# Forums

## How to Charge a Model S faster than you can fill a tank of gas?

What if the whole battery pack were treated as smaller individual battery packs?

This may be far-fetched, but here goes...

The invitation and Elon's twitter comment says: "There's a way for a Model S to be recharged faster than you could fill a tank of gas"

Clearly it has nothing to do with any car, Gen X or Tesla X. It specifically is referring to the amount of time it takes to charge, that is, relative to the amount of time it takes to fill an ICE tank with gasoline. So I came up with this concept/theory.

What if an 85kwh was treated as multiple individual batteries instead of just 1 large one?

For example, If I were to go to a supercharger location that had 10 superchargers, and split my battery up into 10 parts and gave each individual supercharger that task of supercharging each 8.5kwh battery component (85kwh/10=8.5kwh), then my battery would be charged 10 times faster, because 10 different superchargers are handling the job.

Elon also said that there was something "right under our nose". What if in the electronics of the Model S, there already exists technology that treats the entire 85kwh or 60kwh battery as individual smaller components and delivers a simultaneous individual charge to each to expedite the charge?

If a single supercharger, could act like 10 superchargers and deliver enough power to each battery subset, then would it not be possible to supercharge the entire 85kwh battery pack in 2 minutes instead of 20 minutes?

Disclaimer: I may get ridiculed here, but I'm just trying to think out of the box. This idea came to me when I considered that anything can be done faster, if the task is divvied up into smaller components and assigned to multiple teams.

Are there any electrical engineers out there than can comment on whether this is possible or I am out of my mind.

Thanks,
Max Mindel

ChristianG | 14 giugno 2013

Well I'm not an electrical engineer by far. But as I understand batteries have a maximum of juice they cant manage so you can't just say at 10amps it charges one hour so with 600 its 1 min. As I understand Tesla splits the input of electricity to all individual cells and through that you more or less charge all of them at the same time and therefore the input to a single battery stays in acceptible levels. I also think that this is why it gets slower in the end as more and more batteries get full and so not the full current can be used anymore.

But then I can be totally wrong on this one too. It still might be possible that the Pack allows a lot more energy as it gets now. But I don't think with the battery tech we have now in the model S a 1-3 min charge will be possible.

daoops | 14 giugno 2013

Yeah the topic has been up before. How long would it take to charge one of the 7000 batteries, and then in theory that would be the time needed to charge them all. Say you put four charge ports on the car (one in every corner) and connects superchargers from all sides.
The only downsides to this is that is is not tesla-ish, and there are missing three charge ports on the car.. :)
But good thinking out of the box!
(Since battery swapping/cartridge thing is so un teslaish I do not believe in that either personally.)

TI Sailor | 14 giugno 2013

I had this "conversation" a few weeks ago and Brian H stated the same thing OlaCarlander said, the time is limited at the cell, not pack, level.

However, as I've given it more thought, I've wondered if there might be a way to "hyper charge" individual groups of cells (I forget what Tesla calls them) by cycling between groups. For example, input one group at 2-3C for a small amount of time then move to another group, allowing the first group to cool down and balance. Do this until the pack is at the desired charge state.

I too am not an engineer and don't have a clue if that's reasonable.

TeslaRumors.com... | 14 giugno 2013

If Elon's statement was, "How to get a Tesla Model S 85 another 265 miles of range faster than it takes to fill an ICE tank", then I'd consider that this is about battery swapping. But he specifically is stating that this is faster recharging.

Consider his statement: "HOW TO CHARGE A MODEL S FASTER THAN YOU CAN FILL A TANK OF GAS?"

That's why I have a feeling that it is specifically about faster recharging.

TeslaRumors.com... | 14 giugno 2013

Hmmmm, re-reading this and rethinking this.... How to charge a Model S, not how to recharge.... could be about battery swapping.

Jolinar | 14 giugno 2013

if fast charging one cell takes 45 minutes, than whole battery takes 45 minutes or more, there is no way around it (except battery swaping).

wcalvin | 14 giugno 2013

Re "if fast charging one cell takes 45 minutes," it surely depends on the heat sink. And if there is a coolant circulation to take the heat away quickly, a la Tesla, then what are the recharge times?

edcalis | 14 giugno 2013

Charging while in motion, could be the answer. A combination of energy sources like solar and wind for example. By the time you get to the supercharger, you just need few minutes to charge the rest.

AtlantaCourier | 14 giugno 2013

Charging while in motion? Nobody has mentioned an energy-storage flywheel and small generator in the frunk. It'd work like this:

1.) You'd pull into the station
2.) Simultaneous with supercharging the battery, counter-rotating carbon-fiber flywheels in the frunk are spun up to about 60,000 RPM.
3.) When the supercharging of the batteries is complete, you drive away.
4.) The flywheels continue charging the battery via the small generator until they run out of energy.

