BMW Details Range Extender Option On Upcoming i3, 160 More Miles On Gas

JAN 22 2013 BY STAFF 40

An interesting aspect of the all electric i3 when in comes to showrooms in the fall of this year, is that it doesn’t have to be all electric at all.

For a price (which is still undetermined), buyers of the 90+ mile electric vehicle, can also add a range extender engine option to enable the car to travel even further, while taking the worry (and the wait) out of finding a charger when the vehicle is away from home and low on power.

“I imagine many buyers will order the range extender to cure their range anxiety, discovering later they need it very seldom,” Herbert Diess, BMW’s head of Research & Development Diess told Automotive News at the NAIAS this week.
This extender is not on par with the likes of the Chevrolet Volt, or C-Max Energi, but is intended to serve more as a back-up to primarily driving on electric power.

BMW Has A Nice Little Spot Set Aside For A 2 Cylinder Engine In The i3 (Concept)

The 2 cylinder motor is taken from a motorcycle and is housed smartly in the rear.  The unit does not directly connect to the wheels, but rather to a generator that charges the battery, so output (and performance) is sure to be very low.

We imagine that being under-powered when switching to gas, is still much more preferable than being completely out of energy to drivers of the BMW plug-in.

The range extender option adds about 160 more miles of range to the vehicle, bringing the total range up to about 250 miles according to Mr. Diess
“I imagine many buyers will order the range extender to cure their range anxiety, discovering later they need it very seldom. For those who plan a daily use of the range extender, the i3 is probably not the right choice and a plug-in hybrid model is a more suitable solution.”
The BMW boss says he expects about 50% of the i3s sold initially to be optioned with this feature, but eventually settling down to about 20%.   It is expected full pricing details on the standard i3 (estimated around $45,000) and the range extender will be announced at the Frankfurt Motor Show next September just before the car goes on sale.

BMW i3 Concept On Display Earlier In London

Automotive News, photo via Bimmerfest

Categories: BMW

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40 Comments on "BMW Details Range Extender Option On Upcoming i3, 160 More Miles On Gas"

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I think the efficiency and performance of this vehicle will make it a real pleasure to drive or ride in in all battery mode. Like many others; I am looking forward to learning about the driving characteristics when in range extended mode. Will you be able to continue driving on the highway at 75mph or will you have to slow down to an unsafe highway speed?

I really like this concept. A full range electric car with a small, unintrusive, theoretically inexpensive, generator backup for when you need it.

No disrespective to BMW, but it is kind of a shame the idea had to come first from them, because the price point will start higher than most can get too. But a few thousands dollar option on a inexpenisve EV, like the new $28,800 LEAF base model, would make that car wildly versatile to everyone, and I think would be a runaway winner.

Given the BMW program is staffed with Volt “plankholders” it suggests that this design was considered and rejected by GM. Kudos to BMW for bringing this option to production. Let’s see how the market receives it.

Well, I imagine the “motorcycle” engine was off the shelf for BMW being that they make motorcycles themselves. GM also took an off the shelf motor at the time for the Volt, with the intention of having a more purpose-built motor in future generations.

Would have been nice if GM had kept Frank Weber. A true-believer of the Volt if there ever was one.

I think the fact that Diess believes that 50% of the early i3 sales will include the range extender option points to the REx option not being too expensive. If it added $5,000 to the price then I don’t think they would be predicting anywhere near 50%.

Like BlindGuy I’m looking forward to finding out the capabilities of the REx as well as the price. I’m thinking the top end would be 70-75 and that’s on flat grade. I doubt you would be able to go up a steep incline at 70mph. The REx isn’t there to operate like a Volt can. It’s main purpose is to get you to a charge point so you aren’t stranded, not to the vacation home on the mountain that’s 200 miles away.

In the case of the vacation home in the mountain – suppose the driver knows they will need to use the REx. Do you know whether the car will offer the ability to turn it on ahead of time? Similar to the Volt’s hold mode or the C-Max’s EV Later mode. If you turn on the REx at the beginning of your trip to the mountains, you may be able to get there without a reduction in performance.

Yes – that would be sufficient for us, north westerners. You can’t go far higher without climbing mountains.

ICE in the rear, no need for exhaust piping. Smart thinking.


If it does not drive the wheels directly, why does it appear to be connected to the drive shafts?

David. That’s a picture of the electric motor. The space next to it is where the speculation is the range extender will be. There are no available pictures of the range extender to use.

