BMW i3 REx, BEVx Restrictions And My Plea To CARB To Unleash The REx


Today, This Is How CARB Loosely Defines BEVx

Today, This Is How CARB Loosely Defines BEVx

“Our calendar this weekend is clear,” my wife, September, informed me as I walked through the front door, returning from work. “We should take your shiny new toy to Tahoe and go hiking.” I had just parked our new BMW i3 in the driveway. It had less than 1,000 miles on it.

My mind raced. We had traded in our ActiveE and she knew that didn’t have the range to make it to Lake Tahoe. She also knew the i3 had a gasoline range-extending engine. In less time than it is taking me to type it all out, I thought about explaining the relationship of kinetic and potential energy, how those are subservient to first law of thermodynamics and that the i3 had a whooping 35 HP engine. Then I thought about how to really put that discussion into the proper context, I’d have to explain inane design by committee politics. In the big picture, I definitely married up in the gene pool, but I knew her eyes would gloss over as soon as I used gravity and velocity in the same sentence. All I could muster in response was, “Uhhh.”

Her eyes pierced the slack-jawed look I was wearing. “But the new car has a gasoline engine in it,” she said. I wasn’t sure if she was asking a question or making a statement.

“Yeah, it does, but…” I fumbled for the most economical response I could think of. “Remember the little Honda we had when we first got married? That.” Over the years the severely under-powered Honda was often referred to derisively when discussing road-trips. She knew I meant that the i3 couldn’t tackle a mountain. Maybe I had conveniently forgotten to mention that when we talked about buying it.

“What?!,” she exclaimed.

I knew I was in trouble.

An EV for the Masses. Almost.

Electric Vehicles (EVs) have been lurking in the shadow of the Internal Combustion Engine (ICE) cars for decades. Some EV advocates would have us believe the time is ripe for EVs to become mainstream. Sales figures make it clear that EVs are hot in many regions in the country. It’s pretty clear that EVs are here to stay and gaining market share. But that doesn’t mean EVs are ready for the heartland.

Two things need to happen before EVs truly go mainstream. The first is sufficient infrastructure needs to be deployed so those drivers who do not control their parking spot every night can still charge their car; that’s a topic for another day.

The second thing that needs to happen is to engineer into the EV enough flexibility so that the potential buyer has confidence the car can fulfill all of his or her needs. Not most. All. This is especially true if the potential buyer is buying a car that will be their only car.

It’s not about range anxiety; not exactly, anyway. And it’s not about just slapping in a bigger battery. The driving public isn’t going to embrace a Battery Electric Vehicle (BEV) until adding energy is as thoughtlessly and effortlessly accomplished as is adding energy to an old-fashioned ICE-mobile.

The Battery extended range Electric Vehicle (BEVx) changes this. Almost.

i3 rex

A City Car? The BMW i3 poses at Donner Summit, the highest point along Interstate 80 in California at 7,228 feet elevation.

What the Heck is a BEVx, Anyway?

When people think of a Plug-in Hybrid Electric Vehicle (PHEV) they may think of a Chevy Volt or a Plug-in Prius. PHEV’s typically have 40 miles or less of All Electric Range (AER) and have what one might call a “normal-sized” engine that is connected to a transmission which then mechanically drives the wheels when the battery is exhausted.

This is not how the BEVx works.

The BEVx classification is differentiated from the PHEV, like the Volt, by virtue that the Auxiliary Power Unit (APU) is not mechanically connected to the driving wheels, rather its purpose is solely to generate electricity to extend the AER beyond what the manufacturer engineered in. For an EV to be classified as BEVx under California Air resources Board’s (CARB’s) official designation, one important factor is that the available range while operating with the APU must be less than or equal to the AER. There is another important distinction of the BEVx class, which we will discuss in a moment.

The BEVx is essentially an all-electric vehicle but the APU and on-board generator combine to extend the AER once the battery is depleted. Taken together, the APU and the on-board generator are called the Range Extender, or REx.

As mentioned above there is an additional important aspect the defines CARB’s BEVx designation — the APU is constrained by regulation to turn on only when the battery falls below 6.5% State of Charge (SOC), shutting off once its SOC rises above 6.5%. This artificial constraint on how the APU manages the SOC means that a BEVx class car comes oh so close to being the only car a driver may ever need, but it fails for one important use case.

This is a travesty for anyone who wants to see the electrification of the modern automobile, because it just doesn’t have to be this way.

The APU has seemingly conflicting requirements to be as small and light as possible while also having sufficient power so that the car can be useful. The logical manifestation is an APU with sufficient power to propel the car at freeway speeds. But a problem arises when freeway speeds need to maintained while simultaneously making sustained elevation gains.

