Fast charging

[mpt]

Stopcraxypp: I think; guessing here; that 600A might be a lot; hmm, might not be though; a 200A feed into the house is too thick to bend easily; 600A would be 5 or 6 times as thick (not 3x as electricity flows around the edge; the skin effect) but, as a steel bar that lifts up to contacts touching the base of the car it'd be ok.

Hmm, perhaps 600A at 480V is reasonable; that's 288Kw or, about a 15 minute charge from empty... a long bathroom break and wander round the shops at the service station... hell my family... that's just the bathroom break.

Given that recharge stations would be used occasionally, the cost for service stations and resturants to use 480v would be pretty small and pretty viable.

Sounds good!

 

[vfx]

Phoenix demonstrated to CARB a 10 minute charge.

I would be a good step for Tesla or an organization like Plug in America to set up a very visible high powered charge station and a get a (modified if necessary) Tesla charging in front of a lot of cameras,

Showing this known car can charge in 10 to 15 minutes -the same as filling a gasoline tank eliminates all valid complaints but price.

 

[vfx]

wadayaknow
Tesla rumor roundup: HQ move; 440 volt charging in Model S

 

[mpt]

Didn't Musk say 40 mins was at the limit of the chemistry at the last townhall?

 

[Kevin Harney]

YEAH !!!! I knew that .... that is why I was going with the typical 480V service at a commercial location. Actually most are 3 phase 120 but many of the large ish businesses are 480V at least around here.

 

[stopcrazypp]

Stopcraxypp: I think; guessing here; that 600A might be a lot; hmm, might not be though; a 200A feed into the house is too thick to bend easily; 600A would be 5 or 6 times as thick (not 3x as electricity flows around the edge; the skin effect) but, as a steel bar that lifts up to contacts touching the base of the car it'd be ok.

Hmm, perhaps 600A at 480V is reasonable; that's 288Kw or, about a 15 minute charge from empty... a long bathroom break and wander round the shops at the service station... hell my family... that's just the bathroom break.

Given that recharge stations would be used occasionally, the cost for service stations and resturants to use 480v would be pretty small and pretty viable.

Sounds good!

You are right, after looking at it, 600A is too high a draw. Typically the max draw for these charging stations are 100A. So a 250kW charge will likely need a high voltage source, 480V probably won't do; though it will probably supply 480V at 600A to the battery.

The 60kW chargers can get away with a 480V source.

 

[TEG]

Even if a pack can handle a given "fast charge" it may shorten the overall lifespan of the pack, and may not be the most efficient way to charge it.

If you are concerned with getting as much as possible of the source electricity into the pack and you want to maximize the lifespan of your pack, you might want to avoid fast charging except for times of great need (like on a rushed road trip, or trying to complete a race).

 

[Palpatine]

Didn't Musk say 40 mins was at the limit of the chemistry at the last townhall?

He said that 45 minutes was the limit on the Roadster. But it would really stress that type of battery if you did it like that every day. The Model S Sedan might be a different type of battery. And the smaller battery size would mean a faster potential charge.

I have been told that even if you have 220 volt 70 amp service, you should charge at a lower power if you have the time available all night.

For example, the HPC can be configured in your home garage at 220 volt 70 amps, but then in your Roadster you can set it to only pull 220 volt and 12 amps.

If you have 9 hours at night and you are only topping off a 50% full battery, it is better for the life of your battery to allow a slower charge.

But it is nice to have the ability to do a fast charge if required.
Just don't do it every night that way.

 

[Kevin Harney]

My guess is that with the Model S that with the increased weight and size and possibly range (300 mile version) that the pack will be much larger like 50-70% larger and they needed to go to the possibility of 440V charging to keep the recharge time that they advertize close to that of the Roadster - 3.5 hours. Of course most people will not be able to take advantage of it or probably NEED to take advantage of it but it helps marketing and it enables them to grow easily to a larger size battery or a faster charge when they become available. I think it is a good move.

 

[TEG]

Yeah, I think you are probably right.

The reality is that nearly all the time "charge while you sleep" is they way to go, and most adults sleep around 8 hours, so a 3.5 hour charge isn't even a hard requirement. 240V@70AMP*8hours=134.4kWh which would be much more than I expect they would put in the long range 'S'.

For 'S' to meet the target price point it can't afford to have too much battery cost.

