XR resurrection
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One cell was bad. Replaced it- i now have V output-. The OW still does not power on and still have a hot point. I’m trying to deal with the hot point to see which component is the culprit (this hot point is in one of the MOSFETs -Q4- on the cell balancing-sampling area of the BMS). I think though that this mosfet issue has nothing to do with the no power issue.
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@vulkito Had to look back a little to brush up on the issue.
Is it that large IC next to all the caps that was getting hot and if so did you get the part number for it?
Pasting the BMS pic to help reference it. -
@lia That large chip is Max 14921 that is a 16 cell voltage measuring chip.
I had one Pint bms crippled because one cell on a Chibattery shorted out and took out a m8t mosfet but it also damaged the Max chip, I replaced the m8t mosfet and now the bms always reads 100% and the cells always read 3v5 on Owce, never moved. -
@lia yep, I found the MAX chip getting hot and I replaced it. Then the hot point went from there to Q4 (one of the m8t mosfets). replaced and shorted again. On this one i found the issue (short between the terminals of one of the sample capacitors to read V on cells). But besides this... I really don´t think that a short in the sampling reading of the cells can make the OW to be dead, right? I mean, the only thing i can think of is that the MAX is getting crazy and is sending bollocks to the PIC. the PIC is also getting bollocks with that info and I guess the controller interprets tht something is wrong. But i don´t think this design is that complex.
The summary of the current status is the same: if i plug it in it works (and voltage is at 100% -weird-) and I do not get any error, but if it is not plugged...dead. Should be something related to the power section of the BMS but I don´t know where to look besides the MOSFETS. everything looks good!
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@lemur and did that issue make the OW to be dead or was just a diagnostics issue (voltage not showing ok)?
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@vulkito Just out of curiosity did you manage to try manually triggering the BMS to turn on yet?
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@lia yes, but it doesn’t turn on. I also cheched the button just in case and works. One thing i want to check though is if the switch signal reaches the bms.. but i jumped the wires and nothing happened ;,(
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@vulkito Back to the BMS then :(
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@vulkito On my bms, it turns on, but the voltages are all wrong, I have a Max chip coming and I will try that.
Blew out the first replacement max chip on another bms, not cheap. -
Fixed the hot point. As i was expecting, that issue had no relation with the no-power issue. I measured V on the big mosfets next to the batt connectors. There is no V. However, i have V on the other smaller ones. I’m thinking that maybe they are not receiving anything on the gate terminal. I followed the gate track and looks like that are going to those sOT-23 thingies which i guess are transistors. Looks like those are OK but i do not know who is sending the triggering/gate signal. Do you guys have any guess/recommendation?