BMW’s i3 Rex is the only car manufactured to the BEVx spec to date. For the i3, 6.5% SOC is 1 kWh. It has been shown that 1 kWh is equivalent to about 750 feet of elevation gain. It follows that when the REx kicks in, you can climb 750 feet. If you need any more than that, you going to be doing something that is loosely referred to as Turtle Mode.

Interestingly, it has also been shown that if the REx were allowed to turn on on at a higher SOC than 6.5%, the i3 could conquer any pass in North America.

To propel the car at freeway speeds while simultaneously climbing a significant grade would require a much more powerful (ergo larger and more massive) APU. Sure, the APU could be 200 HP, but this would be the motoring equivalent of driving in a thumbtack with a sledgehammer, as the i3 only requires 35 BHP to maintain 80 MPH on level ground.

In order to climb a hill at freeway speeds, any BEVx will need to dip into the battery’s stored energy; if your drive includes a climb, it has to come out of the battery.

This is where CARB’s BEVx regulations are problematic.

For the specific case of the i3, if you never plan on driving anywhere that might include an elevation gain of more than 750 feet, fret not. It is truly a transitional vehicle bridging the gap from ICE to BEV and has all the spontaneity and long-range capabilities your family may need. As long as you keep its diminutive tank filled, you’re golden.

But if not, not.

The Abysmal Failure of CARB’s BEVx Classification

Before we go any further let’s be clear. CARB’s BEVx regulations impact any car that ever will be manufactured to this specification, and not just in California. For the BMW i3 REx, for example, the BEVx limitations apply to every vehicle sold in North America. Including Canada. The BEVx is a great way to assuage range anxiety if you’re considering an EV. But if you want your shiny new EV to be the only car your family needs, proceed with caution.

Some say the BEVx was never intended to be a car with mass appeal that can be driven like any ICE-mobile. But I ask, why not? Actually, what I usually say is “Why the hell not!” while shouting and pounding the table with my fist. I digress.

I believe that the BEVx class of cars represents the bridge from plain ol’ ICE-mobiles to pure electric that will finally allow the public to embrace EVs without looking back. Except.

The exception that we’ve been discussing is what engineers call a “corner case.” In this situation the “corner case” refers to those people who require a car to maintain freeway speeds over sustained elevation gains. Let me provide an example using BMW’s i3 (as the only BEVx on the planet) to demonstrate my point.

California’s San Francisco Bay Area lies at sea level and the drive east to Lake Tahoe follows the Sacramento river, never gaining significant altitude for about 50 to 100 miles, depending on one’s starting location. Continuing east past the capital of Sacramento begins what is at first a gentle climb into Gold Country. Assuming the route is along I-80, the slope increases significantly past Gold Country until Donner Summit (elevation 7,228 feet) is reached 95 miles east of Sacramento.

It’s simply not possible to drive from the SF Bay Area to Tahoe in a reasonable amount of time with the US spec’d i3 without using the REx. Of course if you have the patience to charge every 60 to 80 miles, you can drive your i3 from the Bay Area to Tahoe or anywhere else for that matter. But that is impractical, even with with so-called fast chargers.

I drive the BMW i3 from my home in Mountain View, California to Donner Memorial Park in Truckee. The state park is placed at one of the sites where the ill-fated Donner Party settled for the winter in 1846. The snow that winter was as high as the memorial behind the i3.

I drive the BMW i3 from my home in Mountain View, California to Donner Memorial Park in Truckee. The state park is placed at one of the sites where the ill-fated Donner Party settled for the winter in 1846. The snow that winter was as high as the memorial behind the i3.

I’ve asserted that such a drive is simply not possible in a US spec i3 without becoming speed limited. How speed limited is a function of the slope of the road as discussed in this post. But what would happen if CARB’s artificial limitation on the BEVx was removed? It just so happens that the European manifestation of the i3 is a perfect comparison tool.

To learn how the Yankee version of the i3 compares to it’s schnitzel eating cousin, I’ll take two test drives. The first I’ll call The Apple Pie Test and the second The Lederhosen Test.

The purpose of these tests isn’t to prove you can drive an i3 to Tahoe by taking logical opportunities to charge. You can. It’s been done. The purpose is to prove the assertions the US-spec’d i3 REx is hobbled as compared to its European counterpart and second (and more importantly) that an i3 REx is more than a great EV; it has potential to be the only car you need.

