Thursday, June 5, 2014

8 BMW i3 Questions with Brad Berman of Plug In Cars

I was recently interviewed by Brad Berman of about my initial thoughts on my i3. The interview just went live on the site so I've bought it over here for my followers to read. Please leave your thoughts on my answers in the comments section.

Tom Moloughney, long-time EV driver and first owner of a BMW i3 with the range-extender option, answers fundamental questions about the car.

1) How is the BMW i3’s range-extending system different from the Chevrolet Volt and Toyota Prius Plug-in Hybrid?

The range extender on the BMW i3 works differently than systems on plug-in hybrids (that to varying degrees sometimes power the wheels from the engine). The rear-wheel-drive i3 is the only pure series plug-in hybrid currently available. The i3’s two-cylinder range-extender engine never mechanically drives its wheels. The Fisker Karma worked this way, but that vehicle is no longer in production.

2) Under what conditions does the gas engine come on?

In the United States, the range-extender turns on when the state of charge drops below 6 percent. Unlike the European version, the operator cannot manually turn on the engine to maintain a higher level of charge. In Europe, once the state of charge drops below 75 percent, the range extender can be turned on manually.
BMW eliminated this feature on U.S. models, so the i3 would qualify for the California Air Resources Board’s BEVx designation. While BMW never announced why they chose to eliminate the hold feature in favor of getting the BEVx designation, observers believe BMW took the step in order to get more ZEV credits per REx vehicle sold.

3) How does the driving experience change after the gas engine comes on?

So far, I’ve had the opportunity to drive my i3 for about 100 miles in charge sustaining mode. I intentionally didn’t charge it for a couple days so I could fully test the functionality with the range-extender operating. The power is slightly muted. I’d say maybe 85 percent of how it feels with a full charge.
When the range-extender turns on, you cannot hear it at all from inside the car because it initially runs in the lowest of the three power levels. If you continue to drive at speeds higher than 40 miles per hour, it will kick up to the next power level and you can then hear a low hum from inside the car. If you are driving at highway speeds, it will jump up to its highest (28kW) power output, and then you can definitely hear it. It’s nothing that you can’t overcome with the radio.

The REx turns off when you slow down to less than 15 mph, unless your state-of-charge is lower than 3 percent. I’m impressed by how well the little motor can sustain the charge. I’m convinced it can do whatever I need to do, and I will have no problem driving long distances with it running.

On level ground, the car can continuously sustain speeds up to 75 mph for as long as you need to drive. You have plenty of power to pass cars at that speed, and to climb hills that are a few miles long. There really aren’t any mountains in New Jersey where I live, so I haven’t tested driving up long steep inclines, but there is definitely a point where the range extender will not be able to maintain highway speeds.
If you exceed the range extender’s capability, it will slow down to 40 mph. At that speed, it can maintain just about any climb. I will be taking my i3 on a 230-mile trip to Vermont soon. Hopefully I can do some mountain testing there when I do. I haven’t noticed any difference in the handling when the REx running.

4) What's the top speed for the i3 before, and after use of gas engine?

The i3’s top speed in electronically governed at 93 mph. It pulls strongly all the way up there, with or without the range extender running. As noted above, it’s just slightly less powerful in charge sustaining mode.

5) How did BMW make its decisions about the of the i3’s engine and gas tank?

The i3 was not initially designed to have a range-extender. BMW added the feature after the car was more than a year into development. Perhaps that had something to do with what size motor they could fit, but that is just an educated guess.

The size of the gas tank is another thing entirely. In the United States, the i3 REx has a 1.9-gallon tank, and the European version uses a 2.4-gallon tank. The 1.9-gallon tank for the US was announced only weeks before the i3 launch. The reason for the reduced size is probably tied to the BEVx designation that BMW clearly wanted the car to attain. BMW has not confirmed the reason for the reduced tank size.

One of the qualifications of the BEVx certification is the vehicle’s all-electric range must be greater than its gasoline range. Again, this is speculation, but if the i3’s electric range was certified by CARB at lower than BMW expected, that would explain the need to reduce the range when running on gasoline.
Personally, this isn’t an issue for me. I’ll be using the range-extender only on those rare days when my electric range is just slightly insufficient. It’s a good backup strategy, and allows me to not even think about those times when I’m pushing the limit of the car’s range.

6) Should drivers think of the gas engine as a way to extend range to 160 miles—or only as a backup to an 80-mile EV?

I’m not going to tell anyone how to use his or her car. I don’t think there is one simple answer. I believe there will be people that routinely drive their i3 REx 130 to 160 miles and more, and don’t mind filling up frequently when they need to. I can say this about filling up: with such a small tank, you pull in, fill up and pull out of a gas station in about two minutes.

