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Overkill bms #8 lead not reading voltage

D

dustonlarsen

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Jan 23, 2021
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Anyone know what would cause this? The batteries have been running fine since January. I did have something similar in January but it was a loose crimp on a wire. Once I recrimped it was fine. I removed #7 and #8 lead and tested continuity from the lead to the pin connector and both were fine. When I looked at this it did have an over volt reading but all the batteries were, and are, at 3.445+/-.01. Overvolt reset is at 3.5. Bulk charge is set to 3.5 per cell. I did submit a support tix to overkill. Thanks
 

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Did you also pull the connector from the BMS and check the voltage?
 
I also just tested at the negative cell terminal and the bms connector pin and got 3.440 so it is traveling to the bms
 
How about voltage at the connector?

I think we posted at the same time ..... shouldn't negative to cell 8 be full pack voltage?
 
And to clarify I have top balanced so I don’t think there was an actual cell over volt. I think the one cell reading dropped and it caused the readings to go haywire.
 
From negative to connector cell 8 should be 27.5V if that is what the pack voltage is.
 
Bob B said:
How about voltage at the connector?

I think we posted at the same time ..... shouldn't negative to cell 8 be full pack voltage?
Click to expand...
That was from the cell #8. Full pack from cell#1 terminal to #8 connector pin reads 27.44
 
Let us know what Overkill says ..... if the voltage readings are correct at the connector, it is pointing to a problem with the BMS.
 
And of course once I fully remove the battery and put on a work bench it starts reading
 

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Yep ...... I would get a different crimp tool .... maybe better quality terminal connections .... and re-do all the crimps.
 
Since you had a bad connection before .... and another intermittent now .... Kinda seems like a major re-do would be in order.
Head off more problems before they happen.
 
I think I just need a better crimper. I have an i crimp which is like the wire fly I believe. I wasn’t trying to skimp on the tool just didn’t know which to choose. Or maybe go with metal leads and add the heat shrink rather than already has the heat shrink.I did notice the #8 was the issue I had before because I didn’t heat shrink after I recrimped.
 
Well it doesn’t seem to be the crimp. Recrimped 3 times using a ratch and a simple cline crimper For whatever reason that cell #8 once it hits 3.45 the bms starts shorting out almost like it’s hit an over volt and shutting it off. Once it gets to 3.42 or so it kicks back on. Works fine charging and discharging up to that voltage. Looking more like a bms issue unless someone else has an idea.
 
sunshine_eggo said:
Sounds like an email to overkill is in order.
Click to expand...
Yep I re emailed them. 100% the BMS as I switched them from my other battery pack that has no issues(should have done that first) The problem followed the BMS and it was throwing numbers all over on the other battery pack. Thanks everyone for chiming in.
 

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