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Making Electric Vehicles work!


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#151 pugfan

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Posted 17 February 2013 - 22:15

I doubt many here think that technology is at a standstill, he says typing away on a throwaway netbook on a wireless internet connection, both things that 10 years ago were far from ubiquitous. The only place we see large scale technology freezes is F1, bizarrely.


On the flipside, Windows XP still lingers on outside of the home.

You can add the military to F1 for technology freezes. A platform might be state of the art when designed but by the time it is delivered and in service, it will likely no longer be state of the art and may in fact be obsolete. I would cite the F-35 as an example but I don't think that was ever state of the art and also hasn't been delivered yet.

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#152 Lee Nicolle

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Posted 20 February 2013 - 05:41

Hey - have you heard? There's this liquid explosive being pumped the entire length of road-going vehicles from back to front and back again. Not only are the lines they pump the fuel through on the underside of the vehicle, exposed to the elements and subject to damage from all sorts of debris, but it's under huge pressure too so it's not like it's just leaking out under head pressure. New DI fuel pressures are significantly higher meaning that a leak under under the hood will be catastrophic! A rolling, high-speed fireball is what they are. Death traps. I saw one burn due to a fuel leak when I was a kid.

Yeah, I agree. But it does seem to be a far safer deal to me.Though hi pressure injection is far less safe than an old 6lb carby system. Walk through a salvage auction, the number of burnt Prius's and the like just about matches the number of petrol ones. Generally from seeminly minor accidents. Apart from cars burnt from the outside,,eg arson attacks. Here recently that was Hyundia Excels. Somebody literally had a torch for them!
The most flammable cars are ofcourse LPG, though often a installation problem. There is some LOUSY fitters out there!

#153 carlt

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Posted 20 February 2013 - 09:11

Let's face it if something fails on a plane it's a lot more serious than it failing on a car. Even if the car starts to burn chances are you'll stop and get out unharmed. On a plane...


they don't like it when I check my parachute in as carry on baggage

#154 Powersteer

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Posted 20 February 2013 - 16:02

Maybe there should not be fully electric car unless designed as pure city car range. What would be practical is hybrid vehicle's that would be either light hybrid or heavy hybrid with a small internal combustion engine. Pretty cool to have a wind mill or any natural energy for that matter charging the car at night and then using those energy while the combustion engine would be more active on long trips.

:cool:

#155 Tony Matthews

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Posted 20 February 2013 - 16:42

they don't like it when I check my parachute in as carry on baggage

I disguise mine as explosives.

#156 Kelpiecross

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Posted 21 February 2013 - 04:19

Speaking as a fairly ignorant person on the subject of electrics/electronics etc. - when an electric car is fully charged I presume it holds the energy equivalent to 5 or 6 gallons of petrol. In a crash can this energy be catastrophically released in a fashion analogous to a petrol explosion? I have seen a spanner accidently dropped across the terminals of a car battery - plenty of sparks and the spanner is red-hot in seconds - and a 12 volt car battery has a lot less energy content than an electric car.

Also - I read recently in a model plane magazine a story of someone trying to dispose of a charged but damaged lipo battery. Apparently the approved method is to put a hole in the battery with a nail and then put the battery in a bucket of water.
This person claimed that within minutes the battery exploded blowing all of the water out of the bucket.

Again the question is whether this could happen in a big electric car crash - especially where the car ended up in a creek (or whatever).

Strangely enough I am not anti electric car (all my modelling activities have changed from IC to lipo) - but I still think the range/recharging problem will never let them be really useable. Another advantage of the IC-powered vehicle is that its range can be vastly extended by carrying extra drums of fuel (I used to carry up to about 100 gallons of extra petrol when I drove a Landcruiser in the Oz outback desert) - an electric car can't carry extra drums of electricity.

Edited by Kelpiecross, 21 February 2013 - 04:21.


#157 Canuck

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Posted 21 February 2013 - 04:30

HA! You do not - ever - want to expose lithium batteries to water. That's a huge no-no.

