I recently found a lead acid battery balance IC .
Linear Technology LTC3305.
When series connected batteries are not equal, on charge when the regulator limits the total voltage, the voltage on the best batteries drifts up, and since the total is fixed, the voltage on the rest of the batteries must go down, so the worst battery never gets fully charged.
On discharge, one battery can be flat while the system voltage is still ok.
This chip balances up to four batteries by connecting each in turn to a super capacitor or auxiliary battery until they are all balanced.
Has anyone tried this chip or maybe made a battery balancer?