Lithium chemistry doesn't tolerate over charging.?
For example a single cell on a constant current/constant voltage charger could charge a cell at a max current rate of 1C, in the constant current portion of the charge cycle, and? then the current will taper to zero?
as the max charge voltage would be set to 4.20V.
Problem occurs if there are series connected cells. Cell to cell variation, or temperature differences in a pack will cause the cells to age differently so the capacity will vary.
So the cells with lower capacity(mAhr) will charge first and then be over charged unless there is a balance or Battery Management System( BMS) attached to each series connected cell in a pack.?
Basically, the balancer/BMS clamps each cell to a max of 4.20 V
If possible I prefer not have have an integrated BMS( there is some self discharge).? Also integrated BMS's can't tolerate high speed charging as they can't shunt a high current.
I will wire a connector to each cell so an external balancer can be connected, and it also allows me to check each cell voltage in a series connected pack.
Most model RC LiPo packs have a balancer connector.
Paralleling batteries of the same brand/model number is nominally not an issue.
P