The Apple Pie Test

The Apple Pie Test is simple: try to “REx it” to Tahoe and see how far you get. (Oh, I’ve made REx a verb, but the Oxford dictionary hasn’t caught up yet.) Since this is my test, I get to make up the rules. The rule is simply to take a BMW i3 REx as CARB intended it to be delivered to the public and drive it along I-80 until the car becomes speed limited.

To do this test I left the Benicia, California, CCS fast-charger with 90% SOC and a predicted range of 60 miles. The drive toward the Tahoe region is essentially flat for about 63 miles along I-80, then the road climbs into the Sierra Nevada mountains. I planned this section of the drive to be all electric until such time I hit the foothills. The goal was to set the cruise control to the posted speed limit (65 MPH) and simply keep driving powered by the REx until the car became speed limited.

At first the speed limitation was subtle. I started to suspect the car was speed limited at around 800 feet elevation (750 gained); “flooring it” to coerce an increase from 65 MPH with the cruise control set, I achieved about 67 or 68 but no more. But by 950 feet elevation gain the effect was no longer subtle. Not only could I no longer keep pace with traffic, but was feeling very vulnerable and searching for an exit in earnest. On some of the steeper portions of that section I was under 55 MPH indicated with traffic whizzing past at 70 MPH and above.

The BMW i3 was clearly speed limited on this section of road after leaving Sacramento powered solely on the REx

The BMW i3 was clearly speed limited on this section of road after leaving Sacramento powered solely on the REx

This photo was snapped moments after the previous photo

This photo was snapped moments after the previous photo

Anyone who has owned a BMW for very long can tell you that the speedometers are optimistic by at least 5%, if not 7%. So, that 58 MPH in the photo is closer to an actual speed of 55 MPH. On steeper section the i3 would have been limited to less than 50 MPH; this has been corroborated by legions of i3 owners who have tried similar drives around the world.

This demonstrates that you can’t just REx it to Lake Tahoe in an i3. Luckily, there is a CCS fast-charger in Sacramento, so moments after the above photos were taken I turned around and headed straight for it. With the miracle of regeneration the i3 got its SOC back up to a respectable level and I REx’d it all the way back to that CCS charger with no issues.

Hold Mode and Coding

The Lederhosen Test requires the use of a feature known as “Hold Mode”, which is on all Euro-spec i3 equipped with the REx; perhaps even all such cars destined for anywhere in the world outside of North America. What Hold Mode does is engage the REx (or more specifically in CARB-speak the APU) to maintain the battery SOC. Sounds a bit boring and perhaps it is.

The fact of the matter is, US spec’d cars have Hold Mode; the car’s onboard intelligence switches it on automatically when the battery SOC reaches 6.5%. The European version of the car also will switch on Hold Mode automatically when the battery SOC reaches 6.5%, but the European version also allows the driver to manually engage Hold Mode whenever the battery SOC is 75% or less.

The difference in the US spec’d car and its European counterpart is perhaps subtle, but as we shall see, the difference means everything if you require a car to maintain freeways speeds and gain significant elevation simultaneously.

What is important here is to understand that the US-spec cars do in fact have the European-spec Hold Mode programmed into the car. The menu option that allows the driver to engage Hold Mode manually is simply hidden from the i3’s iDrive menu. For someone skilled in the seedy underbelly of the BMW tuner world known as “coding,” enabling this hidden feature in the iDrive menu is trivial. To be clear, this practice is most likely frowned upon by both BMW NA and CARB.

To satisfy scientific curiosity, I “coded” my i3 to enable Hold Mode, Euro-style. On to the Lederhosen Test!

The Lederhosen Test

As noted in the Apple Pie Test, as soon as I became speed-limited near Auburn, I turned around and returned to Sacramento and specifically to the CCS fast-charger. After plugging in and after i3’s SOC had reached 90%, I once again set out along the same route toward my final destination in Truckee, California, near Lake Tahoe. Hold Mode is only available if the SOC is 75% or less, so after leaving the CCS charger I drove the first 12 or 13 miles all electric.

The CCS fast-charger in Sacramento in Sacramento is at an elevation of 50 feet.

The CCS fast-charger in Sacramento in Sacramento is at an elevation of 50 feet.

The only difference in the two drives was the SOC at the bottom of the hill and manually engaging Hold Mode. This simply means the REx was used in the Apple Pie Test to “hold” a 6.5% SOC but on the Lederhosen Test, it was used to “hold” a 75% SOC.

The CCS fast-charger in Sacramento in Sacramento is at an elevation of 50 feet.

Engaging Hold Mode at 75%. Note there are 88 miles to my destination, with 39 miles of all-electric range available.

