[McQueen (OP)]

Hi! I have been reading a lot about the new Tesla EV and the lithium-ion batteries it uses. There are some fantastic claims, i.e., the whole battery pack charges in just 8 - 10 minutes!!! and it has a range of 270 miles. The only thing is it costs 100,000 dollars to buy one! Check out http://www.teslamotors.com

[another_someone]

Looking at the various sites (not least, Tesla's own).

No price has is quoted (despite many of the sites quoting 2007 delivery, it now seems to be talking about 2009 delivery).  $100,000 seems to be where people expect it to be, but with wide levels of uncertainty.

I suspect these things have always more problems than anticipated.

Recharge times are 3.5 hours (not 8 to 10 minutes) using a specialist charger, and longer without that charger.

The battery life is expected to be 100,000 miles, but it would not surprise me if the was not somewhat optimistic.

Finally, it does nothing for us guys who need saloons rather than roadsters.

This is not to deny the remarkable technical achievements embodied in the design, but I think it probably glosses over a lot of real world limitations.  It looks like a giant step forward in EV, but still far from the final step that needs to be made.

Bear in mind all the fuss that was made about the Toyota Prius, and other hybrid vehicles, when they came out.  All of this now seems rather stale in the light of all the subsequent limitations.  It is only when the vehicle is on the road that we actually find out what it can't do, as well as what it can do.

[Pumblechook]

I think the Tesla Car is a bit of a joke.  Li-ion batteries are expensive and start to deteriorate from day one and would need replacing at huge cost every few years. The claims are stupid.  The GM EV1 only achieved only  1/3 to 1/2 of the claimed range.  The battery pack is 53 kWh and you could charge it in 3.5 - 4  hours domestically but that would use 100% of a domestic supply.  Everything else would have to be shut-down.  6-8 hours is more practical.

A 10 minute charge would require a 350 kW supply (Typical household supply is 16 kW max).  That could be done at a special 'industrial' charging stations but you would seriously reduce the life of Li-ion batteries charging at that rate. 

Also li-ion have a fire risk.  Laptop batteries have been known to burst into flames and that is only a low power pack.

The US Dept of Energy has concluded that electric cars are expensive to run when all the factors are taken into account. 

Electric cars are no-no really until...

1) Battery technology makes a quantum leap particular regarding the very poor energy/weight ratio which is 1/80 to 1/200 that of petrol.

2) We have the infrastructure to charge or exchange batteries. 

[Pumblechook]

Very good site on batteries...

http://www.batteryuniversity.com/

Li-i

http://www.batteryuniversity.com/partone-5.htm



Quote......

""Aging is a concern with most lithium-ion batteries and many manufacturers remain silent about this issue. Some capacity deterioration is noticeable after one year, whether the battery is in use or not. The battery frequently fails after two or three years.  At the same time, lithium-ion packs are known to have served for five years in some applications.""

[McQueen (OP)]

I have been doing some calculations of my own and find that to recharge a 54 KW hr. battery in 3.5 hrs would take approx. 14KW/sec, if there were just 10 cars in the same neighbourhood charging up at the same time, it would seriously compromise the grid! If  the charging takes place over 8 hours each car would still require around 5 .5 KW/sec, if you had 50 cars recharging at the same time you would still  have the same problem. Two questions, why should a reputed company like Tesla fail to bring up this point in its write-up and how in the face of this did they get official backing from the US Govt. ?  All this aside there is no doubt that the lithium-ion battery does represent a milestone in electrical storage capacity. The obvious solution is a hybrid. The ideal engine to use would be the  Rotary Pulse Jet Engine http://www.geocities.com/rotarypulsejet the engine, is not only small enough and light enough to do the task but also gives pure rotary output and can be attached to low-weight (50Kg) fly-wheel running at (relatively low rpm ( around 25,000 – 30,000 rpm) . The whole engine and fly-wheel combo would have to be set on a gimbal system so that precession in the fly-wheel is countered. Otherwise the fly-wheel would want to go in one direction while the car was going in the other. Using such a system it might be possible to get the best of both worlds. The output from a rotary pulse jet would be the equivalent or better of a 1.5 litre IC piston engine, more than enough to recharge the batteries or even to run a generator to directly power the electric motors.  Of course this still not give a completely pollution free solution but should be extremely efficient (comparatively) since the fly-wheel would be doing most of the work and the RPJ would only need to fire once in a while to keep up the desired momentum of the fly-wheel.   

