Audi e-tron Battery TMS: How Does It Stack Up Against Tesla Model 3?


It looks to us like Porsche will have a tough time keeping Taycan’s battery cool with an approach like Audi e-tron.

Porsche has been advertising some pretty high power charging for their Taycan up to 350 kW and 800 Volts. They are claiming 0-80% charge in 15-20 minutes and in a recent articleAudi is now claiming 0-80% in 12 minutes! That’s a high C rate and lots of heat to get rid of.

Audi e-tron has gotten the ball rolling with 150 kW and a charging time of 0-80% in 30 minutes.

To be fair, Porsche has not released a lot of technical details on their Taycan battery system. However, based on our analysis, they will have a tough time cooling the battery with a system similar to the Audi e-tron.

Audi e-tron pack built for crashworthiness, not heat transfer

This pack is built like a tank. First Audi puts 12 cells into an aluminum module (36 total).

These modules sit inside an internal aluminum crash structure which sits in the housing tray which sits on top of the cooling tubes containing the glycol cooling fluid. The outside of the pack is surrounded by an external crash structure as well.

Audi e tron pack built like a tank!

On the other hand, Tesla uses the vehicle body structure as the primary crash resistance (ref).

In the Audi e-tron system, the heat generated in the cells during high power charging must travel thru multiple layers of resistance: There’s the module housing, the tray, and the cooling tubes. On the other hand, Tesla attaches the cooling tube directly to the cell with a highly conductive thermal adhesive. So the heat goes straight from the cell to the cooling tube. It’s fairly obvious why Tesla’s cooling system (described in articles 1 and 2) has superior cooling to this Audi system.

The results of ME systems detailed thermal analysis are presented below. The number is a measure of how much heat the TMS system will transmit. Think of it as the opposite of resistance. The higher the number the more heat the system can pass. If you need to transmit more heat then you must run a higher cell temperature.

Here’s how ME systems chief engineer Keith Ritter summed it up:

“I have concluded that the Model 3 TMS with glycol-cooled micro-channel snake tubes glued directly to the cells has better heat transfer capacity than any system that uses flat glycol bottom-plates with either passive conductive fins or natural-convective thermal loops. It is just physics and geometry. more effective heat transfer area + better effective U value. So I don’t see how Jaguar, Audi, Merc or Porsche can beat Tesla in the charge rate game if pure TMS heat transfer capacity is governing. The only way I can see that Audi (and maybe Porsche) can get away with high charge rates is because they “may” have significant electrode/tab-cooling (if our engineered-fluid scenario is correct) and therefore can let the cells get hotter than other designs. Safely charge despite a lower W/ deg. K”

Implications of these results

What does this mean? What does Porsche/Audi have up their sleeve to cool the battery when charging at 350 kW?

Here’s a list of possible ways we think Porsche/Audi will make the system work.

-First and foremost, it seems obvious that they are relying on some new battery design that has lower internal resistance and an ability to withstand higher temperatures and charging rates. Maybe NMC 811?

We modeled the Taycan 800v pack using the e-tron model as a starting point and ran it at 300 kW. When we did the model, cooling load went from 1.2 tons for e-tron to 4.7 tons due to the increased C rate. The cell temperatures increased 8 degrees C … despite having doubled the pack voltage to 800V.

-Another conclusion from our modeling is that doubling the pack voltage does not change heat rejection (amperes) within the cells. You might think that at first since the pack voltage is doubled the pack current is half which is true (for the same power). The catch is you are running half the number of cells in parallel and twice the number in series so you just doubled the current through the individual cell after reducing it in half at the pack level, resulting in the same heat rejection (current). The cells don’t see a difference whether they are configured 4P108S or 2P216S. Another way to look at it is at the pack level. When you double the pack voltage you cut the pack current in half but now you have one half the cells in parallel and twice the number in series so your pack resistance went up by a factor of 4. The net result is no change in cell/pack I2R heat loss when we double the pack voltage. The benefit comes in the wiring of the cells and the size of the charging cords (and possibly the inverter loss).

