Help! Battery not charging after Winter (err. and a bit)

[point5clue]

Hi All,
I left the bike with about 50pc SoC, but coming back to the bike after a much longer than expected break I saw that I had left the charger lead in (I'd think I'd given it a just a little top up and must have just switched it off at the plug).

I could easily be 6 months - I had a lot going on in my life at the time!

Its a 36V 17Ah battery - I'm not sure if the link will work for others, but it still shows for me.

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Maybe it would have died anyway over that amount of time, but I wonder if the charger has been slowly draining it?

I say its not charging - the controller unit won't switch on, with or without the charger lead in, and the light on the charger stays green when I plug it in.

I have a basic multimeter, and various security screwdriver bits, so would be happy to open it up if anyone knowledgable would have the patience to guide me.

 

[wheeliepete]

What voltage reading do you have on the battery?

 

[point5clue]

What voltage reading do you have on the battery?

Sorry took a while to find the multimeter and untangle the leads in the frame bag.

90mV - this is the same with or without the battery switch on ?

 

[scott gaza]

disconnect the battery and read the voltage off the terminals

 

[point5clue]

Yes, same from the terminals - again with or without the switch on

 

[wheeliepete]

90mV

Oh dear, that doesn't look good. If that's a true reading your battery is toast.Are you sure your meter is OK?

 

[wheeliepete]

I'm nor sure if leaving the charger connected could have caused this total drain, hopefully someone else could verify this.

 

[point5clue]

Yes, just checked with another meter - same.

I've taken the case apart - is there anything else worth checking ?

 

[point5clue]

A couple of the cells I can reach either end on read 0.6V

 

[wheeliepete]

A couple of the cells I can reach either end on read 0.6V

Unfortunately, if cells fall below around 2.5v for any period of time they generally suffer irreversible damage. If the voltage was a little higher, say 2v, I would suggest gentle charging each group manually with a mobile phone charger, but this could be hazardous in your case. A real shame as it looks like a good battery with decent LG cells.

 

[Nealh]

Time for another battery or get it re-celled with nice cells, the LG F1L is low power cell. The Samsung 29E is a low power cell but much better.
Generally 2900mah cells are the sweet spot for battery life and longevity but there are a couple of stand out cells of 3500 mah, both LG the MJI & M36.

Samsung 50E 21700 looks to be a future star cell.

 

[Nealh]

A couple of the cells I can reach either end on read 0.6V

Show a pic of the BMS multi sense wire connector, for an exercise you can get all the cell group voltage readings via the connector when you pull it out/disconnect it.
It will tell you the voltages of all 10 cell groups, but it does sound like the battery is toast.

 

[point5clue]

Show a pic of the BMS multi sense wire connector, for an exercise you can get all the cell group voltage readings via the connector when you pull it out/disconnect it.
It will tell you the voltages of all 10 cell groups, but it does sound like the battery is toast.

Is that the connector with all the white wires ?
Thankyou for everyone's help by the way - its appreciated.

 

[Nealh]

Is that the connector with all the white wires ?
Thankyou for everyone's help by the way - its appreciated.

View attachment 34775

Yes the multiwire connector with the ten White & one Black wire, carefully pull it out/disconnect it from the BMS . You can then use your meters probes on the wire connector to get ten cell group voltages, write them down 1 -10 & xxx volts.
For cell group one Black probe on Black wire pin out and Red probe on first White wire
For cell group two Black probe on first White wire and Red probe on second White wire .
For cell group three Black probe on second White wire and Red probe on third White wire, continue like that all the way along the pin outs until you have ten voltage readings.

As I thought they are LG F1L cells a very cheap lack lustre low power cell.

 

[point5clue]

Yes the multiwire connector with the ten White & one Black wire, carefully pull it out/disconnect it from the BMS . You can then use your meters probes on the wire connector to get ten cell group voltages, write them down 1 -10 & xxx volts.
For cell group one Black probe on Black wire pin out and Red probe on first White wire
For cell group two Black probe on first White wire and Red probe on second White wire .
For cell group three Black probe on second White wire and Red probe on third White wire, continue like that all the way along the pin outs until you have ten voltage readings.

As I thought they are LG F1L cells a very cheap lack lustre low power cell.

For what its worth 0.81, .68, .83, .75, .66, .62, .81, .85, .85, .87

So I'm guessing that a confirmed kill on this pack.

You mention re-celling - is that something I'd do myself or send it off ?

 

[Nealh]

Yep the battery is dead with those voltages, unless you have a spot welder then no.
JImmy at ebikebatteries.co.uk will re-cell he arranges couriers both ends, give him a call.

 

[point5clue]

Just to close off the thread - I did indeed contact Jimmy - it took me a while to decide (waiting to be sure I still had a job to cycle to eventually) but I now have a fully re-celled battery returned to me £375 including collection and return.

I did a 'range test' on my regular commute and the capacity seems at least as good it was originally.

I have now put in a once a month calendar reminder to check the battery !!!!!!!