Mountain Climbing With an i3 REx

Loveland Pass, Continental Divide, Colorado. Elevation 11,990 ft

A few weeks ago Don Parsons of Denver, Colorado took his i3 REx on a 128 mile road trip from his house to Loveland Pass (Continental Divide, Colorado). On his way up to the 11,990 ft elevation of Loveland Pass he stopped at Beau Jo's Pizza for lunch and to charge on their public ChargePoint EVSE where his i3 REx accepted 8.9kWh's of juice to help with the rest of the climb up the mountain. 

The car showed 18 miles remaining at the top of Loveland Pass, and he nearly made the trip entirely on electricity when 62 miles later the range extender kicked on and he was only 2 miles from his home. 

The trip summary: 
-64 miles each way
-8,960 feet of climbing, 2329 Feet of descending on way out
-2329 feet of climbing, 8,960 feet of descending on way back

Having heard about this Continental Divide conquest, I asked Don if he wanted to write a guest blog post about the trip, but he offered to do one better. His next challenge was to take his i3 REx up to the summit of Mt Evans which is the highest elevation paved road in the US. The trip would take him over 14,000 feet above sea level and would most certainly push the range extender beyond its limit. This was not the kind of road trip BMW envisioned people taking the car on when they designed the REx, but nonetheless they have to expect some people like Don would do just that. So what happened? Read Don's words below to find out:

I’ve had my BMW i3 REx for almost two months now and haven’t really used or tested the REx engine.  Before today, I’d driven about 1750 miles total with only about 10 miles using the engine.  I decided to drive from my house in Denver to the top of Mt. Evans and return without stopping for gas or topping off the charge.  Using the REx engine in the mountains can be tough because the output of the small engine can’t really put out enough power to go both highway speeds and climb uphill.  However, the road to the top of Mt. Evans is pretty narrow, has steep drop-offs, no guardrails and a lot of cyclists sharing the road so you really don’t want to go much faster than 35 mph.  For this reason, I thought the small engine could hopefully handle the climb.

For those that don’t know, Mt. Evans is the highest paved road in North America with an elevation of 14,130 feet above sea level!  I live in Denver which is at 5,280 feet above sea level.  It’s 63.5 miles from my house to the top Mt. Evans.  With some up and down hill climbing, the total ascent is 12,446 feet and the total descent is 3,686 getting to the summit.

I set the car into Eco Pro+ and set out on city streets of Denver, then I-70 west up the mountains to Idaho Springs.  Mt. Evans highway winds its way south from Idaho Springs to the Mt. Evans summit in 28 miles.  When I originally entered the destination into the navigation system, the guess-o-meter said 61 miles of range.  I tried to keep the cruise control set to about 5 miles over the speed limit.

I was surprised to find that the Rex engine didn’t turn on until about 52 miles into the drive (about 10 miles from the summit) with a total trip average mi/kWh of 2.8 when the REx kicked on.  However, about 1 minute after the REx turned on I got a Brake error message that ended up making the brake pedal feel stiff and pretty much unusable.  Fortunately, I was still heading uphill and the regen seemed to be working normally.

I could hear the engine speed up during the straight parts of the switchbacks and as I slowed down for the sharp curves, the engine almost immediately slowed down as well.  I never really wanted to travel faster than 35 mph so I didn’t notice any performance hit until near the summit.  On the last few switchbacks, I put my foot to the floor and couldn’t get the car to travel faster than 26 mph.  At close to 14,000 feet of elevation, the engine was probably severely limited from its usual output at sea-level.  I’ve heard people say that an ICE reduces power output by 5% for each 1,000 feet of elevation.  In any event no other cars were traveling any faster than 25 or 30 mph so I didn’t feel unsafe.

I finally made it to the top at 14,130 feet!  The temperature had gone from 68 degrees in Denver to 35 degrees and quite windy.  This road usually shuts down for the winter sometime in September so they will be expecting snow to start accumulating up there pretty soon!

As I was getting ready to head down, I was worried about whether I would have any use of the brakes since I had turned off the car and walked around the summit for about 5 minutes hoping the error would reset but it didn’t and I still had a stiff brake pedal.  Since it was 35 degrees up there, I was pretty cold and didn’t feel like waiting any longer so I thought I would start to head down and see how well the regen worked to keep the car in control.  You can imagine how happy I was to have such a high regen rate because I felt like I was in complete control all the way back home.

