The end goal is long-distance, all-electric travelling. I know the simplest and easiest solution is to use the proper vehicle, but I just have this urge to build something and make my i-MiEV the end-all transportation solution. A small, lightweight vehicle for most of my driving, with the ability to hitch up and go across the state on short notice, on more than one route. Sometimes, it would be nice to jump on the highway and drive the 50-55 miles to my destination and cut my travel time in half. Not always possible around here.
1. I don't like burning fuel, and that has gotten worse since I had a solar array installed. I try all the time to convince my parents to take the i-MiEV instead of the C-Max on local trips, even though it gets 44 MPG. Gas engines just seem so, clunky, even in hybrid cars.
2. An electric pusher trailer also has the benefit of being used with our pickup truck for electric assist and regenerative braking. The main goal is regenerative braking since the engine doesn't hold back very well, and we usually use it when driving in hilly areas. The brake rotors are already warped, and there aren't that many miles on it.
3. A high capacity battery would tie-in nicely with solar to provide emergency/backup power to our house or for events. Just yesterday I saw a truck unloading three solar-powered mobile work lights
4. Since I plan to utilize second-hand lithium-ion cells, I'm hopefully preventing a good portion of lithium from being dumped in a landfill. I'm taking the small-format, Tesla-style pack route. Other folks have had success. One guy powered an electric VW bus with them, and another made a 100+ mile range eBike. I'll cut my teeth on a custom pack for my lawn mower first.
5. With an extra 50 kW of motive power, the i-MiEV could really out-accelerate other vehicles
, and stealthily at that.
I've thought about a couple of suitcase battery packs that I could put in the back and plug in when I need extra miles, but like you said, the extra strain on the car's system plus the warranty concerns keeps me from wanting to touch the car's drive system. A trailer hitch could easily be unbolted before taking the car in for warranty, and there is little recorded evidence of tampering with the car. Controlling the trailer can be accomplished with an RC plane control system. I can have servos controlling the throttle and regen pot boxes on the trailer. The only wiring in the car that I would be tapping into are for trailer lights (brake, turn signals, etc.).