Alternative Commute Cars
Car Two = C2, uh oh...
The expensive mismatch between my 24 mpg car and my 126 mile roundtrip commute started me looking, somewhat frantically, for alternatives. I wrote up a long list of alternatives, but those relevant to efficient, probably electric, cars are:
The electric car world contains disappointments, too. Some people are so invested in EVs that, in my opinion, they bend statements to suit their special interests. It's not unusual to hear that EVs can go 80mph or that they can go 100 miles - but the 80 mph car wasn't necessarily the same one which went 100 miles, etc. You'll find, too, that EV'ers will bristle at the comment that "EVs are under-powered". The term "under-powered" is sadly subjective but, in truth, EV's store much less total energy than gas-powered cars (power is not the issue; energy is).
I encountered enough misleading or incomplete performance statements that I decided to plunge into the technical books myself rather than risk money and time on a mediocre outcome. Many cars converted to electric have ranges less than 50 miles and I need well more than that. The web page organizes my findings for myself and, I hope, for similarly interested readers.
As a result of my studies so far, I now believe a $14k, 75mph, 75 mile range vehicle is possible. Charging stations seem plentiful to prepare the car for the return trip. The best construction approach is not to convert an existing car but, rather, to build a lighter weight, 3-wheeler design. It would have to be "spartan" in its creature comforts but could be good looking. It would not have most of the safety features typical of modern cars. I suspect that the ultra light weight of the vehicle would make the cost of lithium batteries a possibility, since only a few would be needed.
The EV tried to emerge several times over the last 100 years but gasoline was always more attractive, in part because gas was so cheap and because gas-powered cars could be refueled much faster than an EV's recharging cycle. With gasoline prices passing $4.50/gallon in July '08, the EV arithmetic may finally win out. And gas/electric hybrids circumvent some of the problems of each.
During many of these attempts to promote EVs, new models would be priced at ridiculously high values. I consider the $108K price tag on the current Tesla to be in this ridiculously high arena. EVs will never be really accepted unless the "common man" can afford one.
A January 2009 announcement suggests that Tesla has a competitor! Their recharge vs range figures seem wild but it seems to be an accomplished company. Check out the Shelby Ultimate Aero EV.
Another slice of the EV history details how big corporations manipulated the EV vs gas contests. These distressing stories aren't completely past us either.
LOTS of activity at LOTS of levels. LOTS of foreigners aiming at the US. LOTS of subtleties await the uninformed. LOTS of dated and/or misleading information out there. LOTS of disappointments, burned out people, skeptics... a tough history. LOTS of cautious excitement about what's coming. LOTS of energy and money being thrown into 'conversions', NEVs, crap. What I think the EV world needs:
The financial side of buying and fueling an electric car looked expensive at first. But it all works out to a happy ending. Stick with the text to the end of this section; bailing out early could leave you with a wrong impression.
Electricity is billed "per kilowatt hour". If you run a 1500 watt hair dryer for 1 hour, that's 1.5 kW x 1 hour = 1.5 kWh. The national average cost for a kWh is 10 cents; Washington state pays 8 cents; California starts its billing at 12. So "10 cents, 12 cents" etc don't sound like much but a kilowatt hour is a tiny amount of energy. There are, theoretically, 36.1 kWh in a gallon of gasoline. 10 cents x 36.1 gives $3.61 per gallon. Does it still sound cheap?
We don't, however, get all the theoretical energy out of our familiar gallon of gasoline. So much wasted heat is made by our auto engines, called ICE here, that the net efficiency is only 30-35%. That means that each gallon we buy contains 36.1 kWh of energy but only about 1/3 of that, 12 kWh, ends up providing motion to the car. So, considering only our gasoline cars, for which we'll readily pay $3.60/gallon, we're happy (more or less) to get 12 kWh of motion out of our $3.60. So, our energy (12kWh) seems to be worth $0.30 / kWh (from $3.60/12).
To make an accurate comparison of the gasoline and electric worlds, we have to be fair and ask the efficiency of electricity used in an electric motor, powered by batteries. It turns out that charging batteries typically heats them up and 10% of the ingoing current is lost to that heat. And the motors are 90% efficient so the net for a typical EV is 80%. To get 12 kWh to the rear wheels of an EV, we must buy 12 / 0.80 or 15 kWh. Thus, one gallon of gasoline costs (say) $3.60 and provides the same energy as an EV which extracted 15 kWh, costing $1.50 at the 10 cent rate, from its charging plug.
The electric billing is both better and worse than what was described above. The apparently bad news is that, in northern California anyhow, the billing only starts at 0.12/kWh. If you use more than 363 kWh, the next rate level is 0.13, the next rate level is 0.22, the next 0.31 etc. Before you grab your calculator, a call to the power company suggests that they'll put you on an "experimental" rate plan known as "E-9" which will let you charge an EV at about 0.05 / kWh. A typical, 4000 lb EV stores about 24 kWh of energy. You never go from completely empty and you expect to lose 10% to heat but, for a rough round number, you could plan on 20 kWh per charge, or $1.00. If your EV goes 100 miles, you're down to one cent per mile.
My Mazda conversion isn't as good as the above figures. A charge might be 16 kWh and a long drive might be 24 miles. Before the E-9 electric rate, I paid $0.31/kWh = $4.96. Add 10% for charging inefficiency ($5.45) for a cost per mile of $0.22. With the E-9 rate that drops to 3.6 cents per mile.
Also, some of your charging can be done at public charge sites. While not exactly "plentiful", there seem to be quite a few, even now in Sept '08. See, for instance, evchargernews.com. Costcos, Honda dealers, civic centers, and some airports seem to be installing chargers. If half your charging is done at public locations, your 1 cent / mile is halved.
