chopsywa Posted October 1, 2016 Share Posted October 1, 2016 Hi All I am looking for some advice on my BMS I will preface this post with a background. I am an electronics technician who has been out of the business for 25 years. I can still fix a lot of things, but I have lost my edge, particularly with MOSFET power circuits as these were just coming to the fore when I left the industry. I purchased a new Gotway MCM V3 which was a DOA from the point of view that it would not charge. The excellent seller in Australia (urbanlab.com.au) organised a new pack to be sent from China, but due to flight restrictions this will take 40 odd days to arrive. I would like to point out too that the reseller offered to replace the entire wheel, but I was impatient and wanted to get riding. As the reseller said I could keep the old pack, I figured I could get it going while I wait for my new pack. What I did was to create a small harness with a male/female XT10 soldered back to back and then teed off a small connector to charge directly on the load side. This works fine and I have had many good rides. Today I decided to see if I can repair the BMS, so I cut into the heatshrink over the circuit board. I was hoping to find a dry joint, or something obvious, but no such luck. Essentially the issue is that the main power mosfet is open circuit. I am not sure if this is because it is being driven as such, or it is faulty, but it looks to be just an overvoltage protection MOSFET. I am not sure if it is a multi layer board, or even double sided in situ, but it looks like the negative charge lead goes to the mosfet and nowhere else. If this is the case, then the MOSFET is most definitely just there for protection. This would also mean that the balancing circuitry is active all the time and will shunt cells even when the unit is switched off and idle. I find this a bit disconcerting. Anyway, what I am asking is am I correct in my assumption about the role of the MOSFET and that the balancing circuitry is perpetually active? If that is the case, I will just leave the rig I made in place as the genuine charger won't over charge anyway and my pack is being balanced (assuming the rest of the circuitry is in fact OK). Cheers Mark Link to comment Share on other sites More sharing options...
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