RE: Driven: Tesla Roadster

[Mr Gear]

simonrockman said:

xyphod said:

Rather than charge the batteries, why not just change them at your local petrol station. If car makers could come up with a standard size that would solve most of the problems.
I think the electric drive train will be the future. Either via batteries or powered via fuel cells.
A h2 based compustion engine if far less efficient compared to fuel cells.
At the end of the day a power station is far more efficient that our beloved internal compustion engine.
The near future (50 odd years) will be a combination of Nuclear/Alternative and CO2 capture, unless there is a massive break through in nuclear fusion.

Hopefully cars will become lighter as well with improved mass production of carbon/glass fibre.
The Tesla looks like a great car. Alas I don't think they will last as a company, they will either be bought for the technology or be outdone by BWM/VAG (can't see GM or Ford catching up at the moment)

Because the battery is a wearing part. You have to think of the charge as the fuel, not the battery. A battery typically has about 1,000 cycles before it holds too little charge to be useful. If you'd just bought a new car with many thousands of pounds worth of batteries would you really want to swap those with someone whose car is three years old and on their last legs?

There are ideas for rental schemes but it needs a massive mindset and infrastructure change.

Simon

I actually think battery swaps are a great idea... the problem described is overcome by non-ownership of the batteries, and a sophisticated battery management system not only allows the batteries longer life, but shows how close they are to failing.

That said, I was chatting to a guy who makes automotive batteries, and he disagreed. He thinks the problem with battery swap systems is that you need about 3 batteries for every car and he strongly believes that optimising battery tech for each make and model of car is far better.

I can't quite see it myself, but he is the expert and I am not.

[The Wookie]

It would be so limiting with regards to packaging and chassis design that it would impose a serious compromise on the vehicle you wanted to fit it to, and would limit vehicle diversity.

As said before, the limitation in the near future will not really be the rate you can charge the battery but the rate at which you can supply charge to it.

[Mr Gear]

I guess packaging comes into it too.

It's fair to say that the Tesla battery is a massive bodge-job, with a compromised location and construction, but fair play to them, they made it work pretty well considering.

[JonnyVTEC]

The Nissan Leaf is to be based on you 'buy the car but rent the battery' model. Makes sense when entering a market with such a product and its known concerns.

[skwdenyer]

simonrockman said:

xyphod said:

Rather than charge the batteries, why not just change them at your local petrol station. If car makers could come up with a standard size that would solve most of the problems.
I think the electric drive train will be the future. Either via batteries or powered via fuel cells.
A h2 based compustion engine if far less efficient compared to fuel cells.
At the end of the day a power station is far more efficient that our beloved internal compustion engine.
The near future (50 odd years) will be a combination of Nuclear/Alternative and CO2 capture, unless there is a massive break through in nuclear fusion.

Hopefully cars will become lighter as well with improved mass production of carbon/glass fibre.
The Tesla looks like a great car. Alas I don't think they will last as a company, they will either be bought for the technology or be outdone by BWM/VAG (can't see GM or Ford catching up at the moment)

Because the battery is a wearing part. You have to think of the charge as the fuel, not the battery. A battery typically has about 1,000 cycles before it holds too little charge to be useful. If you'd just bought a new car with many thousands of pounds worth of batteries would you really want to swap those with someone whose car is three years old and on their last legs?

There are ideas for rental schemes but it needs a massive mindset and infrastructure change.

Simon

In which case, let's review the battery model and look at something like, say, mechanical storage devices - flywheels, running in a vacuum, sitting on gimbals to mitigate gyroscopic effects, and packaged somewhat like, err, batteries. With the extensive knowledge of bearing technology, it ought to be possible to design such a device to last the life of the car.

[JonnyVTEC]

Let me guess, you would charge the flywheel at home with.... an electric motor. Energy storage would be even more of an issue. The Flybrid only really wins out on how quickly it can store energy and its wheel to wheel efficiency to supplement another type of main powertrain. Ie you brake to a stop and capture close to all the energy unlike batteries where they prefer a slow charge (this is where capacitors also make sense) then you can reuse the energy to accelerate. Makes a massive difference around town for example.

[skwdenyer]

JonnyVTEC said:

Let me guess, you would charge the flywheel at home with.... an electric motor. Energy storage would be even more of an issue. The Flybrid only really wins out on how quickly it can store energy and its wheel to wheel efficiency to supplement another type of main powertrain. Ie you brake to a stop and capture close to all the energy unlike batteries where they prefer a slow charge (this is where capacitors also make sense) then you can reuse the energy to accelerate. Makes a massive difference around town for example.

You put the electric motor in the vehicle; plug it in and spin up the rotors. I'm not talking about the Flybrid (which has a different purpose), but genuine mechanical-electro storage devices, of which there are legion in common use in (for instance) large-scale UPS installations.

[JonnyVTEC]

Can you imagine the energy in a wheel like that to stored enough energy for 100 miles? Lets say 25kWh. The mass would soon drop how much range you would get out of such a system aswell.

Where would the electric motor for your suggested system get its power? More efficient just to drive the wheels directly.

The idea you 'charge' them up rather than heating up your brakes. Storing only the energy one one speed retardation event that you then recycle when building your speed back up. Much like a hydraulic system one some commercial vehicles that sports 80% round efficiency. Basically if you stop from 45mph you can get back to 36mph without starting the main engine up.

Air cars seems another alternative for the urban car model.

Edited by JonnyVTEC on Friday 4th December 21:02