BMW i3 REx In Real-World Use

AUG 19 2014 BY CHRIS NEFF 62

BMW i3 REx

BMW i3 REx

Today I got to experience the REx in the wild. What I mean by that is I actually needed it. I experienced the REx twice before but those were not when I needed it. One was driving around town and letting the battery drain low enough for the REx to fire up because I wanted to see how it would perform. The other time was a maintenance mode that the i3 runs during long periods of inactivity.

This time was different. This would be about a 100 mile trip with 90% of it being highway and the car would be full of family and stuff. Some might say 100 miles….maybe I could make it on electric alone, well nope. With extra bodies it weighs the car down and the biggest draw is I would have to use the climate control so everyone was comfortable and I don’t mean just a little πŸ˜‰ .

*Editor’s Note: This post appears on Chris’ “My BMW i3” blog.Β  Check it out here.

Off we go, I put the car in Eco Pro+ but of course right away I was asked to roll the windows up and turn the AC on so back to Eco Pro since in “+” mode there is no climate control. On the highway I kept my speed to 65mph to extend the range as much as I could. Things were looking good…I was driving well enough to do about 90 miles guessometer. I was pretty pleased with myself and began to think of i3 REx EV masterfulness where I might actually reach 100 miles in EV mode. Then one glitch, with about 30 miles left I pulled over to make another stop so the family could pick up some food. I turned the car off for about 10 minutes. Once everyone was back in the car I turned it on and range dropped to 20, I lost 10 miles just like that…I’ll explain what happened there in just a moment. With this event I really wished for that State of Charge (SOC) readout that for some reason BMW decided to remove from the US version. Our ActiveEs had it and it was much easier to determine actual range. This guessometer in the i3 is truly guessing. BMW bring back the SOC, this is the ultimate driving machine not the ultimate guessing machine.

Ok…so those lost miles…as mentioned a few sentences earlier I parked, turned the car off for 10 mins then back on and noticed the guessometer showed 10 miles less. I was not running the AC, doors were closed and it was not hot, so what gives. Well it seems the navigation is tied to the guessometer. During that 10 mins of parking I programmed in my final destination, the nav calculated hills and speed along the highway and adjusted. Confirming this…umm feature….this morning I was on my way to Tom’s i3 gathering and my range showed 92 miles…I punched in Tom’s address, chose start navigation and right before my eyes the range dropped to 77. Ok, now I stop navigation and we are back to 92 range. Not really liking this, though I get what BMW is doing, with that said please let us disable this. I looked and could not find a way to turn that off..bummer. So here is a thought, if the nav says a shorter range but I turn it off and I have more range…will the REx stay off longer or will the guessometer adjust near the end….to be determined.

Nice of Serenity to warn me but I have a REx

Nice of Serenity to warn me but I have a REx

I did take a look to see what would pop up and there we have Tom Moloughney's charger at Nauna's

I did take a look to see what would pop up and there we have Tom Moloughney’s charger at Nauna’s

Back to the story. As we drove along the miles ticked away, down to 4 left and 82 miles of electric the REx kicked in. There was a slight vibration, I felt it because I was waiting for it, my family noticed nothing. We were burning fuel, it just felt odd, I noticed no reduction in power and the AC ran fine. I did notice the battery bar start to drop below 5% or at least best I could tell. When that happened the little 2 cylinder revved up, now we all could hear it even on the highway. It was not bad but it was there. That little motor revved until the blue bar moved a bit right to reach the upside down grey triangle then it quieted down. Each time that blue bar lowered it revved back up, it was working to maintain a level of between 5% and 7%.

Again the REx was not loud, when revved up you could feel it though not bad and keep in mind an EV has no vibration so everything feels enhanced, it was odd to hear a little put put going on from an EV. Of course that sound is much better than the sound of my family complaining we are stranded.

Once off the highway the REx relaxed a bit and at stop signs or red lights turned off. We did about 16 miles with the REx and my over all kWh/miles for the trip was 4.6. Not bad for highway and AC running.