Lithium reacts intensely with water, forming lithium hydroxide and highly flammable hydrogen. The colourless solution is highly alkalic. The exothermal reactions lasts longer than the reaction of sodium and water, which is directly below lithium in the periodic chart.

2 Li(s) + 2 H2O -> 2 LiOH (aq) + H2(g)

At 750oC lithium reacts with hydrogen to lithium hydride (LiH). The white powder that forms releases hydrogen gas upon later reaction with water, in amounts of 2800 liter per kilogram hydride. As such, lithium can be applied as hydrogen storage.

Li + H2O


#158 Kelpiecross

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Posted 21 February 2013 - 04:37

HA! You do not - ever - want to expose lithium batteries to water. That's a huge no-no.

Lithium reacts intensely with water, forming lithium hydroxide and highly flammable hydrogen. The colourless solution is highly alkalic. The exothermal reactions lasts longer than the reaction of sodium and water, which is directly below lithium in the periodic chart.

2 Li(s) + 2 H2O -> 2 LiOH (aq) + H2(g)

At 750oC lithium reacts with hydrogen to lithium hydride (LiH). The white powder that forms releases hydrogen gas upon later reaction with water, in amounts of 2800 liter per kilogram hydride. As such, lithium can be applied as hydrogen storage.

Li + H2O


I have no idea what is actually in lipo batteries (li and po I would imagine) - but I would have thought lipo batteries had their Li in the form of a compound - surely Li itself would be far too dangerous.

#159 gruntguru

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Posted 21 February 2013 - 07:03

when an electric car is fully charged I presume it holds the energy equivalent to 5 or 6 gallons of petrol.

Tesla claim 65 kW.hr battery capacity for the Roadster and that is a large capacity by EV standards. 65 kW.hr is the heat energy obtained by burning about 7 litres of petrol.

Mind you, I wouldn't want to be very close in either case.

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#160 Tony Matthews

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Posted 21 February 2013 - 09:14

(li and po I would imagine)

:up:

#161 DogEarred

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Posted 21 February 2013 - 10:01

I have no idea what is actually in lipo batteries (li and po I would imagine) - but I would have thought lipo batteries had their Li in the form of a compound - surely Li itself would be far too dangerous.


Wasn't it Profeseur N. Seagoon who came up with the formula:

Ying Tong = iddle I po?


Sorry, I'll go ohm now...

#162 Tony Matthews

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Posted 21 February 2013 - 11:11

Sorry, I'll go ohm now...

Backwards across the Irish Sea, I presume.

#163 bigleagueslider

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Posted 22 February 2013 - 05:02

Tesla claim 65 kW.hr battery capacity for the Roadster and that is a large capacity by EV standards. 65 kW.hr is the heat energy obtained by burning about 7 litres of petrol.

Mind you, I wouldn't want to be very close in either case.


Like many things, the performance or range claims made by EV car companies are a bit subjective, and open to interpretation. Actual results can vary greatly depending upon how the vehicle is driven, or what the weather conditions are (Is it hot enough that the A/C is being run hard? Or are there sub-freezing temperatures that reduce battery performance?). While Tesla has a pretty good record so far with their battery designs, other EV companies like Fisker have not fared so well. The most publicized battery failure with Fisker was the large number of new cars sitting in a storage lot in a NJ port when hurricane Sandy hit. When the flooding from seawater covered the car's battery packs, many of them caught fire. And a couple million dollars worth of new Fisker EVs burned to a crisp.

There have also been issues of permanent damage being done to EV battery packs by running them to full discharge.


#164 Kelpiecross

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Posted 22 February 2013 - 05:39

Tesla claim 65 kW.hr battery capacity for the Roadster and that is a large capacity by EV standards. 65 kW.hr is the heat energy obtained by burning about 7 litres of petrol.

Mind you, I wouldn't want to be very close in either case.


7 litres - about a gallon and a half - I didn't realize it would be as little as this. How can electric cars ever be viable with figures like that?