-Redesign the cooling system. This could be done in any number of ways: add a top cooling plate (explained here), attach the cooling tube directly to the cell (explained here). Or run the refrigerant directly in the cooling tubes (eliminate glycol) like BMW does in the i3 (see article here).

-We are short on details about what is happening inside the modules. We think that Audi may be injecting the modules with some sort of heat transfer gel or liquid that allows them to pull heat from the tabs of the cells. This is called tab cooling and is described in an excellent video by Imperial Mechanical Engineering here. Tab cooling results in a more even distribution of temperature within the cells and allows the cells to withstand higher temperatures. Tab cooling is assumed in figure 3. The benefit is derived because the cells can withstand a higher operating temperature.

Don’t confuse what we are theorizing inside the module with the gel that has been discussed in the media which is between the modules and the cooling tubes. We are talking about a heat transfer media that pulls heat from the cell tabs.

-Design the battery specifically for high charge rates. It’s done all the time but generally, it leads to lower energy density of the cell.

Here’s what Elon Musk said about this last approach:

“The thing about a 350 kW charger is it doesn’t actually make a ton a sense – unless you’ve got a monster battery pack or have like a crazy high C-rate, in which case your energy density is going to be poor.”

How do you readers assess the situation? What do you think the Taycan battery system will look like? Let us know in the comment section.

Thanks for reading our articles.

George and Keith

*This article was a collaboration between the author and our heat transfer engineer Keith Ritter, BSME and owner of ME Systems in Redding, Ca.

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69 Comments on "Audi e-tron Battery TMS: How Does It Stack Up Against Tesla Model 3?"

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Tesla have better cooling so they can use cheaper cell for same charging performace. Audi need to use more expensive cell reducing car economical margin. Tesla need to make margin to make money , Audi don’t need to have a selling margin because the expense of the EV R&D are covered by selling petrol car

Model 3 owned- Niro TBD-Former 500e and Spark EV

and that makes economical sense beyond zev credits

AUDI Has To Take all These Unnecessary Steps & Pay A Premium $$ For Cheap Sub Standard Batteries Because “They are Clueless” & Don’t Know What they’re Doing When it comes to EV’s & Their Rolling Brick Design . Tesla Has The Best Engineered/Designed EV On the Planet Right Now ! AUDI Has A Long Way To Catch Up..You Guys Just Don’t To Get It , You Just Cannot Grasp That ….! WHY ?

As consumer, really matter that or the important is what’s the better car for you?. If Audi is capable to make a better car than Tesla, even cheaper, is a good news for the electric change.

@Simone Rambaldi
“same charging performace.”
Tesla’s charging performance is far below the Porsche charging discussed in this article.

As you can see in test audis battery did not produce so much heat than Tesla did, that’s why you don’t need that kind of cooling. Audi didn’t lose so much power than Tesla when batteries got hotter. For me in my climate we have very hot summers and very cold winters. Audis batteries are more suitable than Teslas. But we will se what will happen in more praksis tests, Which system will work better.

This is just more proof that Tesla is WAY ahead when it comes to thermal management, battery layout and charging tech.

Same for any company using lithium ion. You should only charge close to the ceiling capacity of a battery, when you need all of it for a trip. They all experience closer to one “full cycle” of their “cycle life”, when they are closer to fully charged and discharged.

To put another way, you use up battery life much less quickly when going 2/3rds, to 1/3 charged, three times, versus going to 100% charged, to 0%, once.

Tesla only allows a maximum charge of ~90% and minimum of about 5%, before it shuts down. That’s part of why their batteries last so long.

Tesla Makes A Good Common Sense Build..These Guys are Cheaping Out On Design & Technology ….BECAUSE THEY JUST DON’T CARE ABOUT EV’s…..PERIOD!!!….They Think EV’s are a Fad That will Go Away…. They’re In for a Rude Awakening ! !

The specific situation described there sounds like some sort of software bug…

More generally though, while many other companies limit the usable capacity to less then 90% of nominal capacity up front, Tesla makes some 96% or so available, and leaves it to the users to charge fully when needed, while advising to keep it lower when not needed. That’s got nothing to do with technological advantage or disadvantage — it’s just a business decision to give users more capability along with more responsibility…

I say we stop assuming that Audi engineers are incompetent and wait to see the actual product.