With Hold Mode engaged, as one drives the i3 the REx keeps the battery SOC constant at the level set. If driving conditions are such that the REx (due to its limited power output) cannot keep the battery SOC maintained, then energy from the battery makes up the difference and the battery SOC falls commensurately.

It was the perfect day for such a drive; the sky was a beautiful blue, the temperature was in the mid 70’s, the traffic light and SiriusXM’s Classic Vinyl accompanied me. During the drive I took pictures of the i3’s displays every 1,000 feet of elevation gain, but suffice it to say that the battery SOC slowly dropped in an expected and predictable fashion as I glided up the mountain’s slope. Not once did the car fail to maintain the 65 MPH that I had set on the cruise control. No one from The Guinness Book of World Records greeted me when I arrived at Donner Summit, but I’m pretty sure mine was the first i3 to make that drive using the REx.

The i3’s other “fast charge” port. I don’t like to use this method of adding energy, but sometimes a guy’s gotta do what a guy’s gotta do.

The i3’s other “fast charge” port. I don’t like to use this method of adding energy, but sometimes a guy’s gotta do what a guy’s gotta do.

The i3, with Hold Mode engaged, used a mere 31% (75% at the bottom of the hill less 44% at the summit) of its SOC to gain nearly 7,200 feet of elevation.

The i3, with Hold Mode engaged, used a mere 31% (75% at the bottom of the hill less 44% at the summit) of its SOC to gain nearly 7,200 feet of elevation.

In simple terms, one can think of it as if the REx’s power output is used to propel the car forward, the battery’s power output is used to climb the hill. By using less than a third of its battery to gain those 7,228 feet, the i3 REx is obviously capable of much more. In this post I asserted that the i3 with the European-style Hold Mode was probably capable of summiting any road in North America. After making the drive over the Sierra Nevada’s I-80, I believe that point has been verified.


The i3 REx with the European-style Hold Mode is more than capable of conquering Donner Summit simply by engaging the feature at the beginning of the climb and keeping the tank filled. The US spec i3 REx is not. But the implications are far greater than this.

The entire thesis of this article is much larger in scope than “can BMW’s i3 make the drive to Lake Tahoe.” The thesis is much more than the car or the corporation. It’s about an idea. A brilliant idea.
It’s about a transitional electric vehicle that the public can embrace without looking back, without asterisks and without range anxiety. The embodiment of that transitional electric vehicle is the BEVx class.

The corner case I tested in both the Apple Pie Test and the Lederhosen Test, that the i3 is fully capable of, may be an inconsequential corner case for the majority of owners worldwide. But it is a legitimate use case and one that the many buyers consider. And the public makes purchasing decisions based on the corner case, especially if it is their only means of transportation.

Until such time that adding energy to an EV takes as much thought and effort as adding energy to an ICE-mobile, technologies like the BEVx are going to be required to get the public to embrace electric mobility. The infrastructure for BEVs just isn’t there yet, so the car that best fills the role of “being transitional” is the car that will finally allow the public to embrace zero-emissions vehicles and drive the maximum number of zero-emission miles.

The BEVx addresses this issue. To date only one car is made to that standard. It’s a brilliant piece of engineering. Yet that brilliant piece of engineering is emasculated by regulations imposed by a governing body that should be championing it.

I’m surprised that Sir Isaac Newton hasn’t leapt from his grave and set his hair on fire.

If removing the restriction on the operation of the APU is not made, the genius of the BEVx classification will never bear fruit. That’s because even though the average driver does less than 40 miles a day, they also want the flexibility to take their car wherever they want, whenever they want. For this reason, PHEVs are about as “electric” as the general public is willing to go.

Once the current limitation of the APU software managing the SOC is understood by the public, the public will eschew the BEVx classification for PHEVs, such as a Volt. While that may be a better choice for the environment than, say, a Camry, the Volt driver will not be able to drive as much on electricity as if he bought a BEVx, such as an i3.

That’s why I’m writing; to beg CARB to Unleash the REx. It’s been said that the PEHV is the gateway drug to a pure BEV. If that is so, the BEVx has the potential to be crack — instantly addictive. Make it so.

Facts about my trip from Mountain View -> Truckee -> Mtn. View

  • Left home with 100% SOC
  • 528.2 miles round trip
  • 246 miles on REx
  • 6.6 gallons of gas purchased
  • Ended trip with about ½ gallon more gas in the tank then when I left
  • 4.1 mi/kWh
  • 4 CCS charging sessions totaling 62.8 kWh
  • 0 Level 2 charging sessions
  • Arrived home on the REx (6.5% SOC)

Categories: BMW, General

Tags: , , , , ,

Leave a Reply

99 Comments on "BMW i3 REx, BEVx Restrictions And My Plea To CARB To Unleash The REx"

newest oldest most voted

OK, I get it, you’re a modern day adventurer. We all hope your fate on the summit doesn’t mirror the Donner Party’s. For half the price of your Teutonic adventure sled, you could get a Prius PHEV. Fill the gas and battery and the range is ~550 miles.At similar speeds and driving style you’ll get ~70 MPG round trip, and you’ll actually be able to make the round trip, and not die of old age.

