Wurth has written an application note about balancing series-connected supercapacitors. There are other similar resources on the web, but this one stands out as, alongside the usual resistor, Zener and op-amp circuits, it includes balancing using Advanced Linear Devices’ unusual regulating mosfets, and ADI’s LTC3128 charger and balancer that flips power from the most to the …
This story continues at Wurth super cap app note is worth a look
Or just read more coverage at Electronics Weekly