Cyberpower PR1500 won't charge battery

[elmo]

I have a Cyberpower PR1500 UPS that has been working well for about ten years. The other day we had a power outage. The UPS failed to supply power. When the power came back on, the unit failed to come back. It was absolutely dead. Pushing the "ON/OFF" button did nothing. When I found out that most UPS units will not operate if the battery voltage is too low, I checked the battery voltage. It was about 34 volts instead of 48. I removed the battery pack and charged it up to about 46 volts. I put it back into the UPS and pushed the "ON/OFF" button. The unit came on and showed about half charge. After about two hours the unit was indicating only one quarter charge. This tells me that the battery charging circuit is not working. I removed the circuit board from the unit and gave it a good visual inspection but did not see anything that looked burned out. I thought I could trace the output to the battery back to some semiconductor that I could test, but I was not able to trace it far enough to do any good. There are a couple of diodes marked "HER305" that look heavy enough to carry some current, but they don't show any visual signs of distress. I don't have a schematic or know where I could get one. Does anyone have any suggestions?

[stj]

Re: Cyberpower PR1500 won't charge battery

one idea is for you to understand the battery life - it's far less than 10 years.

[budm]

Re: Cyberpower PR1500 won't charge battery

10 years? you'll be lucky if get 3~5 years.
What DC Voltage do you get at the wires (red and black) to the batteries without batteries connected, around 55VDC?

[elmo]

Re: Cyberpower PR1500 won't charge battery

Thanks for your replies. I understand that batteries don't last forever. However, they seem to be taking a charge and holding up fairly well. I now have them charged to 48 volts. I don't want to invest in new batteries if the UPS won't work. If I can get the UPS back to working, I will consider buying new batteries.

[budm]

Re: Cyberpower PR1500 won't charge battery

So what is the charging Voltage you are getting? That Voltage should be present the minute you have the ups plugged into the AC outlet. I will not be surprised if you do have bad caps in the switching power supply for the charging circuits.
Open load voltage of 48 does not indicate batteries are OK unless it is tested under load, the ESR of the batteries is probably high right now for 10 years old batteries.

[kc8adu]

Re: Cyberpower PR1500 won't charge battery

do those batteries hold up under a load?even a car headlight on each?
chances are NO.
48v unloaded is nearly dead.
those are way past replacement time.

[budm]

Re: Cyberpower PR1500 won't charge battery

Please up load good clear pictures of the whole unit with boards in place and then good clear pictures of the boards.

[elmo]

Re: Cyberpower PR1500 won't charge battery

Will do as soon as I can. I don't know how to do that yet.

[Agent24]

Re: Cyberpower PR1500 won't charge battery

How to upload photos: https://www.badcaps.net/forum/showthread.php?t=1868

[tester272001]

Re: Cyberpower PR1500 won't charge battery

OK here is something you can try. Some of these Cyberpower have a FUSE under the transformer. I had the same thing happen with one and I traced the power backwards and when it hit the traces for the transformer area it was dead. I had no schematic and the PCB said nothing about a fuse. Once I pulled the transformer I saw it (hidden under xfmr)! I replaced the fuse and I was back in business charging battery Mine happened after a power outage as well, I think a lightning strike or surge.
Oh I found a copy of the service manual for you and the schematic is in there too! Good luck man!

[budm]

Re: Cyberpower PR1500 won't charge battery

If that service manual is correct, then you need to check and see if the charger diagrams matches your chassis.

[elmo]

Re: Cyberpower PR1500 won't charge battery

Thanks for all your helpful replies. I especially appreciated the schematics. However, my UPS is a PR1500, no suffix. It is designed for 120VAC input and has 6 NEMA 5-15R outlets. I don't know if the schematic is the same. I have been studying the schematic for the charger parts but could not figure out how the 55 Volt charging voltage is generated. 120 VAC input should generate about 168 VDC across C2 and C3. I couldn't figure out what happens after that. After a lengthy search of my circuit board I was not able to find D17. C1, which is across the line input does not show on the schematic either. I have attached three photos of the UPS and the circuit board as requested. I labeled some of the parts since you probably can't read much in the photo. So, I am still stuck as to how to test my board for a malfunction. Any further suggestions would be greatly appreciated.

[elmo]

Re: Cyberpower PR1500 won't charge battery

It appears that the photos did not get attached. I will try again

[tester272001]

Re: Cyberpower PR1500 won't charge battery

Ok, try a simple approach. Use DMM to check continuity, starting from the positive lead of the batter and follow back as far as you can. If there is a defective component you will eventually get an open circuit.
Oh, i looked at pics. Definately look under tge transformers for a possible FUSE. You can tell under the pcb (under transformers) if there are pads in the middle. Might be hard ti see tge fuse from the top.

[elmo]

Re: Cyberpower PR1500 won't charge battery

tester

Thanks for all your suggestions. I, too, thought I could trace the battery charger circuit back from the output to find the malfunction. However, I only got as far as the output capacitors. There was only one small trace from there, leading to a small transformer which didn't make any sense. This is a difficult board to trace because all the traces are covered by a protective layer and covered on top by components. And, no, there was no fuse under the transformer. I didn't find any sign of a fuse under any transformer.

I worked with the schematic for quite a while and finally came to the conclusion that it isn't the correct one for the PR1500. I will probably need the correct schematic or someone who has had experience with this model, to be able to repair it. It might help if I had some idea of what the various sections of the board do; like where is the 55 volt charging voltage generated. If anyone has any suggestions please let me know.

[budm]

Re: Cyberpower PR1500 won't charge battery

FYI: I am still looking at the board layout.

[budm]

Re: Cyberpower PR1500 won't charge battery

OK, replace C40 (100uF 25V) startup cap, you should also replace the output filter caps C44, C47 (100uF 63V), C45 (47uf 50V) at the same time.
Replace C40 will make the charger circuit work again.
Use good caps such as Panasonic FM/FC/FR series from Mouser or Digikey.

[elmo]

Re: Cyberpower PR1500 won't charge battery

budm

I got the replacement capacitors for Digi-key yesterday and started replacing them today. I first removed C40. After removing it from the board I checked it with an ohmmeter. It seemed to check OK. The resistance first measured a short and then climbed toward infinity (>2Mohm). Could it still be bad or could something else be wrong?

[budm]

Re: Cyberpower PR1500 won't charge battery

Capacitor cannot be check by Ohm meter since if it still have capacitance but not the correct capacitance, it will still show that it is charging up on the meter, you need capacitance meter and ESR meter to verify the cap.
For example, you can measure the 10uF and 47 uF, you will see both caps can be charged up by the meter so if the 47uF capacitance drop down to 10uF but the circuit requires 47uF to run, you meter will not show that. Then you have to verify the ESR of the cap also.
So are you getting the 55VDC at the black and red wires to the batteries, batteries are not needed to be connected?

[elmo]

Re: Cyberpower PR1500 won't charge battery

budm

I have not replaced C40 yet. I wanted to make sure that that was still the right thing to do. I will go ahead and do that as well as C44, C45, and C47. This will take me a little time because the capacitors are hard to remove. I will get back to you as soon as I have replaced them and reinstalled the board in the UPS.