At the same time, automakers are shying away from giant, costly batteries—which make EVs heavier, less efficient and downright unprofitable. So, what’s the solution? Enter extended-range EVs—or EREVs.

Although you can indeed buy electric Vespas, there are tons of the iconic scooters that are still equipped with combustion engines. If you have one of those classic rides and want to make it electric, ...