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Cells missing - JK/Heltec BMS (100 cycles without issue until now)

UV-PWRD

New Member
Joined
Jan 13, 2021
Messages
174
Recently noticed some increased in cell wire resistance values, powered everything down and put some new washers on all my cells, just steel, nothing exotic, little bit of carbon grease also because that's what the store had, and check connections where noticed a few connections between wire and terminal were just a little loose so gave those a twig up with the crimper and now I'm missing half my cells.

Tried removing washers/grease etc, no change.

I have tested continuity between each balance lead terminal and the pin on the plug into the BMS and it's fine, no issues

Pack voltage is perfect also so all bus bars are fine.

Also I confirm I have voltage readings across each pin on the BMS loom side that goes up with each cell up to the full pack voltage, so pin 0 = 3.3v, pin 1 = 6.6v, pin 3 = 9.9v all the way through.

I know the main pos and neg are good because BMS doesn't power up otherwise.

I have tried factory reset and have made sure cell count is set correctly in the app.

Confirmed pins into the BMS itself are straight, tried applying some gentle pressure both directions also, no change. Wires into the BMS connector appear to be seated correctly and the metal tabs are clearly visible on the right spots on the underside (which is where I was taking readings from).

I have contacted the supplier, but is there anything else I can test? I have bypassed it for the moment which I dont like doing.


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the BMS PCB might be defective?

based on your description, it sounds like the resistance at the terminal connection ought to be low enough for at least some voltage measurement.

also based on that you checked the pins into the BMS JST-XH connector, and did the jiggle check, maybe that can be totally ruled out as well. i admit that the JST-XH connector format feels kinda sketchy to me but i digress.

i cannot really come up with a theory of why all those cells would stop showing up.

either the cell terminal interface has become poor (seems unlikely?) or the wire has degraded, or the pin connection to the BMS has degraded, or the crimp on either end.

if it’s none of those then i guess the bms can be blamed in some way?

the system behavior is certainly odd and confusing to me
 
like literally i went back over your post and it really seems like you did check all the things i would check and try before blaming the BMS. anyways good luck and if it gets resolved please feel free to share what it was ?
 
Will do.

I'm awaiting a response from the supplier.

All I can think of is removing the cover and testing to see if voltage is making its way from the connector into the pins, but that only rules out the connector/pin connection.

I've bypassed it for now so I can at least use my pack.

I can't shake the feeling like it just needs a proper factory reset as even the cells that are visible show no resistance data.

The factory reset switch in the app doesn't appear to do a full reset as the internal clock, showing 232 days top of screen, never get reset, only some settings and the cell/cycle counts.
 
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