[UPDATE] Battery not charging after discharging to 0% - Fixed!

This plus change the charger if possible. Just because 42v on the output does not mean that the charger is also outputting a current. If the charger sees always 4.2v from the battery side (out of which reason ever) he will not rise the charge current

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Measure the cell group voltages at the bms plug if all good then bypass charge as suggested. The bms may not be allowing charge to happen if one group is too low. The bms should shut the battery off if any of the cell volts drops below bottom cut of voltage, it should come back on when a charge voltage is applied though. You definitely need to know total voltage and cell group voltages before going any further .

Are these the facts? Have you completely disconnected the bms? The charger is outputting 42v on a multi meter? The battery is reading 34.1 volts? Its still not charging?

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Yes to all questions.

Can you measure all the voltages coming out of the battery?

Main leads should be in the 30s Between any two balance wires, it should be 3.0-4.2

In the end, you should have 10 cell measurements and one main leads measurement.

The reason I am asking is that if you fully discharged, your pack could have gone out of balance. There could be 9 groups sitting at 4.2v and 1 group at 2.0v which could look like all 10 are at 4.0. The BMS is preventing you from charging because you would overcharge the battery and possibly cause a fire. In this scenario if you bypass the BMS, you will 100% damage your battery and maybe blow up your home.

The other scenario is that all your cells are reading 3.x and your charger/BMS is faulty. If you bypass the BMS and it still doesn’t work, then the charger is probably at fault.

Be careful. This stuff is dangerous.


Shame on all of you for advicing someone to bypass the BMS without having knowledge of all the facts. I recommend you stay away from batteries or giving out advice on troubleshooting.

@Trdolan03 no, bypassing the BMS is not safe.

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Point 1 Is this not you advocating the bypass

Shame on all of you for advicing someone to bypass the BMS without having knowledge of all the facts. [/quote] Point 2 is this not you saying not to bypass the bms?

@Trdolan03, @Andy87 @Marsen actually know their stuff and are just trying to ascertain whether the bms is at fault or the charger. I just wanted to appraise myself of the facts before advising. Batteries are dangerous and should never be taken lightly but plugging a charger in to see if it registers is very different to leaving it charging with a suspect group or any other fault.
The next step if you had let it happen would have been a check of the charger (which is probably the culprit to be honest) by plugging it in for a second and seeing if it had a red light. Think it might be you who needs to be in full receipt of the facts before you start to throw shame around.

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Thanks guys. I’m just going to bring it in to @psychotiller to see if he can diagnose the problem. A bad group of cells would explain why I ran out of battery before hitting 10 miles with a 10s6p and AT wheels, even though there was some wind. I usually get much more range than that.

Sorry for doing so, I personal did it, but shouldn’t have advice you are any one to bypass the BMS, It is very dangerous to do so.

one infromation i would like to get from you, just to make my soul relax. I need to admit I forgot to ask you to which voltage your battery cut off is set in the vesc?

34,1V with 0% on the voltmeter with 10s (so still 1V per cell over dead cell level)

That´s exactly what i meant with it. Not “bypas the bms and fuck about it and continue charge without BMS”. Just connect to the battery direct to check if the charger get red and start charging. After that further inspection would be neccesary for sure.

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It was stated numerous times by several people to check cell group voltages. The charger was also checked for correct voltage. I still see no reason after checking all the voltages for not proceeding in a BMS bypass charge. You will still need to monitor the cell voltages to see if a charge is going in or if you have one a dc clamp meter to measure the current. You obviously do not continue charging if either it did accept a charge or not as this would have indicated 1. charging - fault is bms. 2. Not charging - fault in charger or battery.

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I’m actually not sure. @psychotiller did the initial setup. I tried to connect my board to my PC at home, but I wasn’t able to update the firmware on the VESCs, so the software couldn’t connect to them. I’ll update them when I bring in the board.

I believe my battery was above 10% left when the board shut off. I was at 17% when I checked before it shut off after traveling a few hundred feet at jogging speed.

Does the board turn on?

Did you carefully inspect battery for bad connections or any visible damage?

Yeah, it turns on just fine. I exposed the BMS, but I didn’t unwrap the whole battery. I don’t want to mess anything up, so I’ll just bring it in when I can.

And did you get correct reads on all the balance leads? 3,4; 6,8; 10,2; all the way up to 34,0 aso or whatever voltage your individual cells are at…

No. Like I said, I didn’t unwrap the whole battery. I do not want to cause any further damage, so I’m bringing my board back to get it looked at.

Please report your findings once you get them.

I understand. But you said the BMS was exposed, so you should be able to get the reads off of the connector/pcb.

Ah okay. I think I’ll leave it alone for now until I bring it in next weekend. I’ll update as soon as we find the issue.

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Thats the best bet my friend. Good luck

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