In my years of IT, I've been through a number of UPS devices. I seem to recall when I had a gigantic APC SmartUPS 1500 (15+ years ago), if the batteries "failed", it would still turn on, and power the devices plugged in once power returned. I didn't need a UPS that big and didn't want to replace the batteries (I did it for many years every 3-4 years when they failed), so I opted for a cheaper and smaller option when we built a home with a whole house generator - I just needed to keep things up for 10-15 seconds before the power transfer.
So I’ve now had a second UPS (battery) die on me while on vacation. It always happens at the worst time, having to walk a house sitter through disconnecting it and putting a power strip in its place. So if the battery is “bad” or “failed” and power restored, why won’t it fail open and power back up when power is restored?
Does anyone know of a unit that will do this that is small-ish? No more than 150w of electronics. It would be completely fine if MOST of the time be batteries can keep it up, but when the battery dies or fails, I want stuff to come back without intervention.
Is this a lost cause? I did find this rat hole last night but it wasn’t really helpful.
When running on battery, once the battery is exhausted and the load is turned off, most UPSs are designed to keep the load off until such time as there is enough battery power to sustain the load for a period of time. This allows for safe shut down in the event of a second mains failure. If the batteries are too low (or have failed), bringing the load back online would expose it to sudden power loss without sufficient time to shut down safely. In order to override this and bring the load back online without sufficient battery reserve should be a manual process.
In other words, what you are looking for is kind of the opposite of what a UPS designer would expect you to want. I don't know of any UPSs that behave that way. Of course the fact that I don't know of one doesn't mean that nobody makes one.
You might consider a small Lithium unit. Instead of 3-5 year battery lifetime, you get 8-10 years. At least you won't encounter the problem nearly as much.
Well, an APC rep in your rat hole thread did confirm that the normal behavior for their units. I had one that had an issue where it thought the battery was shot. Everything stayed powered through mains and the UPS just kept alarming.
As far as I know, even if the battery is full, you still need to turn it on when after you plug it in (or power is restored). I've never had any UPS from any brand that would let the load turn on at the same time the UPS is plugged.
