Quoted,
"Active balancing redistributes charge among the cells in a battery pack to ensure that they all have the same state of charge with a dedicated circuit, which monitors the voltage of each cell and adjusts the charging and discharging current accordingly. Active balancing is more accurate and faster than passive balancing. On the other hand, passive balancing relies on Ohm’s Law and the natural cell and balance resistor characteristics to bring cells to the same state of charge. Passive balancing is generally less accurate and slower than active balancing and may take longer to achieve the desired result. "