Odd BMS, recovering a friends battery

[pdarnett]

Friend of mine dropped her battery in as it wouldn't charge. So lid off and measured the cells, they were a bit unbalanced with a few under 3v so used my Imax to top those up, so all cells about 3.5v or above. But when using original charger it lights up red then after a few seconds goes back to green without adding any charge.

I've tried my SANS charger but same deal, red then green.

BMS board looks undamaged apart from cells 1 and 10 aren't on the main plug.

In the mean time I'll persevere with topping up all the cells right up to the limit.

Any ideas anyone?

 

[Deleted member 4366]

Has the BMS switched onbthe discharging? If not, try resetting it by disconnecting all the sense wires, then unsolder the B+, wait a few seconds and resolder it. Finally, plug the sense wires back in.

 

[pdarnett]

Good thinking. I'll give that a try. When I've dug my garage out of the snow!

 

[pdarnett]

Look in the top left of the picture where the positives are, I was going to disconnect the one labelled pack+. The batt+ seems to go to the discharge connector. Does that seem right?

 

[Deleted member 4366]

P+ is normally BMS output positive (power +). B+ is the pack positive (battery +). Check again. Whatever the marking is, disconnect the positive from the cell pack to the BMS.

 

[pdarnett]

Disconnected them both in the end. And the balance plug. left for ten minutes but still the same. Shame really as its a well put together battery. I'm going to carry on getting all the cell packs up to full voltage and then reconsider.

I've suggested she buy one of the square bottle battery packs from Eclipse Bikes (same as the ones Woosh are doing but a bit cheaper) if I can't recover this one.

 

[pdarnett]

Think this may be a dead loss. I left the battery for a few hours and re-measured all the cells:

1. 3.8v
2. 3.7v
3. 3.7v
4. 3.8v
5. 3.8v
6. 3.6v
7. 3.6v
8. 3.4v
9. 3.2v
10. 3.3v

So all a bit low, I may try another bms as a last resort.

 

[Deleted member 4366]

Did you check the bottom of the battery or pull the cell-pack out to see if water has been in?

 

[pdarnett]

I pulled out the pack and there doesn't look to be any corrosion or water damage. I just think it's been left too long without a charge and is struggling to recover. I've got a woosh bms thats not as complicated I can try. Just a thought, I wonder if the temp sensor is faulty, would that shut the BMS off?

 

[Deleted member 4366]

Before wasting a lot more time on it, you should charge all the cells manually up to 4.2v. Then do a discharge test by using the wires from the cell-pack (by-passing the BMS). When you're confident that the cell-pack is OK, get another BMS.

 

[pdarnett]

yep my thoughts, just going to take a while on my Imax !!

 

[pdarnett]

may have to invest in a charger that does 10s

 

[pdarnett]

Well its a dud. Did a 6s charge on the first 6 cells and it finished fine. Did a 4s on the top 4 and after an hour the charger stopped with an error and cell 7 is now reverse voltage. Tried to get the pack open but it's a nightmare. Would have to cut it out totally and I'm not happy doing that. She's going to have to buy a new one. I'm not happy with how erratic this pack has been. Anyone selling? Should have got a couple from CycleCharge when I had the chance.