Sunday, April 7, 2013

Enter the Honda Fit EV

I've leased a 2013 Honda Fit EV.

I'm not really one for "green" thinking. I've said more than once that I think that most of the things that are supposed to be good for the planet are either foolishly costly or ineffective or both. But if you find a way to save me a dollar, you have my attention.

I've talked about this a bit of Facebook, but I think it's worth adding a bit here about the math.

A gallon of gasoline has 33.4 kW-hr of energy in it.

Silicon Valley Power rates are 8.877¢ per kW-hr for the first 300 kW-hr and 10.205¢ for kW-hrs after that. 300 kW-hr isn't a lot, so let's assume the worst and say that it's the 10.205 rate. If you were to magically turn electricity into gasoline at 100% efficiency, you'd be able to gas up that way for $3.41 per gallon. That's not such a big difference, but it is a pretty good deal. But still, the cost of the energy isn't where the big difference is.

Gasoline car efficiency is traditionally measured in miles per gallon. EVs are measured in either miles per kW-hr or kW-hr per 100 miles. The EPA rates the Fit EV as a combined city/hwy of 29 kW-hr/100mi, or 3.44 mi/kW-hr. Convert that into mpg and you get about 115 MPGe.

Despite that, the Fit EV is almost a muscle car in its ability to launch itself off the line. I'd love to take a day off some day to make a trip up to Sonoma to try the quarter mile (of course, it means stopping in San Francisco to charge up... It's just always an issue). I'm pretty confident it could turn in a sub-15 second time. I'm an unapologetic lead-foot and this car is a downright joy to drive. If you put it in "sport" mode, you get a full 123 horsepower and a healthy 189 ft-lb of torque. That's only a little less than Volkswagen's TDI engine (140 hp and 256 ft-lb of torque, but the torque curve of a diesel engine is far narrower than an electric motor).

Though using electricity is a very efficient way to obtain motive power, it's horrendously slow to deliver it and difficult to store. The 20 kW-hr battery represents the energy in less than 2/3 of a single gallon of gasoline and weighs more than 800 pounds. By contrast, an 18 gallon gasoline tank is 600 kW-hr. If I had a 600 kW-hr battery, I'd be able to go almost 2000 miles between charges.

But even that isn't the big issue. The charger built-in to the car is rated at 6.6 kW. In other words, 6.6 kW-hr per hour. So it takes 3 hours to charge completely from empty. Recharging the mythical 600 kW-hr battery above at that rate would take 90 hours - almost 4 days. Even the CHAdeMO HVDC chargers they have now are 62.5 kW - 10 times faster (though it should be noted that the Fit EV isn't equipped with a CHAdeMO port, and frequent use of high-power charging will decrease battery life long term). But those require 3 phase 480v power feeds. My house has a 200A @ 240V service panel - that's only 48 kW, and that's my whose house.

With these sorts of limitations, EVs are reasonable "second cars." But you can't seriously consider taking one on a road trip. No, not even a Tesla. Tesla's strategy is to deploy so-called "supercharger" stations at strategic locations to enable road trips. They have one at Harris Ranch, one in Bakersfield, as well as in Los Angeles.

I'm sure Elon Musk has thought about this longer than I. But I think this strategy is misplaced for a couple of reasons. Let's use my occasional trips to San Diego as the basis for my argument. The trip is 450 miles and takes a total driving time of about 7 hours. It takes longer than that for the trip because of refueling stops (for the car and the driver). In a gasoline car, I've been known to make it in 8 hours or less. Refueling takes about 15 minutes.

The range of a model S is not particularly relevant unless it doesn't make it between Supercharger stations or unless it can "skip" one (no way). Tesla knows this and placed them strategically along I-5. They say they can charge about half way in half an hour. But half a charge won't get you to the next station.

This strategy will only work if the cars stay rare, which clearly is the opposite of Tesla's goal of selling cars (duh). But setting that aside, the trip to San Diego will require 3 intermediate stops for refueling, which will take around an hour each. So the 8 hour trip is now 11 hours.

No. It's just not going to work.

The only solution to this conundrum is temporary auxiliary power provisioning for long trips. This means one of three things:

  1. Liquid fuel powered pusher trailers
  2. Liquid fuel powered generator trailers
  3. Swappable battery pack trailers

Petroleum powered pusher trailers are actually a fairly mature idea. Many tinkerers out there have taken a front-wheel drive vehicle, chopped off the back half, locked the steering, added a trailer hitch and attached it to an EV.By contrast, the idea of using an engine and generator to power the car isn't so great. Scooting down the highway, the car requires something like 20-30 kW just to maintain highway speed. A 20 kW generator is going to be one heck of a trailer. Still, it has been done before (note, however, that the EV hauling this monster is an SUV).

I think the battery pack trailer has the best long-term prospects. Tesla could replace their supercharger stations with a trailer exchange station. Trading out trailers would take probably less time than filling the tank of a conventional car would. The problem there is that 40 kW-hr of battery weighs a good 800 pounds. That's bound to have an impact on the car's performance. Still, 3 100 mile battery swaps, plus the car's internal 150 mile range (remember, we're talking about a Tesla model S) is the 450 miles of the benchmark trip.

However you decide to provision auxiliary power, I think having it be available for temporary rental for road trips is the way to go. If the APU is petroleum (or methanol) powered, the agency renting it will be on the hook for proper maintenance of the emissions controls. Additionally, a rental fleet can be turned over more quickly as technology improves.

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