To give you a better idea of how small the gas tank on the BMW i3's range-extender will be, it's about equal to a quartet of those two-liter plastic Coke bottles you'll get at the supermarket for your next football bash. That's it.
The German automaker is limiting the size of its range-extender's gas tank to 2.4 gallons in order to comply with a California Air Resources Board (CARB) mandate, Green Car Reports says. Specifically, CARB is classifying the i3 as a "BEVx," or a range-extended battery-electric vehicle. To qualify for this status, instead of a range-extender set-up like the Chevrolet Volt's, where the gasoline tank provides about 10-times the range as the electric battery does, the Bimmer's gas-powered range can not be higher than that on electricity, putting the range-extender strictly in "auxiliary" territory. And with the i3's electric range estimated to be anywhere from 80 to 100 miles (BMW says it's 118, but that's using the European scale), the gas tank has to be rather miniscule.
Either way, the range extender will both reduce the all-electric range supplied by the vehicle's 22-kWh lithium-ion battery pack and lengthen the acceleration times of the 170-horsepower vehicle, albeit very slightly. Check out AutoblogGreen's fresh-off-the-press First Drive impressions of the i3 here.