“The same basic idea as a diesel electric locomotive”
Nope. Locomotives don’t use batteries for propulsion.
The next question is how many kW will these gas engines produce to power the EV car (charge the battery)? Let's say we're getting 2 miles / kWh while driving 80mph down the highway. That means we're consuming 40 kWh in an hour. Will the gas generator in the car provide at least 40kW of power to keep us going indefinitely? Maybe a 4-cyl engine can do that. If not, then the car will still be very dependent on the battery for long trips, and the article says they're looking at 60 miles on battery alone.
If the engine can produce at least 40kW of power to power the motors and charge the batteries, then it'd be a practical car for most people. For local driving, the 60 mile range on battery alone would save a lot on gas (use up practically no gas for local driving while adding only a little to your power bill), while on long trip driving you don't have to stop to recharge every 200 or so miles like in a BEV.
My Christmas Tree train does