I think the William Arnold & Sons 1897 car was the first. On the bottom of page 13 of this link it states...."William Arnold & Sons built Benz-like cars with their own 1.5 hp engines. One was fitted with the first electric self-start dynamotor, which also assisted the engine on hills."
Pioneer Vehicles for Car the Definitive Visual History of the Automobile
The single cylinder motor was ONLY 1,190 cc and the car would run 16 mph