How to rebalance a 4S5P LiOn battery

[Mondo]

I have a 160Wh V-lock battery that has somehow got out of balance (the manufacturer is claiming it is the PAG charger I used - don't ask me how, but I guess it's possible that he charger simply isn't compatible with the protection board installed. I do have a sep V-Lock charger that I purchased with these). I pulled it apart and I'm getting readings along the line of 3.5, 4.2, 3.6 and 3.8 - I've tried balancing it with my iMax B6 but it seems like it is too far out of balance.

Obviously there could be a bad cell in the high pack that means it is down on capacity and that's why it charge before all the others.

Question - is there any way without pulling the 4 packs apart of re-balancing it manually?

Should I discharge it all the way?

Sorry - I know I can balance it if I disconnect the cell packs but everything is glued together and difficult to access (I've already re-built one of these successfully with LG 3200's) so I'd rather not mess around with it physically till I've determined there is actually a faulty cell...

thanks - pictures to follow in next post when I get home.

 

[dogman dan]

Use your I max to charge one cell group at a time. somehow or other, attach the wires directly to the terminals, and us 1s setting on the charger.

Don't need to disassemble, just connect somehow. Might be able to do it through a bms plug, using bare male pins harvested from a Jst plug.

 

[Mondo]

Thanks

Actually it did eventually balance on the B6 - took probably 60-70 hours. I thought it would cut out after 180 minutes because of the safety timer but I think in balance mode it just keeps trickle charging until the cell is full. The cells are now within a couple of hundredths of a volt of each other, with cell 2 being a tad high. I discharged it down to about 3.6V a cell and it charged correctly back up to approx 4.2V a cell on it's native charger so I'm going to put it back into service and see how it goes.