[Pumblechook]

You have to allow for a charger not being a 100% efficient..more like 85 - 90 and the charging process itself  being around 90% efficient.

I just can't see series/parallel Li-ion battery packs being very good.  One cell starts to go high resistance what happens to that chain? What happens to that cell?  Does it burst into flames?   You would need all sorts  of control and monitoring and maybe steering diodes to prevent current flowing the wrong way through a chain (more loss). 

 

[McQueen (OP)]

Granted that there is still a long way to go till lithium-ion cells are modified so that they are absolutely safe. According to the literature at the Tesla site, one cell failing to work should be no problem. If you think how the cells in mobile phones, i-pods, mp3 players etc., have been improved in only the last few years, (cell phones used to be almost as big as a normal desk phone), you will see what I mean. Further lithium is bio-degradable and can actually be re-cycled, so that is a big plus point. Most important of all is that they could be used in cars if a satisfactory power source were avilable to power a generator to re-charge the battery pack.

[Bored chemist]

What is a "kilowatt per second" a unit of?
Charging a 54KW Hr battery in 8 hrs would take 6.75Kw (assuming 100% efficiency). That's about  twice the rated power of the immersion heater I use for hot water. It's nowhere near crippling the grid.
It might be expensive but it's not going to kill the power distribution network until most people have one.
Trying to charge it in 3.5Hrs would take more power than my house supply is rated for.
A more interesting question is where does all the electricity come from?

[Pumblechook]

I think my car's petrol tank holds about 200 kWh of usable axle energy and I get a little over 400 miles range on that.  54 kWh is the battery capacity.  The usable axle energy will be less.

A 200 kWh battery pack would take some charging and even with Li-ion would weight a heck of lot and most of its energy would be used to cart itself around.

You could say that petrol vehicles have unlimited range as there are filling stations everywhere and 'charging' take a couple of minutes.

The history of electric vehicles is a story of failure really.  There is a long list of special vehicles and electric versions of common models.  They tend to last a few years in the market place and then are withdrawn.

The electric version of my car would have cost a lot more and cost more to run. 

I hate to agree with Clarkson but he is right to sneer at electric vehicles.

[another_someone]

The trouble with electric cars vs. petrol cars is that there advantages and disadvantages are different, and the infrastructure they require are very different.

I suppose the real reason why petrol won out in the end is that it is more convenient for warfare, and transportation systems (aircraft, road transport, rail transport) really get their big boost from the military.

Electric vehicles are range limited, but have their advantage in urban transport.  In that context, an integrated system where electric is used for short range urban transport, while mass transit is used for long range transport, could well work, but we cannot get there from here.

The option of home charging for electric mainstream cars is really a no-no.

Ofcourse, I suppose you could have an integrated domestic power generation system, where you burnt your domestic refuse to drive a steam engine to generate electric power for your vehicle.  That would be cheap, but not sure if it would create anything like enough power, and still leaves the vehicle restricted to journeys near home.

A better integrated system would be to have overhead electric supplies for long distance trunk roads, and allow the vehicle short distances at low speed away from the trunk road.

But all of this requires an overhaul of the infrastructure, and not just to try and slot electric vehicles into what we have.

[McQueen (OP)]

What is a "kilowatt per second" a unit of?
Charging a 54KW Hr battery in 8 hrs would take 6.75Kw (assuming 100% efficiency). That's about  twice the rated power of the immersion heater I use for hot water.

