Aluminum cars better for EV conversion

[Photonfanatic]

Drivers.com: After 50 years, aluminum cars are back

I was thinking of the Audi A8 that he mentioned. From the article:

"But at the 1999 Frankfurt Motor Show, Audi unveiled a new five- door hatchback it claims is the world's first aluminum car to be signed off for volume production. The A2 weighs approximately 43% less than it would if built from steel using conventional processes, having a considerable effect on fuel consumption and handling agility.

The primary reason for the increased use of aluminum in the automobile is cost-effective mass reduction. In combination with advances in power train efficiency, aluminum can achieve significant gains in fuel efficiency and reduced atmospheric. A 10% reduction in weight, for example, can achieve at least an 8% increase in fuel efficiency.

Aluminum permits manufacturers to reduce vehicle weight while maintaining size and strength, offering the possibility of radical redesign."

Sounds like aluminum is the only way to go for an EV. I don't know offhand if the Leaf is aluminum, but at its cost I kinda doubt it. Maybe getting some used, scrapped audi A8 from the junkyard could make a good EV conversion? Might be more practical due to its increased size and lighter weight. Aluminum cars are a little hard to come by, so it occurred to me that maybe no one around here has used on in an electric vehicle conversion.

[jakobnev]

Kerb weight 4,045 pounds (1,835 kg)

lol

[NeilBlanchard]

I think that weight is a lot more important when you have a internal combustion engine, than when you have an electric motor. Because when the engine is wasting about 2X more energy than it is producing, acceleration is a huge loss. With an electric motor you are losing only 1/10th the energy, so acceleration is not as critical -- and you can return 60-75% of the excess kinetic energy back to the battery with regenerative braking.

[Ryland]

Did any of those ever go in to production? back in 2007 when that was written it sounded like nothing was set in stone.
Also, there are plenty of light weight steel cars that are much easier to find and cheaper to buy, of course it is nice and fun to have an aluminum car, my Commuti-car is an all aluminum frame and safety cage with a plastic body over it, very light, even after 500 pounds of batteries the car only weights 1,400 pounds, the Honda Insight (first generation) was also all aluminum and back in the early 1990's I saw first hand one of the all aluminum Ford Taurus that was used for the future car competition where it won first place by getting over 60mpg on a course that was supposed to require normal driving.
Personally I would opt for a car that had good aerodynamics for building an electric car out of.

[ConnClark]

Originally Posted by NeilBlanchard

I think that weight is a lot more important when you have a internal combustion engine, than when you have an electric motor. Because when the engine is wasting about 2X more energy than it is producing, acceleration is a huge loss. With an electric motor you are losing only 1/10th the energy, so acceleration is not as critical -- and you can return 60-75% of the excess kinetic energy back to the battery with regenerative braking.

Electric motors are least efficient at start up and low RPMs so weight is still an issue. Less weight would reduce the load peaks which in addition to saving battery charge would also extend the lifetime of the batteries.

[mcrews]

02 Infiniti Q45 had a lot of alloy and allum bringing it's weight to 3801lbs.
In it's class bmw 745, lxeus 430, mercedes etc it was the only car below 4000. the next lightest was 4300 lb.

with the 2.78 rear end gear, I have been able to get 30+ mpg on the highway

[user removed]

Consumer reports calculated the emergy loss in charging a Leaf at 15%. That makes your 90% figure 90% of the 85% you actually get into the battery.

76.5%

regards
Mech

[DJBecker]

Originally Posted by NeilBlanchard

With an electric motor you are losing only 1/10th the energy, so acceleration is not as critical -- and you can return 60-75% of the excess kinetic energy back to the battery with regenerative braking.

Not even close. A reasonable estimate for full-cycle regenerative efficiency is 20%, with 30% being feasible.

Actually, by a generous interpretation, your statement isn't completely untrue, just misleading. It's possible to "return 60% of the energy back to the battery". It's just that you are going to lose another 15-20% with the battery charge/discharge cycle, and then be only 60% efficient returning that energy during acceleration. And be pretty much at 20-30% full-cycle efficiency.

Continuing my hope-vs-reality theme, I don't see the opportunity for a 43% overall weight reduction by replacing the steel with aluminum in a modern car. Most of the feasible drivetrain parts have long been lighter alloys, such as heads and transmissions cases. You aren't going to convert the brake disks, crankshaft or transmission gears to aluminum. And there are big chunks of the rest of the car, glass and interior furnishings, that will remain the same.

[redpoint5]

Isn't the frame itself something that could be made of aluminum to substantially reduce weight? I once made an aluminum frame for an electric vehicle that we raced in high school endurance races. The entire frame could easily be picked up with 1 hand (best guess is 15lbs).

Reducing weight is one of those things that allows you to further reduce weight exponentially. A lighter car doesn't need such beefy suspension, axles, brakes, etc. It can have a smaller and lighter engine since it accelerates easier. Get the engine small enough and it will operate closer to peak efficiency on the freeway as you have to give it a greater percentage of throttle to overcome aerodynamic drag.

For coastal or snowy areas, an aluminum car would be impervious to the corrosive environment.

How much extra would it cost to build a conventional frame car out of aluminum? Lotus uses an aluminum chassis in the Elise as shown here.

[user removed]

Lets say you have 600 HP seconds of energy to collect in 20 revolutions of each of 4 wheels (60 to 0 panic stop 130 feet).

How much of that are you going to get into your battery?

How much of that percentage are you going to get back to the wheels?

You're going to do that with no transmission, IE direct drive or gear reduction?

30% is very good.

Hydraulic hybrid systems were pushing 80% 5 years ago.

regards
Mech