David Murray

And for a fraction of the price of a Prius PHEV, you could buy a 1996 Honda civic from a used car lot and drive that. Point is, the cost of the vehicle isn’t everything.


Yeah he could have, and then he’d experience the joys of electric driving 1/5th of the time, and 100% of the time he’d have the handling and acceleration of a Yugo.


LOL +1

Willy F

There is probably nothing more cynical to this movement than the Prius Plug In. I wouldn’t be surprised if driving it caused more people to dismiss the whole idea of a plugin, or EV future.

LOL + 2


BMW will put the Euro hold mode after a family gets killed in limp mode and sues. Or the dealers could warn the customer’s in writing that they acknowledge a performance drop. Yes, other cars that are cheap can’t climb mountains but no one would expect a BMW to fail or limp ever….

David Murray

I actually do not understand the purpose behind the CARB rules on hold mode. I sort of get the idea behind the smaller gas tank. They want to make sure people buying these cars are driving them on electric and not just using them to get carpool lane stickers. It would be a hassle for somebody to buy an i3-Rex and drive it purely as a gasoline car because they’d be buying gasoline every day.

But how is the lack of a hold mode going to affect somebody? I mean, if they have no intention of driving in EV mode, they’ll just wait for the battery to run down and then drive on gasoline every day. What purpose does it serve to keep people from having a hold mode?


Agreed. It’s just stupid.

The gas tank rule is also a bit dumb in that it too will hold back EV adoption as more automakers make similar drivetrains, but I get it.

I really think the range extender has huge potential. Once the market is big enough, they will get commoditized and produced for ~$1500 each.

Lindsay Patten

Perhaps I can flip the question around. Should CARB give the i3 more credits than the Volt just for having a smaller gas tank?


BEVx cars, like the i3 get more credits than PHEV40 cars, like the Volt.

If BMW would settle for just getting PHEV credits, they could enable hold mode.

I do hope this BEVx restriction on hold mode is lifted however, for all the reasons mentioned in the article.

The small gas tank will cripple the car enough to meet ARB’s objectives, and more will be sold if they could safely climb grades.



The lack of hold mode will force more overall miles to be driven on battery power…


If the purpose of the rule is to give right wingers a good example of how government agencies never gets things right, CARB has definitely succeeded.

Tony Williams

I would suggest CARB made a mistake by extending ZEV credit status to BMW for a gasoline burning engine.

Further, I suggest that BMW failed to install a large enough gasoline engine to actual power the car.


yep ,the best so far.I have a Leaf same range but no motor .man it would be nice to have a rex .next car,or 40 kilwatt battery or another it great to kick gas!


Can you please tell us how you enabled “HOLD” mode?

Lindsay Patten

In my view, it would make more sense to “beg” BMW to offer the European spec i3 in North America. The fault is not with CARB, it is BMW that has chosen to sacrifice capability for more CARB credits.


You can’t just expect a company to make money losing decisions on purpose.

Those credits are worth a lot, whether you buy them from someone else or pay the fine for falling short.

The blame is entirely with CARB.

Lindsay Patten

My understanding is that the BEVx category was basically negotiated between CARB and BMW so it’s not like BMW just designed to what existed. It negotiated extra credits in return for measures to ensure that the vehicle wasn’t just used like a Volt.

CARB offers a certain number of credits to cars like the Ford Energi models that go 20 miles all electric. With hold mode kicking in at 25% charge the i3 with hold mode on would perform basically the same as the Fords, why should CARB give more credits to the i3?


The difference is that you would only bother with the hold mode if you had a long way to go.
For most journeys you would not need to so would not switch it on.

So for umpteen journeys of 20-60 miles or so the i3 would do more miles on electric than the Ford and not need the Rex.


I’ve made a similar argument before. It’s easy to point the finger at CARB, but the BEVx category was designed hand-in-hand with BMW. BMW got what they wanted (BEV credits for what would have been classified as a PHEV and also not allowing the Volt getting any piece of that pie).

BMW can immediately enable the European hold mode tomorrow if they really wanted to. CARB is not stopping them from doing so. It’s just that the cars will get counted as PHEVs instead of BEVx.


