BMWBlog recently interviewed Jose Guerrero, BMW USA i Product Manager, asking him some questions about the REx (Range Extender) in the i3.
In the case of the BMW i3, the REx is just a 25 kW engine-generator, which is designed to enable the driver to finish a journey if the battery is depleted.
The main electric motor is 125 kW peak, so i3 performance can drop off when running on REx.
BMW always intends to have more all-electric range than 50% of the total range combined with REx, because this fits BMW's goal of making the i3 more electric than otherwise.
BMWBLOG Question: "Hypothetically, if you increase the electric range, will that allow you to unlock the full REx?
Jose Guerrero Answer: That’s actually a two-part answer. The way the emissions certification for the vehicle has been certified for the REx, no matter what the strategy that BMW has selected, has been to turn the REx on only to get to a charging station. In Europe, it’s different. Here, we’re putting our focus into infrastructure, always trying to push that side of the business. We believe, at the core, even REx driver’s who’ve unlocked the REx, we still expect their driving behavior not to change and it’s almost like training wheels for the BEV. People with the REx, knowing how it operates, feel that it’s sufficient. So now, people are having REx anxiety. We really talked to our dealer network and told them that “these are the conditions and expected use of this car is” and let people know what their going to buy the car for. If they buy the car, and do 100 miles a day, and expect to use the REx, it’s not the car for them.
BMWBLOG Question: How does the emissions certification work, is the REx range supposed to be a certain percentage of the electric range?
Jose Guerrero Answer: The two things we believe, as a brand, that the certification targets are: One, we want the BEV range to be more than the REx range, because we believe that this is an electric car first, born electric, and the REx is only there for when you need it. Let’s look at the Chevy Volt, that’s reversed, where the gasoline range is further than the electric range. Could we build that? Of course, we already do with the X5 xDrive40e, but that was not our intent. Two, it’s the driving pattern. If you have the REx coming on at 50 percent state of charge, at the end of one month or one year, you could actually have more gasoline driving miles than electric, so how could we, as a brand, say that it’s born electric? So we’re definitely carrying that flag of electric mobility and if we really believe electric driving can cover 90 percent of a driver’s commute, how do we then change the behavior?"
As you can see from this brief REx Q & A, BMW really treats the REx and a get-home feature and does not want owners relying on the REx each and every day. So, if you routinely drive over 100 miles per day and don't have the opportunity to charge along your commute, then BMW thinks the i3 REx is not the car for you.