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## What is the max charging capacity for a 85kwh battery pack?

From some other subjects I got curious why Tesla isn't further improving the charging capacity. Therefore this question.
Can someone calculate the maximum charging capacity of a Tesla 85kwh batterypack.
A start:
A tesla with a 85kwh batterypack has 7,104 lithium-ion batteries. Each battery, therefore, has a capacity of 11wh. The charging capacity of a lithium-ion appears to be equal to the capacity. Lets start with 10 amps. At a charging voltage of 15 volts, a battery can take up to 150 W power. The largest superchargers give only 120,000 w. This makes that 120,000 / 150 = 800 batteries are charged at full power.
Is it possible to increase the charging capacity so that the charging time can be reduced to 5 minutes?

georgehawley.fl.us | 22 décembre 2014

@Gert: you have some things correct but are a little mixed up on some of the details. The 7,104 cells in an 85 kWh battery pack are organized into 16 modules of 444 cells each connected in series. Each module consists of 6 groups of 74 cells each. The groups are also connected in series while the 74 cells in each group are connected in parallel. Therefore, the charging current per cell is approximately 1/74 of the total current. A 120 KW supercharger supplies charging energy at about 400 volts resulting in a charging current of about 300/74 or about 4 amps per cell at a voltage of about 400/96 or 4 volts per cell. The nominal discharge voltage of a cell is about 3.6 volts and 4 volts of charging voltage is enough to ensure that charging takes place. By the time the cells are about 50% charged the cell voltage increases and begins to limit the current, slowing down the rate of charging. The cell capacity of the Tesla cells is nominally about 3.1 ampere-hours or about 11.4.-hours per cell.

Fully charged, 7104 x 11.4 = about 81 kWh. These numbers are all approximate because Panasonic builds cells to a Tesla specification and precise cell parameters are not published for the Tesla cells.

I hope this helps.

Iowa92x | 22 décembre 2014

All he said plus a buffer, so only 75 kWh or so is available for use on a fully charged pack.

jjs | 22 décembre 2014

@georgehawley.fl.us Such precision and clarity in your post may endanger you currently unchallenged position as the Rube Goldberg of Tesla patentable ideas. Careful! :)

Soon they will start to believe you actually know what you are talking about.

georgehawley.fl.us | 23 décembre 2014

it is a sham abetted by Google and an electrical engineering education that predates Nikola Tesla.

aljjr2 | 23 décembre 2014

oh my.... did he call Georg Ohm a liar? Please restore my faith...

Brian H | 23 décembre 2014

There's a lot of resistance building up to Ohm!

vandacca | 24 décembre 2014

I think this pressure against ohm is being multiplied by the current resistance.

georgehawley.fl.us | 25 décembre 2014

Re-volt-ing...

Brian H | 25 décembre 2014

Very amp-big-you-us.

georgehawley.fl.us | 25 décembre 2014

Watt nonsense!

james | 25 décembre 2014

This of course all depends on the chemistry and capacity of the cells current-ly available ...

georgehawley.fl.us | 26 décembre 2014

got a charge out of that:-))

Red Sage ca us | 26 décembre 2014

This thread is positively charged with pun-difference.

Brian H | 26 décembre 2014

An ohminous development; the ampossible dream.

vandacca | 27 décembre 2014

Not Anoder pun, please. Let this be the terminal post.

jjs | 27 décembre 2014

I don't get the connection?

georgehawley.fl.us | 27 décembre 2014

18,650 ways to kill a thread. I'd be "Li-ion" if I said I didn't enjoy this.

vandacca | 27 décembre 2014

This battery of puns is due to an overcharged imagination. I think you all need series help in parallel with stern punishment.

EVino | 28 décembre 2014

mr hawley, you are hereby elevated to a level above Teo. That was great.

Alright, sorry for interrupting this flow of positively fun puns. You may resume bonding.

Brian H | 29 décembre 2014

georgehawley.fl.us | 29 décembre 2014

@evamos: Teo is the supreme Tesla digital bibliophile, not to mention indefatigable purveyor of future battery possibilities. No one can claim to ascend to his heights. We lowly ones can only look up to his enthusiasm with awe. He is the Tesla electro-lite.