I’ve driven my Volt from LA to Tahoe, in the dead of winter, with the cruise set at 75-80 when possible, without any problems whatsoever. For all intents and purposes it was a normal “car” trip, no compromises in any way, either in comfort or performance. Yet during my daily commute of 70 miles RT I use no gas at all. Truly the perfect vehicle


Corner cases by definition are outside of the normal use cases, so this is something that may affect some users at some point.

Given that there is a way for the user to enable Hold mode, I don’t see this as a fatal flaw, but something that can be addressed by enlightening the user to enable it.

In time, owners will learn about the US REx flaw and will enable the Euro Hold mode.

BTW, does this “coding” have to be done once or every time the i3 is started?


I don’t know how much extra gradated incentives would cost in administration.
Having on/off qualification for incentives tends to lead to daft results and compliance cars.

If the aim is to encourage non-petrol driving then something like variable incentives, with every mile of AER credited would seem likely to be helpful.

Ivo Aroso

how many electric cars would bmw need to sell to achieve the demanded CARB credits?

given the fairly high percentage of sales (relative to ICE sales) they currently have, could they achieve that number without the extra credits that crippling the REX is giving them?

(i’m not from US. i do not fully understand how this CARB/ZEV credits works)

Tony Williams

The credits for CARB-ZEV are public, and are published after 30 September of each year.

BMW is in their first model year (2015) of required compliance. They have credits from their fleets of previous MiniE and ActiveE cars.

They could quite possibly meet all the regulatory issues without their hybrid i3 at all. I don’t know.

But, I do know that those Zero Emission Vehicle credits are extremely valuable (Tesla has earned over $100 million selling those credits), so BMW has negotiated with CARB to produce a car that burns gasoline in very strict circumstances in exchange for those credits.

BMW is the only company that receives credits in such a manner. They stand to make a LOT of money selling the credits.

That means, no change to the cars that CARB doesn’t approve.



Unless I missed it, you left out some important details/factors in your “Lederhosen Test.” Were you driving solo, and how much additional weight over the i3’s curb weight did the i3 carry (weight of driver and cargo? Also, how great of an affect would carrying four American-sized adults and some luggage have on the i3’s ability to make it up to Donner Summit? Let’s say 800 lbs is the weight of four adults and their luggage. Would such a fully loaded i3 be able to pass the Lederhosen Test?

Thanks for the great article! 😀


Temperature would presumably also have an effect.
If it gets cold batteries loose much of their oomph.


Trying to have your cake and eat it too. Carb purposely defined hard goals to encourage it to be mostly BE. Want to get up a mountain and meet the specification? Put a bigger battery in it. Have more range. A tesla model s can do it.

Don’t like the restrictions? BMW could have made the i3 not conform to the spec. Then it could turn on the engine sooner, but you loose the benefits CARB provides for a BEVx. Can’t have your cake and eat it too.

ICE can do it. BEV with long range can do it. Doesn’t sound like a problem.

It is quiet shocking that the CARB does such a sabotage of the i3 and that BMW agrees on that. From the start the i3 was internally sabotaged by the suicide doors, the ridiculous gas tank and only 4 seats. Now we have this weird hold SOC restricted at a mere 6%. Well go ahead without refrain, add the communicating tank and the code change and lets hope the hypothetic i5 will come as a true sedan with a normal tank and of course total user freedom on what the Rex does even at 100% SOC if he wants to use it as a generator for his house or whatever else. This hold mode sabotage makes me think of the EV mode switch on the Prius II that was also sabotaged only on the US cars. Back then I contributed trough my yahoo gridable hybrids group to spread informations on how to install it like on my own original Belgian Prius II. More car manufacturers should be proposing sedan with the i3 type system but of course not the sabotage version and with a normal tank. It could actually be that Toyota ultimately does that because they now have a… Read more »

Great article, John.

Tony Williams
Well written piece with an intriguing dilemma. Of course, the simple answer is that there is no one correct answer. If BMW wants Euro spec “hold mode” in Califonia (and let’s be clear… this is not a USA thing, but a California Air Resouces Board – CARB issue), they can do that tomorrow. No rule changes required. Millions of Americans can buy the car that way. The world is saved. The car just won’t be classified under the CARB “APU” rules and ZEV credits. Obviously, it’s super important for BMW to get those credits, because they are worth A LOT OF MONEY. So, instead of doing what is best for you, the consumer in mountainous California, BMW is doing what is best for them. And, they will likely continue to do so, unless the rules can be changed to meet BMW’s objectives. I personally am not keen on this approach to rule making. The hydrogen group led by Toyota was very successful in lobbying rule changes that favored hydrogen over battery cars (since that’s what they have) and further, those same hydrogen then became exempt from sales outside of California. The result of changes to the hydrogen CARB- ZEV rules… Read more »

I don’t think changing the rules to reflect the amount of emissions and pollution a vehicle will create is “catering” to his needs. It’s just having a rule that gets the result rather than a rule that doesn’t.

