Friday, September 13, 2013

i3 Range Extender Closer Look

If you look at the two pictures of the i3 chassis above, you can see the one on the left has a large empty space to the right of the electric motor with only a support brace in the empty void. In the picture on the right there isn't any spare room and it appears as if the entire unit there is one large piece of machinery, which of course it isn't. That's the i3's optional range extender and BMW certainly used every inch of space they had to squeeze it in there.

The engine used in scooter trim
When equipped with the range extender the i3 weighs 330lbs more, is slightly slower (because of the added weight) and has a lower all electric range since the rage extender comes on automatically once the state of charge reaches about 20%. The driver will have the ability to manually turn the range extender off so it doesn't come on at 20%, and many will likely do so as long as they can make their destination to recharge safely before they run out of charge. However many will be willing to accept these drawbacks because of the added utility the car when equipped with the range extender, as well as having the peace of mind knowing you'll never get stuck somewhere if you fail to calculate the cars electric range properly or need to drive further than expected.

The i3's range extender is a modified version of the 650cc Kymco engine used in the BMW C650 GT scooter. It's highly optimized for this particular use and puts out only 34 horsepower compared to 65hp when used for the scooter. It has a tiny 2.4 gallon gas tank which is positioned in the front of the car close to the filler door which is above the front right wheel. BMW claims the range extender will add up to 87 miles of range before needing to refuel but whenever a manufacturer says "up to" I've found you can easily discount that number by as much as 20% so without any proof  I'm guessing it will provide around 70 miles of additional range.

The range extender tailpipe is shown here. This picture was taken from the rear of the car and you can see how it won't be possible to see any tailpipe unless you bend over and look under the car.

The Frankfurt Motor Show just opened a few days ago and Horatiu Boeriu, the managing editor for BMWblog was there covering the event. I have been providing content for BMWblog for a few years now and Horatiu usually asks me to cover electric mobility topics on his site. I asked him to get a picture of the underside of an i3 because I haven't seen any good pictures of that yet. I tried to get one myself at the i3 premier but the lighting was so bad my picture wasn't clear enough to use. So Horatui got the picture I asked for and I was pleasantly surprised to see the car he picked had the range extender option on it and he got a great picture of how BMW managed to conceal the range extender tailpipe so it's not visible from the outside unless you crawl under the car like Horatiu did to take the picture. This is important because many electric vehicle owners have expressed how they are proud they don't have a tailpipe on their EV. They don't want to see a tailpipe on their car, even if it's a range extended EV that happens to need a tailpipe. This is the very first picture I have ever seen of the range extender exhaust, and may just be the first one ever published.


  1. not sure I want a tailpipe on my EV, but running my leaf near empty isn't a fun experience. a rex would take the worry away.

    While I do like the option to disable the Rex at 20%, what happens if you do that - and still don't make it to a charging station? do you need to manually re-enable the rex? what happens at that point - does it run really hard to get back to 20%?

    1. You should really know you are going to make your destination but if you don't, I'm sure the REx will run at full throttle to try to get the charge back up to 20%. I would think you could just drive slowly for a bit and it will generate much more than you consume and allow you to finish the journey. Hopefully at that point you won't be far from your destination.

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