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Author Topic: What is holding back electric car technology?  (Read 144311 times)

Offline Pumblechook

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What is holding back electric car technology?
« Reply #75 on: 15/03/2009 23:26:23 »
Electric vehicle manufactures tend to claim double or even three times the range that actual  owners get.

They use the magic phrase..'up to'.. and is done on rollers.

And a 50 kwh battery needs more like 80 kwH to charge it. Chargers are not 100% efficiency and neither is the charging process.. In any case a 50 kWh battery wouldn't last long if we deep discharged,

Electric Vehicles = inefficient..  far from green..  Basically a waste of time.
 

Offline wolfekeeper

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What is holding back electric car technology?
« Reply #76 on: 15/03/2009 23:38:52 »
Shrugs, I don't think you're right in this case, but either way, don't care. My electricity supply can still handle that with total ease.

And don't forget that electric cars are a lot more efficient than IC cars. Tesla gets about 80%, whereas a petrol engined car might be ~20%. And the electricity they use is made more efficiently at the power station using gas turbines, and may be produced using nuclear or hydro.
« Last Edit: 15/03/2009 23:40:58 by wolfekeeper »
 

Offline wolfekeeper

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What is holding back electric car technology?
« Reply #77 on: 15/03/2009 23:50:58 »
FWIW I checked, and LiIon batteries are about 80-90% efficient as regards charge/discharge, and I don't agree about the 'not last long', they have charge cycles of 100-1000s, which is adequate for a car (I worked out the cost of the Tesla battery and electricity was less than the petrol per mile for example.)
 

Offline Pumblechook

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What is holding back electric car technology?
« Reply #78 on: 15/03/2009 23:53:53 »
Waste of time.  That is why they have barely advanced in decades and there are very few on the roads.  

So what the efficiency of a petrol engine is 20%.. calorific to mechanical output.  It remains that petrol has the order of 100 times the axle energy per kg of a bettery.  Burn the same fuel in a power station and the overall efficiency of an electric vehicle is much lower.  Make more sense to burn the fuel directly in the car.  Hydro is limited and nuclear ain't cheap.
 

lyner

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What is holding back electric car technology?
« Reply #79 on: 16/03/2009 00:06:57 »
My household supply could fill up a 50 kWh battery as used by Tesla Roadster just fine thanks, overnight, from completely empty.

I mean, even the cooker circuit is rated at 7.2 kW. It could do that in 7 hours.

And my daily commute is nothing like the 200+ miles that the Tesla manages; more like 20.
What I meant was that your energy supply will need to increase to something like double what it is now if your transport energy is to come down the same cables. It's not only peak power that counts.
http://www.after-oil.co.uk/energy.htm
claims that, by 2020, transport will represent 50% of energy consumption in the UK. I estimate that personal transport costs would be a similar fraction of total personal consumption. That is a major issue.

Pumblechook's points are also relevant - I think the percentages are still not enough for the case to be anything like as clear-cut as wolfekeeper makes out. For a start we should need a lot more information about the actual performance of these new cells when used for ultra high power / energy applications. Without data on the internal resistance of the cells, we cannot know the efficiency of the charging process. I have a feeling that even the voltage drop across the rectifiers (about 0.5V) represents a big percentage of energy loss - at any charging rate, for large capacity batteries.

The 80% vs 20% figures are not comparing like with like and they well overstate the case. The use of hybrids allows a significant clawback on the 20% figure. A small IC engine, operating under ideal parameters could be much more efficient.

The quoted charge efficiency of 80-90% - what rate of charge does this apply to?

You'd need to break out a proper spreadsheet to deal with all the factors - including extra payload etc. etc. before you could give a convincing case that these new cells are the answer to the (driving) maiden's dream. Of course the developers of the new tech are going to overstate their case where they think they can get away with it. I am just being healthily skeptical.
 

Offline wolfekeeper

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What is holding back electric car technology?
« Reply #80 on: 16/03/2009 00:21:17 »
I did some more checking. They reckon that petrol engines are about 30% efficient (I say, probably on a good day only), whereas the point of use electric power efficiency is about 35% in the UK (about 30% in the US).

All inefficiencies together, they're about the same.

However, the electric car probably has much more upside potential- CHP can achieve about 90% efficiency so there's a possibility of generating power locally, to charge your car and give you hot water and heating at the same time. Also, dealing with pollution at a power station is much easier (or you could use nuclear or whatever, this is base load power supply we are talking about, which is cheaper). Also increasing the efficiency of a petrol car further is not as easy as improving a power station.

And around town, there's no contest, an electric car uses regenerative braking and similarly standing in traffic is completely more efficient.