To wit, an EREV (which is what his i3 is) that he can drive every day eliminates more pollution and emissions than a BEV that he has to leave home whenever he needs to go more than 80 miles.

That’s the obvious point the geniuses at CARB haven’t managed to understand.


“To wit, an EREV (which is what his i3 is) that he can drive every day eliminates more pollution and emissions than a BEV that he has to leave home whenever he needs to go more than 80 miles.”

It might do that, but on the flip side, an EREV can also drive 100% on gasoline and not use any electricity and there is no way for CARB to prevent that.

The BEVx provisions are designed to make that extremely impractical, so that CARB can feel safe that the ZEV credits they are giving out actually are from ZEV driving.


If BMW made the Volt and GM made the i3 everyone would be laughing at GM. Don’t see why the change of the logo should change the result.

BMW screwed up by designing the i3 for CARB rather than for its customers. The result is an overpriced dog of a vehicle.

On the positive side, BMW is doing a pretty good job of marketing the i3, which is very refreshing.

Tony Williams

I can only imagine what the BMW marketing department could do for Tesla!!!

They are good. I have to cringe at some of the statements, but the public seems to lap it up.

Mike I

This is perfect opportunity for smarter software. The GPS already knows the altitude, as shown in the screen pictures and the altitude information could also be incorporated in the map database, if it’s not already. When you set a destination, the computer could then forecast the energy requirement and turn on the REx at the proper time to minimize the fuel usage yet maintaining the battery level to make the summit without power restriction. Going down the other side will gain battery energy, so the REx will be able to turn off as soon as the summit is reached.


The problem isn’t CARB. It is BMW. If BMW didn’t need the Carb credits, then it wouldn’t have to hobble the i3. Look, live by the sword, die by the sword. EVs get preferential tax credits, but only if they are, you know, EVs. The Chevy volt isn’t hobbled, because GM decided it wasn’t worth crippling the car to get ZEV credits. BMW decided to hobble their car… If you have a gripe, take it to BMW…


Cosmacelf, I totally agree with you.


It really comes down to how many people will have to die in cars classified as BEVx before CARB will make changes.

Tony Williams

If BMW built an “unsafe” car merely to comply with the ZEV classification that BMW asked for, perhaps they should fix their car or withdraw it from the market.

CARB gives ZEV credit to lots of cars that don’t have gasoline engines and that are not dangerous.

Lindsay Patten

The change I would really like to see CARB make is to offer an additional credit for cars with 120+ EPA AER. I think that would significantly increase the number of electric miles driven.

Tony Williams

Yes, we need to reward AER and not reward enhanced gasoline use.

For ZEV, they currently get 3 credits for a “100 mile” car like i3, which means that everybody builds a 70-80 mile range car that “can” do 100 miles on the EPA LA4 City Cycle test.

Then, the next jump is 200 miles to get 4 credits.

There is no reason we can’t have:

100 miles – 3.0 credits
110 miles – 3.1 credits
120 miles – 3.2 credits

190 miles – 3.9 credits
200 miles – 4.0 credits, etc.

Let the gasoline motor rules largely remain, but the REDUCE the credit by the amount of gasoline miles the car is capable of.


Whatever the local Californian rule, keep it local and don’t impose it to the world. If you can’t change that world effect it is better to do nothing at all since it has weired consequences all over the planet.

Tony Williams

Every country has different rules for vehicles sold there. The USA is no different, and California in particular.

The cars have to meet those standards. California rules don’t apply to cars built and sold in Germany, where the i3 hybrid has a larger gasoline tank and a 75% battery charge “hold” mode for the gasoline engine.


I don’t know of a standard 12 gallon tank on the German i3. It is 9 liters only not 45.

Instead of all these complicated rules that can be gamed in so many ways, why doesn’t CARB simply give 1 ZEV credit for every mile driven with zero emissions? Isn’t that the real goal here? Since the meaning of a credit would change, you would have to change the number of credits required. You could limit the credits to the first year a car is on the road to keep things from dragging on too long and to make it less likely the car will be resold to someone in another state. You would have to have some mechanism to log the zero emission miles and the manufacturer wouldn’t find out exactly how many credits they got for a particular car until it had been on the road for a year. But the incentives would align with the big picture goals, there would be much less of an incentive for manufacturers to do the minimum required to get to a certain credit threshold, and manufacturers would have an incentive to encourage infrastructure such as the installation of fast charging stations. But perhaps governments actually like inefficient rules that leave room for lobbying, gaming the system, etc. . . .

