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Repair instructions for APC Back-UPS RS 500

Discussion in 'General Electronics' started by Stig Vidar Hovland, Dec 27, 2006.

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  1. I have two APC Back-UPS RS500 units which failed at charging the battery.
    It was a capacitor which failed on both of them and I have also found out
    that this failure is rather common for this UPS. Here is my description on
    how to repair them. If you have a similar problem that the UPS seems to
    work OK with a new and charged battery connected, but fails after a short
    time (days) with the 'replace battery' light on, then this could help you.

    Stig Vidar Hovland
  2. Thanks for the info. This capacitor failed because it was a general purpose
    85C part. General purpose capacitors fail due to heat & developed high ESR
    in a switching power supply. APC used the wrong capacitor. A 105C capacitors
    should be used in the secondary side of a switching power power. They do not
    dry out as fast and develop high ESR as soon. A 85c capacitor works well in
    the primary 60hz side. If you would to keep your backup working long term
    replace the capacitor with a Nichicon low impedance, high reliability 105C
    Part. Digi-key part number 493-1811-ND is a Nichicon 22uf 16vdc 105C. Cost
    $0.27. Nichicon part number UPW1E220MDD (WWW.DIGIKEY.COM)
    Panasonic General Purpose 85C part is $0.15.
    APC may know that the part will last a year or they could have made a
    mistake but Look at the cost savings of using a 85C part.
    I all ways use a 105C capacitor unless it is used on the 60hz side.
    I use the Dick Smith ESR Meter designed by Bob Parker to test power
    supplies. This meter saved me more than $10,000.00 in time saved since I
    built the kit.
    THANKS Bob Parker for your outstanding designed ESR meter.
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