Gert van Veen | 13 juin 2015

If I understand well, there charging spreed can be increased:
“Instead of wrestling a good-size snake into the car, it’s a really supple cord,” said Musk. “It also has the potential of increasing the amount of power that can go through the cable in the future.” This suggests Tesla wants future Supercharger stations to charge up cars faster. Currently it takes about 20 minutes to charge a car to 80 percent capacity."
This wil be a great improvement, charging 20 minutes.

georgehawley.fl.us | 13 juin 2015

The Tesla SC already dumps 4 amps/cell into the battery pack which is double the Panasonic recommendation for their 18650 B cells. Maybe they figure they can up the charge rate (current) even further. The coolant circulating through the new skinny SC cable takes away the heat but doesn't reduce the energy loss in the cable. It actually increases if the skinny cable has more resistance than the fat cable and will increase further if they up the amperage.

Red Sage ca us | 13 juin 2015

Maybe they've figured out how to use fiber optic cables to digitally recharge batteries?

~*ducks*~

Iowa92x | 13 juin 2015

I was thinking the charger upgrades are to support faster charging rates for a larger X pack.

Unsure if the 85 pack can take much more charge current without modifying cell makeup or increasing cooling.

Gert van Veen | 14 juin 2015

Increasing charging speed is probably the best way to reduces range anxiety. Not so long ago cars didn’t use to have a much longer range then 250 miles but it toke only 10 minutes refill. Stretching yours legs every couple of hours isn’t to bad. And superchargers are much cheaper then gasoline stations.
It might be that increasing charging speed is an important strategy of Tesla.

georgehawley.fl.us | 14 juin 2015

@Iowa: the SC currently maxes out at 120 kW. If they were dump that much power into the battery pack continuously, one could suck up 60 kWh in 30 minutes. If they come out with a pack with more capacity, this charge rate would be the limit until they soup up the SCs (There has been talk about 135 kW.).

Today I think the 85 kWh pack can accept almost 40 kWh in 20 minutes before slowing down. If you have a 110 kWh pack for example, you might be able to continue charging at the max rate for a few minutes longer before slowing down but I don't think it would be much of a difference overall in time required to acquire K kWh where K > ~40.

raffael s. | 15 juin 2015

So after hearing all about the possibility of charging faster or not, I made some calculations. I assumed a cable of 1m length and a 4cm diameter made of copper. Now after knowing the electrical resistivity of copper and an assumed voltage of 400V, the amperage now flowing through the cable should be 300A. With a resistance of 1.34*10^-5 Ohm the power lost would be 1.2 watts, about 0.001%. If you decided to charge with 360kW, you would need 900A, and lose about 11 watts, about 0.003% of the power you put in. That isn't impossible financially and especially physically. Even if the charging cord had 2cm in diameter and 2m in length, your power loss would be less than a quarter, of a tenth, of a percent.

georgehawley.fl.us | 15 juin 2015

@raffael: correct as far as your numbers are concerned but a 1 meter long charging cable would probably not work. How about 3 meters? A copper wire 4 cm in diameter (1.6 inches)? Yikes! I don't think I could bend a wire that thick.:--))

For 300 amps of current standards call for 000 gauge wire that is 1 cm in diameter and .0006 ohms for 10 feet, dissipating 54 watts at that current, still not a lot to your point. But, when they use a coolant to reduce the wire gauge, the power loss increases proportionately. The coolant doesn't affect that. It just carries away the heat.

vandacca | 15 juin 2015

On a theoretical side, I believe that resistance is temperature dependent so if you can cool the wire, you will gain efficiency and more power will be used to charge the batteries and less will be used to heat the wire.

What we need is super-conducting cables. :)

raffael s. | 15 juin 2015

@george: It was just a example of what is possible conductively ;) If you had a 1cm diameter cable and 3m of length you still could transport 900 Ampere with more than 99.85% efficiency, but if you don't want the cable to heat up extremely fast (100k in 2minutes) you need cooling, but a 1kW cooling system should definitely work, keeping the efficiency still far above 99%. Those standards are meant for non cooled wires, not because of efficiency fun because copper tends to get hot very fast, it takes, for example more than 10 times more energy to heat water at the same rate. If you don't cool it, it will burn the isolation.

gordonbremer | 15 juin 2015

I have not read all the responses, so I hope that I am not repeating a response.
A (lengthy) wire need not be a limitation if there is no wire. A floor-mounted charging device under the parked car could automatically raise up, aligning itself with an automatic-opening mating connector on the car itself and then connect. The interconnections can then be as beefy as desired and handle current without heat risk. Moreover, there need not be just one current-supporting "pin", allowing faster, parallel charging. Of course, power still needs to get to the floor-mounted device, but that need not be a problem: my home gets 300 amps at 240 volts (72 KW) from 200 foot away.

georgehawley.fl.us | 15 juin 2015

@gordon: with inductive charging the car needs more stuff. It needs a coil of wire to pick up the AC charging energy. Depending on frequency, it might need a different rectifier. The rectifier would certainly have to be beefed up if inductive charging is to compete with the SC 120 kW DC connection straight into the batteries.

grant10k | 15 juin 2015

@george, he's not talking about inductive charging, he's talking about a connector under the car that physically rises up and presses against some connector on the underside of the car. Like a really advanced slot car or something.

vandacca | 15 juin 2015

Under car charging is not a good idea for 2 reasons:
1) Too close to the ground, connectors can get really dirty, rusty and/or damaged
2) Would make it a lot less convenient when trying to charge at a charging station. Most other third-party charging stations would require a manual solution.

