EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: Laughwvst on July 29, 2020, 12:41:04 am
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Hi everyone!
So I recently had this wonderful little software bug on my 19€ ebay "Imax B6" charger: Previously it has only allowed to discharge a battery with a current of 1 amp. It even says it on the box, everywhere and there has been no way to discharge with a larger current than 1 amp! However, now as I had completed a charge on a 5S Lithium ion pack, it suddendly did allow the discharge at 2 amps. I of course (being an intelligent person) decided to try that even though I had a hunch something horrible is going to happen and so it did.
It seems that one transistor completely exploded burning a big black hole on the board, but I also cannot find any other pictures of this type of circuit board where that transistor is located there. I am talking about the nonexistent transistor, not the one that is seen on the board still. There is also a possibility, that some other component was also next to the transistor, but I really cannot find any info of this board.
The charger still powers on and detects voltage, it is now over 2 volts low though, but it seems that it tries to charge and knows when the battery is not plugged in, but it just does not charge at all. Would be nice to know exactly what that tranny did and what other components blew up. Also if schematics are found, it would be bonus if I could fine tune the detected voltage (if this ever gets fixed), because on this model it always read a bit low and there is no software calibration (as far as I know the button combinations). It seems that there were three traces coming to the black part of the board, so it would suggest that there only was a single transistor there.
Thanks for any advice!
- Beni
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Okay, well I figured out that it had something to do with discharging, probably to control the discharge mosfet on and off and I noticed that it was pulling the output to ground. I just removed the whole discharge mosfet and now it works as a charger again. :D Quick and easy fix and now if I try to discharge, it just says "Connection broken", so nothing horrible happens even then.
I found some schematics where there was a comparator in the place of the black spot on the board. Like a dedicated chip. However, this board seems to be quite a lot different and I would still highly appreciate if someone would have those schematics to that board. I would like to see whether there really was just that single transistor and nothing else.
Also if someone else has had that kind of software bug I had, it would be interesting to know. I don't still understand at all, because it has never allowed me to select over 2 amps for discharging, but it is still showing it up to 2 amps. Can it just corrupt like that? ::)
- Beni