The red flag on the upper left means we won't make it on electricity alone

The red flag on the upper left means we won’t make it on electricity alone

I probably could have made it with the pure electric i3 – it has slightly better range being lighter but it would have been white knuckle driving wondering if we would make it, I’ve done that before and it is no fun. Added I’d slow down and get off the highway and turn off the AC making the trip longer and less comfortable which my family would not be happy with. There are no convenient public EVSEs along the route and that adds to the stress. When winter arrives there would be absolutely no way I could have made it without the REx, the REx did its job, it added mobile convenience as well as peace of mind.

I took a whole half gallon and paid with cash

I took a whole half gallon and paid with cash

Do I wish the i3 had more battery range….of course…but it doesn’t so the REx is a viable option. It works and with that I will be driving my EV more which is a good thing, as well as letting my family take it out on runs.

Categories: BMW

Tags: , , ,

Leave a Reply

62 Comments on "BMW i3 REx In Real-World Use"

newest oldest most voted

I absolutely love the idea of the optional Rex that BMW has introduced. Honestly, I think it should be an option on every EV. I don’t even care if it is capable of operating the car at full speed or not. At $3,800 I think it is definitely an option worth having. And I’m willing to bet with more advancement in this area, the price of a small Rex like this could be brought down to maybe $2,500. The piece of mind and convenience it brings is worth it.

I’ve read many stories about people driving up to fast chargers in their Leaf only to find the station inoperative and then having to call a tow-truck. I want to drive on electric power as much as anyone, but I don’t want to have to deal with those kinds of problems in this early stage of EV deployment. The Rex is the perfect answer to that problem.

Incidentally, the Rex would be a lot more useful if the gas tank were at least 3 gallons, preferably 4.

If a REx is an available option on every EV, then you have a gaping hole for those of us who don’t want/need it. (raises hand) Just like the gaping hole the i3 has for electric-only models.

That makes no sense.. If it is an option, then just don’t buy it if you don’t want it.

He is complaining about the space where the REx would have been. It is a potential space lost for those BEV only buyers…

It’s BMW’s choice not to use that space for more batteries. It’s not an inherent flaw of the REx or even the i3. Look at VW group’s irregularly shaped battery pack. There’s no reason BMW can’t fit more cells in there if they wanted to.

You’ll have to ask BMW why it skipped that option, and why they didn’t at least make a bin in the space. Maybe they intentionally held back upgrades for future model years.

I keep thinking that with GPS, after you enter a destination that is far away, the car should be able to run the gas motor in charge-depleting mode. It knows how much extra electricity it will need to complete the trip, and it can run the gas motor at the most efficient (or least annoying) RPM long before the battery is down to 5% charge.

The part of the story where the REx was rev’ing up to noticeable RPM’s seems entirely avoidable with smart GPS integration.

Your proposal makes perfect sense- but BMW can’t implement it without losing some perks from the California Air Resources Board (CARB). See question #2 here

Yes, I like BMW’s direction. BMW management has chosen the REX path vs. Tesla’s path of higher and higher EV range.

If it was REx option AND larger battery option then I would agree. However, at the current rate, manufacturers that offer a REx do not offer a larger battery option (they assume the REx covers this use case). Also, having a REx de-emphasizes the need for fast charging infrastructure.

I would much rather the industry move beyond sub-100 mile AER than continue to stay at this level and rely on the PHEV band-aid.

Sounds like the Nav option is good and you should get used to entering your destination when you have need to know your range. I would hope that the ‘flat road range, guessomiter’ might learn your driving habits and adjust down to better match the nav option.

I was thinking that too. If it really does estimate based on terrain, I would go with the GPS-enhanced guess every time.

If it doesn’t actually improve the guesstimate though, then sure, a SOC meter is certainly warranted.

*kWh/mile – please don’t drop the h, if the experts and enthusiasts can’t keep it straight, the general public will have a hard time understanding this basic concept.

Fixed…thanks for catching the error

4.6 kwh/mile would get you very far.

