Dave, who converted a Delorean to electric, made & installed the same kind of LED battery monitor in his car that Ivan & I put in the ForkenSwift:
The monitor is described here (parts list, DIY instructions):
EV Weblog: LED Bargraph battery monitor part 2
Here's Dave's vid
The Delorean's is a somewhat cleaner installation than the ForkenSwift's
Unless you have a BMS with a current limiter or some kind of alarm (to alert you about a failing battery/module), I think a gauge like this is a must. Otherwise, you WILL murder batteries as they age, pretty much guaranteed.