Paranormal activity...WTF BMS? Cell from 2.9V to 8.5V???

[Pablo_1985]

I have paranormal activity in my e-bike.

Everything started when i hit bumps at full throttle, the e-bike shuts down and turn on in a matter of one second... i thought it could be a bad connector or something similar... but yesterday i had to pedal home because it shut down and didn´t turn on. I get home and started disassembling everything, check connectors, cables, try to charge the batteries, etc. I saw the phase wires hitting the bike frame and thought they could be messing around, and the bike was working again... so problem fixed until today :O, same thing i hit a bump at full throttle (40km/h?) and i felt how the bike turn off. when i got home i tied to see if the phase wires were messing around agina, but not, i isolate them properly yesterday... everything seems normal... anyway in the meantime i put my batteries to charging, but the charger did not turn on :O. so i started to check the voltage cell (no smoke, no heat.. just barely warm...). everything quite normal at 3.28V but one cell at 8.45V!!!... i follow the cable to see if there is anything wrong but the cables are ok, i put out the charger i check the cell temperature (everything normal but the voltage)... i check again voltages and now it says 2.9V instead of 8.5V, put the charger and then it goes again to 8.5V.. put out the charger and connect the power to the controller, and after the typical spark cell voltage goes to 3.28V, and bike is running...?!?!?!

So I guess something is wrong with my BMS, do you know what could it be?

Regards

PD: I´m running a Conhismotor motor (similar to 9C 2806), with 9 fets Lyen controller @1500W, with 16 headway 38120S cells.

 

[dnmun]

all the cells were at 3.28V when it was charged? what is the output voltage of the charger?

post up pictures of the pack and the wiring. where did you measure the voltages you used? what voltage does the pack normally charge up to?

do you have a wattmeter or Cycle Analyst?

 

[Tench]

You have tried new batteries in your DVM?

 

[Pablo_1985]

The voltage of the charger was normal aroun 58 volts i can not remember exactly.

All the cells were 3.28 when i got to my destination, so not fully charged but 50%.

I measure the voltage at the input of the BMS, and the 8.5V also directly in the cell.

I have done 2500km with no problems, wiring and so on is perfectly fine :S.

Sorry, I do not know what DVM stands for but i haven´t try any other battery.

Now i have to ride it... and it will work, (after unpluging and pluging the controller and "touch" every cable it started to work again :S), at least if i don´t hit any bump at high speed :S

I will check later now i am at work.

 

[Pablo_1985]

Ok same thing... I rode home and at some point it just failed again. Now at home i have diconnected the controller from the battery and tried to charge it.... Nothing, it does not charge i guess it is the same thing BMS messing around cutting the fets thinking "SORRY MAN NOT CURRENT ALLOWED"... i have not propper tools overhere and i will have to wait until the weekend.

I do not know if i should just start thinking about buying another BMS... But it pissed me off i want to know wtf has failed.... I use it everyday 2 times for a 11KM trip with no bike it is not cool at all!

Regards!

 

[Tench]

Hi, DVM is Digital Volt Meter, they can act up when the battery is low but in this case that may not be the problem, have you considered running the bike directly from the packs output wires bypassing the BMS on the output side, just use it for charging, you would need some other form of LVC, low volatage cut off, either the controller maybe) or a CA, cycle analyst could do this.

 

[Pablo_1985]

Oh, DVM, hehe ok, yeah i know that, one day i though my battery was going to explode, voltage was getting higher and higher, up to 90 volts, it was crazy! but then i understood that that didn´t make any sense and must be because something else... battery level. I will try to bypass the BMS, i am sure that will work... I am completely sure that the problem is in the BMS not the controller, because i can not charge the battery and i know it is not fully charged.... and this with the controller disconnected.... but why does it fail with bumps?... no idea yet.

I will check deeply this weekend or sooner if i manage to make some time.