There’s a truck manufacturer called Edison motors. They make hybrid electric trucks where the truck is powered by batteries and there’s an onboard generator which charges the batteries when it gets low.
Their current generator is an off the shelf diesel generator, placed where the engine would be.
Now the company is Canadian, but assuming they made a similar truck in the US, would the diesel generator have to meet the emission requirements of a truck engine or a mobile electric generator?
From what I’ve seen posted about the truck - the truck is purely electric, it does not need the generator to function. When the generator turns on, it only charges the battery. The generator does not perform any role in providing power to the wheels. The generator can also turn on when the vehicle is moving.
The generator uses the Caterpillar model C9 and the manufacturer claims it meets EPA Tier 4 emission standards.