[TomA]

400 19.5Ah A123 pouch cells is about a 25kWh pack. 80% of that is about 20kWh, so if you can get the car under 200Wh per mile, you can have a 100 mile range. I heavy car with a pinion drive rear axle isn't likely to get 200Wh/mile. 300Wh/mile is more likely, maybe even higher.

Fortunately 100km is only 62 miles. You'll probably be close on range with 400 pouch A123, especially if you strip your Mercedes like a track car. OTOH, it would sure be easier to start with something smaller and lighter...