Sounds like you meant 4.6 mi/kwh

Otherwise, great article! I’ve been eager to hear more about REx performance.

I did some searching and found roughly 2-3x more inventory of BMW i3 than Cadillac ELRs in several US cities. The best price I found for the REX was about $42.5k, a $2500 premium over the cheapest i3 BEV listed.

Looks like slow sales and excess inventory is making some dealers drop prices considerably, which can still be useful to negotiate with your local dealer.

How about “$35,000″…OFF – (Yes, that includes a fed/state credit). 2014 Volts are also looking like they are getting 2X-3X as much off an already lower price. GM’s on a mission (like with a zero on the side, and everything).

Thanks for the write-up, Chris.

They need a bigger gas tank. For the $4K price of the REx, they could have added $4K more batteries and got the same amount of additional range. OK, the Rex does allow you to refill fast which more batteries wouldn’t but who wants to refill every 50 miles?

“Then one glitch, with about 30 miles left I pulled over to make another stop so the family could pick up some food.”

In my Leaf, that would translate to “We looked up a charging station on and pulled over for something to eat”.

So yeah, you probably *could* have done it all on electrons, if you weren’t trying to review a “real life” usage of the i3’s REX. πŸ™‚

They likely couldn’t…. they stopped for 10 minutes and the i3’s QC port has no charging stations on the East Coast AFAIK.

But yeah, in a Leaf you’d stand a fair chance along many major highways, to time your food-pickup stop with a quick ChaDeMo, and Voila.

Either way, both work. We’re all family here πŸ™‚

I always laugh when I read the “just stop for a quick charge and get a bite to eat”. That’s exactly what I DON’T want to do…load up the family, hop in the car, hit interstate speeds only to stop a scant 65 or 70 minutes later for 20+ minutes. We stop for about 4-6 minutes now maybe once in a 2 hour trip (bathroom break)…I don’t need to “eat” an hour after I leave home. One thing that would definitely do is “eat” any gas savings I was getting by driving electric.

yeah – assuming that a station existed. And assuming it was the correct standard (Chademo, tesla, ASE combo) and assuming it wasn’t in use, and assuming it wasn’t broken.

I just completed a trip in Europe (Germany to Norway) with 10 CCS charging stops and none were broken. On the other hand I’ve encountered a broken one once and with an hour at the nearby Type-2 AC I got enough range to make it to the next one (this was in Netherlands with Fastned).

In Europe do you have a problem with “scrappers” stealing copper like we do in North America?

I currently drive a 2012 Volt and have been thinking about replacing it with an i3. I’ve driven the i3 twice; once in Germany and once here in NH. I love the BMW feel and performance. I’ve gotten to like the quirky i3 looks but just don’t get the puny added gas mileage that the Rex brings, especially when compared with the Volt. In the Volt I get 50 electric miles and about 300 gasoline miles. Anyone else struggling with this?

Well… it’s the difference between a PHEV and an EREV.


The mindset is that >95% of the days you don’t even need it, so why bother having a full-fledged ICE system in your car?

That’s certainly true Assaf. For me personally, when I do need the range extending capabilities, I need to go through mountain passes that cause even the Volt’s larger engine to work fairly hard.

Yup… it’s not a one-size-fits-all game, at least not until BEV tech+infrastruc. matures much more.

I’m guessing you don’t have any optional insurance of any kind (ie. house, life, term).

An EREV is a type of PHEV.

That being said, the Volt is an EREV. It is fully electric until the battery runs out. It is symantecs that it uses the electric motor as a carrier afterwards to transfer mechanical energy to the wheels in -some- conditions to maximize efficiency.

The major differentiator to me between EREV and PHEV is that a standard PHEV will use the gas engine if you floor the accelerator or go at high speeds. An EREV will not.

Outside of CARB and visitors to this site :), I am not sure who cares about these distinctions–certainly not the general public who is cross-shopping models–I think they would see it the way Ray positions it.


Do you mean an EREV vs. BEVx?

