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Issue with 18650 charging circuit

Discussion in 'Power Electronics' started by supraman215, Dec 13, 2018.

  1. supraman215

    supraman215

    8
    0
    Nov 5, 2018
    I purchased a 5A 12v CC CV charger to power the 3s BMS charger.

    5a CC CV charger
    https://www.ebay.com/itm/292316891852

    3S BMS
    https://www.ebay.com/itm/3S-10A-12V...pid=23015876544&hash=item2cdfb0c45c:rk:1:pf:0

    Here is how I hooked it up
    https://photos.app.goo.gl/1Xp24GhYFC1ziB1W9
    https://photos.app.goo.gl/HKdX4XxgqpyUf2Kw9
    https://photos.app.goo.gl/kDw3YbpsAeqy26Ar8
    https://photos.app.goo.gl/kemRaGknDQqTtPox6

    I hooked up the BMS first testing the voltage at each point and then on the output and saw 11.8v output as I expected.

    Then I hooked the 2 outputs from the BMS to the output of the charger. Then strangely the large black thing that looks like a transistor or something bubbled up and smoked. No input was hooked up only the batteries to the output. The green light comes on on the charger even though nothing is hooked up to the input. But when I hook up a power source to the charger no power ever comes out the output. No amperage. Not sure how I hooked this up wrong from the beginning.

    Any thoughts? What did I do wrong?
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    8,877
    1,751
    Nov 17, 2011
    The connection of the BMS to the batteries looks o.k.
    Assuming the lose wires next to the power supply's output connector were wired to the nearest terminal this connection seems o.k., too.

    There's insufficient information on the power supply module. My guess is that by connecting the battery but no input power source you may have powered the power supply module reversely from the battery (as indicated by the LED) and thus may have blown the transistor and possibly other parts, too.
    I suggest you get a new power supply module. Put it in operation without load and set the parameters (output voltage, current limt) as desired. Connect the battery/bMS pack to the running power supply.

    An additional measure to protect the power supply from reverse power is a diode in series from teh '+' output of the power supply module to the '+' input of the MBS. Anode of the diode is to the power supply module, cathode (usually indicated by aring mark on the device) is to the BMS. The diode needs to be rated for the charge current you plan to use. Set the output of the power supply module such that the voltage on the input of the BMS is as required (a few hundred millivolts will drop across the diode).
     
  3. Bluejets

    Bluejets

    3,154
    616
    Oct 5, 2014
    Just be aware that the exposed jacket of those cells is the negative pole.
    I can see several exposed areas.
    If you have any exposed jacket near where either of those boards are resting, it could cause a short problem.
    Didn't happen to solder those wires while the boards were sitting on the cell insulation by any chance?
     
  4. supraman215

    supraman215

    8
    0
    Nov 5, 2018
    @Harald Kapp So the process you describe is the first thing I did. I hooked up the 12v supply and set the voltage. I couldn't get any AMP readings though, maybe because I didn't have a load, and I did turn the dial a lot? But I figured I could use the battery as a load so that's why I hooked it up but I NEVER hooked it up WHILE the 12v power source was plugged in since I never got a chance to because as soon as I hooked the battery up is when the problem started. I could try the diodes but I don't have any so it's something I would have to order. There is no specification about having to use another component between the CC CV charger and the batteries. hmm ok. Maybe a different CC CV charger?

    @Bluejets The boards are to the cells attached with hot glue.
     
  5. Bluejets

    Bluejets

    3,154
    616
    Oct 5, 2014
    You missed the point I was making.
    I'd suggest you read my reply more closely.
     
  6. supraman215

    supraman215

    8
    0
    Nov 5, 2018
    All the soldering was done before the board was attached to the cells.
     
  7. Harald Kapp

    Harald Kapp Moderator Moderator

    8,877
    1,751
    Nov 17, 2011
    Of course. Current flows only when a load is attached.
    Better use e.g. a 12 V lamp.
    As I stated, this may have caused the issue.
    That's not the point. Make absolutely sure there is no contact at all between any of th eboards and the battery except by the wires. A goof thing to test the setup is to have all parts separately on the desk, connected only by the wires, then get it up and running. Once you have ensured everything is o.k. you can assemble the boards and batteries to your liking. A sheet of insulating plastic between the parts is not the worst idea one could have ;).
    From my point of view there is no specification at all - or at least what is given as 'specification' is not worth the bytes used to write it. A good specification would give application examples, detailed technical data etc.
    But what can you expect for such a small prize?
     
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