#165 bigleagueslider

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Posted 22 February 2013 - 06:58

7 litres - about a gallon and a half - I didn't realize it would be as little as this. How can electric cars ever be viable with figures like that?


Maybe I'm wrong, but wouldn't 65kW-hr equate to something like 4 gallons of gasoline at a BTE of around 35%? There is also the issue that the battery probably cannot deliver the entire 65kW-hr of energy, while the gasoline fuel could.

#166 Fondles

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Posted 22 February 2013 - 20:03

7 litres - about a gallon and a half - I didn't realize it would be as little as this. How can electric cars ever be viable with figures like that?


Don't forget that electric motors are roughly three times more efficient than petrol engines, so you need about a third of the 'fuel' to go the same distance.
(I think ....)

Battery technology is still getting better slowly and I'm hoping inside a decade or so they'll be to the point where they have at least 1/3 of the energy density of petrol, and so be roughly competitive with petrol engines.
Charging, however, is another story.

#167 gruntguru

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Posted 23 February 2013 - 00:13

Maybe I'm wrong, but wouldn't 65kW-hr equate to something like 4 gallons of gasoline at a BTE of around 35%? There is also the issue that the battery probably cannot deliver the entire 65kW-hr of energy, while the gasoline fuel could.

You are correct but we were considering how much heat is released in a fire as opposed to how much work is availaable from an ICE.

#168 bigleagueslider

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Posted 24 February 2013 - 04:58

Don't forget that electric motors are roughly three times more efficient than petrol engines, so you need about a third of the 'fuel' to go the same distance.
(I think ....)

Battery technology is still getting better slowly and I'm hoping inside a decade or so they'll be to the point where they have at least 1/3 of the energy density of petrol, and so be roughly competitive with petrol engines.
Charging, however, is another story.


The total cycle efficiency of a battery-electric propulsion system (ie. charging the battery, discharging the battery, power electronic losses, and motor losses) is indeed better than the cycle efficiency of a combustion engine propulsion system (ie. combusting the fuel and converting the thermal energy to mechanical work). But the better economics and practicality still greatly favors IC engines.

However, as you note, battery technology is rapidly advancing. I would predict that we will see battery technology improve enough such that we will have truly practical and economical EVs within 8-10 years. Take a look at this recent news release from the US ORNL labs. They claim to have developed new Li battery technology that will allow a 5x increase in performance. If true, this would be sufficient to permit battery-electric systems to displace IC engines for most automotive applications.


#169 Fondles

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Posted 24 February 2013 - 05:34

The total cycle efficiency of a battery-electric propulsion system (ie. charging the battery, discharging the battery, power electronic losses, and motor losses) is indeed better than the cycle efficiency of a combustion engine propulsion system (ie. combusting the fuel and converting the thermal energy to mechanical work). But the better economics and practicality still greatly favors IC engines.

However, as you note, battery technology is rapidly advancing. I would predict that we will see battery technology improve enough such that we will have truly practical and economical EVs within 8-10 years. Take a look at this recent news release from the US ORNL labs. They claim to have developed new Li battery technology that will allow a 5x increase in performance. If true, this would be sufficient to permit battery-electric systems to displace IC engines for most automotive applications.


Bah!
Graphene FTW!

#170 AlexS

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Posted 24 February 2013 - 05:54

If true, this would be sufficient to permit battery-electric systems to displace IC engines for most automotive applications.


First of 5x of what? "performance" is PR wording.

How much time you need to fill the batteries? Even if 5x it can't beat a combustion engine.

#171 carlt

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Posted 24 February 2013 - 13:00

technology supply and demand
this is posted with a device i can hold in one hand
a laughable idea only a very few years ago

#172 Kelpiecross

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Posted 24 February 2013 - 13:05

First of 5x of what? "performance" is PR wording.

How much time you need to fill the batteries? Even if 5x it can't beat a combustion engine.


If it were genuinely 5X better (in range for instance) - it probably would be better than IC. Whether the report is "spin" or not is another matter.