 

[graham]

The reality is that nearly all the time "charge while you sleep" is they way to go, and most adults sleep around 8 hours, so a 3.5 hour charge isn't even a hard requirement. 240V@70AMP*8hours=134.4kWh which would be much more than I expect they would put in the long range 'S'.

It is an interesting number to have at hand. It gives an idea for an upper bound for electric vehicle range. If you assume:

1) people will not want to have a car take longer to charge than 8 hours
2) the residential upper limit for power will remain 240V @ 70 Amps
3) 53kWh gives you ~ 200 mi range and that range increases linearly as battery capacity increases.
4) there is no external fast charge/battery swap system

If none of these assumptions change EVs will start self-limiting to about a 500 mile range. (the maximum range you will be able to charge overnight at home).

(134.4 kWh / 53 kWh * 200 miles =~ 500 miles).

Given the idea of battery capacity doubling time is about 8 years, this means at current rates of change we have about a dozen or so years to change one of these 4 assumptions if we don't want EV range to stagnate.

 

[Palpatine]

If none of these assumptions change EVs will start self-limiting to about a 500 mile range. (the maximum range you will be able to charge overnight at home).

(134.4 kWh / 53 kWh * 200 miles =~ 500 miles).

Having driven across the country when moving, it is really tough to drive 500 miles per day. I think the maximum that we did was 700 miles in one day. There are several stops for rest room and/or meals.

So as long as 220 volts / 70 amp recharging is available in hotels or highway exit restaurants, then 500 miles of range should be enough even for cross country trips.

I think in a given day of long distance driving, there are likely 2 hours of stops for eating or stretching legs, etc. If during those stops you had recharging available, that would easily add to your daily range about 150 miles.

The state of Washington has a bill about the pass the legislature that would require all highway reststops to make available electric recharging stations. I think they will try to get at least 220 volts /50 amp recharging stations.

 

[mt2]

Having driven across the country when moving, it is really tough to drive 500 miles per day. I think the maximum that we did was 700 miles in one day. There are several stops for rest room and/or meals.

So as long as 220 volts / 70 amp recharging is available in hotels or highway exit restaurants, then 500 miles of range should be enough even for cross country trips.

I think in a given day of long distance driving, there are likely 2 hours of stops for eating or stretching legs, etc. If during those stops you had recharging available, that would easily add to your daily range about 150 miles.

The state of Washington has a bill about the pass the legislature that would require all highway reststops to make available electric recharging stations. I think they will try to get at least 220 volts /50 amp recharging stations.

Agreed. I recently sat down with Google maps and figured the range between myself and a dozen or so destinations. I shot for eight or nine hours of driving, which is the most I'm comfortable with in a single day. Everything came back with between 500 and 600 miles. Considering a long lunch break in there where we can unwind, stretch our legs and charge the car (240V @ 70 Amps), 500 miles is a good top end.

But I want to challenge Graham's first assumption. I sleep six or seven hours a night. Eight hours is the minimum amount of time from when I park at night till I take off in the morning. It's usually closer to ten, giving me well over 625 miles of range. Sure, people will balk when they hear "10 hours to charge from empty". But try rephrasing that to "over 600 miles a day without stopping".

In fact, if we're assuming that I spent nine or ten hours on the road (includes breakfast and lunch), that leaves at least 14 hours to charge. Trim off a couple hours to find a meal and motel with a charging station, and we're still at a 12 hour charge and a possible 760 miles nonstop the next day!

Assumptions 2 through 4 are limited by technology and infrastructure. But the first assumption is perception and not a true limiter. Instead, I'd suggest that the theoretical limit is a 760 mile range (my house to Atlanta, GA). That equals 12 hours of nonstop driving and a 12 hour charge.

 

[graham]

But I want to challenge Graham's first assumption. I sleep six or seven hours a night. Eight hours is the minimum amount of time from when I park at night till I take off in the morning. It's usually closer to ten, giving me well over 625 miles of range. Sure, people will balk when they hear "10 hours to charge from empty". But try rephrasing that to "over 600 miles a day without stopping".

In fact, if we're assuming that I spent nine or ten hours on the road (includes breakfast and lunch), that leaves at least 14 hours to charge. Trim off a couple hours to find a meal and motel with a charging station, and we're still at a 12 hour charge and a possible 760 miles nonstop the next day!

