Yesterday I was contacted by John Voelcker, senior editor of Green Car Reports, kindly asking what I thought of a piece he wrote comparing what is known of the pending BMW i3 with range extender to the Chevy Volt.
His article ponders whether BMW is possibly setting itself up for a new variant on “range anxiety” in the North American market because the motorcycle-based two-cylinder petrol backup may not be enough to match the output of the EV it is meant to support.
In BMW’s view, the “ReX” range extender – its displacement may be 800cc but this is not official – may lead the car to dip into its 21-22-kwh battery’s energy buffer.
Power may be fine in range-extended mode on a level grade, but up long hills, or at speed, or in other taxing scenarios, the performance may tail off in range-extended mode.
The i3’s electric motor is expected to deliver 170 horsepower (125 kw) of peak power to its rear wheels. A suitable ratio for the gas-to-electric output would be 1:2. The Volt is set up this way. Its electric output is rated at 149 horsepower (111 kw), and its gas range extender is around half that at 74 horsepower (55 kw).
It’s not out of the question that an 800cc BMW motorcycle-based engine would be able to deliver half of the 170 peak horsepower of the i3’s traction motor, but that would be pushing it. A parallel twin from one of its liquid-cooled 800cc bikes is capable of 85-90 horsepower, but usually they must be spun to around 8,900 rpm to achieve peak power.
Do you think BMW will make the genset in the i3 a 9,000 rpm screamer? If not, its gas-to-electric ratio will likely be less than the Volt’s, and this is assuming it’s an 800cc. BMW also has a 650cc parallel twin motorcycle engine, so this is an open question.
What is known to date is the stated design parameters set by BMW are not the same as GM established with the Volt. The Volt, as you know, can be driven on gas alone if someone wanted to do it, but the BMW’s tiny range extender may not be able to do this as well.
“Consider, for example, a heavily loaded range-extended electric car on a 10-mile uphill grade at freeway speeds,” writes Voelcker of a situation where the i3 may come up short in range-extended mode, “Once the buffer capacity of the pack is depleted, would a 40- or 50-kw generator be enough to keep the i3 at maximum speed on that freeway?”
BMW has said it expects the estimated 100 mile or so EV range its i3 will provide will suffice, and so its range extender is there mainly like a spare gas can to get the driver to a charger if needed.
The car’s fuel tank is only expected to be 2-3 gallons which would only double the EV range. These decisions are being made by BMW in order to comply with California’s arcane requirements to still be considered a “zero-emissions vehicle” (even if it does emit some hydrocarbons anyway).
One thing that’s true of GM’s engineers is they know the American mindset, and what will satisfy drivers for the most part.
A contrast may be seen in BMW’s philosophy as evidenced by BMW’s global R&D chief, Herbert Diess, who was quoted recently saying the i3’s range extender is not designed to be used day in, day out, as the Volt’s range extender is capable of.
“The range extender is not intended for daily use. It’s for situations when the driver needs to extend the range of the vehicle to reach the next charging station,” said Diess. “Therefore, the i3 probably won’t be the choice for customers with a need for an extended range.”
Instead, a plug-in hybrid would be a better choice, Diess said. He also said BMW expects people may flock to the range-extended version at first, but as the car becomes known, those opting for the range-extended i3 will diminish from half of all buyers, to just one-fifth.
“It is more of an issue for those who have not yet had a chance to use an electric car,” said Diess of the range-extender option. “After a few days, they usually discover that a base range of [100 miles] is sufficient to limit recharging to about two times a week. In most cases where people first think they need a range extender, it actually never is used.”
BMW is making the i3 a global car aimed also at Europe and Asia where distances traveled are more often shorter, and driver requirements are different than in the U.S.
The i3 is due for U.S. delivery early in 2014, and BMW says it will lack nothing as a family member of the “Ultimate Driving Machines.”
It may be an EV, but this will be a BMW EV, and presumably more fun to drive than a Nissan Leaf. But will the BMW wilt nonetheless in range-extended mode?
That is one mystery, but as Voelcker concedes, there is room for speculation. Even the specific cost for the range-extender is not officially known. Word has been it could be an additional $2,000-$3,000 more for the car possibly priced in the $40,000 range. If this is so, this is not a lot extra for an installed engine, and frankly it sounds too low.
To be sure, we’ll need more answers from BMW, but judging from what it is saying, do you think it is misjudging the American market, and what most people would want? Why bother with a range extender if it cannot meet power supply demands in full?
GM already gave America what it thought was the best engineered compromise – an EV that can travel coast-to-coast on gas if needed – but BMW’s criteria doesn’t appear to be up to the same standard.
Is it possible the i3 with range extender will be a near-miss for most Americans? Or could BMW re-think its priorities before launching the car here in the land of high expectations?
This entry was posted on Wednesday, March 13th, 2013 at 5:55 am and is filed under General. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.