Toyota engineer explains how long range EV's aren't practical

You are missing the basic physics of electricity. If you charge a large battery in 5 minutes you need to transfer a lot of kw-hrs in that short amount of time.

kw-hrs = watts * time = volts * amps * time

Since you've made the time very short, you have no choice but to have large values for amps and/or volts. Power is delivered in most residential and non-industrial commercial at around 440 volts (3-phase), I believe. In a home you'll have 2 phases at 120v each and a max of 200 amps, going in...typically (if a newer house). You get 240v by tapping off of both phases. Most distribution panels can only feed 40 amps, max at 240v. Technically, I suppose you combine 2 or 3 of these together to charge a car.
This is almost 10 kw. In 5 minutes this gives you a bit less than 1 kw-hr, which is enough to go 3 - 5 miles.
Rewiring every house and neighborhood to handle 100 times this much doesn't make sense, especially since 90%-95% of the time most people with an EV can charge overnight and that's all they'll use the next day.
For long trips to be viable with an EV, faster charging is certainly needed. This will require new infrastructure...not impossible, but costly.
At 500 volts, you'll need about 2000 amps to give you 83 kw-hr in 5 minutes.
That requires about a 8-10" diameter cable if my math is close. Up the voltage and you can lower the amps and cable size. But you can't just keep upping the voltage. The battery voltage/amps has to be able to feed the charging circuit and go to the battery and work with the battery chemistry, etc.

Mike

 

What about all those electric cars that'll never go outside their range other than once a year, charging every night at home?

Presently a petrol equivalent will be hogging the filling station at least once or twice a month.

 

The point you are missing is that faster charging is not required.
EVs don't have to work for 100% of people in order to work for a large market.
There are some for whom an EV is simply not a good option.
There are others for whom a Prius is simply not a good option.

 

wrong thread ..

 

Not the one that started this discussion.
His supposition has nothing to do with battery technology.
In his picture, one that would charger faster would actually be worse because the peak load would be higher.

 

Fortunately , being an EE I actually understand the physics extremely well. 2000 Amps is approximately 10 times the area of AWG 0000 wire (200 Amps at 0.1662 sq. in.), so that ends up being a diameter of 1.4 inches give or take a little. Certainly within the range of a large gas pump line although a supply and return line would be needed. Much smaller than a lot of industrial electrical cables used in big installations. In all likelihood, something that big would likely to be automatically connected to an EV. Not trivial, but extremely straightforward and safe with the generation of a national standard. I don't see that being anywhere close to the cost of all the infrastructure of a modern day gas station.

Right now, it is present day battery technology limiting charging rates. The limitations are the thermal and other chemical ripple effects of charging, not any physics limitation on electron behavior. All of these recharge limits are going to be continuously researched and refined to enable faster recharging over the next decades. The actual recharge times of future EVs may end up being longer than 5 minutes, but truth be told, most 200+ mile stops are for a lot longer than 5 minutes anyway.

 

Good point. I had to go back and reread. I also think that is an even worse rationalization for thinking EVs are bad.

 

....I like it in the white (Model X)

 

The cable to the car is not the problem as one can always up the voltage. The real challenge for fast battery recharge are the electrodes, internal resistance, and chemistry. Those pesky ions have to move. But for me with my wife, a 'fast' stop after 200 miles is 20-30 minutes.

Bob Wilson

 

People charging at home aren't going to need to charge in 5 minutes. The majority of times they pull into the driveway, they aren't even going to need a full charge. A hundred mile round trip commute is near the extreme end of what people in the US drive. With a 240V 50amp outlet and 10kW onboard charger, a BEV can fill those hundred miles up in three and half hours. Such a BEV will have at least another 100 miles of range left when it got home, so the owner doesn't have to wait if they have an unplanned trip before the charge is done. Another outlet and charger would cut the charge time down to nearly half for those with long distance commutes. Which is already possible with a Tesla S.

As for 5 minute charging presented by the OP, it ignores the use of onsite electric buffering at the charge location like a bank of capacitors. Yes, that means increased installation cost, but removes to need of infrastructure upgrades and effecting nearby residents and businesses. The buffer bank can do some peak shaving duty to reduce utility bills for the station.

Toyota's supposition also ignores the fact that not every fast charger at a station needs to be the absolutely fastest one. Take an interstate rest stop. Some people are in a rush, so they need the super fast, near liquid fuel refueling fast charger. In a future with just BEVs, the pit stop will need less of these chargers than they would of gasoline pumps now, and set up like pumps now. Most people, after sitting in a car for 2 to 3 hours, want to stretch their legs and hit the rest room. They could use slightly slower, say 15 to 30 minute, chargers at short time parking. These are the majority of chargers available. Then for those stopping to eat, there will be Supercharger level chargers.

Then there is no reason to not set up the charge station so that the super fast chargers are limited only 'dispensing' a set amount or to a max battery capacity. Say 150 miles or 80%. It will be quick, be enough to get them to the next station, and limit lines. They can then can choose to use a slower charger to top off. Car pulls in and gets its quick charge in 5 minutes, and then driver parks at a slower one while they do the stretch the legs bit.

