What is a Passive Balancer?

Most BMS’s will have a built-in balancing function, however for the majority of BMS’s currently available this will be a Passive Balancer.  A Passive Balancer will attempt to balance cells within a bank by increasing the resistance to cells with a higher voltage/State of Charge (SOC), allowing for more current to flow to cells with a lower voltage/SOC.  A Passive Balancer only works while the bank is being charged, which means cells within a bank can still fall out of balance while being discharged.