“It’s fairly obvious why Tesla’s cooling system (described in articles 1 and 2) has superior cooling to this Audi system”.
No, it isn’t mate. Because you never really saw the Audi cooling system.

Not questioning Audi’s engineers competence at all. If anything, our calcs suggest that Audi and Porsche and their cell suppliers may be using some thermal and cell chemistry concepts so advanced that we don’t fully understand them and can’t effectively model them using conventional battery pack TMS modeling rules. It is driving us nuts!

To quote the late great Arthur C Clarke:

“Any sufficiently advanced technology is indistinguishable from magic.”

We understand from an engineering perspective how Tesla can support their high charge rates, but Audi’s and Porsche’s stated pack charging rates appear to George and me (and we have been studying pack TMS systems quite a while) as “magic”. We can’t wait to eventually learn the technologies that are behind this “magic”. Anyone out there have any ideas?

I’ll go with low internal resistance cells, compromising some energy density and cycle life. The hobby world has some pretty amazing stuff (20C++). I’d love to see the cycle life and capacity of these if charged only to 4v and discharged to 3v. (standard = 4.2-2.5 IIRC)

To some of us reading your posts, you’re treating the approach of Audi and Porsche in the same manner that ICE drivers treat Tesla.
So you don’t have all the details of how the Germans setup of their TMS, but you’re ready to downplay their approach/engineering.
The 1 thing I can say for the Germans is that they will thoroughly test their cars, systems and whatnots before launching. Why don’t we wait and see what they’ve done before making judgement? They’ll have to release information on how the TMS works eventually.

Sometimes it’s good to have an inquisitive mind, .. try to figure things out ‘before’ someone else gives you the answer ….. don’t you think?

/the whole article is one big question … not like they’re passing judgement.

ht_010, “Wait” is all they make people do, and we shouldn’t when the tech is here. The R8 etron, the Q7 PHEV, the etron above, is not. So, why don’t we stop waiting, and listen to the experience on this forum. Why don’t we look at the past, away from etron and wonder if .07 grams/mile from a “Lien NOx Trap” was also “magic”. Call me jaded, but if there is one auto company for whom the benefit of waiting has worn thin, it’s Audi (VW Group). Perhaps the Audi won’t reach much above 150KW charging, but its motors aren’t anywhere near the output (or heat rate) of Taycan, either. Faster C-rates, from 95KWh are lost on this vehicle. With Tesla’s lower 5-7X max “C-rate” and 100KWh, the Model X’s motors already beat what could otherwise have been fitted to the 95KWh Audi. Taycan? We’ll see, but you need to soak a motor (not fry it) in order to heat a battery. If the heavy Taycan (and, Jesh, Audi already called its battery “700kg”) isn’t going to come with a sprint sized battery, I don’t see how we can have too much faith in its track handling. I hope I’m… Read more »

As I have been pointing out before, ~3C is nothing unusual for power-oriented NMC cells — AFAIK it’s quite normal for batteries used in PHEVs, among other uses. And the huge weight of the e-Tron battery seems to confirm that they are indeed using more power-oriented rather than energy-oriented cells…

BTW, I doubt they are using NMC-811 already in the e-Tron. VW will actually stick with NMC-622 even for their first MEB (ID.) cars scheduled to start deliveries in Q1 2020; only moving to NMC-811 “after 2020”. (Taycan might be a different story, though…)

Also, I don’t see why NMC-811 would help with internal resistance; and AFAIK temperature stability is actually one of the *challenges* of increasing nickel / reducing cobalt contents…

Thanks for the great analysis. I completely missed the doubling of the per cell current when doubling the series cells to halve the pack current for constant power. Obvious now that you point it out.

It seems that Tesla’s use of 2170 cells, very much smaller than the large flat cells used in every other design, has an advantage in that the largest distance from the center of the cell to an aluminum case is 10.5mm. Checking thermal conductivity of plastic separator materials shows aluminum is at least 100x greater. So the very short path to a great thermal conductor helps get the heat out of the cell compared to longer thermal path designs.