 

The battery technology has nothing to do with his statement. If you charge a 100kw-h battery in 5 minutes, you will need 1200 kw-hrs of generating capacity. You are going the wrong direction, and the generators care nothing for the batteries efficiency. In order to mitigate the peak load demand, you need to slow charge...probably overnight. That is why EV's make a lot of sense for local use. A 50 mile charge over 10 hours is several orders of magnitude less demand than 350 miles in 5 minutes. Also, load shifting for better electrical rates mostly works at home, not on the road.

 

But the pull of a BEV being fast charge in 5 minutes doesn't have to pull on some generator at some distant power plant.
It can pull on a capacitor bank, or other energy storage system, that is onsite with the charger. The buffer bank then charges back up at a slower rate. If we ever actually need charging at such rates.

This is all misdirection and obfuscation though. Toyota wants you all thinking about BEVs and FCVs and the longer trips most of us only drive a few times a year. Because of the BEV's limits of such, few trips, they are hoping support shifts from plugins to their FCVs. They don't want you thinking about how for a large majority of BEV use, home charging is enough, and isn't a burden on the grid. Better yet for them, is if you forget that there is another option; the PHV. Which gives nearly of the benefits of a BEV for daily use, and can be refueled in 5 minutes with out need for grid upgrades now.

 

I'm not sure if I follow the problem. A new ccgt plant typically is built for at least 500 MW. If say the technology came to afford-ably charge a battery at a rate of 1.2 MW it would take approximately 5 minutes. There is a loss in getting the power to the charger, lets say of 7%, so we could provide power to 500 * 93% /1.2 MW = 387 sockets simultaneously. Let's say it takes a minute to change between cars, then we could do 10 cars an hour, or 3870 cars per hour on that power plant. How far could each car go? A bmw i3 gets 124 mpge, the toyota rav4 ev 76 mpge, lets assume that is the range so 225 miles on a rav4, 300 miles on a tesla 70d, 367 on an i3. That seems doable.

If the cars were evenly spaced over the week, and each charged once a week that would be 168*3870 = 650,000 cars. That power plant in California costs about $700M to construct and hook up to the grid, so it would take about $1000/car to build the plant and it could run at 100% utilization. If the plant lasts 30 years then you are talking about $35/year/car and the natural gas is only about $1 to charge those 100kw. Not very likely any of those figures. Cars are going to mainly charge at home not at these chargers, even when you pay a lump sum when you buy a car like tesla. Lets say 10% charge at these quick chargers in any given week, and 10% of those charge at the peak 10 hours, you need to have power for 1% of the cars each hour. 3870/1% = 387,000. Use your own numbers if you don't like mine. Let's say payback is in 10 years not 30 as typically is used for power plants. That means $700M/$387K/10 or $181/car/year for ten years to pay for the additional power plant infrastructure. That doesn't sound like that much money. If too many people are charging at peak, build a surcharge of $50/100kwh. That will build plenty of extra infrastructure on the grid. The california first plan is 1M plug-ins, only 3 plants would be needed to stabilize the grid to L3 charge these.

Wind and solar cost more, and the fuel is cheaper. I used a 10 year payback in case renewables were built to make the new natural gas plants unnecessary. These cars are not coming over night.

 

Curious .... his graph of sales omitted Tesla. Would their inclusion defeat his point?
.

 

does vast physics knowledge cause the reality of how small a minority of drivers there are that typically drive >200 miles a day?
. . . . . & of that super minority, the minority of those that are EV?
.

 

nice catch on the missing tesla sales.

 

The only physics knowledge I know of that causes >200 mile/day driving is mushroom cloud and meltdown physics. Whether it is an EV or donkey being driven probably matters less.

 

I'm a little confused where the idea of a big supercharger is a serious peak load problem. In downtown St. Pete where I work, all the condos, multistory office buildings, Baseball dome, etc. have MONSTER air handlers with On/Off cycles that make multi-kW sudden demands all day long during the summer. The cycling is totally engineered to be completely problem free with these huge loads. Why would what turns out to be a dinky car supercharger not use the same engineering load solutions used by these really huge monster loads? I do see the problem with powering a supercharger station from a home wall outlet.

If the issue is overloading a power plant during peak hours, then the utility will expend effort to solve that issue. That is how they become rich, by selling electricity. In the meantime, there are a huge number of manageable loads that can be shed when extreme conditions occur. If a grid goes down, it will not be because of car superchargers, it will be due to 10,000 office building and 1,000,000 home air conditioners operating at peak capacity all at once or mismanagement by the utility. Unfortunately, trying to avoid utility mismanagement by avoiding EVs is a lost cause.

 

I'm not missing that point...I think you missed the part of my post that said:

Rewiring every house and neighborhood to handle 100 times this much doesn't make sense, especially since 90%-95% of the time most people with an EV can charge overnight and that's all they'll use the next day.​

Mike

 

I fully agree with that part. I got the impression you thought rapid recharging had permanent prohibitive physics limitations. Sorry if it came across as a total disagreement.