If you look at my post you will see that I had in fact estimated an 8hr. charge to take 5.5 Kw. (I'm not so sure where the Kw/sec comes in either). So  OK this begins to look good, although it might be a bit inconvenient, and if it does work there are a lot of pros going for it. For instance the electricity would come from a centralised source such as a power station and so would be much easier to control pollution. Also you can use a wide variety of fuel including coal to supply that electricity. Again the huge dependency on Middle Eastern oil would be reduced. The point is exactly how many cars could you charge at 6.75 Kw before it affects the grid? A thousand cars charging at the same time would make it 6.75 Mw?  Just looke it up and it seems that the power grid can easily bear a hundred times that load so it is interesting.

The history of electric vehicles is a story of failure really.  There is a long list of special vehicles and electric versions of common models.  They tend to last a few years in the market place and then are withdrawn.

Right, so what about my idea of the Rotary Pulse Jet Engine used in tandem with a fly-wheel and an electrical generator. I have been looking at my last post on the Rotary Pulse Jet Engine and find that it is a bit pedantic and repetitive. So what I am going to do next is to post a new thread in which I will outline a simple experiment to show that the RPJ does in fact work as stated. Complete with pictures so that any one who feels like can DIY.
   

[Pumblechook]

You are moving away from purely electric vehicles if you are on about hybrids.

I gather the Prius fails to live up to the claims.

I think I read that the Peugeot 107/Citroen C1/Toyota Aygo has the best MPG figure. 

[Pumblechook]

""The option of home charging for electric mainstream cars is really a no-no.""

Very true. 

Would you want to drive a few miles to a charging station and leave the car for a couple of hours?   I think I would rather forget about the car and take a bus to my destination. 

I think battery changing at a charging station might make some sense if there was a breakthrough in battery weight.....like a ten+ fold reduction.   

[lyner]

Electric vehicles are absolutely perfect for some applications; particularly when the requirements are very predictable - the milk delivery has been suitable for decades. That number is increasing every year but not at a very high rate. As a second 'town runabout' vehicle, they just about make it - that's all, at the present time.
If they were given specific tax advantages, many people could find them attractive.

[Bored chemist]

It's a thought that has been mooted in the past but what about a battery pack that you swap for a charged one at the "rechraging" station? That might be nearly as quick as filling up with gas and gives more flexibility on charge times.
The problem with electric vehicles isn't (so I believe) intrinsic to the cars, or their means oof propulsion. The problem is with drivers who want to go everywhere in a hurry. Human nature is a problem here but I guess as petrol gets even more expensive the alternatives will look better.

[Pumblechook]

Battery changing is not really on when the battery pack weighs 450 kg as in the Tesla.  This is the weight of 4 - 6 people.

The other snag is ensuring that the battery pack you get at the charging station is in good order.

You have to bear in mind (home charging) that a 100 km range means you wouldn't want go further than about 40 km from home.  I would find it very restricting. 

I would be scared or having a flat bat.  I could imagine being stuck by the roadside for a couple of hours while an emergency  generator van (diesel) gives me a charge.

[Freeman]

That is a real problem.I have a design of a (can call it a type of UPS) that delivers power way beyond what a car battery can give and on a longer period.Still in the design stages though. []

[lyner]

I await your results with interest.

[Freeman]

Thanks sopiecentaur.

Will keep posted on latest results. []

[McQueen (OP)]

The other snag is ensuring that the battery pack you get at the charging station is in good order.

 
That's not really the problem! OK! So you can charge a hundred thousand cars per city without even affecting the power grid. Each of those charges gives over 250 miles. What's the problem?? This is money for jam, right??? I could drive for a whole fortnight on 250 miles per gallon ( read 1000 km or more)
The only draw back is that lithium is a highly volatile substance, something like the sodium we did experiments with in the chemistry lab, it spontaneously ignites under contact with water or oxygen. So with all those batteries under the seat, I am just waiting for the first real test trials.