......To e-beach, how do those cells hold up after overnight off the charger? Or just 2 hours later. That's when you'd know if one was self discharging a lot.
Haven't tried that in a while....it is rainy today so I won't be riding much today...might as well try it out and see what these slightly used Headways and bms got. I will put it on the charger for a while then unplug it and get back to you in the morning.
@MAGICPIE3FOCUSPOWER
OK, please tell me again why you are not using the BMS now?
Hahah without bms was in the past (just for a weeks) for testing at high torque and speed..... :lol:
Because I was speed and torque addict >>>> so for no current restriction I had to use the pack wthout bms.
you are not able to charge up that cell with the single cell charger? is the shunt transistor turned on and is there voltage across the balancing shunt resistor? or is this without the BMS again?
Yes I was able to charge cell separate with rc charger.
Nope I am riding with a new bms (from my spare parts stock).
But I will test it for a while and see how the cells voltages will be.
I am not able to measure the voltage across the shunt, because it's in de middle of bms.
So I can't acces to measure it...
I am looking for new bms for spare....so anyone knows a good one?
yep, the 16S BMS that jimmyD sells has the digital controls for the shunt transistors and has something like 14 of the big Ruichip mosfets with 3.5mR resistance. very compact too compared to the old headway BMSs.
there is still no evidence that your BMS is bad. it is normal for the cell voltage to drop when it is taken off the charger but i asked for you to measure the voltage across the shunt transistor while it is charging to see if the shunt transistor on that channel is now turning on at a lower voltage than normal to cause it to balance that cell low during charging. you need to make that measurement. otherwise it has not been shown the BMS is not functioning normally.
It's nice and easy with a cellog, but I would double check with a good M.M.. After 3.5 the voltage goes up very fast and when discharge will burn off very fast to 3.4 volt. Discharging. As this is the meat of the cell.
O.k. I didn't say fluff. Fluff. Voltage above 3.5v in most lifepo4.
I have many miles now.
Cells are still balanced well with the new bms.
Only cell nr. 1 is stil the problem.
Always low voltage when charging and and when disconnected form charger.
Now I did some troubleshooting.
Battery pack is disconnected from charger.
I have measured the voltages across cell nr. 1 100 ohm resistors.
The measured voltage is 3,38V and current 68 mAh ( cell nr. 1 sense wire).
So channel 1 is faulty? so what could it be the problem?
yes, if there is current flowing through the sense wire when the cell voltage is below 3.6V then the shunt transistor is shorted.
the current flowing through the shunt resistor will cause a voltage drop across the resistor. that voltage will not be there when the shunt transistor is turned off. you can measure the others in the BMS.
you can test the shunt transistor with the diode tester on your DVM since it is a p-channel mosfet. so forward bias would be from drain to source, and it should be open circuit when the red probe is on the source and black on the drain.
Yup are you are right.
I had nothing to lose, so replaced the mosfet and no more voltage across the shunt.
And when charging the cell nr. 1 voltage is now close to other cells.
I had no spare mosfets....
With this repair action I have destroyed my old bms, yes very hard to desolder the little mosfet (there some hard black stuff over the compontents).
you can buy them, and i have tons of old BMSs for spare parts. the hardest to replace are the little 5 pin comparator/gate driver for the shunt transistor mosfet. it usually burns up when the mosfet shorts out and is almost impossible to unsolder from a spare parts BMS and then resolder into another BMS. glad you got it working finally. this should solve your problem.
I have watched the cell nr.1 for a while now.
I see the voltage will go up to 3.9V and the charger will cut off.
While other are balancing when reaching reaching 3.65V.
So I think there is still a problem in the balancing circuit, which chip is for balancing?
I've been trying to follow this thread but I'm a bit confused...could you recap a bit?
Did you replace your BMS at some point or fixed #9 by replacing a MOSFET on your current BMS? Did you also replace #9?
Now #1 is slightly low but not nearly as much as #9 on your fixed BMS? Nothing changed with charging setup?
(there some hard black stuff over the compontents). 