“So the very short path to a great thermal conductor helps get the heat out of the cell compared to longer thermal path designs.”
… which, .. along with Tesla’s ability to isolate the smaller cells (if/when they fail) without significantly impacting overall pack performance/integrity looks to be Tesla’s competitive edge.

/even though Bob Lutz sez Tesla doesn’t have any “secret sauce”.
//for extra irony, … cue the Mercedes SNL “joke” showing all the small cells spilling out of the car
///– or not — maybe Audi has their own “sauce” figured out, … all we have to do is wait 6 or 8 years for the real world results

If the heat actually has to travel from the centre of the cylindrical cell to the outside, it has to pass a similar number of separator layers as in a flat pouch sell… From what I gathered, most of the heat is actually transferred through the connection of the negative current collector to the cell can.

(Pouch cells don’t have a can — so to cool the electrodes / current connectors directly, the cooling system would have to be connected to the cells’ electric contact tabs externally somehow…)

Thanks for sharing.
Looks like all the battery modules are in series, with each module setup as 2s3p for approx 90kWh capacity.
The module design looks optimized for lowest cell resistance.

I wonder how they plan to handle pouch swelling?
Losing one 21700 cell is no biggie and there’s space in the Tesla pack for that, the cell fuse isolates it too. For this Audi pack, losing one cell is potential Critical-to-Function failure.

There are 36 modules in series, then 2 series doesn’t bring the voltage up to a near 400v system. If they are 3 series, this is 108 cells in series or about 400 volts. Thus, 12 cells in a module gives a 3s4p configuration per module for a 400 volt overall battery pack.

Based on Porsche’s stated range figures, I’ve long suspected they are sacrificing energy density in pursuit of higher C rates.

I too think they have compromised somewhere. Be it battery density, price, longevity, or the truth. But I hope I’m wrong and we’ll soon understand something magical.

Just like with range, until we actually see these “promised” cars in customer hands, it’s all speculation – and somewhat FUD. There are a lot of promises out there related to electric cars from a lot of different players, all due “soon”. Promising is the easy part. Delivering is the hard part, as Tesla has found out. It’s that much more impressive that Tesla has been able to work through the issues without some one else showing them the way.

Promises aren’t FUD — they are actually pretty much the opposite of FUD.

The presumption here is that arbitrarily high charging rates can be achieved if only the battery can be kept within thermal limits. That is intuitively appealing but is not generally true. According to the goal is [both] to avoid lithium-plating on the anode AND to keep the temperature under control. They state that “charging and discharging Li-ion above 1C [full charge in an hour] reduces service life. Use a slower charge and discharge if possible. This rule applies to most batteries.”

This is just assuming stuff and also stating nonsense.
„If you need to transmit more heat then you must run a higher cell temperature.“
This is not factually correct. You need a higher delta. Instead of a higher cell temperature you can also use a lower coolant temperature. The author surely knows this.

Also the article completely omits the role of the interface surface.

Let’s do some calculation :
Power losses are calculated by using the formula : RxIxI
For Tesla Model 3 :
Max charging rate : 120kW with a voltage battery pack at 345V
Max current during charging : 345A
Internal resistance : ~15mOhm (based on Panasonic NCR20700B specs)
Power losses : 1785W

For Audi e-tron :
Max charging rate : 150kW with a voltage battery pack at 400V
Max current during charging : 375A
Internal resistance ~8mOhm (based on NCM 43Ah LGChem cell)
Power losses : 1125W

For Porsche Taycan
Max charging rate : 350kW with a voltage battery pack at 800V
Max current during charging : 437A
Internal resistance ~8mOhm (based on NCM 43Ah LGChem cell)
Power losses : 1527W

So due to higher voltage of battery pack the current needed to increase the charging rate is not so high. As the NCM cell has also a lower internal resistance compared to NCA cell, the thermal disipation requested is similar or lower even if we increase the charging rate.

