Fixing APC XS1500

[Narumi]

Hi All, looking for some advice here. I am trying to fix an APC XS1500 with LCD. Taking it apart I found the battery fuses to be blown so just today I replaced those. Now when I plug the unit in something happens and the batteries are getting warm.

Thing is the unit will not turn on, and now that I have tested the batteries they have gown down from 24v to 19v! so it seems that the UPS is draing rather than charging the batteries.

Also the battery pack consists of 2 12v Lead acid ones.

 

[heymrdj]

Are the batteries connected properly? They aren't reversed and shorting?

 

[Narumi]

Are the batteries connected properly? They aren't reversed and shorting?

I believe they are. Before putting the ups back together i tested with my voltmeter with the batteries plugged into the holder not connected to the board. Red to red. Black to black and it was reading +24v

 

[mindless1]

First off, unless there was a known cause for the fuses being blown, you seldom should just replace them and try it again before determining and fixing what caused the blown fuses.

Are they inline with everything going to the battery pack, or are there parallel leads to the pack and only one set is fused?

Offhand I would "guess" that the inverter circuit has a leaky driver or shorted driver or main output transistor, which would be the largest one(s) on the heatsink(s) and the IC or discreet transistors just before them in the circuit, but of course a visual inspection might turn up something else like burnt components or vented capacitors. There could also be a thermal fuse that has tripped and won't reset.

Proceed with caution, since the live circuit would be outputting 110VAC. If you are not comfortable with tracing circuits and pulling transistors to test them, it is probably time to buy a new UPS assuming the warranty has expired.

 

[Narumi]

Yeah the warranty has expired. I obtained it from work and they were going to throw it out so I figured I would give it a go. At this point I don't have the time or the equipment to pull out transistors and test each one and there seems to be a relay that is not operating properly.

I figure the amount of time and money spent into fixing this I might as well have bought a new one with warranty and call it a day. Thanks for the help though!

 

[Puffnstuff]

They get warm when they charge and if one of the two cells has failed the unit will attempt to ;bring it up to full charge making the unit get hot. When you hear the cooling fan kick on it's a warning that something is wrong. I had to replace a battery in my 1500 several weeks ago when the unit couldn't charge a failing cell and started to heat it up. When I polled the cells one was still good and the other had failed. You might test each of the cells and see if that is the case for you.