I think it should at least be capable of driving 75mph in extended mode. Because the engine adds 160 miles. That distance is not to get you home safely, but for The occasional longer highway trip to visit your granny 120 miles away. Otherwise they would add a smaller gas tank

I love the idea! It’s what I thought (and some people still think) the idea behind the Volt would be. A true optional serial hybrid. I’m really curious what the output would be. Any idea? I guess in the 100-150hp range like the output of the R1200GS motorcycle’s engine.

150hp, God no!

Back in the pre-production days of the Volt, I suggested a dual battery configuration with a small range extender. Use two separate 20 kWh battery packs. Start with both fully charged and cycle usage between the two. When pack A depletes down to a certain percent switch propulsion to pack B while pack A goes into charging mode using range extender and brake regen. When pack B depletes to the set percent, switch propulsion back to pack A while pack B goes into charging mode. The cars performance while one pack is being recharged should be the same. If you know you’re near where you’re going to plug-in turn off REX.


I agree that this is a nice option and a unique approach that many thought that the Volt would be.. Is Tom M. going to get this option?? Seems like he has an order in for the i3 electric.

In typical BMW fasion this will be an expensive car though. However one must admit that it is loaded with high tech.

PS I swear I have seen a photo of the RE on the chassis. I will try to find it.

I’m considering it George. It depends on the price. I have lived the past four years with a ~100 mile EV and drove over 30,000 each year. Honestly I don’t need the range extender, but it wouldn’t be the first thing I bought that I didn’t need! I also want to see all the technical specifications first and the weight of the entire REx system. I’ll be lugging that stuff around 100% of the time and only using it 2-3% of the time so I want to figure out how much efficiency I’ll lose just by having it onboard.

Plus, it’s then a PHEV even if I don’t use the REx hardly at all. I’ll have to pay sales tax in NJ (currently EV’s are sales tax exempt) so that will add another ~$3,000 or so and every time someone asks me “Is that all electric?” I’ll have to go into the explanation on how it is 99% of the time. I’ve gotten used to saying “Yep, no gas in this car, just solar powered electricity!”

Tom, heck out the proposed (may be new by now) vehicle classification in California of BEVx – Range extended Battery Electric Vehicle. Has to be a BEV with range approaching 100 miles with a motor/generator that at least doubles the range and has a gas tank smaller than 2.5 gallons.

Perhaps you will still be able to avoid sales tax on REx.

Well I was wrong about the pic. I thought I had it but it is like Tom M said it’s not the RE it’s the elctric motor/ transaxle assy.

I like the skateboard design and the carbon fiber body too 🙂

In regards to the “skateboard” chassis…here here!

BTW, does i3 have a “frunc” ?

Yes, but it’s not big. Probably something like 20″ X 20″ X 16″

Not bad – that is enough for $200 worth of groceries from Whole Foods 😉

It’s hard to see but this is one of the only pictures of the frunk open:

LOL Tom. All I see is the charging cables! Not the best PR but I see what your talking about (the frunc)

I did say it was hard to see George! 🙂

Looks like 12V battery trouble.

About time.. Now, if they send the waste heat to the heater a la my ’64 vw beetle from the mufler, then it would be just about perfect. For everyone who wants to travel at 75 mph I dont see why you couldn’t do that for a while. There’s no law saying the engine has to stop when stopping at a rest stop, and the thing could recouperate. It would fall behind when you’re driving, but then just take another break.

Another variation would make the output be a ‘standard’ voltage, that way it could be used for ‘export’ power for tradesmen, or emergency power for your neighborhood.

I’ve always wanted a 1 cylinder option for a Volt like vehicle. Honda already makes a water cooled 1 cylinder for its motor cycles and its household micro co-generators, where they take in natural gas and make 800 watts of electricity so that the thing ends up being 100% efficient since the waste heat heats the house, and you get low cost electricity besides.

I’d think a 20 horsepower atkinson cycle (power stroke longer than compression stroke) 1 cylinder engine running all the time at the driver’s choice, could be used to provide heat for the battery and cabin in cold weather, plus greatly extend the range of an electric car, with almost no weight/cost downsides. Since electric heaters are so hard on the battery during cold weather, use this very small engine as a gasoline heater, and send the fresh air inlet past the engine to cool it and warm the cabin and or battery… I can’t be the only one who has thought of doing this…HONDA are you listening? Add a stainless steel muffler/ heat exchanger and you’d have a condensing heater.

