# supercharging?



## BikerA (Jan 9, 2008)

How can Tesla charge so fast when all I see in battery ads is relatively low "C" maximums?


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## Karter2 (Nov 17, 2011)

BikerA said:


> How can Tesla charge so fast when all I see in battery ads is relatively low "C" maximums?


Several reasons..
1)..large capacity packs..85kWhr
2)...good quality matched cells
3)...well thought out and tested charge management system
4)...optimised charge rate profile to match the cell.
5)...active thermal management with liquid pack cooling.

PS:- "C" rate is a measure of cell discharge ability, with no direct relationship to charge performance.


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## Hollie Maea (Dec 9, 2009)

BikerA said:


> How can Tesla charge so fast when all I see in battery ads is relatively low "C" maximums?


How fast are they really charging? It takes more than a half an hour to recharge, so that's less than 2C. Most batteries can handle that.


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## IamIan (Mar 29, 2009)

Hollie Maea said:


> How fast are they really charging? It takes more than a half an hour to recharge, so that's less than 2C. Most batteries can handle that.


Super Charger rated for 120kw .. does a max peak of 135kw DC charge rate.

The smallest Tesla Battery ~40kwh.
The largest Tesla Battery ~85kwh.

C rate is about amps not power (kW) .. but it's between about ~1.4C and ~3.4C.

At that scale it's less about the C rate of the batteries .. it's more about the control electronics , and the utility demand load.

- - - - 

The Tesla battery swapping stations take as little as 90 Seconds ... Which is on par with how fast the average gas station will refill .. but that's a physical swap with another battery .. not a charge of the battery that is in the car.


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## Hollie Maea (Dec 9, 2009)

IamIan said:


> The smallest Tesla Battery ~40kwh.


Tesla never ended up making the 40kWh model. Smallest they ever made was 60 kWh and the smallest they make now is 70 kWh. IIRC, Supercharging wasn't going to be an option for the 40 kWh version (Supercharger was only 90 kW back then) and if they did offer it it likely would have been at a derated speed.


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## JasonA (Aug 8, 2013)

Hollie Maea said:


> Tesla never ended up making the 40kWh model. Smallest they ever made was 60 kWh and the smallest they make now is 70 kWh. IIRC, Supercharging wasn't going to be an option for the 40 kWh version (Supercharger was only 90 kW back then) and if they did offer it it likely would have been at a derated speed.


You're wrong, there are plenty of MS-40 owners out there. The 40kw version is actually just a 60kw pack derated and software limited to only charge to 40kw of power (aka 3.915 or so)

So their packs are going to last a VERY long time. And they did have an option for SC'ing as well but it's unknown how many of them ordered it.

As for the charge rate... it's about 1.69c currently on the fastest stations. What is stopping them is not the batteries or the chemistry... is the handles and the wires going to the car! 

But now they are testing "LIQUID COOLED SC CABLES" and connectors!

 more power!

http://www.teslamotorsclub.com/showthread.php/48766-S40-Max-range-change-with-SW-6-2-(2-4-239)

http://www.teslamotorsclub.com/show...plus-supercharger-enabled-No-Longer-Available

http://www.teslamotorsclub.com/show...a-60-in-waiting-could-current-the-85-be-a-10x


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## Sunking (Aug 10, 2009)

BikerA said:


> How can Tesla charge so fast when all I see in battery ads is relatively low "C" maximums?


Maybe because you do not understand the battery type/manufacture, and capacity.

Tesla over sizes their batteries. Large enough discharge and charge rates are 1 or less. For example the Tesla Roadster uses a modified Panasonic LiCo battery. It is modified by removing the safety features to lighten the battery up. Anyway they us 18650 LiCo cells which have a Charge rate of up to 5 C, and 10C discharge. But the battery never ever sees any C-Rates of that magnitude. Well maybe for a few brief seconds accelerating from stop to 60 mph in 5 seconds. However the battery is a 60 Kwh capacity in 99S configuration which makes the battery about 400 volts @ 150 AH. So to obtain a 1 C fast charge charge requires a 60 Kw charger. That i snot fast for their battery. Neither would a Supercharger be considered real fast at 2C

The kicker is Tesla clearly states for maximum battery life is no higher rate than C/2 charging to only 80% SOC. 

Point here is with an over sized battery, changes the picture. A 60 Kw charger on say a Leaf would make the batteries glow in the dark because they are much smaller. But for a 60 Kwh or larger battery and larger, and 60 Kw charger is not all that fast or fast as you might be thinking.


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## Sunking (Aug 10, 2009)

IamIan said:


> C rate is about amps not power (kW) .. but it's between about ~1.4C and ~3.4C.


That is not completely accurate as power the product of the two variables of voltage and amps. Or th ereal work done in a specified time. Amp Hours is meaningless without a known voltage, and if you know the voltage and amp hour, then you know the energy in watt hours. A 60 Kw charger, charges a 60 Kwh battery at 1C. I don't need to know anything about amp hours or voltage to determine the charge rate.