#173 Rasputin

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Posted 24 February 2013 - 15:54

The total cycle efficiency of a battery-electric propulsion system (ie. charging the battery, discharging the battery, power electronic losses, and motor losses) is indeed better than the cycle efficiency of a combustion engine propulsion system (ie. combusting the fuel and converting the thermal energy to mechanical work). But the better economics and practicality still greatly favors IC engines.

However, as you note, battery technology is rapidly advancing. I would predict that we will see battery technology improve enough such that we will have truly practical and economical EVs within 8-10 years. Take a look at this recent news release from the US ORNL labs. They claim to have developed new Li battery technology that will allow a 5x increase in performance. If true, this would be sufficient to permit battery-electric systems to displace IC engines for most automotive applications.


Even if you can develop the batteries to ten times today's capacity, charging still remains. If you fill your 60 liter gasoline tank in what, 60s perhaps, that's the equal of 34 MW. Serious stuff.

Edited by Rasputin, 24 February 2013 - 15:57.


#174 Canuck

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Posted 24 February 2013 - 16:41

Agreed. While a fan of electric, I haven't been able to imagine a liquid-fuel speed recharge scenario that doesn't invlove a small nuke plant on-site. However...born and raised in a locale that requires plugging in your car for the better part of the year, it's completely normal to plug in my car. I don't travel farther than a single tank of fuel (or a single recharge) in a week except in unusual circumstances - same for my wife. We have the luxury of off-street parking so the mechanics of plugging in a car are simple.

However - ignoring maintenance costs and purchase/depreciation, I'm not sure that operating an electric car is any less expensive than a gasoline vehicle when factoring in the $12,000 battery replacement at 8 years. Depends on the variable cost of fuel and electricity mind you, which can be without rhyme or reason some days. And quite honestly - that's the biggest driver for me - cost of ownership. There are too many rather un-green issues glossed over by electric vehicle proponents to make it a truly green purchase.

#175 gruntguru

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Posted 24 February 2013 - 23:17

:up: Agree with all that . . . . and when the 5X whatever comes along?

#176 Greg Locock

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Posted 25 February 2013 - 03:21



While we wait for the fairydust to be sprinkled on the current battery chemistries (I imagine Boeing could do with some fairydust right now - quick pop quiz how many Li batteries have failed on customer 787s?), why not popularise EREV trailers for EVs, so that when you make your once in a blue moon trip you can hire one, and higher mileage people can buy one?

They would admittedly be rather attractive for thieves. And they aren't very efficient. But they do extend the life of your battery, and they could easily be flex fuel, and they eliminate at one stroke the other main whinge about EVs.





#177 Kelpiecross

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Posted 25 February 2013 - 04:13

If it were genuinely 5X better (in range for instance) - it probably would be better than IC. Whether the report is "spin" or not is another matter.


I should have said - outperform an IC car on the one charge/tank of fuel. The recharge problem (which presumably would now be 5X worse) would still make the 5X electric car not very practical.

#178 gruntguru

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Posted 25 February 2013 - 05:39

The recharge problem (which presumably would now be 5X worse) would still make the 5X electric car not very practical.

Disagree. If the 5X car has a range of say 800 km, most people will never need more than that between overnight recharges. Recharging is something you would do every night whether you have driven 100 km or 800 km that day. So every day you head out with a full tank. More convenient than a normal fill-up.

Not sure about the recharge problem being 5X worse. Charge rate is capped initially by the battery. Most Lithiom ion batteries can be fully charged in a few hours (usually much less). For a high capacity battery (like the 5X) the charge rate will be capped by the charging system not the battery so yes, if the charging system remains the same, it will take five times as long to charge.

#179 Kelpiecross

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Posted 25 February 2013 - 12:55

Disagree. If the 5X car has a range of say 800 km, most people will never need more than that between overnight recharges. Recharging is something you would do every night whether you have driven 100 km or 800 km that day. So every day you head out with a full tank. More convenient than a normal fill-up.

