High Cell Count LiPo Balancer/Charger
The cell balancing is performed by a specific circuit a BMS (battery management circuit). Balancing allow to protect a lowest cells from venting and thermal runway. Your configuration is 25S4P, so using a BMS to control current and voltage is the best solution. If you use 100 single cell charger, it will be difficult to control them, since they have different Stat of charge, so the weakest will be rapidly damaged.