I agree my assumptions are not based upon anything but my own musings on the subject. Today we have no fast charging solution - this means people pretty much have to charge at home -- and that is great for most people in reality, but not great for most people in perception. Will cars be built with batteries with larger capacity than can be charged in 8 hours? Maybe, maybe not. Will very high capacity / long range (> 500 mi) EV cars be built with no existing high capacity recharge stations? Maybe, maybe not.

Much of your belief of everything you would want to drive to is between 500 and 600 miles, so that range is sufficient is going on the assumption that there will be an external high powered charger waiting there for you to recharge when you get there. With no external charging system (today) you would need a range of 1000-1200 miles to get back to your home. Then you would need 16+ hours to recharge it again.

That may be great for some/most/all people - and it might not for others. If it isn't, then we will have to
1) increase the amount of time people are willing to deal with recharging their car
2) increase the rate that people are allowed to recharge their car at home
or
4) come up with a way for people to recharge quickly outside of their home.

All of these things are technically possible today - but don't exist in any widespread fashion yet. Once we hit a range of about 500 miles, at least one of those other things will need to be in widespread use, or EVs will pretty much always be seen as a second, less-capable car to many.

 

[Palpatine]

Once we hit a range of about 500 miles, at least one of those other things will need to be in widespread use, or EVs will pretty much always be seen as a second, less-capable car to many.

If you understand the reality of Peak Oil, EVs will likely be seen as the superior, most convienent method of powering your transportation miles.

When long gas lines are the norm and $10 per gallon gasoline is the cost, when it is available at all, what makes more sense?

a) wait hours in a gasoline line and pray that there is still some left in the gas station tank when your turn comes? and then get your ration of 3 gallons that week?

or

b) plug in your EV in your garage and start the next day with a full battery of USA domesticly produced electrons?

When Peak Oil starts squeezing supply, EVs will rule the road.

 

[AntronX]

Line for gas in 2005 after a hurricane in Florida:

 

[PeterW]

SCENARIO: You have an EV with a battery range of 1000 miles. Next weekend you are going on a trip; first day 900 miles. I want to know why you do not have a full charge before you left. Did you forget to charge your car all week? Did you go on an 800 mile round trip the day before?
Your home charging capacity does not limit useful battery range until AFTER you have travelled a distance further than your over-night charging range. Even if you were staying at a friends and could only get 600 miles charge over night. Are you really likely to be traveling more than 600 miles after just driving 1000?

 

[Joseph]

"Line for gas in 2005 after a hurricane in Florida"

What fun!

 

[Palpatine]

In reality, auto manufacturers will install battery packs that provide the most useful amount of range.

I think most people believe that 200-300 miles is about the ideal capacity to have in a battery pack.

Auto manufacturers won't go much higher because the cost and weight do not justify the expense. So even though the technology may enable longer ranges, instead they will likely just aim towards reducing costs and doing smaller battery packs as the range/weight ratios improve for battery technology.

I am sure we will see some vehicle models come out that are designed for long range. We will also see models designed for shorter ranger and very low cost to the consumer.

We will see some creative designs to meet different needs.

I am just happy that this appears to be happening now and all of the major manufacturers appear to be serious about their EV programs.

I just hope it happens in significant volume to help deal with Peak Oil.

 

[mt2]

Much of your belief of everything you would want to drive to is between 500 and 600 miles, so that range is sufficient is going on the assumption that there will be an external high powered charger waiting there for you to recharge when you get there. With no external charging system (today) you would need a range of 1000-1200 miles to get back to your home. Then you would need 16+ hours to recharge it again.

True enough. But by "high power" I assume you mean the aforementioned 240V @ 70A in assumption #2. I assumed by the tone of the thread we are talking some time in the near future when batteries progress to where such charging and range are possible. Given that, I extrapolated that high-power (not fast-charging) stations will be moderately available at many hotels and motels looking to differentiate themselves. I believe it is a reasonable assumption. A hotel or motel can add a couple of 240V 70A charging stations fairly easily, I'm sure.

Which all gets back to the discussion of whether a fast-charging infrastructure is necessary. Why build an infrastructure to charge a car in 10 minutes if the existing infrastructure can be tapped to provide a days driving overnight? All we need is the batteries (sigh).

PeterW, the last time I drove 900 miles in one day was 35 years ago with three other teenagers who rotated driving during spring break. Probably not the demographic to build an automotive infrastructure around.