Not sure about the recharge problem being 5X worse. Charge rate is capped initially by the battery. Most Lithiom ion batteries can be fully charged in a few hours (usually much less). For a high capacity battery (like the 5X) the charge rate will be capped by the charging system not the battery so yes, if the charging system remains the same, it will take five times as long to charge.


Oddly enough I am inclined to agree. A 5X battery would at least make an electric car vaguely feasible - which they really aren't at present.

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#180 blkirk

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Posted 25 February 2013 - 15:08

Bah!
Graphene FTW!


Now you can make your own graphene supercaps with tools you probably have laying about the house. The materials may be a bit of a problem, however.

I haven't done the math to see how the volume and mass efficiency compare to Li-Ion.

#181 Rasputin

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Posted 25 February 2013 - 15:26

Disagree. If the 5X car has a range of say 800 km, most people will never need more than that between overnight recharges. Recharging is something you would do every night whether you have driven 100 km or 800 km that day. So every day you head out with a full tank. More convenient than a normal fill-up.

Not sure about the recharge problem being 5X worse. Charge rate is capped initially by the battery. Most Lithiom ion batteries can be fully charged in a few hours (usually much less). For a high capacity battery (like the 5X) the charge rate will be capped by the charging system not the battery so yes, if the charging system remains the same, it will take five times as long to charge.


For the sake of argument, 800 km at 80 km/h and an average of 30 kW (41 Hp), would mean a 300 kWh battery, or five times the best Tesla battery of today.

To charge that overnight would then take 25 kW, which is some 65 Amps at 380 Volt.

Needless to say, gruntguru is correct, overnight charging is the only possibility, and even then quite a challenge for the typical homeowner.

#182 gruntguru

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Posted 25 February 2013 - 23:15

For the sake of argument, 800 km at 80 km/h and an average of 30 kW (41 Hp), would mean a 300 kWh battery, or five times the best Tesla battery of today.

More like 80 kW.hr.

According to THIS POST 20 Kw is all it takes for a medium size car to maintain 120 km/hr. From the same post we get estimates of 4 km/MJ highway (100 km/hr) and 3 km/MJ urban. 1 kW.hr = 3.6 MJ or about 10 km urban so 80 kW.hr should give 800 km.

For comparison, Tesla claim 300 miles (480 km) from their model S with 85 kW.hr battery and that is a heavy, high performance car. 800 km from a medium sedan with an 80 kW.hr, 5X (lightweight) battery is very realistic.

#183 Greg Locock

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Posted 26 February 2013 - 01:24

I think you're out by about a factor of 2 - it is very hard to get a legal 4 seater down to less than 200 Wh/mile (horrid units). Plus, you don't want to run modern batteries much over 65% of their nominal capacity.

If you can accept a new classs of 2 seater vehicle with inbuilt active safety then you can pull out weight and tire performance in a virtuous circle.

Incidentally BMW's new electric car has an optional tiny range extender engine. It only charges the battery. Rather like the Volt, I'm glad somebody is buidling enough for us to see if it makes sense to many people, and like the Volt, I expect the answer to be 'no' at the moment.

#184 Canuck

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Posted 26 February 2013 - 02:04

A 5X battery would at least make an electric car vaguely feasible - which they really aren't at present.

No. The Tesla models, with their current battery technology and guessing 65% of their real-world mileage are not vaguely feasible - they are entirely feasible right here, right now. If I was inclined to buy new, I'd replace our 20-year old van with their Model X SUV without a moments hesitation. None. The once or twice a year I travel outside it's claimed range in a single jaunt, I'll rent a car or plan an overnight stop.

This notion that they can't possibly work in the "real world" because you can't drive an electric like a liquid-fuel vehicle is such nonsense. Sure - 65 amp / 380 volt is pretty tough but why in the hell are we waiting until it needs to be charged from dead? In my office of 40-ish people, there are none that have a round-trip commute that would require more than an overnight charge. I don't expect our sales force to drive them (and we're in the oil and gas biz so likely none of us will), but they're the exceptions and more days than not, they'd also be fine. While I have no doubt that the world is not an extended version of my own, I don't know anyone in my circle that travels outside the 400km stated range on a daily basis via car. Viable now. As is. (except I'm cheap)

#185 Greg Locock

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Posted 26 February 2013 - 02:45

I must admit the whole EVs are utter crap line doesn't make much sense to me either. If your household needs two vehicles that can tow a 1 ton tailer 500 miles a day, yes you are unlikely to consider an EV. The main things stopping me buying one are dollars.

