The charging system in the Porsche is of a custom design. In order to maximize the life of the battery pack, I decided to build 16 individual computer-controlled chargers. I chose this solution over the typical series string charger and regulator arrangement to keep the batteries equalized on every cycle, as well as to provide a means of monitoring individual battery state on a nifty in-dash vacuum fluorescent display - even while driving. :)
The chargers are based on power factor corrected 10A, 15V industrial power supplies, to which I added a custom microprocessor board. The board allows for voltage and current monitoring, as well as charge level control. All of the chargers are daisy-chained together on an opto-isolated network running at 19.2 kbps. The master controller in the dash polls the status of all the chargers and displays the pack status. It can also command the chargers to enter special charge modes.
Following are pictures of the chargers in various states of design and construction:
