Sunday, August 4, 2013

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.

13 comments:

  1. Well said, Tom. I spent the weekend driving in the mountains with my Volt and made heavy use of Hold* mode, and it was very enjoyable. But I was thinking a lot about how different my experience might be if I was in the BMW i3 with no such capability.

    * actually Mountain mode for me, but that's a long story

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  2. Christophe DanheuxAugust 5, 2013 at 11:43 AM

    Tom, I agree. This is a no-brainer. I can envision an automatic "hold mode" that would use the GPS to evaluate the most likely topography the car is about to encounter (provided the destination is known), and take actions accordingly. Such feature may not make it this time around, but no doubt it will sooner than later.

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  3. This is definitely an important subject. I really hope BMW listens to you Tom. This could be the deciding factor whether or not I get one. I live near the top of a 2,000 foot mountain and I don't want to have to worry about crawling up the road at night to get home.

    One more thing if I may; do you know whether or not I'll be able to get one by May of next year? I have an expiring lease and I am really thinking the Rex-i3 will be my next car. I live in Colorado will it be available here initially or will we have to wait like with everything else?

    Thank you kindly and thanks for this blog. It is the best resource for the i3 I have found anywhere

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    1. Thank you Dan. I do try to keep the latest i3 info here.

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  4. Dear BMW:

    Read the above post and listen to your customers. Tom is on point about this. Why should all i3 range extender customers have to compromise because the people in LaLa land want carpool lane access???

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  5. Thanks Tom! I also greatly support such a hold mode as well. If we find ourselves in situations where e have the foresight to conserve battery for later use we should absolutely be allowed to do so.

    Your detailed REx coverage does make me wonder: if REx is capable of generating up to 25kW, could you use any excess unused kW to actually build-up more battery charge rather than to simply "maintain" existing? In your example of 10 or 11kW used to maintain 60 mph on flat land, couldn't REx be used to generate an additional 10 or 15 kW of actual charge to apply to the battery to go from 20% capacity back up to 50% or even 100%?

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    1. No it won't function that way Rich. It is designed to keep the charge at 18% so you can continue along. That is a pretty good buffer and should be able to handle all but the most demanding driving situations, but they can come up so I want the ability to plan ahead for those situations that may occur at the end of my trip when the charge is low.

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  6. Hi Tom,

    I agree with your explanation of why maintenance mode may not be user-selectable in the US, and that it should be in non-ZEV states.

    But: CARB has created a lot of regulations, and I believe the ones you site are part of the ZEV regulations. Several other states have adopted these regulations, including New Jersey. So wouldn't the car still have the same restriction in New Jersey?

    Maybe not, maybe the regulation is elsewhere and NJ hasn't adopted that part. I know that WA has adopted a lot of the CARB rules, but not the ZEV laws, which is why we can't buy compliance cars here.

    States that have adopted ZEV laws: California, Connecticut, D.C., Maine, Maryland, Massachusetts, New Jersey, New Mexico, New York, Oregon, Rhode Island and Vermont.

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    1. Yes, New Jersey is also a "CARB" state, however there are no real perks here for compliance. For example there are some HOV lanes but honestly I don't even know where they are and although I drive all over the state I have never even seen them. HOV access isn't highly coveted here like it is in CA.

      As far as I know there would really be no benefits here if the car is designated a "BEVx" vehicle any more than if it was categorized as a simple PHEV like a Volt.

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  7. Nice write-up, Tom! While the exact energy economy data is not quite clear, I believe that the i3 will consume a bit more than 10 or 11 kW of power to sustain 60 mph. I'm basing this projection on the field experience with the LEAF, which has nearly identical width and height. It has the exact same Cd like the BEV trim of the i3 as well. While the aero wheels could have a noticeable impact, I just don't anticipate that the i3 will behave differently at 60 mph steady speed on a level street. Looking at this from another angle, if the energy consumption of 10 to 11 kW was correct, the i3 should be able to travel 107 miles at 60 mph. I find this a bit unrealistic.

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    1. Yes George you are probably correct. I'm thinking more like a 14-15kW draw, what do you think? The point I was making though, was that it's way less than the maximum output of the REx, so sustained highway driving should be possible as long as you keep you speed reasonable.

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    2. Tom, I gave it some thought and it looks like we could see something closer to 14 kW than to 15 kW. This would then give the i3 a projected range of about 81 miles when going at steady 60 mph on level road. While I'm hopeful that the i3 will fare better than that, this would be a more realistic figure than the 107 miles I calculated earlier. I think we could see about 10 kW draw at steady 50 mph.

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  8. You can manually turn on the Rex when the battery drops below 80% charge ..... so effectively you have a "Hold" button if you wish. This is available in Europe so if its not in the US I would imagine some bright spark will develop a hack to sort you out.

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