Later this year - "A step change in Supercharging technology"

Later this year - "A step change in Supercharging technology"

So I listened to the earnings call yesterday and Elon made some interesting comments about Supercharging, including the fact that they are going to have a fairly large announcement around "a step change in Supercharging technology." Just before he made this comment he also stated that they were working on improving the speed at which cars get charged. He then said that the original reason they reached out to the New York Times was around the announcement that will now come later in the year.

I am guessing that they will find a way to dramatically reduce the time it takes for the car to charge on a Supercharger.

So what's your guess for what the announcement will be?

P.S. - For those of you interested, Elon talks about the Supercharger network around minute 31 of the earnings call.

P.S.S. - I bought the stock today based on the earnings call and the 10% drop in the price

Brian H | February 21, 2013

Guessing about halving of charge times.

sshrivas | February 21, 2013

While excited about this announcement, I just hope that the improvements stay compatible with the supercharging hardware being installed on the cars today.

vgrinshpun | February 21, 2013

The superchargers are actually 12 Model S on-board chargers connected together. The total capacity is 120kW, but I believe that charging is currently starts at maximum of 90kW. The 90kW limitation is most likely due to concerns for the battery longevity suffering due to higher max rate of recharge.

If SC max rate of recharge is upped 33% to 120kW, the total recharge time will be probably reduced more that 25% (factor of 1 / 1.333) due to the fact that charging rate is higher initially and slows down as battery getting charged.

The above will most likely reduce battery life, but if SC are used only for 1 - 2% of the charges throughout the life of the battery, this reduction in life might be negligible. This would be weighted against the positive public reaction to the reduced time one would need to spend at SC.

GeekEV | February 21, 2013

@sshrivas - I hope so to. I think it would be suicide for it not to be...

bsimoes | February 22, 2013

@vgrinshpun--I can't tell if you're joking or not! I was under the impression that on-board chargers didn't come into play with supercharging, but rather, used DC and so it didn't matter whether you got a single or twin least that was the advice I was working off of when I decided on a single charger. Please advise!

shop | February 22, 2013

Yes, the car on board charger is not used when using a supercharger.

bsimoes | February 22, 2013

In the Q4 conference call, Mr. Musk reported that many more stores and service centers would be built. He also stated that a number of superchargers would be built--I can't find a transcript, and I don't want to listen to the whole thing again. Anyone remember how many of each he stated? I keep checking the map of service centers and would love to know the locations of the new super chargers. I also checked the job board--no clues there! Anyone know anything? When do you suppose this information will be revealed? I was hoping that after such a statement, we might be given some general info, even if only at a state level.

Nicu.Mihalache | February 22, 2013

Regarding the superchargers, they should indeed get from 90kW to 120kW (and sometimes form 120kW total for two chargers). But it could also be about the supercharger experience, not only the hardware. And that could mean better software in the car and even internet connected superchargers.

Why? Well, if you tell your car where you want to go, it could compute by itself the range, where superchargers are, adjust to your driving / weather (actual W / m average) and reserve / query superchargers for available spots (in real time, but also by the time you get there - that should be some smart a$$ software to combine traffic statistics, real-time reservations etc. - it would be fun to create / write / debug such software).

Btw, this software should not give too much information to drivers (example: if you get there by 15:02 you have a spot, otherwise it's 15:30) otherwise highways could become a racing ground for Teslas :D

Nicu.Mihalache | February 22, 2013

Call transcript here, usually with some errors, especially when Elon is talking :)

hsadler | February 22, 2013

I think everyone's guess is wrong. It's obvious. Tesla will be installing Keurigs in each Supercharger column. That way you can enjoy a cup of coffee (tea, hot chocolate) while waiting for the charge.

stevenmaifert | February 22, 2013

The Superchargers already have telematics to the mothership. One enhancement might be an addition to the smartphone app that will tell us up/down and in-use status of each unit.

