Tesla Model 3 Battery Cooling Much-Improved … Track Mode?

Tesla Model 3 Performance


Tesla Model 3 battery cooling is significantly better than that of the Model S and X for multiple reasons.

In most of our past articles, I have teamed with Keith Ritter (HVACman) who is an ME and a licensed HVAC engineer in Redding, CA. We now have a new and third member of our team, Scott Fauque (Scottf200). He owns a 2017 Model X 100D and has data acquisition capabilities in his car via the “Scan my Tesla” app and “Teslafi.” Keith is working on a computer model of the Model 3 TMS. We are using data from Scott’s Model X to calibrate the baseline Model X model. That model is not complete yet, partly due to Keith being evacuated from his home during the Carr Fire near Redding, CA. However, we are happy to report he is OK, his home did not get burned, and evacuation orders are lifted.

 This article is just a preview of more detailed info to come when the analysis and modeling are complete.

The new Model 3 battery module is a completely new design. It bears very little resemblance to the Model S. Not only is it cheaper to manufacture, but it also has improved cooling over Model S and X modules. Scott’s Model X 100D has the second-gen Model S/X module design (figure 2) which incorporates two ribbon-shaped cooling tubes, as compared to one in the gen 1 module.

Here are some (but not all) of the reasons the Model 3 has improved battery cooling:

  • better heat transfer between the cells and the cooling ribbon because the cells are now glued directly to the cooling ribbon and the cooling ribbon spans a greater percentage of the cells’ height.
  • fewer cells per pass of the cooling tube

First, we will walk through the gen 1 and gen 2 Model X/S module design. Then, we will show you the new Model 3 module design.

The gen 1 Model S/X battery module only had one cooling tube per module. This single cooling tube had to cool 444 cells. Cells at the end of the cooling tube end up being significantly hotter than cells at the beginning of the cooling tube pass.

The gen 2 Model S/X battery module (see article) had two cooling tubes per module instead of just one in gen 1 design. This new module is in the 100 kWh versions of the Model S and X. Each pass of the cooling tube only has to cool 258 cells instead of 444 = much better.

The Model 3 battery module is machine assembled. Each length of tube with cells attached is nicknamed a “bandolero” because it looks like a machine gun bandolero (see article here). The cooling tube in each bandolero now only has to cool 164 cells. The cooling tube is bigger than Model S/X cooling tubes (cells are larger) and can pass more glycol cooling flow. The tube also covers a higher percentage of the cells’ height.

Seven bandoleros make one module.

The seven bandoleros are then connected in parallel, resulting in better cooling than the old series design and, as mentioned, each pass only cools 164 cells.

In a previous article we speculated that Model 3’s now being shipped are gen 3 Supercharging capable. Gen 3 Superchargers are more powerful, and better cooling is necessary to keep cell temperatures down. The new Model 3 cooling system should help in that department.

The Model 3 Performance has “track mode,” and the new cooling system is beneficial there as well. Check out the recent article about the Model 3 track mode tested by Road and Track magazine here.

Categories: Battery Tech, Tesla

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42 Comments on "Tesla Model 3 Battery Cooling Much-Improved … Track Mode?"

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Nice work George (and team), that looks like a much improved design.

Here we go.. “Yeah, but can the Performance Model 3 run Nurburgring at max speed for 10 straight laps without the battery raising in temperature 1 single degree??? Until then, I’m sticking to my (fill in the blank with any ICE/non-Tesla).”

“O’Doyle Rules!!”

Let’s see what it can do for a single ‘ring run. The Model S has definitely been a disappointment around the Green Hell

I hear you John, but being able to do a hot lap at the ‘Ring without heat fade software kicking in would be cool and really give Tesla some boasting rights. And they aren’t that far from achieving it. I would bet the Performance version will be able to do it within a year or two.

Actually, if they do a fast run even with the software protecting the system from ever overheating by slightly pulling power, and it can keep lapping until the battery needs charged, who cares?

If they leave 2 or 3 seconds on the table, so to speak, the slower time doesn’t sound as impressive as it would have if they had gotten through the entire lap without the heat fade software slowing the car down. A couple seconds is enough to drop you 10 or 20 spots on the list of fastest times. The BMW M3 is a good target for the Tesla Model 3 and the E46 BMW did it in 8:22. That would be a cool time for the Model 3 to beat.
If you are going to compete, do it to the best of your ability, don’t leave a couple seconds on the table because the car is just a tad short on the thermal protection.

