Performance Electric cars

[a tech]

Hi all

Ex tvtech here and now simply a tech. Missed this place immensely with all that took place a while back where crazyness was the order of the day. Fortunately that sad period is over and done with. So, if nobody minds, I am going to try and get things going again with a few little things I find interesting and hopefully you all will too...

Some of you guys might be aware of Tesla Motors. Being from Africa I only dream to even see one of these: https://www.teslamotors.com/roadster

BMW posted on the Sunday Times website today their latest hybrid car: https://www.timeslive.co.za/motoring/2014/03/12/bmw-s-super-green-supercar-i8-coming-soon

Amazing stuff.

Regards,
tvtech

 

[tcmtech]

I had an electric car some years ago. A ford Electrica which was a basic 1983 Ford Escort Hatchback that had been converted by Jet industries to run on a 96 volt DC power system based on 16 6 volt 220 Ah golf cart batteries.

The thing was even for early 1980's EV tech it could easily run 55 - 60 MPH highway speeds for 20 or so miles or do about 45 - 60 miles of slower intown type driving without problems. Very simple very reliable and it's only main crutch was the LA based battery system.

Now skip ahead 30 years latter and we have lithium and other similar chemistry based battery tech that easily packs 10 -15X the energy into a battery of similar or less physical size and mass as the old LA battery based EV tech used.
By that reasoning a simple cheap EV even with a motor that twice the HP as my old Electrica had should have been on the road with a driving capacity some 5 - 10 times the range (100 - 200 highway at speed or 400- 600 in town) of what mine had.

So 30 years later where are they? Oh wait. Never mind. They just made the battery packs 10X smaller so the overall range is still crap plus made the drive systems so overly complicated and expensive that they put the whole validity of EV tech out of price and practicality of daily useage.

Personally if any of the big auto manufacturers wanted to create a practical EV for the market all they need to do is pair up with one of the many industrial electric drive systems companies that makes systems for the large scale commercial mining equipment and warehouse forklift applications. They pioneered rugged reliable and cost effective all electric drive system tech 40+ years ago.

 

[misterT]

It is all about politics and money. We could all be driving electric cars in 10 years or less, if there wouldn't be these greedy oil-people..

 

[RichTheDude]

Considering my old car puts out a "trobbing" 56 HP (still enough to get the car upto 70 MPH on a motorway, given enough days...), that it still approximately 42 kW - from a 1275 cc engine from 71.

The energy storage required to be equivalent to that engine and it's 11 gallon tank is vast and even with present day technology, I think the range will always be a limiting issue. For the UK and Europe, it maybe ok for driving to work and back, but not much else. The range limitation is always going to put people off I think.

Check out the Honda Clarity. A far better option than batteries as far as I am concerned.

 

[Nigel Goodwin]

It is all about politics and money. We could all be driving electric cars in 10 years or less, if there wouldn't be these greedy oil-people..

Crazy idea - where is the electricity going to come from?, and where is the quantum leap in battery technology required going to come from?.

 

[steveB]

The approach I find interesting is an all electric car with a gas engine dedicated solely to charging a battery system and providing electrical power, rather than directly driving the power train. My liking this approach has nothing to do with "green" or any other politically correct viewpoint, but simply from an engineering point of view, I see so many advantages to this design approach. For example, imagine separate drive motors directly on each wheel allowing ideal traction, direct and efficient drive, breaking and energy recovery. Such a car would be efficient and a great performer as well.

Many technologies are now available to make this practical. We have very good batteries for storage, high power fast switching semiconductors for efficient power conversion, control theory advancements that allow good system understanding and high speed processors for advanced, accurate and fast motor/generator control.

Batteries just do not have the energy storage density of gas/oil and other chemically based fuels and really, they can't from theoretical limits (lithium is the lightest element for making batteries and there is only so much improvement possible from where we are now), and people don't like the idea of limited range. However, give them the range with the gas engine charging system, and they will do their best to charge from local wall sockets at home and at work when they are making short range trips. This is an approach without unacceptable compromises, and can work for everyone.

 

[misterT]

Mercedes-Benz SLS:
**broken link removed**
4WD
740bhp
738lb ft
0g/km CO2
0-62mph in 3.9secs
155mph
155-mile range
3hr fast charge
2110kg

 

[Nigel Goodwin]

Existing hybrid cars are pretty interesting, although their 'green' credentials are a little suspect - I've driven a couple of Lexus examples and they are VERY nice to drive, performance is amazing, and it's hard to tell if it's running electric, petrol, or both (for maximum performance it's obviously both - like KERS on an F1 car).

 

[tcmtech]

Considering my old car puts out a "trobbing" 56 HP (still enough to get the car upto 70 MPH on a motorway, given enough days...), that it still approximately 42 kW - from a 1275 cc engine from 71.

The energy storage required to be equivalent to that engine and it's 11 gallon tank is vast and even with present day technology,

You are overlooking the system efficiency comparison factor. Your IC engine will at best put about 20% of that fuel energy into actually moving the vehicle. The rest is just wasted heat. Any decnet EV has at least 90% energy conversion efficiency which if factored fairly to your 11 gallon fuel tank would mean that given similar efficiency your car would only need about 3 gallons of fuel which works out to being about ~100 KWH of electrical energy which by today's battery tech is very doable and would break down into a battery set that would easily fit into where your old gas tank and engine fit.

