Broken battery - what you think?

[crazymaster]

Hello!
I just opened a battery that is not charging now. It was working before.

Currently the battery group which is at the POSITIVE SIDE is not showing any sign of life and i tried to recharge it separately - but without success...

Thats how all cells looks like:
-
4.21
4.22
3.55
3.34
4.21
3.66
4.14
3.38
3.25
0.00
+


What you think about the case? Probably damaged BMS? Do you think that its good idea just to replace the dead battery group which is 0.00V and the BMS?

Also the batterie looks discharged very trange... different voltages and different groups... not a few groups in a row, but in the above pattern you can see... What may be the reason for that ?

The battery is used about 1-2 months and it was fully balanced.

 

[Nealh]

Some pics of the current battery cells/groups from the top and bottom would be good to see.
Do any of the cells or protection to the cells show any signs of damage at all ?


The fact nearly all cell groups vary so much points to a BMS failure to keep balance equally during both charge and more so the discharge stage.
The low groups are likely down to a faulty BMS and looks like the bleed resistor circuit has failed big time on the 3.xx voltage groups , the 0.00 failed group might be down to a bad cell/s in that group or might be down to the fact it is the last group that powers the BMS.

Trying to recharge 0v is pointless and dead.

If only one cell group was low then the issue might be easier to try and fix but with a complete dead group and five other suspect groups it might well be better to call it day and strip the pack to use the cells for something else.

As an experiment/learning process you could replace the dead group as it is on the end so easiest to replace and a new BMS ( I prefer BMS with a pair of switch wires ), for reliable BMS I like and use Ann Battery ones from AliExpress.

Before attempting to spot welding any new cells or soldering a new BMS , you need to manually discharge the high cell groups and raise the low ones so they are all within 0.01v or so, 3.7- 3.9v is a reasonable voltage.
Once all cell groups are fairly equal in voltage let them sit for a few days to see if any self discharge, if they do forget about spending money on it.

 

[crazymaster]

Everything looks great on the battery pack...

The BMS is this one:

36V 35A 10S PCB BMS Li-ion Battery Protection Board with Balancing Protection for Ternary Cobalt Cells : Amazon.co.uk: Electronics & Photo

Free delivery and returns on all eligible orders. Shop 36V 35A 10S PCB BMS Li-ion Battery Protection Board with Balancing Protection for Ternary Cobalt Cells.

www.amazon.co.uk

I had one BMS of these which just stopped working.. and probably one more which is making problems too.

So which one you think is better of these:

Lithium Battery Protection Board 10S 36V 30A Li-ion Cell 18650 Battery Protection BMS PCB Board With Balance Function 1000W: Amazon.co.uk: Electronics & Photo

Free delivery and returns on eligible orders. Buy Lithium Battery Protection Board 10S 36V 30A Li-ion Cell 18650 Battery Protection BMS PCB Board With Balance Function 1000W at Amazon UK.

www.amazon.co.uk

36V 20A 10Series BMS Protection Board with Balancing for Lithium Li-ion LiFePO4 Battery Pack: Amazon.co.uk: Lighting

36V 20A 10Series BMS Protection Board with Balancing for Lithium Li-ion LiFePO4 Battery Pack: Amazon.co.uk: Lighting

www.amazon.co.uk

FTVOGUE 10S 36V 40A Li-ion Battery Protection Board BMS PCB for Ternary Cobalt Acid Batteries w/Balance: Amazon.co.uk: Electronics & Photo

Shop FTVOGUE 10S 36V 40A Li-ion Battery Protection Board BMS PCB for Ternary Cobalt Acid Batteries w/Balance. Free delivery and returns on eligible orders.

www.amazon.co.uk

Maybe the first one with the temperature sensor?


Now i will recharge all the batteries up to 4.20V and wait a few days how it goes until i replace the damaged group and bms

 

[Nealh]

Sitting at high charge causes cell life issue in the longer run, you are better letting the groups sit at a lower voltage like 3.7 -3.9v any self discharge will still be eviden tif left to sit for a several days.

 

[crazymaster]

what you think about these BMS i suggested?
And what about this one: https://enerprof.de/en/accessories-components/bms-pcm/13s/474/bms-13s-20a-fuer-li-ion-akkus-48v-46-8-48-1v?c=153

Its double price... for now it works good... but i wonder if i should buy more of it or stick to the cheaper options which looks even better than this...