Smart-UPS 750 XL issue and question

[Anonymous user]

I recently picked up a used Smart-UPS 750 XL and its 2 external battery packs, that had been declared dead from a voltage spike. Getting into them, the batteries were all shot. I've replaced the batteries, but now have another issue.

The 750 XL will charge the batteries very nicely. However it will NOT power up.

Holding the on button down for several seconds brings the 750 up - ON BATTERY POWER. During the test, the Line Power light blinks, and eventually goes off. The Battery Power light is illuminated.

While it is on, on battery power, it supplies voltage just fine - but again, from the batteries only.

Summary: The battery charger circuits are fine, and the battery discharge circuits to create 120vac are fine. But the circuits to provide (conditioned) 120vac from line power are not.

I have the skill (and tools) to provide some maintenance, particularly if there are discrete components that I can change - but I don't have a schematic, so unless something "looks fried" when I eventually get in there, I won't really be able to do a whole bunch!

I'd appreciate any ideas and thoughts, and particularly suggestions.

Thanks in Advance....

Alamo

[BillP]

137v on-battery is too high. I would expect the Smart-UPS to output 120vAC while on-battery, no matter what the battery voltage.

[BillP]

ok so basically, your UPS doesnt come online?

i'd of course try a different outlet on a different circuit just incase. also try adjusting the sensitivity on the back of the UPS. if you have a serial or USB cable attached to the UPS in anyway, completely remove that and put aside to rule out a faulty cable being attached causing the issue.

one idea may be to install Powerchute Business Edition if none of the above works to just see what the UPS sees for input voltage. If it sees the 120v, then we know it thinks something else is the problem, such as it being stuck on a self test. if it sees 0v, even though we know theres voltage present, then thats another issue.

hope this helps to get you started!

[Anonymous user · Accepted solution]

Thanks, i picKed a winna -

I'm downloading PowerChute now - although it's slow 😉

I've tried it on 2 different outlets - same circuit - same results. Also I've tried all 3 sensitivities.

I just measured 137 vac at the outlets on the back, w/ no load. Again, this is while on batteries only - since the "Battery Power" light is on, the "Line Power" light is off, and the battery power audible alarm is going off.

Having been plugged in all afternoon, the batteries are showing fully charged.

I'll let you know what PowerChute tells me, when I get it loaded up and running.