#186 Lee Nicolle

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Posted 26 February 2013 - 03:01

Agreed. While a fan of electric, I haven't been able to imagine a liquid-fuel speed recharge scenario that doesn't invlove a small nuke plant on-site. However...born and raised in a locale that requires plugging in your car for the better part of the year, it's completely normal to plug in my car. I don't travel farther than a single tank of fuel (or a single recharge) in a week except in unusual circumstances - same for my wife. We have the luxury of off-street parking so the mechanics of plugging in a car are simple.

However - ignoring maintenance costs and purchase/depreciation, I'm not sure that operating an electric car is any less expensive than a gasoline vehicle when factoring in the $12,000 battery replacement at 8 years. Depends on the variable cost of fuel and electricity mind you, which can be without rhyme or reason some days. And quite honestly - that's the biggest driver for me - cost of ownership. There are too many rather un-green issues glossed over by electric vehicle proponents to make it a truly green purchase.

EVs make a old Chinese coal burning powerplant look very green! The whole point of the exercise is green, They are not. As for technology a hundred years ago there was electric carsand the range really has not increased dramatically. EVs have proven they go ok, though that piece of footage from the ring shows they have no driveability with their flat torque curve.
But with all the hooha they are still an impractical toy that cost way too much to run and maintain, major disposal problems, too heavy and are a far bigger risk in an accident, and just being charged. And hybrids are much the same, but cheaper to buy

#187 Canuck

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Posted 26 February 2013 - 03:50

No drivability with their flat torque curve? I thought a flat curve was the holy Grail of passenger car engines. I agree with your un-green assessment and their race-worthiness (now here's where charging and capacity are actually a problem), but the rest is speculation or fabricated hooha I suspect.

Confirmation bias says we ignore information that doesn't support our position / beliefs, and accept that which does. So, perhaps I'm wrong and they're rolling death-traps but given the lack of faux (read oil-industry funded a created) public awareness about the massive safety hazards of EVs, I'm inclined to believe there isn't one. I haven't read anything other than forum speculation that says crashworthiness is an issue (which isn't to say it doesn't exist, only that I haven't seem it). We handle our Li batteries with extreme care. They have a dedicated explosion-specific storage vault and we don't work on them. Am outfit down the road from us had an explosion recently when one of theirs failed and 1 (or 2) guys in Conroe Tx. were killed when they were heat-testing (!!) their Li battery (I want to say with a torch but I don't recall the specifics). I'm a believer that Li batteries have tremendous potential to kill, but so do gasoline, propane forklift cylinders, welding oxy/acy tanks and myriad other things lurkon around the typical home or shop.

I'm not sure about the recycling either and frankly, unless Li and the rest of the raw materials in these new batteries are in abundance around the globe, we're only trading one excuse for war for another. I'd still buy one.

#188 Kelpiecross

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Posted 26 February 2013 - 04:12

EVs make a old Chinese coal burning powerplant look very green! The whole point of the exercise is green, They are not. As for technology a hundred years ago there was electric carsand the range really has not increased dramatically. EVs have proven they go ok, though that piece of footage from the ring shows they have no driveability with their flat torque curve.
But with all the hooha they are still an impractical toy that cost way too much to run and maintain, major disposal problems, too heavy and are a far bigger risk in an accident, and just being charged. And hybrids are much the same, but cheaper to buy


I think we need to get back to the basic question - why do we need electric cars? I think various arguments about GW etc. are pointless - political bias (to both left and right) has skewed the debate so much it is meaningless.

