1. Remove depleted batteries from the battery pack.
2. New cells: Samsung ICR18650-32A x 6
3. Desolder the original controller circuit from the original battery pack.
4. Weld anodes of two cells. Be cautious of the polarity.
5. Connect the other ends (not welded yet) of two cells with a resistor and let the cells sit until the voltage gets balanced.
6. After the cells are fully balanced, weld the other ends. Aggregate the welded cells and form a pack. Attach and solder the controller circuit.
7. Repack in the original plastic housing.