Electron | February 22, 2013

@vgrinshpun I've seen no convincing evidence that supercharging does any harm to the battery. At 90kW they are charging the cells right around 1C which as far as I know with LiIon, fairly comfortable. Going beyond that by 30-50% shouldn't be an issue either. Especially since they back off the charge
when approaching full.

EVTripPlanner | February 22, 2013

Another clue: at Tejon Pass SC last weekend, engineers were checking out massive battery bank being connected between grid and charging stations. This allows storage (over 800 kWh from what I gathered) from solar but also allows very high concurrent peak currents to multiple charging stations. I imagine that powering 6 or more charging stations at 90kW (or up to 120kW) directly from the grid would be a difficult/expensive proposition since a MW feed would be expensive and time-consuming to get installed at remote/inexpensive locations.
Also: confirming that SC is DC charge circuit that is (mostly) independent of AC charge circuit. My P85 charges fine on AC at home, but would not ramp current on DC, probably due to contactor (relay) not switching between circuits.
All my cheat sheets, etc at

gregv64 | February 22, 2013

Just to be clear, when vgrinshpun mentioned 12 Model S chargers connected together, he meant that was the hardware used inside the supercharger itself, not that it involved the chargers inside your car.

Timo | February 22, 2013

gregv64 +1. Those are used to change AC from grid to DC and communicate directly with the battery bypassing onboard chargers.

vgrinshpun | February 22, 2013

@bsimoes, @shop - SC consists of the array of 12 chargers, each of them is the same charger as the one installed on-board of Model S. On-board charger is obviously not used when Model S connected to SC. It is being by-passed. Battery is fed directly from the array of 12 chargers comprising the SC unit:

riceuguy | February 22, 2013

@vgrinshpun, for a lot of folks, citing the NYT as a source of Tesla factual information...well, let's just say it might be too soon--even if it's right!

bsimoes | February 22, 2013

@vgrinshpun: You state that it's obvious...maybe for some, not for me; if you ever watch "The Big Bang Theory" you'll understand my reference when I say I feel like Penny talking to 'the boys.'

@riceguy--very funny, thanks for the chuckle!

Mark K | February 22, 2013

I'm going with the local battery buffer to deliver much more than 1C. As long you terminate promptly when SOC gets within say 50-70% full, the battery is happy and no accelerated degradation occurs.

You can bypass the 10kW charger modules altogether if you go from one pack to another with pure DC battery power. You will still need some kind of charge gating, but you might be able to do that by switching in and out the number of cells in the source to manage the potential difference and hence the current levels.

A very meaningful benefit for users if you can be in and out in say, less than 15 minutes. That's effectively parity with gas refueling (if you don't need to go 100% full). That's doable at 2 or 3C.

The other huge benefit is it multiplies the capacity of the charge bays in terms of refills per hour. Charging faster is like adding 2-4x the number of bays in the network. A tremendous benefit as MS drivers multiply.

Bottom line, shorter wait for a bay, and faster refills.

Lets not forget that the juice is free, and coming from the sun.

Very cool.

shop | February 22, 2013

"Lets not forget that the juice is free, and coming from the sun."

Um, I doubt it, not for a while anyways. It takes big panel arrays to generate the amount of energy being used in the supercharger stations. Now, I haven't actually been to any supercharger stations yet, but for those who have, have you seen large arrays nearby? It is encouraging that they are putting in large battery arrays at Tejon. That would be a first step to having it all powered by the sun. Since solar cells produce DC, the batteries are DC, and the Tesla wants DC to charge, it would be quite efficient. Anyone remember what the DC-AC converter losses are?

Actually, for this application, it might even make sense to use super capacitors to store the solar energy since they don't wear out nearly as fast as batteries do.

vgrinshpun | February 22, 2013

@Mark K - could you post a link for the definitions of 1C, 2C and 3C? I am assuming that these are various charging protocols. Thanks!

Mark K | February 22, 2013

C = capacity

For 85kW battery, capacity = 85 kilowatt hours.