I think one of the main reasons EVs would be useful is in places like China - on the TV you see the air pollution in China (and other places in Asia) is indescribable - do people actually breathe this stuff? And presumably IC engines have a lot to do with it.
EVs, especially a small electric-powered motorbike or scooter could improve the air quality greatly.
But they would still need the possibly-mythical 5X battery to be really practical.

Edited by Kelpiecross, 26 February 2013 - 04:21.


#189 gruntguru

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Posted 26 February 2013 - 05:27

I think you're out by about a factor of 2 - it is very hard to get a legal 4 seater down to less than 200 Wh/mile (horrid units). Plus, you don't want to run modern batteries much over 65% of their nominal capacity.

So where is the problem in the following logic?:-
a) Testla claim equates to about 280 W.h/mile for Model S.
b) Model S is a large, heavy, high performance car so dropping back to medium size, medium weight and average performance should get you down to the 200 W.h/mile mark.
c) 5X battery weighs 1/5th and enables the improvement to 160 W.h/mile (100 W.h/km) or 800 km from 80 kW.hr

I'm guessing a) and c)?

#190 Greg Locock

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Posted 26 February 2013 - 21:54

So where is the problem in the following logic?:-
a) Testla claim equates to about 280 W.h/mile for Model S.
b) Model S is a large, heavy, high performance car so dropping back to medium size, medium weight and average performance should get you down to the 200 W.h/mile mark.
c) 5X battery weighs 1/5th and enables the improvement to 160 W.h/mile (100 W.h/km) or 800 km from 80 kW.hr

I'm guessing a) and c)?


Sorry, I must have got my numbers muddled. Leaf and Volt are around 200 Wh/mile, so I agree with each step.

#191 bigleagueslider

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Posted 27 February 2013 - 01:43

Not sure about the recharge problem being 5X worse. Charge rate is capped initially by the battery. Most Lithiom ion batteries can be fully charged in a few hours (usually much less). For a high capacity battery (like the 5X) the charge rate will be capped by the charging system not the battery so yes, if the charging system remains the same, it will take five times as long to charge.


The article I linked was about a new process for making graphene capacitors quickly and cheaply, and with high densities. Regardless of whether the "5-10X increase in energy storage" is based on volume or mass, it's still quite impressive. The primary advantage of graphene capacitors over chemical batteries is the ability of graphene capacitors to be very rapidly charged or discharged. According to the researchers, a graphene capacitor system sized for automotive use could be fully recharged in just 2 or 3 minutes.

Of course, all capacitor storage systems have a downside versus batteries. The output voltage from capacitors falls as they discharge, which means they require power electronics to produce a constant voltage output from their variable voltage input. Plus, it is not practical to extract more than about 60% of the stored energy in a capacitor system.


#192 Canuck

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Posted 27 February 2013 - 02:13

Aaaaand - while the caps might charge in 2 or 3 minutes, who has that sort of supply available? That's a staggeringly high amount of power to pump.

#193 bigleagueslider

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Posted 27 February 2013 - 05:02

Aaaaand - while the caps might charge in 2 or 3 minutes, who has that sort of supply available? That's a staggeringly high amount of power to pump.


Canuck,

Always seeing the glass as half-empty, eh? Wouldn't it be a good thing if one of the biggest hurdles to a practical EV was eliminated? My house has an electrical utility service of 220V/100A. That would provide enough to power to charge an automotive graphene capacitive storage system within a reasonable amount of time.

#194 gruntguru

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Posted 27 February 2013 - 05:04

Aaaaand - while the caps might charge in 2 or 3 minutes, who has that sort of supply available? That's a staggeringly high amount of power to pump.

A dedicated fast charging facility with a throughput akin to a gasolene service centre would clearly require a significant connection to the grid. "Smoothing" the fluctuations in demand as individual vehicles connect and disconnect could be handled by banks of super capacitors similar to those used in the vehicles themselves.

Pumping the energy into the vehicle is another matter. 50 kW.hr in 3 minutes is an energy flow rate of 1000 kW. At 500V the current required is 2000A. Lets make it 6 minutes and drop the current to 1000A.

