APC Smart-UPS 3000 XL (SUA3000XLI) not reading voltages well

[camisao]

Hello there,

I have a issue with a tower UPS 3000XL with also an external battery tower that has almost new batteries and very little use.

A week ago it started entering boost mode because the read line voltage was below 210VAC, when it was in fact near 225 VAC.
The battery voltage was also low (48 or 49), when in fact the batteries are fully charged to 55.1 VDC.

I opened it up up, cleaned and tried a reset.
I updated lower transfer voltage to 196 with apctest and then used the serial port to adjust the configuration with a terminal in Prog mode to try to get line voltage and battery voltage reading identical to a voltmeter.
I managed to get the line voltage ok, but the battery voltage constant is already FF and the maximum I get now is 46.71 VDC...

Could this be a hardware issue? Is there a way to clear everything and try to configure again?
I tried to look for the schematic, but some links are dead.

Thank you for your support.

[hcs77]

Hello,

At first please replace the low value capacitor first, then the big vales, because the 22uF dryes out over time and causes serious problems. Use good brand low esr capacitor if possible. Higher voltage not a problem.
Please remember these devices works 168 hours a week, 10 year online means 87600 work hour.... Elektrolit capacitors has a limited lifetime. Change the 1uF X2 capacitor and the 300V 20mm varistor at the input. Safety.

If the capacitor change does not solve the problem, check the voltages, especially 78005 (7805 1% version).

Search for the pcb number on the internet (640-xxxx), hope you can find a schematic for it. If you can't find anything you can use the SU2200 schematic for reference, designed at the same company, similar enough for help.

Good luck.

[camisao]

Hello hcs77,

Just sending an update.

I found a schematic in a Portuguese forum of a different model (SU2200/2200XL/3000), but used it as reference, as it look identical.
I opened the UPS again and checked some of the voltages with a scope and used a thermal camera to look for possible problems.
The voltage at the ADC input was 3.12V for 50.6V at the batteries. The 5V, 12V and -8V looked good, though the last had (-8.77V) a bit more than -8...
The ADC is a TLC0838C. The quad Op-Amp (LF347) near the ADC is heating up a bit.
I'm going to buy the Electrolytic Caps, the ADC and the Op-amp to replace them.

I'll keep you posted.
Thanks.



I

[camisao]

Hello,
I got the UPS working today.
I replaced the Caps, Op-Amp and ADC.
At first it was reading the Bat voltage well again, but the line voltage was 100V less than it should (220)...
When I first had the problem I searched all over the web and someone at the EEVblog forum mentioned that APC UPSes sometimes have resistor problems.
I think the issue was in fact a soldering problem (solder joints). I resoldered the sensing resitors arround the ADC and assembled it all again.
It worked.
Lets see for how long .
Thanks.