flashing indicates that there is not a functional battery connected.
This could be caused by the battery being physically disconnected, or by a battery being connected that is unable to provide adequate voltage for the UPS to recognize it.


First we want to verify that the battery is physically connected:

SUA Tower models, 1500VA or less:
There is a black triangular plug on the back of the UPS. Flip this plug up and push it into place.

SUA Tower models larger than 1500VA:
There is no external disconnect, you will need to check the internal battery connections. Remove the front lower bezel of the UPS to access the battery compartment. There will be a plastic Anderson connector(s) to connect the battery(ies). Refer to the user's manual for your model for specific instructions.

All Rack Mount and Rack/Tower convertible models, all sizes:
Remove the front bezel and connect the plastic Anderson Connector.

If you have verified that the battery is physically connected and the UPS still will not recognize the battery, replace the battery with a known-good battery.
This scenario is typically seen when trying to re-deploy a unit that has been in storage for an extended period of time without having the battery charged.

You may also see this behavior if the battery has failed and entered thermal runaway. In  this scenario the battery may be hot to the touch or have a "rotten egg" sulphur odor. In this You should immediately disconnect the battery connector and take the UPS out of service. Once the battery has cooled you can try to remove it from the UPS. If the battery can be removed, replace it with a new battery. If it has swollen and is lodged in the UPS, we recommend that you replace the UPS.

Please contact APC Tech support if you have any additional questions about troubleshooting this issue.

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