Now, do we have an electrical engineer to comment on the feasibility of that?

EDIT. Slider, your 220V 100A is 22 kW so charging 50 kW.hr would take 2.27 hrs - not bad!

Edited by gruntguru, 27 February 2013 - 05:08.


#195 Canuck

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Posted 27 February 2013 - 06:04

Half empty? You must be ignoring all of my previous posts supporting EV, including the willingness and desire to own the Tesla Model X SUV here and now. Skipped over all my responses about battery life and charging characteristics not being a factor for anyone I know in the vast majority of use. Or maybe you just like to argue with me ;-)

However...being a supoorter does not mean I can't point out obvious problems like GG's calculated 1000 amp charging station. That you (and I) have 220v/100a service in our homes does not solve all the issues yet. You can't all of the available supply or your meat and milk will go bad as the fridge and freezer shut down. There is also the issue of charger efficiency - it uses some of that juice is consumed by the charger. All I was trying to say was that charging speed dictated by the battery isn't the big problem (which is a solution for a problem that's not a problem for must real-world use). Grunt rather nicely illustrated my point for me.



#196 Rasputin

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Posted 27 February 2013 - 10:43

More like 80 kW.hr.

According to THIS POST 20 Kw is all it takes for a medium size car to maintain 120 km/hr. From the same post we get estimates of 4 km/MJ highway (100 km/hr) and 3 km/MJ urban. 1 kW.hr = 3.6 MJ or about 10 km urban so 80 kW.hr should give 800 km.

For comparison, Tesla claim 300 miles (480 km) from their model S with 85 kW.hr battery and that is a heavy, high performance car. 800 km from a medium sedan with an 80 kW.hr, 5X (lightweight) battery is very realistic.


8 kW (11 Hp) would hardly be enough even to cruise and car at 80 km/h, let alone to compensate for he odd overtaking, but your correct, 30 kW average was probably an overestimation, but 20 kW (27 Hp) without a doubt.

This would lead us to a 200 kWh for the ten hour 800 km drive, which with a 65% useful charge will mean a 300 kWh battery just the same.

And we haven't begun to consider air-condition/heating, stereo, computer, lights and/or what not.


#197 Greg Locock

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Posted 27 February 2013 - 22:11

My house has an electrical utility service of 220V/100A. That would provide enough to power to charge an automotive graphene capacitive storage system within a reasonable amount of time.


That's 22 kW. Your street is wired on a maximum average load of 3 kW per house, in all probability (check with your electricity provider). If you and five neighbours pull 22 kW each then you'll be lighting candles, and waiting for a big truck with a man on double time in it.

This is one of the biggest problems with the failed Better Place proposal, to get the power needed equivalent to a petrol bowser you need a hefty electrical infrastructure, which does not exist out in the sticks.

#198 gruntguru

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Posted 27 February 2013 - 22:52

This would lead us to a 200 kWh for the ten hour 800 km drive, which with a 65% useful charge will mean a 300 kWh battery just the same.

Tesla are already doing much better than that, with a heavy. high performance car.
. . . . . . .
. . . and yes, it does have air conditioning.

#199 bigleagueslider

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Posted 01 March 2013 - 05:29

That's 22 kW. Your street is wired on a maximum average load of 3 kW per house, in all probability (check with your electricity provider). If you and five neighbours pull 22 kW each then you'll be lighting candles, and waiting for a big truck with a man on double time in it.


Greg Locock-

The 220V/100A number is based on the current limit of the panel's main circuit breaker. All of the wiring between the utility line transformer and the panel have conservative margins of safety for handling the breaker-limited current load. But as you note, the circuit load protection at the nearest utility distribution point would not likely allow each residence to pull max current simultaneously.

Regardless, the graphene capacitive storage device should still recharge much faster than any current chemical battery system.

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#200 Catalina Park

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Posted 01 March 2013 - 08:59

I suppose you could recharge a capacitor bank at home even when the car isn't there and then use that to quick charge the capacitors in the car for a quick getaway.