 

[tcmtech]

It is all about politics and money. We could all be driving electric cars in 10 years or less, if there wouldn't be these greedy oil-people..

Actually the "greedy oil people" have less to do with it than our own greedy governments that take a very large percentage of tax revenue off of petroleum and everything, especially the fuel, we burn off of it.

"The greedy oil people" only make around 6% - 8% profit out of every dollar you spend on a fuel. Now the government on the other hand takes between 40% and 70% of the rest of that dollar in tax of fuel you bought.

As far as the oil companies are concerned you going EV makes little difference being the fuel you don't buy to power your petroleum fueled vehicle would eventually be bought by the electrical power generating facilities that would be built or expanded on to produce the extra electricity that recharging your new EV will take off the grid.

To be honest from their perspective that would work out more profitable being that the vast majority of new co gen power plants can be set up to burn natural gas or lesser refined liquid fuels which for them are the easiest, cheapest to make and potentially most profitable of their products to work with.

 

[misterT]

Actually the "greedy oil people" have less to do with it than our own greedy governments that take a very large percentage of tax revenue off of petroleum and everything, especially the fuel, we burn off of it.

"The greedy oil people" only make around 6% - 8% profit out of every dollar you spend on a fuel. Now the government on the other hand takes between 40% and 70% of the rest of that dollar in tax of fuel you bought.

Who do you think controls the politicians over there? Congressmen are just puppets on a string in the US.

 

[rc3po]

Crazy idea - where is the electricity going to come from?, and where is the quantum leap in battery technology required going to come from?.

It seems to me that it would be better to use the batteries to power a hydraulic pump and operate the car with a hydraulic power system rather than a large electric motor.

 

[rc3po]

Who do you think controls the politicians over there? Congressmen are just puppets on a string in the US.

Not just in the US. Politicians are marionettes just about everywhere.

 

[misterT]

It seems to me that it would be better to use the batteries to power a hydraulic pump and operate the car with a hydraulic power system rather than a large electric motor.

You mean use large electric motor to power the hydraulics? What is the sense in that?

 

[Nigel Goodwin]

It seems to me that it would be better to use the batteries to power a hydraulic pump and operate the car with a hydraulic power system rather than a large electric motor.

Even crazier idea - adding an extra layer of conversion to gain nothing (and lose plenty).

 

[rc3po]

Even crazier idea - adding an extra layer of conversion to gain nothing (and lose plenty).

It works pretty good in aircraft and heavy equipment. It wouldn't take much pressure to push a car.

 

[JimB]

As an electronics person who "discovered" hydraulics quite late in my career, I think that hydraulics have some very useful characteristics.
But, as Nigel has already pointed out, there is an extra energy conversion process, with its attendant losses reducing the overall energy efficiency.

JimB

 

[rc3po]

The approach I find interesting is an all electric car with a gas engine dedicated solely to charging a battery system and providing electrical power, rather than directly driving the power train. My liking this approach has nothing to do with "green" or any other politically correct viewpoint, but simply from an engineering point of view, I see so many advantages to this design approach. For example, imagine separate drive motors directly on each wheel allowing ideal traction, direct and efficient drive, breaking and energy recovery. Such a car would be efficient and a great performer as well.

Many technologies are now available to make this practical. We have very good batteries for storage, high power fast switching semiconductors for efficient power conversion, control theory advancements that allow good system understanding and high speed processors for advanced, accurate and fast motor/generator control.

Batteries just do not have the energy storage density of gas/oil and other chemically based fuels and really, they can't from theoretical limits (lithium is the lightest element for making batteries and there is only so much improvement possible from where we are now), and people don't like the idea of limited range. However, give them the range with the gas engine charging system, and they will do their best to charge from local wall sockets at home and at work when they are making short range trips. This is an approach without unacceptable compromises, and can work for everyone.

That would probably be c

You mean use large electric motor to power the hydraulics? What is the sense in that?

It wouldn't take a large motor because a car wouldn't require very high fluid pressures. But the pump would need to be high volume. Also, the mechanical advantage of a hydraulic system would out way any energy conversion concerns.

 

[tcmtech]

It wouldn't take a large motor because a car wouldn't require very high fluid pressures. But the pump would need to be high volume. Also, the mechanical advantage of a hydraulic system would out way any energy conversion concerns.

I have worked with industrial hydraulics and have a good understanding of them and I can assure you your way way off in your reasoning.

A good rule of thumb for figuring out hydrostatic flow and pressure requirements is the the rule of 1500 which means that for every one horsepower of mechanical energy put in or taken out 1500 units of flow times pressure have to be accounted for. 1 hp = 1 GPM at 1500 PSI or 1500 GPM at 1 PSI or any combinations of the two that multiply out to 1500.

Power in equals power put minus losses which admittedly in modern hydrostatic drive system can be less than 5% in worse case working conditions but still it's a 5% loss as is.

 

[Nigel Goodwin]

It works pretty good in aircraft and heavy equipment. It wouldn't take much pressure to push a car.

For moving heavy things slowly, and with no regard to efficiency, it's excellent - and has it's place.

However, it would be absolutely useless for a car - have you ever driven an hydraulically powered vehicle? - aircraft aren't powered in that way, and most heavy plant uses a diesel engine for it's motive power, those that use hydraulic motive power only do 2-3 mph.