You know those 18650 battery that won't charge can be saved.
A charger refusing to charge a dead LiPo cell is basically a safety feature of the charger.
AFAIK most LiPo chargers have a trickle charging mode if the battery gets below a certain voltage.
And full charge only starts when the cell recovers to a certain voltage.
If it doesn't, then the cell should be discarded, not revived.
Leo..
Dont do this.
The dead cell will get hot when its being force charged, and there is as risk of the cell exploding due to the heat.
Even if you do manage to revive it , its capacity will be only a fraction of its normal rating.
That's a neat way of turning one bad cell into two bad cells. You have a good chance of damaging both cells with the basically unrestricted current that flows when you connect a fully charged cell to a low voltage (already damaged) cell.
Lipo chargers refuse to charge low voltage cells because they know that any lithium cell run down that far is already dead or at least badly damaged. Lithium chemistry simply does not recover from extreme depletion like that.
Steve