Note that there are several types of charging systems! My new Mazda truck just has a common 3 prong, 110v plug. A more common charging station is the Magna-Charge. The cited link also mentions the "Avcon plug"
63mi/trip x 2 trips/day x 22 workdays/month = 2772 mi / month divided by 24 mpg = 115.5 gallons x $4.00/gal = $462.00 / month The same commute in an electric, charging it at home each night and at work each day, results in 2772 * $0.005/kWh_E9 = $14/month. The $448 savings can go to EV car payments, vodka tonics, etc. Outline of the rest of this section ------------------ buying an EV. rebates total cost of ownership. battery lifetime. carbon footprint. insurance. resale solar _sustainability_ concept. do-gooders can't _support_ green.
The study was approached without regard for engine type. The equations unearthed would apply equally well to an engine-less cart screaming down a hill. The equations scream "keep the weight low!" and "If you want to go fast, make it sleek!". Here are the details.
TODO: example table. pickup vs indyCycle/Aptera. TODO: note that a partial measurement is useless. It needs power, speed, weight, body style, conditions (if applicable)
ICEs and electric motors are remarkably different from one another. Horsepower for an ICE is determined under ideal conditions under no load. Horsepower for an electric is defined as the power it can output continuously without overheating; its true peak horsepower is often 2-3 times that value.
Electric motors have maximum torque at low rpm; ICE have to idle at a few hundred rpm just to keep themselves running. They have no extra torque to give out at that rpm. That's why letting out the clutch too fast stalls your gas engine.
Electric motors are 90-95% efficient whereas ICE are 30-35% efficient. Most of the energy from your gas tank goes into making heat, not motion. But electric car batteries have their own inefficiencies which must be tallied when looking at system performance. Charging a battery pack can waste 10% of the energy; that is, you have to push 11kwh at a battery pack to store 10kwh. And there is waste when extracting the energy and the amount of this waste is dependent on the type of battery (say Lead Acid vs Lithium), and the rate that you extract the energy. System level efficiencies are:
TODO unfair? does 35% include drivetrain etc?
Electric cars are much simpler to maintain because there are fewer parts. However, many of us are not accustomed to managing large, expensive battery packs.
The weight of an EV's batteries can be prodigious, requiring changes to the suspension, brakes etc.
Gas-powered cars are very fast to refuel. It only takes a couple of minutes at a gas station. Electrics take hours to 'refuel'. There is at least one group trying to address this by standardizing on battery packs which could be swapped at '? stations'. Towns like Sacramento and San Jose publish maps to their EV recharging stations. This idea of swapping battery packs quickly apparently dates back 100 years when electric busses used to do just this when their batteries were depleted.
Realize also that the 'electric-only' car is at least a little more capable of leaving one stranded than our familiar gas-powered car. Someday, charging stations might be plentiful but, for now, there's a least a disquieting risk to an electric-only vehicle.
All-electric vehicles get a white sticker in California. This lets them drive in HOV lanes and pay nothing for bridge fares.
The Lead-Acid battery is expensive - until you look at the alternatives! Let's pretend to put cost aside for a moment and elaborate on the following problems with LA:
First note that 10kwh of LA have the same range as 10kwh x DOD x PE = ~4.8 kwh. This is because the 10kwh LA battery pack doesn't deliver 10kwh; it delivers 4.8 usable_kwh! In fact, it's worse than that because the weight of the LA batteries reduces range by increasing the rolling resistance. Moreover, the support structure for the Li batteries can be lighter because the weight of Li/usable_kwh is ~1/7th that of the LA's (.48 usable_kwh x 1/3.3 the weight per unit energy). The Li batteries cost ~10x as much per energy so the outlay is about 4.8x (.48 x 10). If you were going to spend $1400 on LA; you'll now spend $6720. The two car designs (LA, Li) would have the same usable pack energy, 4.8 kwh but the battery weight of the Li car would be 0.48 x 1/3.3 = 0.14 or about 1/7th the weight of the pack in the LA car. (0.48 because you only needed this usable Li energy for the comparison and 1/3.3 because that's the energy density ratio of the 2 battery types.) This 91% reduction in battery weight means your rolling resistance will be much slower and that, in turn lowers the required wh/mile which increases the range. The exact magnitude of the change depends on the non-battery weight.
Also the calculations don't understand issues like "that model of battery isn't sold to home-builders" (yes, that happens).
If the chassis designer was aiming to carry 12 people in your candidate donor car, you can be absolutely sure that frame is going to be very heavy. If your plan for final weight brings your final weight up to the weight of the original car, a driver, and 3 passengers, look for a 4 seater car. If you see the final car not carrying much more than yourself, consider a sports car like the Porche 914 for the donor. Such a choice should result in great handling, too.
Consider the donor car as having 2 very distinct parts, the chassis and the body. Note that the body can be replaced by a much more aerodynamic fairing/body. When considering body shapes, consider race car designs like the Indy car. The designers have the same goals you do: lightweight, low drag at high speed. And such an approach gives you a "racey" result!
My notes for the next rewrite (#37?): plan each slowdown. can you prevent wasting gas 'driving' to a stop? hills. really _coast_. This means shifting into neutral, not just taking your foot off the gas pedal. tires pumped up. choose times of day, when possible, to avoid stop and go traffic. At high speeds, close the windows and use the AC.
Some govt study I ran across said that 6% of a car's energy goes into heating the brakes! The study suggested that could be reduced considerably by planning your stopping manuevers to avoid as much of this waste as possible. Choose a commute time with less stop-and-go. Let the car coast more, especially as you're approaching a light. This takes more concentration but works for EV's as well as gas-powered cars.
Electric motors supply no friction when turned off; therefore, it will roll even when it's left "in gear".