I hear the words, but you are also doing a ‘sleight of hand here’ . 4 identical cells arranged in parallel (1/4 the voltage of the series configuration), or these same 4 cells in series (4X the voltage of the parallel configuration) *DOES NOTHING* as far as the individual cell is concerned. The cell HEAT produced is basically unchanged regardless of the system voltage, whether it is 3.7 or 3.7 thousand volts. The overall charge rate is the only thing that matters to the CELL, since at a given charge rate the current going THROUGH THAT CELL is still identical, no matter what system voltage is chosen. 4 cells at the same charging rate per cell, will have 4 times the heat. But then the battery system will gain mileage at 4 times the rate a battery 1/4th the size at the same charging rate would have.

The other point of your analysis of the model 3 having 1785 watts of loss – assuming that figure is correct (I’d really think it would be MUCH HIGHER) – is an INCREDIBLY SMALL amount of heat – only 1/2 a ton. This is trivial for ANY car refrigeration system (the old large caddys of old had 5 ton refrigeration systems – TEN TIMES this heat removal rate).

So please rework your numbers.

For Mr. Bower constantly disparaging any Non-Tesla 3 design, I’d get some particulars from VW Group before somewhat arbitrarily declaring they’re incompetent.

But, the guy doing the objection here doesn’t understand numbers.

Sorry, you can’t use the internal resistance of a single cell to correctly estimate the resistance of the entire pack. You need to consider the parallel connection of the cells which reduces the pack resistance, the series connection of the cells which increases the pack resistance, the connectors and wiring resistance between the modules which increases the pack resistance, as well as the wiring resistance outside of the battery pack to get the current to/from where it needs to go. When you have computed the overall resistance of the pack then you can do your overall power dissipation calculations.

Since these are series parallel strings at either 350 or 700 volts – the heat generated within any given identical length string is going to be identical. A 700 volt string may be twice as long, but it will have twice the number of cells, and be twice as large but have twice the resistance – so the heat coming overall from all the strings will be identical no matter what the individual length since if the strings are 1/2 as long there will be half the resistance and heat, but you’ll have double the number of strings overall thereby making the length of the individual strings relatively irrelevant since the total heat in ANY configuration is the same. It doesn’t seem like a big deal to make relatively low resistance connections to the final system battery bus to be relatively lossless, since the connections are few, and it is relatively cheap to make good connections compared to the internal resistance of the cells themselves. The ‘Lowest’ system voltage we are talking about here is 300 volts. If it was 3.7 then agreed, there would be some loss at the connections. But this is much higher – and the 700-800… Read more »

@morrisg Yes of course, it’s to explain the principle and the main advantages to increase the battery pack voltage and to reduce the internal resistance of the battery pack in order to increase the charging rate.
The principle is similar by using the whole battery pack resistance and the number of connections will also increase the internal resistance of the system.
The value for the whole battery pack internal resistance is more on the range of 0.1 – 0.2Ohm
See below the example of the internal resistance of the whole battery pack measured on Kia Soul with NCM battery (192cells) and Mercedes B class with NCA cell (3696 cells)

Kia Soul :

Mercedes B class

Your chart seems to indicate the resistance stays relatively constant, yet you don’t define BOT, ICD1 or ICD2. Since there is plenty of space to fully indicate what the chart is supposed to indicate, why use Silly undefined labels? Also, Charge Pulse Resistance of exactly what?

As I keep saying – Specificity while technical writing is a lost art. Putting out a random chart which does not CLEARLY indicate what it is trying to portray, is a waste of everyone’s time.

The charts are extract from AVT INL test report with the following informations :
Bot = measurement done at 400miles
ICD1 = measurement done at ~4000miles
ICD2 = measurement done at ~12000 miles

The chart illustratre the battery charge calculated pulse resistance, which indicate internal resistance at each 10% depth-of-discharge interval.

I don’t believe this. I ask for a CLEAR explanation and I get a partial one.. What is a Bot? What is an ICD1, What is an ICD2. I assume the Pulse is just to calculate the Equivalent Series Resistance, or maybe that is reading too much into it. More to the point, What is your point?

I am sorry if you are not able to understand.
The lab take the vehicle at three different mileage (BOT = 400 miles, ICD1 = 4000 miles, ICD2 = 12000 miles) and perform a measurement on the battery pack on different parameters to see the degradation of the battery. This chart show the evolution of the internal resistance of the battery pack.
We can see that the value increase a little bit after each measurement (ICD2>ICD1>BOT)

Perhaps english is not your first language. To repeat, what is ICD1, What is ICD2, and what is BOT. They are not in my dictionary. In the Mercedes ‘B’ Class, the batteries seem to get better with age.