During the descent from the summit down to Idaho Springs I was excited to see that the regen had built up a full 25% of the battery SOC and the guess-o-meter said as high as 28 miles of range on the battery.  I drove home significantly on battery but the REx kicked in a few times where there was some climbing.  It also stayed on once I got out of the mountains but I was easily able to maintain 75 mph on the highway leading east back into the city.

Here's a screenshot of the elevation and speed of the whole trip

Some stats on the whole trip.  I traveled 127.6 miles and averaged 4.9 mi/kWh and average speed was a total of 39.6 mph.  I used a little over a quarter of the rex tank which I think is pretty minimal for traveling almost 130 miles! As you can see from the picture, the brake error was still in place when I arrived home.  However, after being on my EVSE for a little over an hour, everything was cleared out and a quick trip to grab lunch showed that everything was back to normal.

I should point out that I haven’t gotten any software updates yet as I haven’t been able to set aside the time.  Until this trip, the only error I’ve seen from the car is the Check Engine Light, which remains illuminated. There is a software update that will eliminate this waiting for me at my dealer, so I guess it's time to get the car into the shop for the updates.  Hopefully the brake error is related to the 12v battery issues that others have discussed and will also be fixed with the latest software version I'll be getting. 

When I thought about getting the i3 Rex, I figured that I would use the battery over 95% of my driving miles.  So far, it seems like I’m using the battery over 97% of my miles.  That said, I’m still happy to have the Rex as it completely takes away any range anxiety when I’m traveling in the flats of the front range of Colorado.

What about the mountains?  I was concerned about using the i3 REx in the mountains and still believe that having a REx hold mode similar to the European version of the i3 or the Chevy Volt would make this an even more enjoyable car in Colorado.  That said, a couple CCS fast chargers placed strategically off I-70 would go a long way to helping the issue.  Locations in Idaho Springs, Silverthorne (where the 8 Tesla Superchargers are located) Copper Mountain, and Vail would be ideal spots to get a quick top-off and be truly useful in the mountains.  I’ve also kept my 335xi for long distance ski trips since it has all wheel drive and is still a great car. However, even without the fast chargers I was able to make it to the summit and home without a problem.

I’m very happy with the the i3.  The performance, handling, smoothness, and quietness all contribute to a great experience.  Like others have said, it’s hard to go back to a regular internal combustion engine after experiencing electric!

BMW i3 Range Extender: How Robust Will It Be?

There are still many unanswered questions about the i3. What will the EPA range rating be? How will is fare in NHTSA and IICA crash tests, will it cost more to repair, and so on. However there is one particular feature of the i3 that continues to dominate the discussion boards and forums: What can and can't you do with the REx?

Back in June before the i3 was officially introduced, I did a blog post on this very topic which turned out to be very popular. In fact, it's one of my top viewed posts and has been viewed over 5,000 times so  far. We now know a few more details since then so I thought it was a good time to give an update here. While I have driven in REx i3's, unfortunately I haven't had the chance to thoroughly test on while it was in range extender mode. That wasn't a coincidence. BMW has still be fine tuning the software for the REx and hasn't allowed the press access to them for complete testing. However, somehow over in the UK The Telegraph got hold of one and was able to take to for a long drive and use the range extender. Overall the review was pretty favorable and the author gave the i3 four out of five stars. However that's not the whole story. The real "story" within this story is that the author reported this about the range extender and it's caused a but of a stir:

"I thrummed along at 70mph, but it soon became clear that at this kind of speed our comfortable range between fill-ups was more like 40-50 miles. Still, it was impressive how, even when it says it’s flat, the car maintains enough battery power to give an instant shove of torque. Only if you really run it down, which you’ll have to try pretty hard to do (or so I’d been told), would you compromise the performance. Which is what happened next. 

I’d just come through a heavy but localised rain storm on the M20 when the i3 started to slow. It was a gradual process, from motorway cruising speed all the way down to 44mph. By this time I was travelling up a slight incline and had effectively become a slow-moving obstacle. Lorries were catching me with quite frankly terrifying closing speeds. It was three or four minutes - which was long enough to make me consider pulling over - before the i3 recovered; just as slowly as it had lost speed, so it crept up. “It’s not a limp-home mode as such,” a BMW spokesman later told me, “but once the charge runs down to five or six per cent and the range extender cuts in, if you keep driving at 75-80mph it can’t maintain the charge.” Rather than damage the battery by running it completely flat, the i3 had restricted our performance."

