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What would it take for Tesla to begin installing the "NextGeneration" SuperCharger?

What would it take for Tesla to begin installing the "NextGeneration" SuperCharger?

So, I know JB has talked about ramping up the SC delivery power to drop the recharge time and the current SC installations in Europe are at 135KW, what would it take for Tesla to begin using 150KW in the US? And what would that drop the "half charge" recharge time down to? Or, would they try and jump to 200KW? Here are my guesses:

Changes required for either the 150KW or 200KW SuperCharger installs:

- One Tesla skid mount 400 KWh storage units per 4 charging bays
- Additional transformation to drop the charging current but up the charging power...not sure about this one...?
- Cooling fans for blowing air across the underside of the pack to help control temp
- New firmware for managing the recharge cycle

I would guess that 150KW charging would drop the "half charge" time down to 15 minutes but 200KW charging might drop it to 10 minutes. These new stations would have a larger footprint and be much more expensive but might be really popular in areas where there is a high density of Teslas.

Anyone have any other ideas or thoughts about how this might be achieved?

Thanks!!

Bighorn | 02/03/2015

135kW chargers still only charge to 120kW, so it's more than just the SC at play.

hillcountryfun | 02/03/2015

Thanks Bighorn...I didn't realize that...good to know -

hillcountryfun | 02/03/2015

A few more thoughts on this:

1) As I understand it SuperChargers operate in pairs, if only one is in use then it can get the full 120KW...if they are both in use then one gets 65% of 120KW and the other receives 35% of 120KW.
2) If a typical SuperCharger location had 8 bays then the site would max out at 4 * 120KW = 480KW.
3) A standard 480V 500 KVA distribution transformer would handle this load
4) If you had the same installation but increased the power to 200KW per pair then the site load would be 4 * 200KW = 800KW
5) A 750KVA or 1000KVA transformer would support this load but at an increased cost
6) Perhaps one of Tesla's 400KWh storage units might not be needed except to smooth out the load curve and reduce the peak demand...?

I had been thinking that the current limit of 120KW was perhaps partially tied to a limit of the distribution delivery equipment but I suppose that it's solely a limit of the vehicle (at this time).

Bighorn | 02/03/2015

I think when a supercharger is shared, the cars are sharing 135kWs.

BrassGuy | 02/03/2015

If Tesla is going to decrease supercharging time, the easiest way is to change the charge taper. All it would take is a firmware update.

Anybody who's supercharged from a low SOC knows 120kW only lasts a few minutes at most. 150kW for the first 3 minutes wouldn't help that much. You'd obviously have to increase the power throughout the charge cycle to make a significant difference. (From other threads, "A" packs that only accept up to 90kW supposedly only need an extra 5 or 6 minutes total charge time.) Sure starting higher would be a little faster, but maintaining a high power draw for longer would make a bigger difference.

0 to 200 miles currently takes about 45 minutes. If you could maintain 120kW, that could drop to less than 25 minutes. Tesla will decide what's safe for the pack.

garygid | 02/03/2015

On a typical 120 kW SC, a first car might get 120 kW initially, but
the car will begin to taper off its charging rate after the first 10 minutes or so.

If a second car attaches to the same SC to "share", the first car will drop
down to 90 kW, and the newcomer will get 30 kW max, until the first
car drops to below 60 kW, freeing up an additional 30 kW for the
newcomer.

It appears that there are other possibilities for "sharing", assigning 10 kW
units instead of 30 kW modules, but I do not know if or when these
are employed. Watching the Amps, or kW, as you are charging should
be illuminating.

TeslaTap.com | 02/03/2015

I may be wrong, but I thought 135 kW Superchargers were Europe only due to differences in available power. I think all USA Superchargers are 120 kW. As pointed out, 135 or 120 kW Superchargers charge at the same rate if you're the only one of the pair. The extra 15 kW only helps a small amount when two cars are charging at the same time.

It's not clear if the car's internal battery, wiring, or the connector can safely handle more than 120 KW. I suspect charging speed improvements may come if Tesla determines the slow-down ramp (as the SOC nears full) can be extended closer to the 100% SOC without affecting battery life. It's a very complex issue that may conclude the current design is at the limit.

This does not mean a new battery/car design couldn't do better. I just wouldn't hold out a lot of hope that current cars will suddenly get a lot faster charging via a software update and new Superchargers.

hillcountryfun | 02/03/2015

Many good points, thanks -

OK, assuming no losses and an 85KWh pack with a usable size of 75KWh then a SuperCharger running at full speed of 120KW would take:

75KWh/120KW = .625h = 37.5 minutes best case

or

200 Rated Miles (as shown in BG's post) = 58KWh => 28.99 minutes (very close Brass Guy as losses are low)

So, I agree that removing power tapering would be the easiest and obvious first step to reduce charging time.

If you could stay at full speed with the SC and the SC ran at 200KW:

75/200 = 22.5 minutes for a complete refill from empty.

Having said that, the tapering may be one of the biggest challenges to overcome...especially when the pack is near to full. What if you could maintain full charging up to 80% full:

(.8 * 75)/200 = 18 minutes to go from completely empty to 80% full at 200KW, or

(.6 * 75)/200 = 13.5 minutes to go from 20% to 80% at 200KW (most of my SuperCharging starts at 20%)

So, I think a combination no tapering until after 80% full and moving to a 200KW SuperCharger would have a huge impact on reducing SuperCharger times. Seems like a couple of great targets for Tesla!!

Bighorn | 02/03/2015

@TTap
135 had been a given for about a year in my mind, here and abroad, but I'm willing to be wrong.

Brian H | 03/03/2015

Elon spoke of reducing final taper to a less conservative last 10% or less, now that the initial cautious approach was showing to be "overkill". Don't know if this is released Now or Soon.

hillcountryfun | 09/06/2015

Ok, after Elon's comment today at the 2015 annual Shareholders meeting about the new SuperCharger cables being able to support more power, I'm bringing this thread back up! I suspect that at some point in the near future the next rev on the SuperCharger hardware will be released. Will it only be a incremental step or will it get us all the way down to JB's 10 minute charging time?

I would look for a combination of reduced tapering and a dramatic increase in delivery power for a short period of time. Maybe 5 minutes at several hundred KW...I know that sounds crazy but that's what's required to charge in 10 min.

Fingers crossed.

MountainVoyageur | 10/06/2015

To make any big improvement ins charging time they are going to have to decide that the battery can take 2C or 3C, at least for a limited time, without degrading the battery. Do you suppose they now have enough experience to be confident that can be done? Perhaps improved batteries from the Gigafactory can do that? I have seen no mention of being able to move to higher charging current.

hillcountryfun | 10/06/2015

MountainVoyageur: That's exactly what I believe, maybe 3C for 5 minutes. One thought is I've always assumed that the limiting factor for the existing 120KW feed was the car but perhaps not. Yesterday, after the Annual meeting, I guessed at the cable size contained within the SuperCharger and looked up the ampacity limit for that size...turned out, it was about the max current I've experienced at SuperChargers. So, maybe one of the limits was the SuperCharger cable...? There may be others, but if so I expect Tesla to eliminate those one by one.