Your wattage dissipation numbers make no sense at all. If you are only worried about cell connections, a battery twice as large, at the same charging duration, with dissipate twice the heat. But 1785 watts is unreasonably low loss for the ‘3’.

So… your complaint is that he didn’t mention why the lab labeled their 400 mile test “BOT”, their 4000 mile test “ICD1”, and their 12000 mile “ICD2”?

That’s probably because the lab didn’t define their naming schema in the report… as if it matters since they did define what the labels represent.

I’m a native English speaker and after seeing him clearly state what BOT/ICD1/ICD2 represent, I had no clue why you followed up with such a rude comment.

BTW, he probably felt they didn’t need to be defined because his intent of the charts wasn’t to show how resistance changed with the increasing lifetime of the battery, but rather what type of resistance a full battery pack would have.

You’re complaining, and quite rudely, about something that doesn’t even matter with respect to his original statement.

Now, if your complaint is that he’s misreading / misinterpreting the charts, or you’re taking issue with his numbers, then so be it. Get off your high horse. State your complaint. Point out the faults. Move on.

The only one who is rude here is YOU……

He is putting out factually incorrect information that reasonably intelligent children know differently.

Which I’ve just proven in my nearby example of connecting just 2 cells different ways.

The pack voltage is irrelevant (except for connectors) — the chemistry and other internal optimisations of the cells is what makes the difference here.

How did you arrive at the resistance values for the packs?

Please read my first message to see the advantage to increase the pack voltage.
The power losses are dependent of current not of the voltage. (P=RxI^2)
In order to increase the power rate without higher losses you can increase the voltage applied to the battery pack.

The resistance value for the pack of B Class and Kia Soul are provided by a external lab AVT INL

DEAD Wrong. The only way you can increase the power rate with no increase in losses is to have a totally different storage cell. P does equal I * I * R, but in this higher voltage case R quadruples. If you don’t understand this you don’t understand the first thing about DC power. MOST EE’s (elec eng) learn this at 10-12 years old. Example. Assume we are going to charge 2 cells, each with 1ohm Equivalent Series Resistance… The charging voltage is 4 volts. The charging current THRU the cell is to be 1 ampere. Now assume the system voltage is 4 volts. The cell current is 1 ampere. the Heating loss at each cell is 1 ampere * 1 ampere times 1 OHM or 1 watt. The second cell paralleled across the 4 volt system bus is likewise going to dissipate 1 watt. TOTAL SYSTEM LOSS FOR THE 2 cells at a 4 volt system voltage equals 2 watts. The Overall System Charging current is 2 amperes. As a check lets use your formula again for the the entire battery. 2 AMPS * 2 AMPS * 1/2 OHM = 2 WATTS HEATING, WITH A 4 VOLT SYSTEM VOLTAGE… Read more »

Good article for the discussion about how TMS enables fast charging. Given current technologies, charge speed is mostly dependent on how fast you can get rid of the excess heat it generates. Any reasonable charger is going to throttle the pack charging with temperature, and that goes a lot way towards explaining the terrible charge curves seen with the leaf.

The M3 achieved a new high in TMS design. We’ll expect the other makers to copy that design just as they copied the “skateboard” battery design.

Copy? This “skateboard design” has been showed off since the 80`s , but that was when they where planning to have a Hydrogen Fuel Cell vehicle

Cooling of cells is not as important as you think.
In fast charge scenarios you would accept a small temperature rise. Exposure time to these events is small. But you have other options like a lower temperature of the cooling fluid. Do you know what fluid temperature Audi and Tesla use? As well you can increase the flow through the pipes. The flow through Audis system might be a lot higher.
In drive scenarios cooling is easy, heat generation might be 8kW assuming 100kW continuous power and 92% efficiency. Thats equivalent to heating 100kg of metal with the power of your toaster. You can imagine this will need quite some time to get warm. The cooler is a lot more capable than that.