1C charge will pump 85 kWh of charge into the battery in 1 hour.

(Have to stop at 50-70% though, to protect against heating degradation).

2C is twice that rate.

Due to internal resistive heating and chemistry losses, efficiency is around 90%. So battery ends up with about 10% less than you gave it.

Superchargers today get power from the grid, but TM committed to contract SolarCity installs for more solar generating capacity than the network uses. So net, less than zero grid use in the steady state.

Inverters are 85-95% efficient.

Supercapacitors don't yet offer the economies TM has on 18650 cells. When they're cheap enough, supercaps will be great, but will still require more hardware to supercharge cars since their internal impedance does not mirror the cells in the car. With a matched pack, you get current limiting for almost free by leveraging the intrinsic internal impedance of the source cells.

Electron | February 22, 2013

@shop The solar arrays for superchargers are just for offsets. They could be anywhere. I don't think we'll see PV panels at the SC sites.

jat | February 22, 2013

@vgrinshpun - 1C is charging/discharging at a rate which will use the full capacity of the battery in an hour. So, for an 85kWh battery, 85kW is the 1C rate. When you stomp on the accelerator, you are drawing energy out at about a 4C rate. The chemistry of the cell itself affects how fast you can get energy in/out, plus the internal resistance of the battery generates a lot of heat at high current (P=I^2 * R, so the power dissipated as heat goes up with the square of the current) and you have to be able to remove that heat. Even with an active battery temperature management system like the Model S, there are limits to how well you can get heat out of the center of the battery.

Li-Poly batteries frequently have support up to 30C, but they have a much shorter lifespan than other Lithium batteries.

Tiebreaker | February 22, 2013

@shop - The solar panels do not need to be near the superchargers. As SolarCity manages them, they can have solar panels at the superchargers locations (or any locations) that are convenient, then they sell the generated energy to the grid. At the supercharging locations, they draw energy from the grid and pay for it. The overall sell/buy averages to zero, probably even positive for SolarCity.

shop | February 22, 2013

I had assumed that the batteries Tesla would be using at supercharging stations would not be 18650 LIon. Wouldn't they use a cheaper battery technology like maybe even lead acid since weight wouldn't matter?

Tiebreaker | February 22, 2013

Oh boy! You folks type fast!

LMB | February 22, 2013

@shop - I visited both the Milford supercharger sites this weekend, and yes, there are HUGE solar arrays - right on top of the canopy over the gas pumps, ha ha! They are offsetting, not feeding it right into the chargers, obviously, but putting them in plain view from where you charge is clearly part of the message.

GoTeslaChicago | February 22, 2013

"putting them in plain view from where you charge is clearly part of the message."


kenliles | February 22, 2013

you can see the panels right in the NY Times article picture

breading | February 22, 2013

I am hoping/guessing this will involve a drop in charging time as well. After all, Tesla has got to keep up with the competition:

jat | February 22, 2013

@breading - yep, I'm sure if you can afford one you will be able to get 1MW service at your house, which is what you would need for a 10 minute charge.

shop | February 22, 2013

Gee, that's only a 4000A service (at 240v). Piece of cake. I'm not sure what that Chreos press release was trying to do. They haven't even made a prototype car yet. 3 years out. Uh huh. And what price? And why, pray tell, does that car have such a huge hood?

breading | February 22, 2013

Well, if they can imagine a car that gets 600 miles of charge in 10 minutes, I can go right along and pretend to get 1 MW service at my house just as easily.

If Tesla can get 150 miles of charge done in as little as 15-20 minutes, I will be thrilled. At least I will be when they finally put some of those super chargers across the Midwest.

teddyg | February 22, 2013

I just hope Tesla is being honest with owners about how often they should be using a supercharger in terms of its effect on battery any owners here know how Tesla is handling this?
I assume the more they try to make the superchargers charge cars faster the more overall battery life will suffer?

