Forgot your password?
typodupeerror
User Journal

DaChesserCat's Journal: Plugging in to reduce gasoline use

Journal by DaChesserCat

I've been looking long and hard at how hard/expensive it would be to make/buy an electric vehicle. I'm currently commuting about 85 miles / day to work (round-trip). Considering that my pickup ('98 Dodge Dakota) gets, at best, 20 mpg, I'm looking at NLT 4.25 gallons of gasoline to go work. That's each day. Considering the $1.70/gallon price tag, we're talking roughly $8/day for gasoline. Considering an average 23 work days/month, we talking over $170/month just for gasoline. That works out to over $2,000/year.

Ouch!

Electricity in our area is about 7.5 cents/kWh. It's due to go up in a month or two; the new price will probably be more like 8.5 cents/kWh. Even at the higher rate, if I can get 5 miles/kWh, that's about 1.7 cents/mile. That's about $33 / month, or about $400/year. We could much more easily part with that amount. Consequently, I need something which can:

  • run year-round (scratch motorcyles; winters get downright NASTY in the midwest)
  • keep up with traffic on the Interstate (70 mph speed limit; 75-80 mph would be a reasonable top speed; effectively eliminates any kind of Neighborhood Electric Vehicle)
  • have at least a 90 mile range (in case I have to divert around a traffic jam; also eliminates NEV's)
  • recharge fully in a reasonable timeframe (overnight is fine with me)

There WAS vehicle which met these criteria: the GM EV-1 (aka Impact). Unfortunately, I can't get one of those because:

  • GM never sold them, only leased them
  • when their leases were up, GM refused to extend them, even though the current lessees were VERY happy with them; many drivers offered to buy them outright, but GM wouldn't sell
  • nearly all of them have now been scrapped; supposedly, they're going to keep a couple to put in museums

The linked page provides some interesting information on the car, as does a Google search. The car didn't have a transmission. The 3-phase AC induction motors they used (two of them) directly drove the front wheels (no tranny, and no differential). This reduced weight and mechanical complexity. Getting the motors to turn backwards (reverse) was accomplished by feeding a different signal to the motors (if it had used DC motors, they'd just switch the polarity of the power connections on the motors to make them turn backwards; AC Induction motors are very different beasts, though). Also, they didn't need gears because the motors turned solid torque from static (non-moving) all the way to 7000 RPM. While the linked page specifies .26 kWh/mile (approx 4 miles/kWh), other pages have claimed real-world performance of .16 kWh/mile (6 miles/kWh). Consequently, in a direct-drive design (like this one), with a pair of AC Induction motors, 5 miles/kWh isn't unreasonable.

The problems with most "Do-It-Yourself" electric conversions include:

  • DC motors are used, rather than AC induction motors. DC motors are heavier and less efficient, but they are simpler to install and operate. AC Induction motors are more expensive because they require a more expensive controller, which converts DC from the batteries to the complex, multi-phase, variable frequency signal needed by the motors.
  • the motor is typically connected to the transmission, which typically includes a significant amount of friction. The motors aren't cheap, so, rather than buying two engines and connecting them straight to the wheels, keep the tranny and buy only one motor. Many owners of converted EV's state that they really only need one or two gears, but they still have all of them, with their inherent friction. While a more efficient method might be to remove the tranny and tie straight to the differential, most conversions are front-wheel-drive vehicles, and such vehicles typically have the differential built into the tranny.
  • Electrical systems for these cars are usually single-purpose. By this, I mean that the car has a system which takes power from the batteries and feeds it to the motors. While most are capable of regenerative braking, the system isn't really designed for this, so it is less efficient. Additionally, a charging circuit is typically something which sits the garage (an external box) and gets connected directly to the batteries at night. Consequently, the vehicles are limited in where they can charge.
  • Lead-acid batteries are typically used. These are cheap, but only store about 25 Wh/kg. This means 88 pounds of batteries for 1 kWh of electricity. If you need 20 kWh, that's 1760 pounds of batteries. As you may imagine, adding that much weight to a vehicle makes a dent in the efficiency.
  • between the weight and the relatively low power output, such cars tend to be gutless wonders

If there is some good news, it is:

  • companies like Metric Mind are starting to appear, which carry AC Induction motors and controllers. These are more efficient than the older DC hardware.
  • newer batteries are becoming available, such as Nickel-Zinc batteries. At 60 Wh/kg, that's about 35 pounds of batteries for 1kWh, or 700 pounds for 20 kWh. If you really want to sink some money, you can buy Lithium-Ion batteries, like these guys. They put about 50 kWh of storage in a vehicle, giving it a 250+ mile range. Additionally, they have the DC-AC conversion hardware (for powering the car) AND the AC-DC conversion hardware (for changing the batteries) built-in, with many components doing double-duty. These guys are definitely on the right track. Since one of their founders was an engineer on GM's EV-1, I guess that's no surprise.

The fact remains, however, that there still isn't an answer in sight. Not, at least, for me. There are no commercially available vehicles with the performance and range I need. I was hoping that I might be able to find an electric motorcycle, which would reduce my commute cost at least PART of the time. No dice. Google searches on "electric motorcycle" refer you to a few pages about people who've done their own conversions, or a limited number of professionally engineered experiments which aren't commercially available.

One other item of good news is found in this article. It mentions a college professor at UC-Davis who has been developing hybrid vehicles, and is currently working on something he calls a "heavy" hybrid. Basically, it's a combo between an electric vehicle and a hybrid. By this, I mean that you can plug it in, charge it up, run about 60 miles on electricity, but still kick on an ICE with generator for those occasions when you're going to be going beyond the battery range. It's also referred to, in other articles, as a "plug-in hybrid" or a "grid-connected hybrid." In my eyes, it's one of the most intriguing technologies I've seen in years. According to the article, more than 80% of commuters drive less than 60 miles at a time. Consequently, with one of his vehicles, you could plug in, charge overnight, and commute to work and back on electricity (no gasoline involved). And yet, if you want to do a major road trip, you don't have to worry about finding charging stations for your vehicle. Just "fill 'er up," and get on with it (with better MPG than most vehicles on the road). Additionally, if the power fails at your house, your vehicle could function as an emergency generator for your household.

Hey, Detroit. Can we get some of these? Please?

This discussion has been archived. No new comments can be posted.

Plugging in to reduce gasoline use

Comments Filter:

Nothing is easier than to denounce the evildoer; nothing is more difficult than to understand him. - Fyodor Dostoevski

Working...