I am designing a new method of boosting weak car batteries. My plans are to use a two-wheel dolly trimmed down to carry a two-stroke engine, belt-driven alternator, voltage regulator, spring coil load and booster cables. In theory, connecting the cables to the battery and cranking the engine should substitute the vehicle recharging system. I have to get a suitable engine before I build this unit. I'll be using loose Ford Motorcraft parts from a scrapped Econoline van, the coil from a battery tester. Once I know the engine rpm I can get a suitable pulley on the engine shaft. there will be several issues to address, including running the engine with the cables clamped to the frame and some sort of a kill switch if things get scary.