Flywheels can be spun-up very quickly and pound per pound, they have an energy-storage density greater than today's batteries.

This idea is totally workable but also totally un-tesla-ish.

I rather think its as simple as he says. They're gonna demonstrate supercharging the battery to a range of 150+ miles in less than 10 minutes.

Mark K | 14 giugno 2013

Well, I'm an EE, and I think it's a range pack in the frunk.

The limiting factor on charge rate is indeed the fastest rate for an individual cell.

It will go up from 1.5 C now to 3 or 4 C in the future, when battery buffers are in the SC's.

But even at 4C you can't get to less than 2 minutes - which is what you need to compete with gas.

The fastest way to do it with the current car design is to add a fresh range pack to the frunk and go.

The frunk pack gradually recharges the main pack while you drive.

rtb | 14 giugno 2013

Maybe Tesla is buying a fleet of semis and you will drive onto one to charge--like Knight Rider. j/k :)

EcLectric | 14 giugno 2013

Mark K,

I like your frunk pack idea.

That being said, I would like to offer another theory just for fun. I will pose a thought experiment with numbers that are the correct order of magnitude but which are otherwise just chosen for convenience.

Cells in parallel = current adds
Cells in series = voltage adds

Say pack has 7000 cells which deliver 3 volts.
Say pack has voltage of 500v

This means the pack is made up of sub-batteries of 500v/3v = 166 cells each in series. So we have roughly 7000/166 = 42 of these sub-batteries wired in parallel to one another.

If this is the configuration while charging, then the current supplied by the supercharger goes to all 42 sub-batteries. What if you supplied supercharger current to each set of 10 (with 2 extra) sub-batteries through 4 different superchargers?

Another idea is this: what if you used relays to change the configuration to make the sub-batteries more parallel (instead of series) while supercharging? What would this do to the charging parameters?

Just thinking out loud...

jbunn | 14 giugno 2013

A flywheel of the size mentioned would act like a large gyroscope. It would dramitacly alter the cars handling. Look uo gyroscopic precession.

negarholger | 14 giugno 2013

It doesn't matter how you arrange the batteries you still have to supply the energy.
3 min would be 20 * 85 kW = 1.7 MW. SC with battery backup would be able to supply, but how to get it into the batter?.... cables would need to carry 4250 A.

AmpedRealtor | 14 giugno 2013

DUH people, Tesla is finally going to announce its hotly anticipated Flux Capacitor...

David Trushin | 14 giugno 2013

Actually, I think I saw this posted a while ago. A high voltage capacitor with associated electronics might be a viable solution. Charge the capacitor at the charging station in a couple of minutes. Then manage the discharge into the battery while you drive on your way. I wonder if the battery pack can charge and discharge at the same time. I haven't done any calaculation, but I think the physics would work. You should be able to control the inital charge on the capacitor based on the remaining charge in the battery and the discharge rate by varying the resistance in the discharge circuitry.

Of course, it might turn out that the capacitor charge would be too high to be safe.

Chuck Lusin | 14 giugno 2013

A capacitor to store the equivalent amount of power compared to a Lithium-ion battery is close to 50 times the size.

Brian H | 14 giugno 2013

Capacitor capacity is crap. Big batteries are better.

Sudre_ | 14 giugno 2013

Remember that Elon is always talking 150 miles of charge not a full charge. This can be done with a docking system that comes up from under the car and automatically plugs in. It would require a redesigned battery pack with a port that opens from underneath. It would plug directly into the battery pack bypassing everything in the car.

If using a docking station like this it could be 4" aluminum ISOphase buss duct which can handle thousands of amps easy. The 600 volt rated stuff I know of goes up to 6000 amps, altho I am not sure what the diameter of the 6000 amps duct is.

Here's an idea of how to move that many amps:
http://www.crown-electric.com/_assets/pdf/IPB_Brochure_02.pdf

lobo426 | 14 giugno 2013

Elon mentioned in the last quarterly presentation, that the design of lithium batteries allows for a lot of initial energy but then it needed to be reduced. The new supercharger @ 120kw seems to be the initial phase of the project as they better understand how to taper the current down at the correct moment for maximum absorption by the battery, the demonstration should be a refinement of that process. Charging at full potential longer, and tapering just in time. Let's just wait and see how much it can handle.

AtlantaCourier | 14 giugno 2013

@Lobo

Yes, he characterized the process as a "high-speed tango" between the battery and the supercharger. I'm convinced this is what we'll see on Thursday.

negarholger | 14 giugno 2013

@Sudre_ aah, now we know what the tail pipe is for...

