Archive for the ‘all-electric cars’ Category

Progress report from BMW on the Mini-e

Thursday, November 19th, 2009

As noted elsewhere on this site, I try to separate prediction and anticipation of what kind of vehicle could be built from analysis based on actual electric cars on the road.  This narrows the field considerably, because only two (currently available) electric cars have been shipped in any volume:  the Tesla Roadster and Mini-e.  I have drawn on results from the Tesla fleet, including Tesla’s data and reports from owners, in several of the articles on kilowatt-car, but it’s only recently that BMW started releasing information on the Mini-e.

The slide show is here if you would like to to through it yourself.  And to add some colour, here’s an owner’s blog.

To give the bare bones, BMW had 450 Mini Coopers converted using a design and components from AC Propulsion in  Southern California.  AC Propulsion is a small company but a significant player in electric vehicles – as well as providing know-how used in the Tesla, the founders had a hand in the EV-1 and several other seminal electric cars.  AC Propulsion provides the motor, controller and the battery pack design (35 kWh gross, 30 kWh usable for a 100 -120 mile range).  The car apparently drives like a petrol Mini, but the battery pack takes up the rear seat space, so it becomes a 2-seater.

Since the  Minis were delivered in June, the report covers the first 4-5 months of use for about 200 drivers in the New York/New Jersey area and another 200 around Los Angeles.  There are two main conclusions:  setting up charging points is difficult, and range anxiety is significant.

First, the charging.  The BMW comment is “BMW/Mini is in the car business, BEV (battery electric vehicles) put us in the infrastructure business”.  As it can take 24 hours to fully charge the Mini-e from a 12A 120V domestic wall outlet, they set out to install a 240V outlet in all garages where a Mini-e would be parked overnight.  This brought up all the usual permitting and contractors’ issues for installation, and also some helpdesk-type issues when the cars wouldn’t charge for whatever reason.  While it’s easy to dismiss objections, I would hope that these were teething troubles that loomed large at the beginning of the programme, and will be forgotten at the end of the 12-month lease period.  And perhaps the owners (and fleet/municipal operators) expected BMW to take care of it, as the cars were leased not purchased – I have not detected anything like the level of concern from Tesla owners, who are indeed owners rather than renters of their cars.  But the concern must be noted.

The second major concern was range anxiety.  This is a well-documented trait:  I discuss different aspects in a ‘changing behaviours’ piece on kilowatt-car, but it has not yet been overcome.  Even though the Mini-e has a practical range of 100 – 120 miles (around 250 Wh/mile with the 30 kWh power pack) drivers were concerned they would be stranded.  BMW’s suggestion is to increase the number of charging stations at work and other spots where people might park for some hours while away from home.  This could certainly help, but I would also be interested to hear whether range anxiety can wear off over time:  will Mini-e drivers get more confident the car will last through the day once they have a few months’ experience?  We must hope they will, or electric cars will be heavier and more expensive than they need to be, because of excessively large battery packs.

The third interesting topic is what is not mentioned in the BMW report – the driving experience.  To be fair, BMW seems to be actively surveying their user base, and probably has this information, but one must assume there were few customer complaints about performance and handling.  This is to be expected in a well-specified electric vehicle (a 150 kW, 200 hp motor), but it should be celebrated.  The blog I linked above makes special mention of the very smooth acceleration and deceleration (under regenerative braking) with a ‘Cadillac ride’ and no gear shifting.

The conclusions?  Great to drive, we need to see whether 100 miles is an adequate range, and electricians should be prepared to install many 240V outlets at homes and office parking spots.

Audi’s e-tron: four motors, all-electric

Monday, October 12th, 2009

Audi announced the e-tron at the Frankfurt motor show in September.  Here’s Autoblog with the full press release, and Audi’s US Web site has some impressive graphics.  It’s a concept car, so it’s unlikely it will ever be made in this form, but the press release throws in all manner of detail, from the lightweight construction to LED headlights, low-drag brakes and the like.

But the core of the car is four electric motors, one for each wheel.  This has to be the best design premise for an all-electric car:  it allows fully-independent traction and braking control, while removing the need for prop shafts, differentials and a central gearbox.  Some have taken the concept a step further, with wheel-hub motors.  But Michelin’s Active Wheel (pdf) has not yet reached production, and the Hi-Pa Drive must be in doubt since PML Flightlink entered bankruptcy in late 2008, apparently emerging as Protean Electric, so perhaps Audi is threading the needle with futuristic but attainable technology. 

Audi gets a lot of credit for not just dropping an electric motor and battery into an existing sports car body, but using the opportunity to re-think the entire design.  One could argue it’s an opportunity to bring back every hair-brained scheme to come out of auto design houses for the last decade, but if today’s big car companies are to prosper, they must use their strengths: financial scale, ability to engineer complex systems across many disciplines, and of course supply chain and manufacturing prowess.  An electric drive train offers the opportunity for a radical departure from traditional design constraints, and conventional wisdom must be suspended while we discover what works and where the engineering tradeoffs find a new balance.

The bare specifications for the motors are reasonable.  Power of 230 kW combined (assume that’s peak output) takes the e-tron from 0 – 60 mph in 4.8 seconds, a little slower than the Tesla (and bear in mind the Tesla can prove it, while the e-tron doesn’t yet roll under its own power) from its 185 kW motor.  Top speed limited at around 125 mph, like the Tesla, which would require about 140 kW continuously from the motor.  Audi claims a light weight , although the overall mass is 1600 kg:  perhaps this really is a low figure, if one considers the large battery pack is 470 kg, almost a third of the total.

Audi doesn’t spend much time on the battery pack.  It’s Lithium-ion, no vendor named, and relatively large at a usable 42.4 kWh, which is supposed to take it 154 miles on a charge.  That’s about 275 Wh per mile, about the same as this Tesla owner’s report.

All in all, an impressive concept, and hopefully a harbinger of evolving thinking on mass-produced electric vehicles.  Here’s one train of thought: once there’s a motor on each wheel for traction and braking, all control can be by wire, and intelligence moves into software. Here it can be combined with many more sensors such as road conditions, traffic sensing and avoidance, even route-learning for a regular commute, so the control intelligence knows when an uphill or acceleration phase is coming and can plan for optimum battery use.

What would it cost?  So much depends on the battery pack:  today’s retail price for a 53 kWh pack alone would be around $20,000.  But electric motors can be mass-produced at a low price, power electronics are not overly expensive, and consider the number of complex mechanical components that can be omitted, and it shouldn’t be ridiculously expensive.  Today we have to compare the mass-produced petrol-engined car, with its high volumes and optimized supply chain with the prototype-quantity, un-optimized electric equivalent.  Once cars like the Nissan’s Leaf get into volume production, we will be able to gauge the cost gap in apples-to-near-apples terms.