As to your specific point about the voltage drop across a rectifier, that depends on the voltage you're using obviously, the higher the better; at 240 volts that's only about 0.5% loss of power. Its about twice the percentage loss of the voltage.
 

Offline wolfekeeper

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What is holding back electric car technology?
« Reply #81 on: 16/03/2009 00:28:37 »
Even without CHP it's reckoned that supply efficiencies of 48% may be achievable. See: http://chp.defra.gov.uk/cms/centralised-electricity-generation/
 

Offline Pumblechook

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What is holding back electric car technology?
« Reply #82 on: 16/03/2009 00:28:44 »
I have a personal DAB radio with a Li-ion battery and they advise you not to buy a spare battery because when you come to use it in 2/3 years time it will be duff.. poor shelf  life.
 

Offline wolfekeeper

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What is holding back electric car technology?
« Reply #83 on: 16/03/2009 00:35:49 »
There's lots of different sorts of batteries out there though. Li-Ion seem good for frequent use and have an excellent capacity/weight ratio. Others are a bit heavier but have much better shelf life.
 

Offline Pumblechook

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What is holding back electric car technology?
« Reply #84 on: 16/03/2009 01:01:58 »
We have gone through the calculations on other talkbords and the conclusion was that 'current' electric vehicle are pretty expensive per km to run.

 

Offline wolfekeeper

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What is holding back electric car technology?
« Reply #85 on: 16/03/2009 01:28:32 »
[[citation needed]]
 

lyner

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What is holding back electric car technology?
« Reply #86 on: 16/03/2009 09:38:10 »
There's lots of different sorts of batteries out there though. Li-Ion seem good for frequent use and have an excellent capacity/weight ratio. Others are a bit heavier but have much better shelf life.

But doesn't your baby rely on Li-Ion and the new technology?

 

Offline wolfekeeper

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What is holding back electric car technology?
« Reply #87 on: 16/03/2009 15:57:01 »
Not necessarily, there's quite a few technologies out there including other lithium based ones with pros and cons.
 

lyner

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What is holding back electric car technology?
« Reply #88 on: 16/03/2009 22:30:08 »
Fast charging, too?
I thought it was the latest thing which made your case.
 

Offline teragram

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What is holding back electric car technology?
« Reply #89 on: 17/03/2009 17:07:07 »
We've been here before. It's the power supply that the filling station would need that's the problem.
If you need to charge a 2000Ah battery in 1/100 of an hour (i.e. less than a minute) you would need to charge at 200,000A. That's going to need around 1,000A of mains power for each vehicle being charged. Then there's all the heat that it would produce during charging.
A petrol pump gets the energy in with much less fuss.

Perhaps I’m wrong, but:-
A 2000A/h battery would be 25Volts (for around 50KWh). The Tesla battery is I think 375Volts, so the battery currents involved are about 15 times lower, i.e., to charge in 1 hour needs (approx.) 50KWh/375V = 140Amps, or in 1/ 100 of an hour 14,000Amps.
Who says you have to charge in less than a minute? 10 minutes would be convenient.
Battery current would then be 140 x 6 = 840Amps.
In a “Charging Station”, mains current required to charge a 50KWh battery in one hour at 440Volts is about 90Amps per phase, so to charge in 10 minutes would be 540Amps. Nowhere is 200,000Amps needed.
And remember that day to day charging will be achieved at home by a very large number of people. Charging from dead flat might be quite rare.

The argument about the efficiencies of battery power versus petrol/Diesel must also account for the energy cost of processing and transporting liquid fuels and crude oil, and of course transporting coal.
 
Yes a petrol pump is more convenient, but what about when:-
a) the human race finally admits that it MUST stop burning oil,
     Or
b) oil gets too scarce?

 

Offline wolfekeeper

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What is holding back electric car technology?
« Reply #90 on: 17/03/2009 17:21:40 »
Personally I think charging at home would be much more convenient than a petrol pump.

I also wonder if you could hire a generator on a trailer; for long distances you could be driving down the motorway and recharging at the same time!

I mean, if you removed half the Tesla's battery, you would still have 100 mile range, and could accelerate even faster.
 

lyner

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What is holding back electric car technology?
« Reply #91 on: 18/03/2009 00:13:30 »
teragram

I question your assertion that 10 minutes would be an acceptable charge time. In 10 minutes, a filling station would become significantly more blocked than with the present system.  Stations would need either more outlets or more waiting space.
It is true to say that the energy distribution would be cheaper to run than for petrol but the installation costs would be enormous. Tankers fit in well with the present system and, as they are an established method, they have a short term advantage still.
As I have already said, an electric based system is desirable but there is not enough hard fact about the new batteries  to allow a switch over to be a choice yet.
 