In my opinion you did not know enough to create a proper simulation and therefor wasted your time. I am pretty sure Audi has engineered the system well and has tested their system a lot.

Yup, these questions remain unanswered with every one of George’s articles. I’ve asked the same SPECIFICITY questions and I’m never given a response. These articles ZERO IN on one TINY characteristic and make broad assumptions, ignoring the rest of the cooling system parameters.

Then someone else who can’t count comes up with totally ridiculous cooling figures (only 1/2 ton cooling required for the Model 3 while fast charging supposedly) and then comes up with inscrutable charts without configuration or labeling explanations. AS if presenting a chart or two makes one the big expert.

Maybe grahene when added to the plates lower resistance thru the battery cell. There are some Chinese cells we use for drone racing that hold voltage under extreme load while staying cool by most standards, while charging at 15c. Reference Hobby King Graphenes.

May be latest generation LiTO

Way too low energy density, and way too expensive.

Liion batteries don’t like heat, even more when they’re charging.
Heat generated is dependent of the cell chemistry. I’ve noticed that high current capability batteries have normally less energy density.
I think in the end there are different ways of achieving the same result.
Per example it seems Tesla battery pack is not structural unlike other cars, like the Mercedes eqc. While Tesla is saving weight in the pack it adds weight in the car structure. In the end maybe there’s no better solution, just a different solution.

Charging speed is very important, maybe not now that there is no charging infrastructure, but I think if there were at least as much super chargers as there are gas pumps (or even 1/4) it would be better to charge at 350kW than having a bigger range – obviously with similar energy density.

It’s not as simple as that. Most people would probably prefer a 30 minutes stop very 2 1/2 hours over a 10 minutes stop every 1 1/2 hours, for example…

What I’m saying is improving obviously the combination of capacity and range.

Until it has been torn to pieces and studied – this is all educated assumptiones.. and assumptions are the mother of all f****** At least 3 things are missing. 1. What is the coolant preassure? 2. What is the cooling temperature? 3. How much heat does the system remove from the cooling liquid. Will be interesting to see it taken appart and studied in detail. Just to add information. I worked for a company that installed hydraulic systems, and some were powered by a powerful engine. The systems was usually installed In a normal climate, but this was in the Persian Gulf. We installed a heat exchanger and installed an extra air condition unit AND used that to cool the hydraulic oil. The radiator fan, for the hydraulic oil system was running at low speed all the time due to the cooling from the air con unit. That shows how much the temperature of the cooling fluid has to do with the system temperature. If we needed more cooling, we could also increase the pump pressure on the cooling fluid, and get even cooled oil. But then again. . We don’t know how well the Audi TMS system is. I… Read more »

That is actually the only way of really judging the cooling system. Bring the battery pack to maximum charging power (200kW under regen according to Audi) and measure coolant delta in/out and mass flow after steady state conditions have been reached. With the heat capacity of the coolant you can now calculate how much cooling work the pack construction is capable of.

Where is my Post??

The following is a quote from the Audi Newsroom concerning their new concept vehicle, the PB e-tron 18. “The liquid-cooled SOLID-STATE (caps mine) battery has an energy capacity of 95 kWh. A full charge provides for a range of over 500 kilometers (310.7 miles) in the WLTP cycle. The Audi PB e-tron is already designed for charging with a voltage of 800 volts. This means the battery can be fully recharged in about 15 minutes.” Isn’t one of the theoretical advantages of solid-state batteries supposed to be less heat? If their own press releases are to be believed, maybe they have the battery breakthrough everyone has been waiting for.

It’s a concept car. It uses prototype cells, which could break down after 50 charge cycles for all we know. Lithium metal batteries that survive 50 cycles have existed for decades… Making them durable (without sacrificing other parameters) is the challenge everyone is working on.

I’m sure solid state prototype cells are of good quality. I got a couple small test cells from the university many years ago, and they still work fine.
The main problem with solid state batteries is nobody have been able to make them in anything that resembles production quantity. The cells was more or less hand made.
We bought pouch cells and button cells, but I don’t know the price. I get a feeling the price did not matter to the university, since they only bought a few test cells.
I know er bought from at least South Korea, Japan, USA and Canada. That was from companies and universities. That was more then 10 years ago. . We got cells between 2005-2007.