Thanks for the pdf.

michael1800 | 14 giugno 2013

Mystery solved. The technology seller is completely out of stock, obviously because Tesla bought them all.

http://www.oreillyauto.com/site/c/detail/EB00/121GMF.oap

negarholger | 14 giugno 2013

Good find - that fits the bill. Web site claims my neighbourhood store has one... will check it out tomorrow. Hope Tesla missed this one and not that the web site wasn't updated.

jbunn | 14 giugno 2013

Good. I want one for the frunk that I can show to people when they ask where the engine is.

daoops | 15 giugno 2013

Someone on the forum said before that the clue is in 'faster', and not by time but by speed. If you are charging doing 60 it is faster than standing still, per def. Even if it takes longer in time,

http://elways.se/?lang=en

I'm not convinced but sounds more reasonable then battery swapping imo (images called battswap included in calculation :).

New cool tech for fast charge is still my bet I would guess, including that you always leave your hose fully charged and save time by not having to pay. Rails on/by the roads sound a bit complex.

biggator | 17 giugno 2013

Could it be something like what Lenovo is doing with their laptops? Those charge about 80% in 30min (instead of the typical 2-3hrs to get to that same point).

Look at RapidCharge

http://www.lenovo.com/mp/x1/features.html

kback | 17 giugno 2013

It just doesn't make sense that one announcement would be faster supercharging - 20 minutes to charge battery half full, and then the next "big" announcement is even faster supercharging. Would Elon really do that? It's got to be something different than just faster supercharging. A swap-able battery in the frunk would qualify, but again this all speculation. Not too much longer, everyone.

justineet | 17 giugno 2013

I am gonna spill the Top SECRET...your Teslas are already equipped with Supercapacitor Pack!! However due to current state of supercapcitor developent, the cost of each capacitor pack is extremely expensive. Therefore Tesla has limited the Max. charging capacity of the installed supercapacitor to 40miles. So as Elon said, the answer to Super-Duper-Charging faster than you could fill a gas tank is under your nose. All you need to do is turn on a switch on your 17" screen to operationalize your supercapcitor pack!!! Once you do that, you can charge 40 miles, not in minutes, but in seconds from anywhere...from your own home or public charging stations faster you can fill your gas tank!!

Bank on it.....this top secret info is sourced from an army of Tesla supercapacitor engineers :))

wcalvin | 17 giugno 2013

Look at the charging curve for the 18650 batteries. It's at bottom left in http://www.panasonic.com/industrial/includes/pdf/ACA4000CE254-NCR18650A.pdf

It shows constant current/constant voltage until 3hr, then falling current with voltage rising until 4hr. That is just an example of how he battery responds to that particular charging regime, not a statement of how things proceed at higher charging current/voltage.

For the 90 to 120 kwh supercharger upgrade, Elon indicated that they had fiddled around with the last part of the curve, i.e., keeping the current higher for the final bit.

Suppose the June 20 demo is a super-high current until late in the cycle, using a lot of heat dissipation via the battery coolant. If they used on-site 500VDC batteries to achieve higher currents than available from the mains, and the wires from the charger port to the battery pack are already thick enough, they might achieve faster charging.

But I have no idea just how much faster. I bet they do.

Bubba2000 | 17 giugno 2013

Elon Musk is about elegant solutions. I will be surprised if the uses something like battery swapping with is too mechanical, too many moving parts, expensive stations. The frunk volume is only 5.3 cuft. Per may calculations, they would accommodate 200 lbs of batteries, including the packaging, cooling. Good for may be 16-20 KW-hr... extra 50 miles may be? If Tesla wanted to extend the range, they can offer hi paying customers the Panasonic 4.0Ah 18650 cells that have 30% more power than the 3.1Ah cells being used now, or nearly 400 mile nominal range. Populate the rest of the battery pack, and Model S may do 500 nominal miles. With that kind of range I will hardly need to use a supercharger. If I do the first 150 miles of range will charge in 10-15 minutes due to the larger battery size. Can charge \$125K loaded, and people will buy more than they are buying the 60KW-hr unit. Range sells.

Anyway, with superchargers at 100-150 mile interval, 20 min charging is no big deal after traveling 200+miles. Al air battery would be an option, but too messy to change. I am getting an 85P with regular tires, because I do not want minimal maintenance.

I am thinking Tesla must have a beta charging algorithm. Elon may do a demo. Final version may take time and may mean an upgrade of the 120A charger software. They may be building that capability in the superchargers already... or need minor hardware upgrade.