If I am going to buy a battery, I do not give a damn about how much the battery cost per AH, all I want to know is how much it cost per Kwh. If I want 60 KWH at $300/Kwh I expect to pay $18,000. At that point I could care less what amp hours is required because I cannot determine that until I know first the energy requirement (watt hours). AH is just what is left over after I select Watt Hours and Battery Voltage. If I am running a 400 volt battery @ 60 Kwh capacity I discover last step I need a 150 AH battery. With say I need a 180 KW motor with a 60 Kwh battery most I am looking at is 3C discharge and I don't care what the amp hours are, I don't need to know at that point. That is just a last minute detail.

To me it is like asking; "how fast and far can I go with a 150 AH battery?"

I guess real dang fast for at least 200 miles with 400 volts.


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## IamIan (Mar 29, 2009)

SunKing said:


> IamIan said:
> 
> 
> > C rate is about amps not power (kW)
> ...





Sunking said:


> A 60 Kw charger, charges a 60 Kwh battery at 1C. I don't need to know anything about amp hours or voltage to determine the charge rate.


As much as I agree about some of things you wrote about power and energy .. C-Rate is not describing power and/or energy.

I don't think the rest of the world has changed the definitions or usage for the C-Rate terminology yet. 

C-Rate is about Ah and Amps... not Power and energy.

60A into 60Ah = 1C .. that is the currently world over accepted usage for the that C-Rate terminology .. not 60kw into 60kwh .. they are as different as current is from power .. and Ah is from Wh.

As incomplete a picture as C-Rate terminology is .. that is the accepted definition and usage for the terminology.

When you become emperor of the world .. you are welcome to change it


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## Hollie Maea (Dec 9, 2009)

There are minor departures from nominal voltage due to load and SOC, but kW/kWh is a close approximation, especially for low C rates.


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## Karter2 (Nov 17, 2011)

Sunking said:


> .........A 60 Kw charger, charges a 60 Kwh battery at 1C. I don't need to know anything about amp hours or voltage to determine the charge rate.


Really ?
I have a 40kWhr pack and a 60kW charger.
What charge rate will I have ??


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## Duncan (Dec 8, 2008)

40Kwhr at 60Kw = 1.5C


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## Karter2 (Nov 17, 2011)

Sorry Duncan , but not correct.!


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## Duncan (Dec 8, 2008)

Karter2 said:


> Sorry Duncan , but not correct.!


OK - why not?

You have a 40Kwhr pack
at 40Kw charging/discharging it will take 1 hour to charge/discharge - 1C

At 60Kw charging/discharging it will take 1 x 40/60 hours to charge/discharge
= 40 minutes 

40 minutes = 1.5C

The only difference will be inefficiencies in the charge/discharge cycle - for lithium not a lot
Inefficiencies in the charger 
A good modern charger should be 97%

So again - why not?


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## Karter2 (Nov 17, 2011)

Simply because the pack is 400 volts , and the charger is only 300 volts max.!
..so it will give an effective charge rate of 0.0 amps.!
..IE, it won't charge at all .

Sorry, I was not intending to tease you, just point out to Sunking the limitations of his thinking and false statement.
You must know more than just the power rating of the charger and pack capacity.!


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## Duncan (Dec 8, 2008)

no Sunking was correct

If you want to know the C factor of a charger all you need to know is the power and the capacity
It is "assumed" that the battery charger combination is matched
The same way that somebody asking "how fast does it go" assumes that it has tires with air in them and is not chained to the wall

If you required to specify all possible factors then you could never actually say anything for all of your
Assuming that you are not hit by a meteorite 
Assuming that you are not dragged away into the bushes by Jennifer Aston
Assuming ........


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## Karter2 (Nov 17, 2011)

Making assumptions can be very dangerous..
Especially with things electrical....
( I assumed the power was switched off !!)
...and see how wrong you were by assuming they were matched voltages !
..but Sunking stated that he did not NEED to know anything else (assumed or informed). In order to calculate the Rate of charge.


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## IamIan (Mar 29, 2009)

Duncan said:


> OK - why not?


Accepted meaning and usage of the C-Rate terminology .. as the terminology is understood and has been used around the world for many decades now.

C-Rate is not about power or energy .. C-Rate terminology is about Ah and amps ... That limited information is just the limitation of that C-Rate terminology.

If someone told you a 20Ah battery was charged at 3C .. The C-rate terminology tells you the amp rate of charging .. 60A .. it does not tell you the power of charging.

Just as constant current is not = to constant power ... and amps are not power .. and Ah are not energy .. the terminology is as limited and specific as it is.

Using C-Rate terminology to describe power and energy .. is just about as incorrect usage of the terminology , as using Ah to describe a batteries capacity to do work (energy).

- - - - - 

Perhaps a Power and Energy based terminology would be better ... a E-Rate ... instead of a C-Rate ... in order to differentiate the two different concepts... Where 60kw of power into a 60kwh battery is a 1E rate .. even if without the Ah and A we don't know for certain the C-Rate.


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