APC UPS auto power-on after discharge

[pgkmopsa]

Hello. I want to know if APC BACK-UPS 950VA (BX950MI-GR) has ability to auto power-on after full discharge? Is it called power passthrough? Anyway, I'll just describe a use case to explain what do I mean.

1. UPS is powered on and running, load is powered also

2. Power outage happens, UPS is discharging, load is powered

3. UPS becomes fully discharged, it shutdowns, so as load

4. Outage ends, power restores

What happens next?

A. UPS automatically turns on, load becomes powered on

B. UPS stays turned off, load is unpowered

[Teken]

That depends on the specific model APC UPS and the firmware. Almost all the lower end Back-UPS once fully depleted from a lights out event will not turn back on until the internal battery cartridge is at a defined voltage level.

When I say turn on you physically can not power up the UPS until the internal battery is at some defined voltage level. Once there, you can turn the unit back on.

While other models once the battery voltage is correct the unit will turn back on (Resume).

In almost all cases the battery must be present and / or be at a defined voltage to start / power up.

Enterprise units allow both cold start (Turn on with battery only) and hot swap. Hot swapping allows the end user to remove the battery cartridge(s) while the system is connected to AC Mains and running without impacting the operation of the unit and connected loads.

Some enterprise systems also incorporate a bypass option. This allows the end user to bypass the battery circuit and power the connected loads directly from AC Mains. 

If you’re curious what kind of system you have. You can complete a few simple tests to validate how your unit will behave during a lights out event or when the battery is in a poor state of health.

Cold Start: Remove AC Mains with loads attached. Turn the unit on and see if it actually comes on and supplies power to the outputs. 

No Battery with load: Disconnect AC Mains from the wall outlet. Disconnect the internal battery cartridge. Reconnect AC Mains and turn the unit on - What happens?

Hot Swap: I really do not recommend you do this specific test. But, if you’re curious it will tell you immediately what happens when the battery is in very bad SOC / Health.

Connect some none critical loads such as lights, radio, TV, etc. While the system is fully operational disconnect the battery cartridge. Some units will immediately drop the connected attached loads while continuing to operate. While other units both the system and connected loads will be dropped and shutdown.

The above test will mimic what people see every day when the internal battery isn’t replaced on a regular interval!

Let me know if you have more questions and if not mark this as a solution to your query. 👍

[pgkmopsa]

Almost all the lower end Back-UPS once fully depleted from a lights out event will not turn back on until the internal battery cartridge is at a defined voltage level.

So it should automatically turn on... eventually? I mean in 5,10,15.. minutes when the battery gets some recharging? If it stays turned off for 10 hours after a power restore - is it a warranty case?

In almost all cases the battery must be present and / or be at a defined voltage to start / power up.

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If I can start the UPS manually via button after that 10 hours - does it say that battery is at a defined voltage to start? So there should be nothing to prevent UPS from autostart earlier, yet it stays turned off all that time...

[Teken]

As stated you can complete the tests I outlined earlier to see how your specific unit behaves. These simple tests will validate what you can expect to see during a lights out event / bad battery / low voltage (SOC) condition.

Complete all the tests and let me know what you see and observe. 👍