First, I'm not looking for an exact number here or anything like that. More just bouncing ideas around and talking out loud. Say you have a mid 90s Ford Ranger with a manual transmission. You remove the original motor and get some type of small diesel engine (Kubota, VW, Mercedes, 4BT Cummins) and install it coupled with a suitable electric generator. Depending on size, the motor/generator combo could be mounted behind the cab in a custom made enclosure. The electric motor would be coupled to the manual transmission and a suitable flywheel and clutch system. Diesel engine fueling would depend on electrical load and the electric motor rpm would be controlled by a suitable controller. My only question is, roughly how many batteries would be needed in a system like this? Would it need a lot or just a few? The plan would be to have the diesel engine running 100% of the time the truck is moving. Like I said, there are a lot of different factors here and I'm not looking for an exact answer. Just trying to see if it is a feasible design.