The i3 is and will be a very expensive way to go EV. I’m glad we’re seeing such diverse approaches to the well-known EV dilemmas such as expensive lithium packs. This car is especially fun to theorize about, especially since it comes from a firm who stakes it’s claim on German engineering. All in, I’d say it looks kind of like a pure EV that’s had it’s ICE genset trailer built in – sans wheels and hitch. An intriguing idea I’m glad someone is trying. As a pure EV, I feel i3 will flop on it’s expensive top since it’s just too little capability for too many dollars. The small displacement genset idea works if the sheer overall weight of the car is so light that it could work. Problem is, lightness is expensive which sort of defeats the whole purpose of going with a small displacement range extender. I keep eyeing Ford’s International Engine of the Year 3 cylinder turbo as a good place to start for a range extending genset. A true multi-use car has to have a balance of size/substance/interior space and enough power to keep pace with conventional vehicles. Gen 2 Volt should have a 3cyl… Read more »

I disagree a turbo motor is overkill and toooo expensive,

Why don’t they just make a 40 mile ev range with extender?


Because a lot of people want EVs – not just PHEVs.

Right but you would already be EV 90% of the time and if your extender runs on bioethanol you are off oil as much as a pure EV.

If I recall correctly, I measured 20 kW on the energy screen when doing 87 mph on flat terrain in the LEAF. The REx might be capable of supplying up to 30 kW, which should be more than enough to sustain reasonable freeway speeds. Although, I probably wouldn’t want to cross the Rocky Mountains in the range extended mode.

That said, please don’t forget that the battery won’t be fully depleted when the REx comes online, which means that the battery will be able to supplement the power produced by the generator if needed. Additionally, I believe that the battery will continue charging, even when the vehicle is stopped at a red light, for example, which means that the battery could act as a buffer.

Hardly anyone will need 20 kW of sustained energy draw in urban traffic. Even in a more challenging topography, there is both uphills and downhills, and potential energy will be recovered on descents through regen. I think this could work almost perfectly, and with no perceptible loss of performance.

George B – I was originally thinking like you, the genset needs to be only 30kw to be a simple range extender. But BMW probably wants to keep the same performance specifications on the car with a completely depleted battery. Even if it only happens momentarily or when climing a long incline, 30kw is going to make a 2800lb car perform like a Yugo. I don’t think BMW customers would go for that.

So, a 80kw (over 100hp) engine would be required. Since they have motorcycle engines with that capability now and they can run them at the most efficient RPM to generate current, that would work well for the i3.

But I’m just speculating. Tom or Jay … any idea what the gas engine output would be?

No, there has been zero information on the range extender. In fact, other than the fact that they are going to have one and that it will be optional, this article offers the first tidbits of info on it from BMW.

Most references have been to a 600c twin-cylinder. I wouldn’t conclude that it would be 80Kw given that it would have to be a screamer (noise) to develop that power level.

While I would like to avoid unnecessary speculation, these fears are likely overblown. I drove a LEAF for nearly two years, and as one of the early adopters, alongside others, I dissected its performance in various ways. Aside from jackrabbit starts, there was rarely a moment when the car required more than 40 kW of power. Most of the time, it was below 10 kW, and even when going fast on the freeway, it wold stay under 20 kW, as I mentioned above. Keep in mind that the LEAF is significantly heavier than the i3 will be, and supposedly also less efficient. While we can only guess at the spec and design of the REx, I wanted to reiterate that the power demand expectations stated here, and elsewhere are not accurate. I believe that it’s entirely possible to come up with a REx option leveraging current BMW motorcycle engines, which would capable of supplying the i3 with adequate power for all major use cases. I’m only saying this, because I believe that some of the references and labels used to describe the REx are going a bit too far. The REx could turn out very well, and be one of… Read more »

Yes George, I concur. I also think that since Diess came out and said it would have an additional 160 mile range while the range extender was running, I think it’s much less likely the performance will be neutered while in REx mode. I could see driving 5 or 10 miles in a limp-home mode, but 160? Not a chance. It it was truly going to be an emergency-only, limp to the nearest plug range extender than they would have just given it a 1 gallon gas tank and said the extended range was 40 or so miles.

Here is an interesting article on compact range extenders for EVs


“The ICE is designed to have two main operating points: If the battery needs to be re-charged, the engine is run to deliver 15 kW (20 hp) at the crankshaft. If the battery charge is to remain high despite a fast cruising speed, the RE is taken to full load at 4000 rpm to deliver its nominal 30 kW.”

BMW may use the same type of approach.. that would be cool.. Let’s hope they do ..