The problem with your suggestion is it is even less efficient as that means CARB will have to maintain a database and continuously collect data for every single car out there, rather than right now only collecting registration data that the DMV already has.


The idea would be to have the manufacturers log the data for all-electric miles and present it to CARB. The Volt and Model S are already logging this type of data because GM and Tesla have presented it.

Incentives can have all sorts of unintended consequences if they are not designed very carefully and it’s almost always a good idea to tie the incentives as closely as possible the behavior you actually want go encourage.


So… you enabled the Euro-Mode for your test but not for the traveling-wish of your wife? 😉


Another issue with BMW i3 REx.

If the author is driving his i3 REx during the winter and requires heat usage, then it would be even more inefficient b/c i3 REx doesn’t have heat pump AND the engine would power the generator to power the electric heater which is the WORST way of generating heat in REx mode. If BMW had done an efficient job of recouping the REx heat, I would have supported it more…

“The hydrogen group led by Toyota was very successful in lobbying rule changes that favored hydrogen over battery cars (since that’s what they have) and further, those same hydrogen then became exempt from sales outside of California.” Just as there are so many E85 vehicles being sold in places without E85 Fuel, a Plug-in Hybrid Fuel Cell Vehicle that had 100 miles of Battery range, but could add to that another 200+ miles from the Fuel Cell, it could be sold where there is no H2 filling srations, on the premise, of a built in future range upgrade, as soon as a local H2 Fueling Station is built! It would be like a scaled up Volt, but like a Volt out in the desert, it better bring some Solar panels! Even in California, and South Carolina, a PHFCV like this, could have even more usability than the current All Hydrogen fueled FCV’s. This way, most local driving can be all battery electric, and if you run over 100 miles on a trip sometimes, the FC is there to carry you, like a Volt Level REx! Plus, since some Volt owners have not fueled up ‘since March’ – the safety of… Read more »

Wow! Lots of typos in that last post! mikes = miles.

Anyway, BMW it seems, did not intend for, nor test the i3 REx, in a REx trip across the great divide in the USA! Hence this Mod to get more usability out of the i3 than it was targeted for in the CARB Qualifications! was a more intense hack to the old Honda Insight 2 seat Aluminum car – to override both the Regeneration and the Boost modes of the car, for similar reasons: the Honda IMA system tracked only battery SOC, not road grade, sometimes letting the Hybrid Battery get lower than needed for a pending hill climb, then start charging it, while climbing the hill, for reduced efficiency. Similar problem in this incarnation of the i3 REx! See their website for how they created the MIMA system. (Manually Integrated Motor Assist).

California has have and does have a serious air quality problem. Air pollution in some cities of California is killing people. As a result they have looked at who or what is causing this problem. One of the main culprits is the automobile (auto mobile emissions). So they have come up with measures to combat this problem. One of which is to encourage the use of zero emission vehicles. This is where BMW comes into the picture. There is the BMW i3 (a fine all electric vehicle). The problem is the BMW i3 Rex. BMW try to put a vehicle together to meet California zero emissions requirements that can also appeal to the mass public. It has a generator (34 house power) that is not powerful enough to replenish the energy fast enough to make this car street worthy. The rate of energy depletion is greater than the rate of energy production. There are smarter people than me that have more fancier ways of explaining it, but that is basically the problem. The BMW i3 can not maintain speeds above 70 mph on flat ground (level ground). The gas tank is less than 2 gallons. The BMW i3 can not… Read more »
Murrysville EV

I couldn’t buy a car with so many question marks about its performance.

My Leaf is predictable, and great for commuting.

My Optima Hybrid could do this trip on less than 1 tank of gas, and without all the stops for charging and refueling. And it has a lot more space inside it than the tiny i3. Yes, it only gets 45 mpg highway (for real), but I only paid $20k for it new. Plus, I have no doubts about its hill climbing capability.

Justin W.

Thanks for the article, John.

While many may argue the classification rules I think your message was clear and I agree with it. As a Volt owner who lives in Roseville and commutes to Auburn (Nevada St. shown in your GPS picture) I am very familiar with the need for a Hold Mode or even Mountain Mode in the i3. It would be a much more useful car if it had those features. Because it doesn’t have them, I never recommend the i3 REx to potential buyers in the Foothills region. Even the Volt will lose a battery bar or 2 flying up I-80 to Truckee at 80mph.