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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

Guessing about halving of charge times.

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

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.

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

@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 charger...at least that was the advice I was working off of when I decided on a single charger. Please advise!

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

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.

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

Call transcript here, usually with some errors, especially when Elon is talking :)
http://seekingalpha.com/article/1209241-tesla-s-ceo-discusses-q4-2012-re...

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.

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.

@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.

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 http://hannelconsulting.com/tesla

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.

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

@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:

http://www.nytimes.com/2012/09/30/automobiles/on-an-electric-highway-cha...

@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!

@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!

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.

"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.

@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!

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.

@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.

@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.

@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.

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?

Oh boy! You folks type fast!

@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.

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

+1

you can see the panels right in the NY Times article picture
http://wheels.blogs.nytimes.com/2012/12/21/tesla-begins-east-cost-fast-c...


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