Issue percentage JK Bms

[talgarnor]

I dont have a solar panel system but
Im using a JK bms using 20s con Bluetooth with my 72v55ah li ion battery of my e bike

First it was working really good and the percentage was very accurate
But since a week after i desconected the bms to change one cell the percentage go up and down very very fast
It tell 100% only after a few minutes of charge and go down at 0 after a few minutes of discharge
For example it tell 0% when I am at 77V and still have a lot of charge in my battery and if i put the charger it will tell 100 at only 78v ....

What i noticed too is the cycle count is little crazy too since sometime it go up 2 after only one charge even once it wen up 100 in one charge !

Let me know how do i fix this issue?
I tried to calibrate the charge with a clamps aon my battery but it didnt fix it...

Thanks for a quick answer !
Leo

 

[Skypower]

I’m thinking you have a loose connection somewhere.

 

[talgarnor]

You are talking about those one ?
If they were loose they shouldn't worked at all no ?
I read that maybe have to discharge my battery to 71v or less and recharge it full for reset the SOC... thats true that I didn't went that much down since now
Normally i charge it when it get to 75v

 

[Skypower]

Have you looked at your “System Log” and seen the events? Tap the three dots upper right to find it. I take it that all your cell connection are resistance welded and your balance leads are soldered to the strips? If you’re confident that all your cells are still welded and your balance connections are good, I would be suspect of your balance harness plugs. Vibration + dust = trouble with those. If it were me, I’d disconnect the plugs the temp sensor too(it shuts down if it doesn’t see those!) and carefully blow out the pin and socket side. Silicone spray or silicone dialectical grease works great for all connections but they attract dirt like crazy and both creep away from application point, the grease creeps a bit less. No-Ox-ID A special doesn’t creep but it’s thicker and may actually get in the way if it not at least thinned by at least 90F temperatures and it also attracts dirt. So I’d put this off as a last resort later. I would vibration proof the harness and leads. With the balance and temp plugs in the bms I’d run a thin small bead of Shoe Goop where the wires enter the back of the plugs. Just one side and very little, just enough so the wires can’t wiggle. Now dab few spots between the plugs and the bms. Again so the plugs can’t wiggle but you can still pry the Goop away and disconnect later if needed. Lastly I’d use some masking or Kapton tape to mitigate dust entry around the bms/harness area. This would be very important should you use a dialectic. Do NOT use common silicone sealant in place of the Goop. Perhaps use electrical grade silicone, however If it smells like vinegar, it’s definitely going to cause problems around electronics and connections.

 

[talgarnor]

Here is the system log...

 

[Skypower]

Anything in that log looked surprising to you?

 

[talgarnor]

Well it did boot a lot on the 20th day no ?
And before this the cell 3 get overdischarge...
This was ten day before on cell of s3 started to lose voltage and burned...
Their is a relation ?

 

[Skypower]

Well if that wasn’t you turning it off and on there’s connection issue somewhere

 

[talgarnor]

Sorry i didnt understand that dates on the log are reverse like 20 days ago and not the 20th day since first activated like i first thought
So yes everything is well with the log is recording everything fine !