Whenever I see an article about EV charging and faster and faster charging, I wonder if we are not stuck looking at EVs from an old school ICE mentality. Meaning the focus on charging fast is because we need to get to a public gas/charging station to fuel/charge up. Now realizing that with the EV 90% of the charging will happen at home, while the car is parked, whether in the garage, driveway, apartment/condo parking space, etc. Or if taking the EV on a long road trip where 30 minutes to stop, take a biobreak, eat or rest is just too long, then, by all means, search for a public charger. But for the vast majority of car owners in the US anyway, there is a place to park and if one is buying an EV, they ‘should’ secure a space with a charger BEFORE buying an EV. That’s just common sense. I ask this because for myself, If I am going on a long trip, I am flying, but over 99% of my driving is within a 200-mile radius, which should require no public charging. This includes short trips to neighboring cities. Which begs the question, how much long… Read more »

Many people seem to insist that they *must* be able to do that 500+ miles trip in their EV, even if it’s only once or twice a year…

But that’s only part of the issue. Even for such trips, increasing charging speed beyond a certain point doesn’t really gain much, beyond bragging rights… There is no consensus where that point actually is, though.

Many people can’t really afford the luxury of a backup ICE car.

I understand the Taycan will also be able to charge at 400V. How does that affect the assumptions being made about how the batteries are connected?

Battery cells are connected as 800 V battery pack. Taycan will use a DC-DC converter for 400 -> 800 V.

“The high-voltage booster we’re working on will also allow the Taycan to be charged at 400-volt stations. Our sports car will thus offer downward-compatible charging options.”

newsroom.porsche (dot) com/en/products/porsche-taycan-mission-e-stefan-weckbach-interview-electro-mobility-christophorus-387-15817.html

But the dealers are really happy about the super high charge rates on the Porche. Because their customers will be coming back with fried batteries every few years, which will mean expensive replacements or chucking the car away as dud and buying an ICE vehicle instead, which also keeps the dealers happy.

I know I’m a cynic, but I just do not beleive that German auto, which has built its entire reputation on ICE vehicles, is interested in electric vehicles at all. I’ll beleive it when I see it.

Just how necessary is charging at those speeds anyway? If you must drive long distances and must have a fast refill, maybe important. But the general public has no need what so ever for that kind of charging speed. And the ones who do – apartment dwellers or similar who cannot afford a garage – they’re down-market. So, the low-priced cars are actually the ones who may need it the most – the ones with the least money to pay for it. I think it’s great research to find a faster recharging method but it’s more of a lifestyle change than anything and can be solved in a variety of ways. Doubling a supercharger recharge only drops a charge from 1 hour to half hour. This means you’re still waiting around for HALF AN HOUR. Gas cars have had the 5-minute pit-stop style which consumers have come to enjoy for their trips. And as such, this is a lifestyle change for true touring families. The only way to make it work is partner with sit-down restaurants which can gain profits on feeding families and offering services while the wait occurs and to ensure people get off the charger when done… Read more »

Also, don’t forget that speed is the thing. Going faster uses more charge – faster. A faster recharge will make people drive faster and use the energy faster… This is anti-sustainability requiring more power generation to appease the desire for speed.

On to the Audi design. Not good for heat-escape. Cooling is on the bottom, layers between. They built this for crash-safety (lawyers secured) rather than taking on more risk (Tesla). Design for outstanding tech results first, then safety second. Crashes may not be as dramatic with the Audi but they also risk battery system early-life and warranty issues if people DCFC a lot in the summers.

“How do you readers assess the situation? What do you think the Taycan battery system will look like?”

About like this 😉

upload DOT wikimedia DOT org/wikipedia/commons/7/71/Plutonium_pellet.jpg

Seriously, how is it hard for people to figure out the obvious answer? Audi and Porsche are frying their cells, and just eating the warranty costs, hoping that most people won’t fast charge very often. I know we’re not supposed to say that, we’re all supposed to just pretend that it’s some sort of secret magic, but the facts are right out in the open. Just say it: they’re shortening their cell lifespan because they can get away with it, if it gives them a marketing advantage.