That’s my point. What if it comes in under your target of the E46 BMW time of 8:22, even with the thermal protection system doing it’s job and successfully protecting the system from ever having a thermal failure?

Who cares if they have a thermal protection system doing it’s job so it never overheats, and it STILL puts in killer times?

because its still the slower car. When it comes to racing, nobody cares why the car gets a lap time, they only car that it gets the lap time.

Perhaps I didn’t make my post clear. If the target is to beat an E46 BMW M3 that laps in 8:22, and the Model 3 Performance DOES beat the E46 BMW M3 by putting in a time of 7:52, who cares if the thermal protection system kicked in and is doing its job?

What if they take it for a run and it beats all other production 4-door midsize sedans, even with the thermal protection system trimming power when needed?

Are you just going to move the goal posts and claim that even if it is the fastest production 4-door midsize sedan around the ring, that it doesn’t count, and it has to be even faster for it to count?

your description is much clearer now. If the model 3’s thermal protection kicks in, but its still the faster car, then thats all that matters.

Also, dont put words in my mouth about moving goal posts or whatever. I dont care for e-racing and fanboy pissing contests. I’ve seen enough of that from various car message boards throughout the years.

In competition sports like racing, the only thing that matters is results, and thats all my post says.

Nix, if they can get close to 8 minutes I will be doing an end zone dance. And I think they will, if not this year, then within a year or two.

(⌐■_■) Trollnonymous


(⌐■_■) Trollnonymous

“without heat fade software kicking in ”

That’s like saying it “would be nice if the thermostat on an ICE car wouldn’t kick on, that would be better”.

What’s the purpose / makes no damn sense / just plain dumb…… /WTF?

My point is regardless if it can do a whole flat-out lap at the ‘Ring, the haters will always move the performance bar. If it did one lap, they’d say it need to do two. If it did two, well, you know what I mean..

The final argument after EVs dominate almost all motor sports will be “yeah but EVs suck at the 24 hour LeMans and against top fuel dragsters. They will never replace ICEs until they can do that.”

A 24 hour race could probably work with battery swapping.

As for dragsters, I suspect that pushing battery (or perhaps supercapacitor) and motor technology available today to their limits, EVs could already be quite competitive. Unfortunately, this segment seems to have pretty much died when A123 went bust and stopped sponsoring these efforts…

Ok go ahead and fill in the blank then.
Which ICE runs 10 hot laps without power fade? I ran track on a SS (V8) and had fade. Even the cabin AC either faded too or couldn’t keep up with the heat.

Missed my point. I agree with you. My point is there’s always a mythical, un-achievable bar for the haters.

It’s simple math, an ice engine is only 35-40% efficient, so the rest is turned into heat, an electric engine is 85% efficient so less heat is produced, they will find a way to cool it, easier than an ICE engine.
So what you are saying is you still use the old dial phone, because a modern smart phone, gets hot?
I think people made the same argument when cars were invented, I’m sure this car gets way hotter than my horse, needs gas,oil,tires, etc. My horse stays cool and never needs gas + maintenance, grass is free, and look if I whistle he comes to me, can your car do that.

Let’s see your chosen LICE car do 10 laps of the Ring without cooling😄

Does the slightly reduced number of cells per tube really make much of a difference? Also, I’m not sure the improved cell-tube contact really matters all that much, compared to cell’s internal heat propagation…

Apart from simplicity, my guess would be that the major advantage of the new design is significantly lower flow resistance, which should allow circulating much more coolant in the same time.

The key factor is getting the coolant to the batteries at the end of the coolant line before the coolant becomes heat soaked. The more batteries it goes by, the warmer the coolant gets, and the worse job it does at cooling the last cells. That COULD cause unequal cooling IF the coolant temp were significantly higher by the time it reached the last cell. The issue is the “ΔT”, and having shorter parallel coolant line runs past fewer cells CAN reduce this problem, if it is a problem.

” ΔT: difference in temperature between the solid surface and surrounding fluid area, K.”

So the natural question of course is, why not have every cell have their own parallel coolant line. The answer is that until ΔT becomes mathematically significant, there is no scientific reason to go that far. It is literally impossible to armchair quarterback this one and say this or that is a better design without knowing what the coolant temp is when it passes by the last cells, and the temp of the battery cell itself.

flow rate and coolant line volume also matter.