This Telegraph video above doesn't mention the difficulty they experienced with the car slowing down at all even though they show it driving along on the M20 while it was raining like they printed version said. That's strange to me since the article seemed to make a big deal out of it. I would have like to have seen video of the car during the explained "slow down" event.

The i3 REx Engine

I've had quite a few conversations with the engineers and product managers at BMW about the range extender and while they are cautious no to over sell it's capabilities, everyone I have talked to promises it's not anything like a "limp mode", and in fact you can do just about anything with it as long as you understand how it works and drive accordingly - I take that as monitoring your speed and if you know you'll be driving up a long steep incline and take it easy for a few minutes before you begin your ascent so the REx can build up a little extra reserve power for the climb. There has been a lot of talk around the fact that in the US, you can't manually engage the range extender once the state of charge is below 75% as you can in Europe. The concern is with the range extender coming on at such a low state of charge (at ~5% SOC) that there may not be a large enough buffer for those instances when the car needs continuous supply of a lot of energy for high speed driving or to climb long, uphill grades at highway speeds.

I don't have the exact answers as to what exactly is possible and what isn't. In fact, I'm not even sure it's possible to offer such a definitive explanation. Sure, the engineers can offer a formula based on total passenger and cargo weight, vehicle speed, head or tail winds, percent of grade you are climbing, etc but who will even understand that let alone be able to transfer that to an actual real world driving situation? There are so many different situations and roads it's just not possible to give a clear black and white definition of what it can and what it can't do and I believe BMW will likely struggle with how to explain this to their customers - maybe that's why they haven't even tried to explain it yet! I have made a request to the program managers to let me drive an i3 REx for a day once one is available. I'll test it in every possible situation I can come up with in the time frame I have including a 220 mile trip to Vermont. Hopefully my request will be accommodated because I believe I can clear the air on this as much as possible, however as I mentioned above there are endless specific driving circumstances so no test will completely satisfy everyone. My advice: Drive one in REx mode to satisfy your concerns before you plunk down your money. I'm sure you can leave a deposit on one and have it refunded if you are not satisfied with the performance once you get the test drive opportunity.

i3 Product manager Oliver Walter

I can say I have spoken with program managers that have driven the i3 REx extensively, and they have assured me that on flat ground, you really have to purposely try to defeat it in order to use more energy than it produces and that it can easily drive along at 70 mph for as long as you need to and still have enough energy for short bursts of power to climb hills along the way. BMW i3 product manager Oliver Walter in particular has assured me the range extender is robust and will be able to power the car in just about any circumstance without the driver even noticing any difference than when it's in pure EV mode. The question becomes how fast can you drive and for how long, up how steep a grade, and right now, we just don't have definitive answers.

So why can't the i3's in the US have the same ability the European i3's have to manually turn on the REx ahead of time, when you know you'll need a lot of energy for demanding driving conditions like climbing a mountain later in your trip? The answer is in the CARB certification of the i3. BMW needs the i3 to be certified as a zero emission vehicle in order to claim the most ZEV credits they can for each i3 sold. However the benefits aren't only for BMW. BMW has been working behind the scenes to make sure that i3 buyers get the same tax credits, tax exemptions and benefits like HOV access that zero emission vehicles get, which in many cases is better than what is offered to PHEV buyers. For example here in NJ, if I buy a zero emission car like a Tesla Model S, I am not required to pay sales tax, but if I buy a Chevy Volt which has a range extender, it's classified as a PHEV and I have to pay sales tax. So if BMW by getting the i3 REx certification approved, manages to get New Jersey to classify the i3 REx as a zero emission vehicle, then I will save about $3,500 in sales tax. To me, that's worth losing the ability to manually turn on the REx early because there will be so few instances that I would ever need to; it's just simply not worth it. This isn't just for NJ though, there are quite a few other States that offer different incentives for ZEV's as compared to PHEV's. However as far as I know, BMW is still working out these details State by State and they haven't announced exactly what the certification will mean in each particular State just yet. As soon as there is more to report on the certification and State benefits I'll have it up here, and hopefully I'll get to report first hand on how the REx performs sometime soon. Happy Holidays everyone!