Offline wolfekeeper

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What is holding back electric car technology?
« Reply #92 on: 13/04/2009 19:48:40 »
It might be much quicker to just swap the battery over:

http://www.ted.com/index.php/talks/shai_agassi_on_electric_cars.html
 

Offline techmind

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What is holding back electric car technology?
« Reply #93 on: 13/04/2009 22:11:39 »
There was a brief sketch on this weeks The Now Show comedy on Radio 4 about the impracticality of running an extension leads from the house to the car parked 50 yards away on the other side of the street (for houses without their own off-street parking)! http://www.bbc.co.uk/radio/podcasts/fricomedy/

There was a paper published a few weeks ago (Nature, I think) on a modification to the electrodes in otherwise fairly conventional Li-Ion batteries which, it is claimed, will allow them to be charged and discharged in a few 10's of seconds, as well as solving some of the lifetime/cycle limitations of existing Li-Ion cells. This was a varient of Li-Fe-PO chemistry I recall. Reckon it'll be 2-3 years at least before the new batteries are commercially available.

http://www.nature.com/news/2009/090311/full/news.2009.156.html
http://web.mit.edu/newsoffice/2009/battery-material-0311.html


My past understanding however was that although existing LiFePO can be charged and discharged faster than standard LiIon, eg in 6-10mins, the penalty was only 60-70% of the 'standard' capacity for the same sized cell. LiFePO is currently used in high-performance power-tools (and maybe toy racing cars/aeroplanes). Unfortunately it seems this capacity limitation also applies to the new superfast anode material:

http://www.technologyreview.com/energy/22280/

Quote
Other researchers have already modified lithium iron phosphate to achieve power levels high enough for power tools and for most hybrid vehicles. Indeed, iron phosphate batteries are already being sold by more than one battery maker for such applications. Ultimately, the energy capacity of lithium iron phosphate is lower than that of other lithium-ion battery materials, making Ceder's advance of limited value, says Jeff Dahn, a professor of physics at Dalhousie University, in Halifax, Nova Scotia. This battery is good for acceleration, but not as much for long range. "A real breakthrough . . . would be a new positive electrode material with quantum-leap performance specs" in energy storage, Dahn says.
« Last Edit: 13/04/2009 22:32:44 by techmind »
 

Offline wolfekeeper

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What is holding back electric car technology?
« Reply #94 on: 14/04/2009 00:21:16 »
True... or just swap the battery over.
 

Offline Stefanb

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What is holding back electric car technology?
« Reply #95 on: 25/07/2009 20:06:00 »
The solution...
Magnetism! :D
We should totally put magnetic tracks everywhere...
Sure, it costs a lot - like trillions of dollars a lot- but it would be awesome!
 

Offline Fearlessmoto

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What is holding back electric car technology?
« Reply #96 on: 14/08/2009 16:55:06 »
why cant we make an electric car that charges as quickly as it depletes?
using a system of alternators and capacitors, you could power an electric motor. the battery starts it going and then it runs and charges itself, using the battery as a sort of "pressure tank" so to speak, to maintain voltage levels, like a pressure tank on an air compressor maintains air pressure consistency. Its a little project im working on with a 12 volt battery, a few old car alternators, and a motor from a 12 volt water pump.
 

lyner

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What is holding back electric car technology?
« Reply #97 on: 14/08/2009 18:20:45 »
why cant we make an electric car that charges as quickly as it depletes?
using a system of alternators and capacitors, you could power an electric motor. the battery starts it going and then it runs and charges itself, using the battery as a sort of "pressure tank" so to speak, to maintain voltage levels, like a pressure tank on an air compressor maintains air pressure consistency. Its a little project im working on with a 12 volt battery, a few old car alternators, and a motor from a 12 volt water pump.
Nice idea BUT. . . . .
I'm afraid that is just another example of a 'perpetual motion' machine which just can't work. Generating your electric energy with which you want to charge the batteries takes more energy than the batteries will actually get. You quickly lose all the energy you started with. Nothing is even 100% efficient - let alone 100+%, which is what you are effectively proposing.

Basic fact of life and there's no way round it -even with a lot of faith.
 

Offline Nizzle

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What is holding back electric car technology?
« Reply #98 on: 24/08/2009 14:16:27 »
But it will increase the electric vehicle's range at least..
 

lyner

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What is holding back electric car technology?
« Reply #99 on: 24/08/2009 17:15:36 »
Actually, no.
If it involves more energy transfers than absolutely necessary then energy will be wasted during each extra transfer.
If you want to extend your journey on the same charge, you can't do better than freewheeling down every slope and using a minimum of (regenerative) braking. Also - and this really hurts - go as slowly as possible!!!
Saving money is seldom fun.
 

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What is holding back electric car technology?
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