Back-UPS Pro 550 not charging battery when powered on

[aislinn_apc]

This was originally posted on APC forums on 11/19/2020

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Hi!

I have a Back-UPS Pro 550. After replacing the battery, I realised that my unit was not charging the battery anymore when powered ON. Tests I have conducted so far:

1. If the unit is powered ON, the battery does not charge
2. When powered ON and I disconnect the battery I can measure 13.78V on the battery poles, so Voltage is there from the DC converter
3. When I shut down the UPS, then the battery starts charging: I see the voltage slowly increasing and after 2 days the battery was 100% charged

Based on the above it seems to indicate that charging circuit is OK, but it might be a SW issue or some failing sensor that cuts battery charging ? Is there any reset function or FW update that I could apply ? Anything else I could check / do to fix it ?

The unit is around 5 years old so not covered by warranty but still not that old 🙂

Thanks

[BillP]

This reply was originally posted by Bill on APC forums on 11/19/2020

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Hi,

You can try and brain dead the UPS to reset it.

See Schneider Electric FAQ FA158947 for instruction. 

[BillP]

This reply was originally posted by Scott on APC forums on 11/20/2020

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the basic troubleshooting steps for the APC Back-UPS Pro with ... The Back-UPS is not connected to AC power, there is no AC power ... The battery will not charge if the temperature is over 50 degrees Celsius 

[aislinn_apc · Accepted solution]

This was originally posted on APC forums on 1/6/2021

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On 11/19/2020 12:19 PM, Bill said:

You can try and brain dead the UPS to reset it.

Hi, thanks for the replies. I did try a brain dead reset + another type of reset I find on the internet, no success.

After opening the device I located a bad capacitor (see picture).

After replacing it, the charging process of the Battery is working again!

Thanks for the quick answers and the help.

[GeneralTweety_apc]

This was originally posted on APC forums on 1/13/2021

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I have the same problem with this model.

APC wont do anything. It seems to be a problem with this model.

I will give a try to search for the capacitor. Thx for the input.

[Sandrus]

Hi. I have the same problem with the same model. Which capacitor have you replaced?

[Keyro]

Hi, 
I´m also facing the same problem. After opening the device I found the same capacitor being dead as in the picture. You can recognize a dead capacitor by its curved top. In my device its labeled as the capacitor C18. You´ll need a 330uF 35V ELKO for that.

[Venko]

Hi ,

it also help me , but change two capacitors not only one

[theone]

I have a similar problem:

https://community.exchange.se.com/t5/APC-UPS-for-Home-and-Office-Forum/Battery-charge-dropping-while...

Battery charging only during OFF and when ON battery is draining slowly even through connected to AC Mains input.

Got it open and capacitors seem fine

Any other suggestion?

[Venko]

Hi ,

one capacitor in my ups looking fine but is only 270 uF and not working properly. After that i change it with new one 330 uF ups is working fine , only one capacitor is looking damaged  but i changed two of us.