Iowa92x | 15 juin 2015

I think the limiting charge speed on current packs is battery limit more than Supercharger limits. You can only charge as quickly as the cells can accept the juice, which will top out before the Supercharger limit.

georgehawley.fl.us | 15 juin 2015

Should have read the post more carefully. Sorry about that. There are some vehicles that use inductive charging. For example this bus system in England that charges at 120 kW. (http://www.newscientist.com/article/mg22129534.900-wireless-charging-for...). I wouldn't begin to know how to implement the direct connect approach. I can't even park straight.

raffael s. | 16 juin 2015

The automated charging, is a good idea. As we know most new Model Ses and all Xes will be able to park themselves. If you had one big plug, connecting to a certain port, at the front, or at the other side of the car, the connector just has to be movable a little bit. After it made the connection, a car could charge as fast as possible, minimizing the need for more superchargers at one station. A supercharging system with 10-100 times as many cars could work a lot cheaper with charging times below 10 minutes, than with more than a half hour. But I have to agree with Iowa92x, charging is limited by the battery and I don't think todays batteries could charge faster. The 60s charge as fast as the 85s to a certain percentage, not to the same energy. Faster charging will need faster chargeable cells. Maybe introducing the new cable, means they are preparing for faster chargeable cells?

georgehawley.fl.us | 16 juin 2015

Come to think of it one could put little dents in the parking spot for charging for the 4 wheels to settle into. That would reduce the tolerances for the plug that rises up from underneath. The charging port in the car would have to be covered to keep out grime and would have to rotate out of the way. That might make it vulnerable to bottom scrapes. The charger plug would have to rise up and find the receptacle. It would also have to be covered to keep out stuff that might gum up the works. It would also have to be protected from precipitation and flooding.

Hmmm. Doesn't sound as easy as getting out of the car and dragging a cable to the current charging port.

johnse | 17 juin 2015

Keep the charge port where it is... use computer vision and robotic arms to connect it. Wouldn't have to be particularly precise on parking.

raffael s. | 18 juin 2015

I found an old article in which JB is saying they are working on 5-10 minutes charging. He said this would take some time to work out, but the article was from summer 2013. I think the liquid cooled cables could be a second step, after making the jump from 90 to 120kw, for making charging faster.
Don't get me wrong, I think 5 minutes will still take at least 5-10 years, but 80% in 15-20 minutes could be possible within the next 2 years.

georgehawley.fl.us | 18 juin 2015

It's possible that the liquid cooled cables enable somewhat higher charge rates but batteries may not accept much more than 120 kW. I think the main benefit of the new cables is ease of handling.

carlgo2 | 29 juin 2015

Tesla has a huge interest in perfecting fast charging. The company can't build acres of Superchargers all over the place to handle the millions of Teslas they hope to sell. Even the biggest hotels aren't going to install a hundred chargers in their parking lots either and will throw the problem back at Tesla.

If there is competition for EV sales, Tesla would not want to be the slow one at the charger.

One would suspect Tesla, and others, are working feverishly on this.

It could be that there will always be those free Superchargers, but also faster and more convenient options that are not free.

Brian H | 29 juin 2015

Carlgo2;
remember that about 90% of all changing will be done at home. Take the space currently required for gas stations and multiply by 10 for time required at chargers, then divide by 10 for away-from-home usage, and only the current real estate, or equivalent, will be required for each slice of the market Tesla takes over.

johnse | 30 juin 2015

@Brian That may be true for the near term. However, as the cars become more affordable, more of the owners will not have the ability to charge at home.

The industry as a whole is going to need to scale the charging infrastructure and Tesla already has a good start at the fast end of charging. That's also why Tesla Energy will likely build charging stations that work with other cars as well. What started as necessary bridges to enable an EV to replace an ICE car will become a profitable business in its own right.

