Most RC chargers do not charge each cell individually, they charge the whole battery and discharge the higher cells to balance, then charge again and repeat until all are charged at the same level.
To charge multiple cells individually, you will need an isolated supply for each cell, ie an inverter circuit for each cell, and a control circuit for each cell. Expensive RC chargers do this, which partly explains the huge price difference between cheap and expensive ones.
From an RC modellers point of view, the only safe way to charge them is in a fire-proof container, either metal or a "lipo bag".
Seems that boeing haven't found a safe way yet either