Yup NonPolluter, some Battery Management Systems use resistors.... but I'd add that MOST battery "balancers" that I've seen use a resistor (or a FET in dissipation mode).... Some BMC are LVC and HVC only, just the cheap solutions for those that want to balance themselves.

I think there were a couple capacitor based ones that shuttled charge from the high batteries to a low battery (Powercheq's). I haven't seen any commercially available power conversion BMS's (they use an isolated DC-DC converter on each battery)..... but I've built one and it worked great (essentially a uC controlled Isolated DC-DC on each battery). I think those are basically all of the types.... resistive, capacitive and power conversion. Most of the commercial ones are resistor based, which can be problematic if they fail and are failed ON, they discharge the battery.