Dead battery - diagnosis help puurrleeease !

[KirstinS]

Ok, PCb out cable has been cut and soldered to black cell to PCB

And everything out back in the case (not so easy!)

All looks good but cannot test till this evening

 

[KirstinS]

Can't test ride till after 5pm but we gave power to motor and all seems good under no load

I'm not convinced the charging is working but hard to tell for sure til I run down battery a bit first to be sure

Will be deliriously happy if it all works !

 

[banbury frank]

Hi

If you bypass the BMS it will work OK for a while Until the cells go out off Balance IE low high voltage also amount off charge per cells I get customers come into the workshop with a duff battery not one off ours

I will link out the BMS and tell them to use it till it fails as they have nothing to loos as the battery was DEAD and useless so any use is better than none The problem is the time involved in replacing the BMS and balance charging all the individual cell is a long job and the battery is probably not worth repairing as a new one is only £200

Frank

 

[Deleted member 4366]

The BMS is still connected for charging and balancing. Only the output protection is bypassed, but that's mostly covered by the controller.

 

[KirstinS]

Good and bad news

Good - battery functioned perfectly all on commute of 15 miles

Bad news - it won't charge

Battery in bits again. 42v are getting to the PCB ( tested underside rather that just the plug)

Any guesses ?

 

[KirstinS]

Also correct voltages on all 10 balance leads (up to 36v now that battery is somewhat depleted.

 

[Deleted member 4366]

Either something's gone wrong in the BMS, or it thinks one of your cells is too low. To eliminate the latter, see if you can check the cell voltages on the pcb. There should be 10 groups of identical components. Tou should be able to follow the tracks from the connector to the sensing components. You can have a look at the BMS to see anything obvious, but if you can't find anything, you need a new BMS, or you can charge through the out-put leads and forget about balancing. You''ll be OK for a while.

 

[KirstinS]

Thanks again - found the 10 components and they all read in increments of 3.6 (making up 36v) so

Looks like I need to just splice the charging leads into output cables and foret about BMS

And get saving for new battery !

Thanks again for help - you have taught me loads and given an extra lease of life to battery

 

[KirstinS]

So last question

Am I confusing myself or am I right I thinking positive charge lead needs to go to negative output ?

 

[Alan Quay]

You are confusing yourself. Pos to pos.

 

[KirstinS]

A final note

BMS has been bypassed and battery charges and discharges just fine

Ok, it won't last but I will order another battery

And the cells I may recycle into further booster packs as they are brand new

See my booster pack thread for details

 

[jackhandy]

Are you going to order another 8fun battery?

The Kudos 10ah bottle battery with Samsung cells looks a promising alternative, if they sell the cradle as well.

 

[KirstinS]

Not from 8fun but my booster battery uses Panasonic cells so probrably best to stick with same cells

I'm scoping out several vendors via alibaba

Btw the woosh sirocco sport also uses the Samsung cells.