There will be others that see filling up every 50 or 60 miles as too cumbersome. Perhaps the car isn’t the right choice for them. A Volt may be a better PHEV for some people that frequently need to cover hundreds of miles in a day, or live in a mostly mountainous region. For daily driving of less than 150 miles or so, it works great.

7) Given the unique i3 system, how does it affect incentives and perks like carpool access?

The i3 REx, like the Volt, Plug-in Prius and other PHEVs qualifies for California’s Green HOV access sticker, which is currently not available. The 40,000 allocated green stickers PHEVs have been exhausted. However, AB 2013 proposes to make 45,000 more stickers available, and is currently headed to the California Senate for vote.

Washington State recently announced the i3 REx would qualify as a zero emission vehicle and therefore gets exempt from sales tax there. BMW i3 sales in New Jersey were also scheduled to be tax-exempt. But just after BMW began selling the i3 in New Jersey, it was announced that the i3 with range-extender would indeed have to pay sales tax. The BEV i3 doesn’t. That essentially doubles the price of the $3,850 REx option, making it nearly an $8,000 option in New Jersey. That is likely to hurt i3 REx sales in the Garden State.

8) Is the i3 REx approach a stopgap measure, or should it be considered a long-term strategy across the EV market?

I believe other manufacturers will adopt the range-extender approach. However I believe it is a short-term measure. (Maybe 10 years?) As battery chemistry advances and energy density improves, electric vehicles will have continually better electric range.

That, combined with increased DC quick charge stations, will make the range-extender unnecessary. Tesla and Nissan are doing the lion’s share of the work getting these fast charge stations installed. It’s about time some of the other carmakers join in.

The i3 is only the first electric vehicle to emerge from the new BMW i brand. More vehicles are already far along in development. It’s my hope that BMW recognizes the need for DCQC infrastructure, and follows Tesla and Nissan. If the combo-cord fast charge standard has any chance of gaining traction in the US, it will be up to BMW to take the lead. It is the only manufacturer currently selling a serious (not a low-volume compliance-only) electric vehicle that uses the combo cord. In my opinion, the proliferation of DC quick charge is absolutely necessary if we are going to get off petroleum, and make a transition to electrified transportation. A small, efficient range-extender like the i3 will work for many people today. It's a great step until battery range grows and more quick charging is installed.


  1. Just got my Capparis White BMW i3 BEV yesterday! Lovin' it so far. Range is substantially worse than Active E, unfortunately. Strangers are taking photos of my car. Acceleration is awesome. Pretty happy!

  2. Tom, thanks for your interview.

    A suggestion (software update) for BMW to improve the i3 REX performance when climbing hills:
    Since in the US the requirement for a BEVx like the i3 REX is that the EV range must be greater than the gasoline range and you have to use up all the EV range before switching to gasoline, one solution to alleviate the limited power of the REX mode when climbing hills would be the following:

    Add a "mountain mode" to the i3 REX software.
    When this mode is selected, the i3 REX as usual, first uses up the EV range and then switches the REX on. But instead of maintaining a battery buffer of only 8-10% SOC, this time the buffer gets bigger, for example 30% SOC.
    This means except in extreme cases, where you are driving uphill at very high speeds from the moment you used up your EV range, the REX has the possibility to build up a bigger battery buffer and thus allow to drive faster uphill when more power is required.

    When charging the i3 at the plug, the mountain mode would be reset and only activate again when you used up the full EV range.

    What do you think?
    You could blog about it on this and other EV-websites and propose it to BMW, perhaps they will listen. As said, such a mountain mode would not break the BEVx rules and would allow for more performance in hilly regions.
    For example if before a big hill comes a flat stretch of road, the REX could build up 30% of SOC in the battery in about 15-20min.

    1. In Europe the i3 REx can be turned on once the state of charge drops below 75% (I believe that's the trigger point but it may be 80%) and here in the US it automatically turns on at 6%.

      Unfortunately a mountain mode feature would not be allowed under BEVx rules. The range extender cannot turn on under any condition until the battery has been depleted and the 6% threshold is indeed the highest point where the range extender can be allowed to operate in the case of the i3. Here are the main rules for BEVx qualification:

      -The vehicle must have a rated all-electric range of at least 75 miles (higher than the 50 miles required of a zero-emission vehicle)

      -The auxiliary power unit must provide range less than, or at most equal to, that battery range

      -The APU must not be capable of switching on until the battery charge has been depleted

      -The vehicle must meet "super ultra low emission vehicle" (SULEV) requirements

      -The APU and all associated fuel systems must comply with zero evaporative emissions requirements

      BMW has had a lot of discussions with CARB on this matter. If they could allowed the range extender to turn on at any higher level they would have.