If I was Tesla and being 100% honest I wouldn't recommend the cars to anyone making frequent (more than once every two weeks) roadtrips involving superchargers AND I would not recommend the cars to anyone travelling more than 25,000 miles per year on average.
Anyone travelling more than this will be looking at a battery replacement in around 5 years. Any less than 5 years of normal operation and requiring an expensive battery change would be totally unacceptable to me.

If I was Tesla I would be asking customers about their driving habits. Mainly their average milage per year and how often they intend to use superchargers. This would help to avoid bad press for Tesla in the future as nobody could say they weren't aware of these issues.

ian | February 22, 2013

I agree teddy.

I think there are some serious misconceptions regarding the SC use.

Then again, it may be that TM doesn't know for sure how much damage the SC use is causing.

jat | February 22, 2013

@teddyg - would you make that recommendation if in fact the effect on battery life were less than many other factors? They do tell you that you are risking your battery longevity when you do a max-range charge, so why would you assume that they would hide damage from supercharging?

I don't know for the precise cells used by Tesla, but in general charging lithium batteries at around a 1C rate can be done with no noticeable difference from slower charge rates. 90kW is only slightly over 1C (C is the capacity of the battery, so charging an 85kWh battery at 85kW is 1C), so I would expect as long as you slow down at higher charge levels (which it does) there will be no damage.

GoTeslaChicago | February 22, 2013


I don't agree. I'm sure Tesla is monitoring very closely the Super Charger's effect on the battery in all respects. If they are about to announce a step up in the Super Charger rate, I'm sure it will be because they have accumulated enough data to say it can be done without shortening the battery life more than what was already allowed.

And if your battery is gone after 5 years it won't cost you a cent, as it will still be under warranty.
8 years, 125,000 miles for 60 kWh, 8 years and unlimited miles for the 85 kwh.

vgrinshpun | February 22, 2013


The Panasonic batteries used in Roadster were tested in conjunction with NASA program. The batteries used in Model S is next generation and are presumably more robust.

It was concluded that batteries will last 1000 full discharge cycles with approximately 20% degradation. For 85kWh battery this will conservatively translate into 265,000 miles life span at rated miles or 200,000 miles at average "real life" miles.

Above results are very conservative because in average everyday use batteries would be cycled between 90 and 65% of charge (for 50 miles/day commute), significantly extending battery life.

The reality is that battery, except for extreme cases will last for the lifetime of the car.

See quote and link below. Note that C/5 charge is 5 times higher than the charging used for the SC

"Preliminary cycle life and safety tests on the Panasonic
NCR18650 cells were performed at JSC. Initial ob
servations show capacity degradation of roughly
4.3 percent over 200 cycles at a C/5 charge and C/
10 discharge rate at room temperature."

GeekEV | February 22, 2013

@vgrinshpun - Good stuff, thanks!

Mark K | February 22, 2013

NASA article is for different charge rates.

C/10 = 0.10C

C/5 = 0.20C

We are talking here about multiples of C with Supercharger, not fractions of C.

As JAT points out, discharge is already demonstrated at 4C, so that's a pretty good indicator of the reasonable charging rate limit with this pack. My money is on 2-3C with the step change improvement.

I believe TM's testing data and conclusions about the safety of Supercharging to limited levels of State of Charge (50-70%).

TM has active temp control including heat elimination, so they can easily outperform a naked cell and protect its life much better.

Don't think you need to worry about using their Superchargers when they are fully warranting the use. Their software prevents harming the battery.

vgrinshpun | February 22, 2013


Thanks for the correction.

Do you have any specific information or maybe an educated guess estimate on design lifespan of Model S battery (end of life capacity = 80%).

I find it strange that this information is so difficult to get. Panasonic got to test their batteries and I am sure that this information must be available internally.

Tesla must have performance specification for the batteries they are using...


Joyrider | February 22, 2013

Gee, are you guys battery engineers? "If I were Tesla I would..." This IS the single most important part of the car and EV cars in general. Tesla has spent years developing their technology and the range and reliability results (see Roadster) show they are at the head of the class.

