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Overkill 4S BMS High Voltage Disconnect

BrianN

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Joined
Apr 8, 2021
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6
Hello.

Has anyone experienced the fault in the Overkill BMS triggering high voltage disconnect? Cell 4 jumps to >3.9v intermittently. I am using Lishen 202Ah LiFePO4 batteries.

I have so far cleaned the terminals and the issue persists. Does anyone have any ideas of a remedy? I have tried searching online and cannot seem to find the same problem replicated elsewhere.
 
I don't open random zip files so not sure what info I'm missing.
How long do the cells stay at > 3.65 volts?
What is your high cell cutoff set point?
What charge current are you delivering at cutoff?
Please post a picture(s) of the pack showing how all the balance and current wires are terminated.

Did you torque all the all the joinery?
 
The most obvious answer would be to top balance ..... but that kinda depends on what the rest of the cells voltages are when the one goes high.

A picture of the pack and cell voltages would good. I'm not gonna open that zip file to see what's in there either.
 
Aside from a top balance, if it's easy, recommend swapping cells and see of the problem follows the cell or stays in the same place. Staying in the same place (BMS Cell 2 tripping off the same Cell 2 wire would tell me it's a problem anywhere from the thin wire to the BMS. Aside from that, the only other thing I can recommend is unplug and replug the 5 wire connector to the BMS.

I have only been able to use my 8S Overkill for a few days, but the readings were pretty solid. I've never seen my cells jump high but have not used it a lot. My guess is wiring, unseated plug, or bad BMS.
 
Jumping cell would be suspect of a poor connection. Verify voltage is jumping or steady with a voltmeter. Measure direct on the aluminum battery terminal not the screw, bus, ring terminal etc.
 
I don't open random zip files so not sure what info I'm missing.
How long do the cells stay at > 3.65 volts?
What is your high cell cutoff set point?
What charge current are you delivering at cutoff?
Please post a picture(s) of the pack showing how all the balance and current wires are terminated.

Did you torque all the all the joinery?
Thank you for the response. I have been travelling away from the internet, so I apologise for the late response.
  • The zip file is a video of the xiaoxiang app. I posted a zip file because you cannot upload videos; I should have mentioned this or chosen a better method of sharing the information.
  • The cell stays at >3.65v for about 10 seconds
  • High Voltage Cutoff was set to 3.6v
  • My charger delivers max 20A
  • I'll post the pictures later this week when I'm back in the city with the setup in question
  • I torqued everything following the recommendations in the Overkill Manual
The most obvious answer would be to top balance ..... but that kinda depends on what the rest of the cells voltages are when the one goes high.

A picture of the pack and cell voltages would good. I'm not gonna open that zip file to see what's in there either.
Aside from a top balance, if it's easy, recommend swapping cells and see of the problem follows the cell or stays in the same place. Staying in the same place (BMS Cell 2 tripping off the same Cell 2 wire would tell me it's a problem anywhere from the thin wire to the BMS. Aside from that, the only other thing I can recommend is unplug and replug the 5 wire connector to the BMS.

I have only been able to use my 8S Overkill for a few days, but the readings were pretty solid. I've never seen my cells jump high but have not used it a lot. My guess is wiring, unseated plug, or bad BMS.
Jumping cell would be suspect of a poor connection. Verify voltage is jumping or steady with a voltmeter. Measure direct on the aluminum battery terminal not the screw, bus, ring terminal etc.
Thank you. I shall try all these and report the results
 
3.1.1 Cell over voltage -- https://overkillsolar.com/support-downloads/

Shows there is a delay after the trigger voltage is reached.
Find that parameter and let us know the value.
I suspect it is too long.
I don't know what the default value should be but I guess it should be 1 or 2 seconds.
Hopefully someone else will share their value.
 
Does anyone have any ideas of a remedy?
Without knowing the full story, all cell voltages, the charger voltage setting, and the top balance history, a constructive comment is only a best guess. My best guess in some cell imbalance together with a high charge voltage. Set the charger voltage to 13.8 volts and see how things go. There is no need to use voltages higher than 14.0 volts for a hobby application.

Mike
 
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