Repairing a battery multi-charger

Discussion in 'General Electronics Chat' started by dk31, May 12, 2016.

  1. dk31

    Thread Starter Member

    Oct 30, 2014
    Hi all,
    I have a hobby digital-display charger for multiple types of batteries that has stop working: when I am hitting the charge or discharge button I get an error message "output circuit problem".
    I have narrowed down the probelm to this:
    Normally , when this model of charger is idle ("on" but not charging anything) is has 60V at the output port. When a battery is connected to the output, the voltage drops to the same as the battery (let's say 12V) and when the battery is disconnected voltage jumps back to 60V.
    In my case, when idle the output is 0V (or a very small value) and when I connect & disconnect the battery, voltage slowly drops from 12V back to 0V (in 2 minutes or so).
    Looking inside the charger, the basic components look like a 4-switch buck-boost converter plus some power resistors (to discharge the batteries?).
    Output capacitors (there are two in parallel) look ok - no distortions.
    Do the symptoms described above prompt to a specific component problem, for example to a faulty capacitor? Or I would be better off unsoldering all capacitors, MOSFETs and check them one by one.
    Last edited: May 12, 2016
  2. wayneh


    Sep 9, 2010
    It's very hard to answer without a model number, photo and/or schematic.

    One possibility is a blown internal fuse, possibly an overheated thermal fuse. You can't really check the capacitors on or off the board without an equivalent-series-resistance (ESR) meter. They can appear fine in avery other way but still fail on ESR.
  3. dk31

    Thread Starter Member

    Oct 30, 2014
    Sadly, schematic is not available anywhere. I will try to locate if there is any thermal fuse and check it. I dont have an ESR meter, so I will replace the output capacitors anyway.
    Thanks for you suggestion.