Of course a robust network of DC quick chargers like the one pictured here would render the range extender irrelevant. But are they coming?

How CARB May Make The i3's Range Extender Less Attractive

The range extender engine for the i3 is seen here to the left of the electric motor

According to the UK price list for the i3 the range extender will automatically come on when the state of charge falls to 18%. I've been guessing that will happen at about 20% so I was pretty close. It will then attempt to maintain the battery SOC at 18%, while allowing the car to continue to drive along relatively uninhibited. The only time there will be a problem is if your driving is demanding a high level of energy output for a prolonged period of time.

For instance, driving along at 60 mph on a flat surface you may only need 10 or 11 kW's to sustain the charge because that's about all you'll be consuming. That's no problem for the REx because it can provide up to 25kW's of constant supply. However if you need to drive up a steep grade at highway speeds for 10 continuous miles or so you may have a problem because the car will likely draw more than 25kW's under these strenuous conditions. The 18% buffer combined with the REx pumping out it's maximum output will allow the drive to continue for quite some time, but after a while of using more energy then it is capable of replacing, it will eventually need to reduce power output. What happens then is unclear but I would imagine the car would slow down to a speed it can maintain power for. Again, this should not happen on flat land, as the energy consumption should be able to be replace by the REx. It will also have plenty of power for most hills and bursts of speed when needed. I'm talking about long, extended drives up steep inclines that happen at the end of your journey after you've already depleated the battery and the range extender has come on. Personally I have a situation where this could come into play myself. My in laws live in Vermont and the last 10 to 15 miles to their house is mostly uphill. I'd already have the range extender on by the time I get to this final leg of the journey so I'm curious if I'll have a problem making it. I could stop along the way and charge for a while if necessary but I'd prefer just driving nonstop. After all, that's why I'd get the range extender; so I don't have to stop to charge along the way of a trip.

So what can be done to alleviate this? The Chevy Volt has a "Hold Mode" that the driver can initiate at any time. This manually turns on the range extender without waiting for it to automatically turn on when the battery is depleted and holds the battery state of charge at the level it was when you turned it on. Sounds like a great idea, so is BMW going to do the same thing? Yes, and maybe no. If you look at page 8 of the UK price list that I provided the link to above, you'll see it says: "Manually activated when the vehicle is below 80%". Brilliant! So if you buy an i3 in the UK, you can turn on the range extender once the state of charge drops below 80%. Therefore if you know you'll be driving up a long, steep hill or mountain at the end of your journey, you can turn on the range extender and "hold" the charge so when you arrive at the mountain you'll have plenty of charge to complete the journey. Perfect, so US customers will get this feature also, right? Unfortunately, maybe not.

CARB's restrictions may hinder the REx

California is the #1 market for electric vehicles in the US and one of the reasons they sell so well there is zero emission vehicles are allowed carpool lane access regardless of the amount of passengers. This is a highly sought after perk in California and cars that qualify for it usually sell very well. The all electric i3 will definitely qualify, but the under the new more strict rules for PHEV's, an EV with a range extender will only qualify for the valuable HOV access sticker if it operates this way: "engine operation cannot occur until the battery charge has been depleted to the charge-sustaining lower limit". So that means the range extender cannot be manually turned on at 80% and still qualify for HOV access in California.

It's clear to me BMW will make the i3 conform with CARB's rules so it will have HOV access is California, but will they do this to all the US cars, or just for the ones shipped to California? I don't have the answer. I tried to get clarity on this at the i3 Premier but nobody wanted to confirm it one way or the other. Hopefully that means a decision hasn't been made on this yet and there is hope for the rest of us. If so and the powers to be at BMW find their way to read this blog post, please consider offering the same ability to manually turn on the REx for US customers outside of California. The vast majority of customers in the US don't need carpool access, why should they have their range extender neutered so people in California can have it? This is a simple software change. It's available in the UK and probably for the rest of Europe so it's not like it will cost BMW anything to develop. Let's hope BMW does the right thing and makes this feature available to US customers outside of California. It really makes the range extender a more useful asset, this shouldn't be a hard decision to make.