VW has several 1.5-2.0L turbo diesels that should produce decent charging power at low RPMs burning only 0.23-0.31 gph (0.9-1.2 lph) and a few are pretty small and can be reconfigured. Bump the battery to 80-90kwh giving you 250ish miles with a turbo diesel tuned to 1800rpm. Air intake in the c...