Volt is EREV by defintion (regardless of what people think about the extended range mode) b/c GM invented the phrase EREV.

And how you extend that EV range is irrevalent whether you have mechanical linkage or not.


Ray, I drive a Volt and agree with Tom M., or any other i3 REx owner, that while more would be nice, the i3’s gas tank should not be a deal-breaker.

You are talking about how many trips per year, where you go 120-140 miles before your first fill, and then another at ~180, if you are going that far, and then 230, etc. My “long” round-trips are all 150-200 miles, so it doesn’t matter to me. On the flip side, you mention NH, a place where the Volt spends half a year as a 20-30 mile electric car. If you are more than that daily, I would strongly consider the i3.

FWIW, My biggest issue is rear access (exit), and windows, for the kids. That, and something bigger. Still in the woods, looking.

Struggling with this too Ray (also have a Volt now), whenever I discuss i3 rex use cases with my wife she always responds with “Tell me again, why we wouldn’t just get another Volt?” – we both appreciate the ZERO, that’s ZERO, worry or hassle the Volt brings to the table (assuming you can live with 4 seats and commensurate cargo space). Even an i3 rex can become a 50 mile (or less) EV in Winter which has you back to tapping in to the gas reserves…but don’t drive too fast..or up a hill for any distance. At the end of the day, the i3 Rex is still predominantly in an-town car or suburban “long commute” car. If your commutes are reasonable then the regular i3 (sans rex) starts to return to the table as a contender.

Ray, the i3 had a very specific design ideal, and BMW calls it a mega-city car.

If -you choose- to try and make it more than that, you can try to use the Rex, but the ICE’s purpose is to cover things like extreme weather, etc. BMW’s position is that you wouldn’t want to use the i3 for family transport 200 miles to visit family, it is purposely Not the car for that duty.

It is Very good at what it is designed for, (below 60mph suburban sprawl) but definitely not as a replacement for the Volt, for single-car families, etc. It can be Done, but not without trade-offs and willingness to adapt to the new no-gasoline-ever paradigm. The Volt, with its many Other compromises, is the only vehicle that behaves as every car you’ve ever owned, IMO (ELR if you can use a coupe).

That was Its design ideal. And unlikely to be copied/improved upon as the competition, and even GM, is treating it like a ‘market failure’ even though the Volt’s owners like it very much as it is Very good at what it does.


I don’t think the BMW i3 REX gas mile range is a big issue. Carry a 2 gallon tank of gas tank, and fill up in 2 minutes if needed. A 2-3 minute stop at gas stations every 200 miles is not too bad to work around the small gas tank size, courtesy of misplaced govt. regulations.

Haha, love this sentence:

“Of course that sound is much better than the sound of my family complaining we are stranded.”

You got it right πŸ™‚

Thanks for sharing!

Range is precisely why a fast charging network is so important.
For a <100 mile range EV, it is not practical to rely on L2 EVSE that only give you 25-30 miles per hour charging.
Imagining that your family will love driving for an hour then charging for two will only work for a limited number of families (not mine!)
In my area we have a single L3 EVSE – count em – one. Its in a dealership so is closed when they are.
Tesla has the right idea – add them on the highway network at places where you can kill 20-30 minutes. Making them free is even better – but sadly they are only free for Tesla customers so my Leaf stays around town.

I completely agree. Luckily in parts of Europe it’s getting set up already. Fastned in Netherlands has already a decent coverage and TheNewMotion is adding some too. Same with Clever in Denmark.

For people complaining about the Hold-mode-less U.S. REx being positively dangerous (to the point of reporting it to NHTSA) when used on long climbs with a depleted battery, see, where some owners are talking about starting a class-action lawsuit.

This is exactly the problem many people were anticipating, when they castigated BMW months ago for crippling the U.S. REx, just so they could qualify for the full $2,500 California credit (as reported by, they failed to meet the BEVx standard and only qualified for the TZEV one, thus negating most of the justification for crippling the car with no hold mode and a reduced tank size in the first place.