With the Bolt and Leaf likely being able to compete in the range category with the Model 3, pricing prepaid supercharger access into the 3 probably is going to inflate the cost of the 3 and make it less competitive on the price front. It would make sense for Tesla and all the other electron suppliers to serve as wide a market as possible which will allow them to expand the services for pay-as-you-go charging without riding solely on the backs of the pre-purchased usage as it is now.

Red Sage ca us | 30 juin 2015

It will be true for the long term. For all the complaints about their 'slowing' the Supercharger rollout, month after month it has been shown that overall Superchargers are being installed at a faster rate in 2015 than they were in 2014. The current ratio of Superchargers built to enabled cars sold, worldwide and in North America, is far better than ICE vehicles to gas stations alreasy. There is no reason to expect that to change anytime... SOON.

Tesla Motors, Tesla Energy, and SolarCity will not be selling electricity to people to charge their cars in public. The various national, state, county, and municipal regulations for selling electricity, or becoming a utility of any sort, are too stringent. Just as anyone can grow their own pot, anyone can generate their own electricity. Notice that you cannot grow tobacco anywhere, you can't refine your own petroleum at home -- that is why those things can be profitable. It would be... EViL, to turn Tesla into the sole source of energizing vehicles, becoming a monopolizing force such as Standard Oil, for the sake of making money.

There will be no subscription based, pay-at-the-pump, pay-as-you-go, swipe a card, punch in a code, limited access, for profit version of Supercharging. There is absolutely no disadvantage to including Supercharger access in every single Tesla Motors product produced from now on. The all-inclusive, aggregate, amortized cost of allowing 'FREE (of additional fees) for LIFE (for the life of the car)!', included in the price of the car, access to Superchargers is, in the grand scheme of things, negligible as compared to either advertising expenses or revenue 'lost' to an 'independent franchised dealership' network.

Brian H | 30 juin 2015

RS;
+10

johnse | 30 juin 2015

@Red
I never suggested that Tesla would be a monopoly. There already are plenty of folks charging for electricity that are not regulated as utilities. ChargePoint, Blink, AV, etc. Tesla is not charging on a per-use basis but they are certainly selling electricity at the Superchargers--some of it they have sourced from the grid, and some from solar generation. Tesla is simply ahead on the deployment of a high-end charging infrastructure.

What is regulated are the providers of electricity via the grid. Another example in current usage would be the providers of natural gas as a utility vs. the providers of CNG as a vehicle fuel. The latter source their natural gas from providers that may be a utility, but are not themselves classed as a utility.

Imagine in 10 years, from now Tesla Energy stations advertising 100% renewable-sourced energy to charge your electric vehicle. Competing with the other for-profit providers. There's nothing EViL about that. It's one of the ways of generating revenue and continuing to fund Tesla's twin goals of electrifying the transportation sector and moving the world away from fossil fuels. And by supporting the entire EV market, they accelerate both of those goals.

The reason that the current model of rolling \$2400 (or whatever they deem would be necessary for Model 3) into the base price of the Model 3 is that they will be competing with others that do not include that cost in their pricing structure. That's 5.7% of the price of a \$35000 vehicle. There are buyers for whom that's going to be a determining factor and many of those will never use anything close to that much SC electricity. It's not that Tesla would be losing money on the Superchargers, it's that they would sell fewer cars. For the vast majority, they would be paying a premium for "free" SC access that would end up being the most expensive electricity they ever bought.

Red Sage ca us | 30 juin 2015

Hrmph? Wait... What?!?

johnse wrote, "It's not that Tesla would be losing money on the Superchargers, it's that they would sell fewer cars."

Sorry, I dund get this one bit. 'splain, please.

Something like 16,000,000 vehicles are sold in the United States of America every year. If Tesla Motors manages to have a 200,000 unit Capacity for Model ≡ in 2018, and manages to Produce 140,000 that year, and 60% of those, or 84,000 units, are Delivered to US Customers it would amount to 0.525% of the market. Trust that if Nissan can sell as many as 30,000 of the LEAF, and Chevrolet can move up to 25,000 of the Volt, Tesla Motors will have no problem whatsoever selling every single Model ≡ they build.

Anyone who does not get it, and complains that they do not want to pay for Supercharger access, claims that they should be offered the opportunity to 'opt out' of Supercharger access so that they can pay less to purchase the car 'at a discount' or 'with a refund' is an unmitigated idiot and will not be sold a car. Period.

The line forms to the left. You are the weakest link. Goodbye.

Brian H | 30 juin 2015

What buyers are getting is not necessarily economic electricity, but the option to drive to a wide variety of locations. Even those who never "road trip" value the ability to do so.