Here are a few photos of the system Ryland just mentioned.
A logic board controls all those relays that route power to each battery individually to top it off. I seemed like a clever system.
Also, my friend Tom, who is building the AC Dodge Neon, is planning on having a custom battery monitoring system. That is going to be a while before that's done, but it may actually become a product to be sold.
If he goes open source with it, I will share the info here.