[SOLVED] APC Back-UPS CS 650 BK650EI dead - "On Battery" on, low voltage on battery

Anyone know where to start with this one? After years of dis-use, I fired up my APC Back-UPS CS 650 BK650EI to no avail. The "On Battery" light stays on and the unit does not respond or supply power. This happens with or without battery. It only supplies 5.86V to the battery terminals so I suspect an electrical failure. Does someone have schematics, or experience with any similar issues?

Re: APC Back-UPS CS 650 BK650EI dead - "On Battery" on, low voltage on battery

From my experience with an old UPS which had gel-cells in it. 6V each, 4 of them...
They go bad gradually after 3 or 4 years, even though we had few blackouts.

The internal smart circuitry may do unpredictable things if one or more batteries is bad.

Try testing and charging each one individually. See whether it will take a charge, and hold a charge. Do not apply current greater than the safe limit. One single application of overmuch current can greatly reduce the useful life of a gel cell.

When I tested the UPS by hooking up the batteries alone, it did not work (even when the batteries were good). I found there is a relay inside, which first needs to activate by power from mains AC. Then when you remove mains AC, the relay switches over to battery power.

Re: APC Back-UPS CS 650 BK650EI dead - "On Battery" on, low voltage on battery

APC Back-UPS CS 650 BK650EI MAIN BOARD 640-0565_REV04
Do not turn on, the battery is discharged.
Typical fault, dry capacitor C38 22uF 50V 105C.
Thread: Help me to find the schematic diagram of APC BK650Ei UPS

Re: APC Back-UPS CS 650 BK650EI dead - "On Battery" on, low voltage on battery

pplus said:

APC Back-UPS CS 650 BK650EI MAIN BOARD 640-0565_REV04
Do not turn on, the battery is discharged.
Typical fault, dry capacitor C38 22uF 50V 105C.

Click to expand...

Thanks for your helpful replies. I tested a bit more and indeed the unit seems to drain the battery at startup, but the voltage of the broken battery is too low. I have ordered a replacement which I expect to arrive in a charged state. I will post the results.

Re: APC Back-UPS CS 650 BK650EI dead - "On Battery" on, low voltage on battery

pplus said:

APC Back-UPS CS 650 BK650EI MAIN BOARD 640-0565_REV04
Do not turn on, the battery is discharged.
Typical fault, dry capacitor C38 22uF 50V 105C.
Thread: Help me to find the schematic diagram of APC BK650Ei UPS

Click to expand...

I hope it will help you.

Re: APC Back-UPS CS 650 BK650EI dead - "On Battery" on, low voltage on battery

Problem was solved with a replacement battery. UPS works fine now. I did not try to replace any capacitors.