Tag Archives: bmw i3 hybrid

BMW i3 REX Range Extender Explained

What is a range extender? Is the BMW i3 a hybrid? In this video Alex on Autos tries to explain one of the least understood cars on sale in America.

The BMW i3 has two versions, the all electric battery version, and another, less well known, battery electric range extended hybrid. In a range extended hybrid, you get a cetrain amount of electric drive, let’s say 60 miles, and then at 60 miles, before the battery runs completely dry, a small ICE engine starts up and powers an alternator to resupply the battery with electricity. Therefore, the range extended hybrid has a gasoline engine and a plug, but the gasoline engine never directly powers the wheels.

The BMW i3 REX is a little different though because it was born from the California zero emissions vehicle (ZEV) mandate. To simplify it, by 2025, 25% of all vehicles sold in California must be “zero emissions vehicles”. But to add flexibility, California allows manufacturers to sell hybrids that are not technically ZEVs as credits towards that goal. The BMW i3 REX is technically classified in California as a BEVx, and that gives it the full amount of ZEV credits even though it has a gasoline engine on board.

The BMW i3 REX is the first of its kind to be classified as a BEVx. It is different from a Prius Prime or Chevy Volt because it has at least a 75 mile range, a range comparable to some other affordable BEV options on the market. When the battery of the REX gets to 6.5% the BMW moped engine quietly turns on to maintain the battery at 6.5% but not replenish it more than that. This is a 2 cylinder 35 hp engine so it cannot do much more. Therefore, the i3 REX is an extremely low emissions vehicle, less than plug in hybrids with larger motors as much as 175 hp.

Sounds a little scary if you are on an ascending highway at 60 mph and the only hope you have of getting to your destination is a little 2 stroke, but Alex on Autos reviews what it actually feels like to be almost out of juice in the BMW i3 REX.

Features & Specs

Drive system
AC Synchronous Electric Motor with integrated power electronics, charger and generator mode for recuperation
eDrive Motor Horsepower (hp @ rpm)
170 @ 4800
eDrive Motor Torque (lb-ft @ rpm)
184 @ 0
2-cylinder gasoline Range Extender
HV battery type
Total Battery Capacity / Cell Capacity
33 kWh / 94 Ah
Max AC Charging Power (kW)
Type of transmission
single speed automatic
Automatic gear ratios (:1)
Coefficient drag
Acceleration 0–35 mph1
Acceleration 0-60 mph1
Top speed2
93 mph
Fuel Consumption
Total Range (mi)
Up to 205
Fuel Tank Capacity (gallons)
Charging Time – Level 2 – 0-100% (hr)
Charging Time – DC 50kW – 0-80% (hr)
Wheels and tires
Tire type
Wheel Dimensions (in)
19 x 5.0 front, 19 x 5.5 rear
Tire Dimensions (mm)
155/70 front, 175/60 rear
Exterior Dimensions
Doors / Seats
Length / Width / Height (in)
157.4 / 69.9 / 62.9
Ground Clearance (in)
Curb Weight – Automatic transmission (lbs)
Weight distribution, front/rear – Automatic transmission (%)
44.0 / 56.0
Interior Dimensions
Headroom (in)
Legroom, front/rear (in)
40.5 / 31.9
Shoulder room, front/rear (in)
53.6 / 49.2
Cargo Capacity (cu ft)
9.2 – 38.8