And even if you are battery engineers what projects have you developed that even approach what is under the floor of a Model S.
All I can say is wow...just wow. But this is the internet and everybody is an expert.

Mark K | February 22, 2013

Well, in my humble opinion, TM has far and away the most advanced battery pack technology on the planet. Their team is second to none, and Boeing would have been lucky to get Elon's help.

And well yes, that opinion does come from an EE who runs a company full of engineers manufacturing hi volume electronics with Lithium Ion cells. So there is a reasonable basis for my opinion about TM.

Because of what some forum participants actually do know, we uniquely recognize just how brilliant team TM really is.

Example: Did you know that the waste heat developed in the motor is actually fed back into the battery pack to warm it up in cold weather? Per Elon, those heat pumps are managed by firmware to work in both directions. Never wasting a watt or a BTU. Do you know how cool that is? That is so elegant, it's sheer engineering artistry.

A thread like this is in fact about speculation, but it's usually more interesting when it's based on fairly well educated guesses.

jkirkebo | February 23, 2013

Nissan recommends not fast charging the Leaf more than once per day on average (multiple times per day occasionally is ok). And that is with a 2C charge rate on a pack with no active cooling.

I wouldn't be worried about 1C charging a pack with cooling at all.

Cattledog | February 23, 2013

vgrinshpun - A bit OT, but if this non-engineer read the NASA report right, the specific energy the test cells output was reduced by about 10% from the base scenario of 20C (68F) to one of the test markers of 0C (32F). Good rule of thumb to know.

lolachampcar | February 23, 2013

Wow, something useful came from the Border piece... A picture of the panels.

noel.smyth | February 23, 2013

@teddy - what is the basis of your 25k per year limit? I expect to be right around there with my daily use of about 75 MPD duing weekdays and 50 MPD on non work days average. I figure I a right in the sweet spot for charging without max (will go to max several times a year for roadtrips but typically not) and not running it even close to the min. and I would save more in gas due to the higher miles. If the battery craps out after 5 years of this, I am fully covered. whats the downside?

vgrinshpun | February 23, 2013

joyrider - I think you are missing the point of this discussion while being a bit presumptive about the reasons you think some of us are engaging in it.

The design life of the battery is one of the major points that Tesla detractors are making against the Model S. With precious little information at their disposal they happily jump to the conclusion that since battery warranty is 8 years, one must include cost of it's replacement after 8 years while considering the lifetime costs of Model S. Than they throw the maximum cost of the replacement they perceive they can reasonably can get away with and victoriously declare the case closed - Model S lifetime costs are too high and the company will be toast because there will be no demand beyond early adopters.

However laughable this argument might sound to people on this forum, the common public perception is closely aligned with it. I am an electrical engineer, and while do not specialize in Lithium Ion batteries have a gut feeling that the battery in Model S, particularly 85kWh one, for all practical purposes will last the lifetime of the car under all except very extreme conditions.

I have the highest respect and admiration for Tesla Motors. Elon Musk is perhaps the most straight talking CEO ever, and I do not believe that he was kidding when he set to engineer, build, and mass produce the best car in the world. I am, however, not prepared to take my gut feeling about the lifespan of the battery as an article of faith (especially when Tesla Motors is not very vocal on this issue). I would like to have some specific independent information which can prove that my gut feeling about battery life is correct, if not for any other reason then to credibly counter the critics.

One last point - I believe that Tesla have multiple legitimate reasons to limit information about battery to the terms of their warranty and prepaid options for replacement. Having worked in various engineering organizations for a long time, however, I am quite certain that this is not because this information does not exist, it is because their battery management system is unique and relatively new. Perhaps the certainty they have about the data is not at the level they would be comfortable with to make data widely available.

jat | February 23, 2013

@jkirkebo - the LEAF fast-charge is actually 1.6C -- 80% charge in 30 minutes and it does have active cooling but only air rather than liquid. But still, I agree with your point.