Faulty chinese battery pack - help please

[ev_convert]

Hello, i wonder if some on this forum can offer help and advice:
I have a Chinese made duck tape Lifepo4 battery pack, it is 16S , 10Ah and has about
200 cycle of use; All of a sudden it now cuts out under load - as in me sitting on my ebike, twist
the throttle to go. eBike moves a few centimetres then stops.
I have a cycle Analyst fitted and was set to limit the amps drawn to 20ah - and hopefully lengthen
the battery pack life;

I removed some of the duck tape and measured the cell voltages - via an old fashion Avometer 8;
See below;

Cell Voltage
c1 0.55
c2 3.2
c3 3.2
c4 3.2
c5 3.2
c6 3.4
c7 3.4
c8 3.4
c9 3.2
c10 3.4
c11 3.4
c12 3.2
c13 3.4
c14 3.4
c15 3.2
c16 3.2

I should point out that when the battery pack is re-charged - it now only appears to
take 5-10 minutes before the charger shuts down. It normally takes 60minutes to re-charge.
There is no physical damage to any cell or the BMS.
I can see that cell 1 is low - beyond that - i have no idea of the fault.

Cells specs are as below:
Specification of Single 17065130 LiFeO4 Cell:
Type 17065130 Prism (Aluminium Hull)
Chemical Composition LiFePO4
Nominal Capacity 10Ah
Nominal Voltage 3.2V
Maximal Charge Voltage 3.65V±0.05V
Discharge Cutoff Voltage 2.5V
Charging Method CC-CV
Maximum Discharge Current (continual) 50A (3-5C)
Maximum Charge Current (continual) 20A (2C)
Cycle Life 1500cycles 1C 100%DOD
2000cycles 1C 80%DOD
Charge Temperature Range 0℃- 45℃
Discharge Temperature Range -20℃- 60℃
Density 118.52Wh/Kg
Internal Resistance ≤5mΩ
Size Thickness 17.0mm
Width 65mm
Length 130mm
Net Weight (g) 284

Thanks for any help or advice in advance.

 

[DAND214]

Per your cell voltage test, cell 1 is dead.
you need to single cell charge it. Then let the pack charger on for a day or so to balance the cells.
if the cell doesn't charge and balance with the other cells you will need to replace it.

Dan

 

[Punx0r]

At 0.5V it is surely already well dead?

 

[wesnewell]

Try charging cell 1 at .5C or less until it reaches 3.3V. Then hook your charger back up and let charge until all cells balance out at 3.5-3.6V. This may take a long time. if you can't get cell 1 to charge, then you'll need to replace it.

 

[Schlafmutze]

Lifepo4 can be recovered from such a low voltage.

 

[ev_convert]

Hello again - thank you all for the advice; I did try to charge the faulty cell alone - it kinda recovered to about 3.5V - whilst charging. I then tried to re-charge and balance the whole pack - again this kinda worked, then over time the faulty cell voltage collapsed to 0.3V. So it looks as though the cell has reached the end of it's life after only 200 cycles.

 

[zEEz]

or it proves that your bms is not good - very cheap, and it is draining lot of juice from the first cell only, this was the case in old bms'es and can be that 20 euro to get a new one could put the pack back on full use.

have fun!

 

[Tench]

To gain a little more info about where the fault lies you could charge the first cell again with a phone charger or similar until it is inline with the other cells then balance the whole pack with your pack charger. Then unplug the balance leads from the bms and bridge the main pack leads around the bms to bypass it. go for a ride to use some current, check the cell voltages again then charge the pack again and measure the cells again. If cell no1 behaves itself then it is probably the BMS, if on the other hand it drops low then that cell will need replacing.