Battery output problem

[spanos]

They are knackered, kaput , fooked, no good.

You forgot "shuffled off this mortal coil and gone to meet its maker "

[emoji16]

 

[Deleted member 4366]

I guess I don't see the harm in doing cells first. And, if still an.issue, BMS after ?

Charge the cells first and see what happens. If they go down again, replace them. If they go down again, charge them and replace the BMS. As long as the replacement cells don't go down too far, they should be OK.

 

[Carinagti]

Thank you all again for your advice and offers of help.

It may be sorted!

I made up a 4v charger from an old power supply and charged the bad string to 3.7v. That allowed the output to switch on.

Put it back on the bike and took it for a gentle run to discharge the pack a little. It was cutting out on heavy load.

Charged up the pack again and it seems to be sitting at 40.7v. Will try it back in the bike tomorrow.

Will keep you posted,
Ian

 

[Nealh]

Good news that you managed to get charge back in to them, now to see how long or if they can keep a charge.

If you charge the pack up then disconnect the bms sense wires you can monitor the pack and may get an idea if the cells are just losing voltage themselves if left to stand for a few a days/weeks. Likewise with the bms connected over the same time scale you can also monitor to see if the bms is bleeding the cell string voltage, one way or the other you may find the fault/issue.