[dcbusman]

I have a Sun 60v battery on my custom ebike, its one of those box shaped shaped batteries with what I call bag cells inside, sorry for the weird discription. Anyway, it won't charge, charger checks out OK so I checked each cell and one feels soft whereas the others are firm. The soft one is only reading 1 volt and all the rest are about 3.5v each. I've removed the bad one from the pack plus one more to get the tabs to line up. Is the BMS still going to work with the 2 cells removed?

 

[kennybobby]

The BMS is not likely to work with cells missing. Most BMS units monitor the voltage of each cell and will cause a fault condition and shut OFF the pack contactors or FETs.

 

[dcbusman]

Thanks, I thought as much. Do you know the correct name of these cells so I can search

 

[floydr]

The cells are pouch cells they come in many sizes and all of the lithium ion battery chemistries.
Later floyd

 

[dcbusman]

I can't find a replacement cell so can someone point me in the right direction for an 18s BMS if that even exists

 

[floydr]

Look on ebay Ant smart bms is one that will do any chemistry of cells of most any series 8s- 20s max or 24s max. There are other BMS's that can handle varying number of cells.
Later floyd

 

[brian_]

Do you know the correct name of these cells so I can search
View attachment 130546 View attachment 130544

As floyd said, they're pouch cells... but you need a lot more information than that to find a suitable match. At the very least, the same electrode chemistry and the same capacity (in amp-hours). Getting a BMS to work with the battery that you have seems like a better idea to me.