Testing UPS with bench power supply

[JustMeHere]

I have 3 UPSes I want to get back into working condition.   Before I buy a set of batteries, I was wondering if it would be safe to hook up a bench power supply in place of the batteries.  I have a Tekpower TP3005T.  It's linear and isolated. 

[PKTKS]

Probably NOT.

vast majority os BENCH PSU are NOT!!! made to sink current

and vast majority UPS will try to make dead sure the
BATs are sinking some current - to determine BAT load percent.

Bad things  may happen

Paul

[Jeroen3]

If the supply can source enough current you can probably test battery only mode.
Do not connect mains. As per reasons described above.

[TheMG]

vast majority os BENCH PSU are NOT!!! made to sink current

True, however...

Bad things  may happen

Most likely not. I have yet to come across any bench power supply where this would be an issue. While feeding external voltage into the power supply will not cause it to sink any current (after all, it's not a programmable load!), it should also not cause any damage to the power supply (as long as the externally applied voltage does not exceed the maximum output capability of the power supply).

It's really no different than, for example, hooking up a charged battery to the output of the bench power supply while the power supply's voltage control is set to zero (or any value lower than the battery's voltage).

As for testing UPSs with one, I've done it a few times with no issues. Note that the inverter in many UPS draws a rather high peak current at a rate of 100 or 120Hz, which may exceed the current limiting of the bench PSU if the UPS itself does not have significant input capacitance. A nice beefy capacitor in parallel with it can help.

[PKTKS]

Most likely not. I have yet to come across any bench power supply where this would be an issue.

Wild guess... any PSU should have a sampling network the most
possible close at the load...  otherwise regulation is crap.

If the  PSU was indeed designed to SINK (C and V - all quadrants)
there should be safe...

otherwise the LOAD income current or voltage will definitely
go wacko with the foreign values leading the FB loop unstable
... not even a guess know what will happen...

Last resource of using a DIODE to suppress  sinking may work
but why not use any old battery? can't figure..

Do the right thing. Put a battery there and do not risk your PSU
unless you have 100% certain it is a 4 quadrant design.

Paul

[JustMeHere]

but why not use any old battery? can't figure..

Don't have any old batteries that will take a charge.   Even when the batteries were new, the UPS were questionable.  However, I'm not sure if the batteries I had were any good in the first place.  It once upon a time was a very good UPS.