Hi George: The numbers don’t add up correctly for me. We know the modules in the Model 3 battery pack are 23 series on the outer sub-packs and 25 series on the inner sub-packs, with a total number of cells of 4416 arranged as 96s46p. So the smallest a bandolero can be is 1s46p, but the 164 number isn’t an integer multiple of 46. Also, if a module is more than 46p then how are the 23s outer sub-packs assembled? 23 is a prime number, so there are no integer number of bandoleros larger than 46p that can be used to make up an outer module.

Given this, doesn’t it make more sense that each sub-pack is assembled from a 1s46p bandolero? This is the only way I can get both 25s and 23s sub-packs without making two lengths of bandoleros. But I could be wrong.

Thanks for these articles on the engineering of the battery packs.

There are two sizes of modules.

The cooling arrangement is independent of the electrical arrangement. Not all cells of a bandolero belong to the same “brick” (group of cells in parallel); rather, each bandolero passes through all 23 or 25 bricks of the module, with only six or seven of its cells being part of each brick. Seven bandoleros each contributing six to seven cells to each brick make up the 46 cells of each brick.

Hey George, thank you and your team for the fascinating, detailed and informative pieces. This one is not way over my head like some others have been, even though I love to learn and grow in knowledge as I read those too…Even back in our GM-Volt days. Of note: To my knowledge, Tesla is forming new nomenclature in using the nickname “bandelero” in describing the rows of tube+batteries in the Model 3’s pack. More accurate would be the nickname “bandolier” or “bandoleer”, which describes a leather belt containing a row of bullets either worn across the chest or waist of a bandolero, otherwise known as a Spanish marauder or outlaw. Ammo belts used in machine guns are called ammo or ammunition belts that feed into an automatic weapon or are belts folded and stored in a cartridge, sometimes also noted as a, “bandolier”, I suppose “Ammo Belt” would be too politically incorrect even for Tesla to use – with a CEO who sells legal flame throwers and equates his factory’s cell manufacturing speed to the output of a machine gun. Sorry if this commentary seems nitpicky to your excellent, educational article. Hopefully, It’s informative and interesting to see how we… Read more »

By cylinder, I meant cylindrical shaped tube.

A good example of a bandelero would be the main character played by Antonio Banderas in Robert Rodriguez’ Desperado cult film series.

Ideally, these lines should reverse every so often. Basically, the front-end is getting cooled decently, while the back-end does not.
In addition, they should consider putting reduction values in front of each of these strips. Basically, unless launching, they do not pull from all cells. They actually are running a circular que on the modules. So, send more coolants through the bandoleros that are heaviest used.

Yeah, I also wondered about reversing the flow occasionally. The temperature difference is probably not big enough to matter, though…

I don’t know where you got the idea that cells are not loaded equally. That makes no sense.

Or do an H bridge where you can switch from coolant flowing from the top left to right or top right to left.

Or why not have flat plastic plates covering the top and bottom of the array of batteries and have the glycol flow in between the gaps of the adjoining batteries. This way, all batteries get equal cooling. Perhaps you machine channels into the plates so the glycol goes from one input in the center to the center of 4 quadrants, then each center of the quadrants splits the flow to 4 smaller quadrants, and so forth until you have 360 individual channels. You might have to 3d print the plates to get the correct coolant flow splitting. Just thinking out loud.

Glycol coolant doesn’t work for submerged cells, since it’s actually half water. However, there are special cooling fluids for this usage. Kreisel Electric for example is using this approach.

While such cooling should be very effective, and save a tiny bit of space, the fairly large amount of coolant probably adds to total weight, though.

Another great article: George, et al

This is my favorite series being posted in IEVs.

I decided to go with RWD config over AWD for the extra range. Hope to have the car this month, just waiting for shipment from CA.

Let me know if there is any data I can gather for you.

– Battery thermal management improved
– Weight of the car improved
– Production capability improved

They just have to step up the interior finishing and then they would improve every weak-spot that the clients were pointing out.

With solid electrolyte they might not need as much cooling.

I keep hearing this claim; but I think it’s only half true at best. While a solid electrolyte should avoid parasitic reactions, thus allowing the cells to operate at higher temperatures without degradation, you still need to avoid unlimited heat build-up during prolonged load. So you probably don’t need to employ the A/C compressor to sub-cool the battery in hot weather; and the glycol flow can probably be reduced — but I doubt it entirely removes the need for a glycol loop for a large battery in a vehicle offering high performance / good fast charging…