View From Behind i3 Sans Body
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.
Tom Moloughney at Live i3 Reveal: Photo Credit - Hugo Becker
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 depleted 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.
Chevy Volt Tackling a Mountain
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.
See Chevy Volt's "Hold" Mode?
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.
A Closer Look At BMW's 34 hp Extended Range Generator's Location Behind The Rear Seats
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 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.
Editor's Note: This post first appeared on Tom's BMW i3 blog. Check it out by clicking here.