You can only set a battery charging voltage. Then the balancing circuit will attempt to discharge the high cells when they get close to the top, while the other cells continue to charge. So if you have cells with great differences in voltage (like in this case), you have to reduce the battery voltage, too.
Battery balancing works by redistributing charge among the cells in a battery pack to achieve a uniform state of charge. The process typically involves the following steps: Cell monitoring: The battery management system (BMS) continuously monitors the voltage and sometimes temperature of each cell in the pack.
Battery cell balancing brings an out-of-balance battery pack back into balance and actively works to keep it balanced. Cell balancing allows for all the energy in a battery pack to be used and reduces the wear and degradation on the battery pack, maximizing battery lifespan. How long does it take to balance cells?
needs two key things to balance a battery pack correctly: balancing circuitry and balancing algorithms. While a few methods exist to implement balancing circuitry, they all rely on balancing algorithms to know which cells to balance and when. So far, we have been assuming that the BMS knows the SoC and the amount of energy in each series cell.
For example a slight increase in charging voltage from 4.2V to 4.25V will degrade the battery faster by 30%. So if cell balancing is not accurate even slight overcharging will reduce the battery life time. As the batteries in a pack get older few cells might be weaker than its neighboring cells.
A low charging current will help because it gives the balancing circuit a chance to discharge that high cell at the same pace or faster. All cells will rise in voltage at a lower pace. Including the "high" cells.