Anyone who tries to use the car for trips that involve serious climbs at freeway speeds when the battery is depleted is going to come face to face with this issue. Since most of the major metropolitan areas in California where these cars are likely to sell have mountains in or near them, unless BMW adds a hold mode this is going to seriously impact what are already limited sales of a car perceived by many PEV supporters as too expensive for its range.

Besides the $2500 rebate, the green HOV stickers in CA were also exhausted when BMW launched the i3 in US. I hear, those green stickers have been increased to 40000 now. So, hopefully BMW can go back to increasing the tank size and making the REX more powerful.

PS: SHows what wrong regulations can do πŸ™‚ The lawsuit should be against CARB, really.

Not exactly. The # of Green stickers had been capped at 40,000, but that was increased to 55,000. They’re going quite fast, as reported by and other sites. I’ve never been a fan of allowing SOVs into HOV lanes regardless of their power source, but that’s the law until 1/1/19. As to CARB’s regs, I understand why it was written the way it was, and have no problem with the BEVx category; my problem is that BMW doesn’t offer customers the option of a hold mode or not. If you’re just going to use the car for running around the city on short, flat-ground trips, no hold mode works fine. But for people who want to use their i3 w/REx more expansively (and if they’re buying/leasing a car worth $45-$50k, I expect most would), the lack of the hold mode and the tiny tank are nuts.

The BMW i3 Rex is just a city car. I was very interested in it until I found out that the gas tank would hold less than 2 gallons of gas and it wouldn’t have a hold mode (mountain mode). I have a Nissan Leaf and next year August my lease is up. I am seriously considering the 2016 Volt. In my opinion the BMW i3 Rex is not a range extender. It is there to relieve stress and anxiety. I am glad that BMW made it. It doesn’t fit my needs but there are a lot of people who love it. There were too many times I had to come home with the Nissan Leaf and pick-up my Chevy express Van because the leaf was running out of Juice. I learned hard way that the leaf is not for me although I enjoyed it most of the time. Every Auto Manufacturer brings something different to the table that will advance the cause of electric mobility. So Cheers to BMW and every one else in the Auto manufacturing Business who put out or is coming out with a car that has a plug.

Living at the base of the Sierra Nevada foothills completely excludes the i3 REx from my list of upgrades over my current Volt for that very reason. I need more power once EV range is exhausted and I can’t afford a Model S.

The BMW i3 REx is eligible for the $2500 CA rebate according to this page –

So there are probably some people in CA that are happy with BMW for “crippling” the REx. Most others would prefer the original version, myself included.

“they failed to meet the BEVx standard and only qualified for the TZEV one”
This is completely wrong. I hope you guys didn’t launch a class action suit on this basis.

The BEVx classification only applies to ZEV credits. It has nothing to do with the $2500 rebate nor with the HOV sticker’s TZEV status (which Inside EVs took from here).

The following executive order on May 1, 2014 shows the i3 REx (Engine Family Number EBMXV00.613R) qualifies for Type IIx ZEV status (see page 2 of the following document):

If you do a bit of googling you will find Type IIx ZEV = BEVx:

So the i3 REx certainly qualifies for BEVx status and thus BMW has absolutely no incentive to make changes to disqualify it from such status.

Thanks for sharing Chris.

It is helpful to hear real EV drivers share their experience with the new drivetrain concept.

Thanks for posting your story, Chris. I currently own a Volt because of the many long trips I make and my unpredictable schedule. Your experience illustrates the design idea behind the REx and it appears to have worked perfectly. Kudos for choosing the right car for your family’s needs.

I loved the article. I’m left wondering why the car needs to stay at between 5% and 7% charge. Obviously BMW has it programmed that way, but why? I would think the smartest thing would be for the REx to run at the ICE premium performance level and run until it has charged as much as the owner likes. Have the car’s current recharge process be a fall back for those that are unsure of what to do.

This is the first positive impression I’ve had of the i3 Rex. Thanks for the story.

Two engins and one that needs a LOT of service.
Still burning gas is bad.
Larger batteri and DC charging solves that problem.