Immersion cooling technology: A promising solution for high-voltage EV batteries

immersion cooling technology

Battery thermal management plays a crucial role in the performance, safety, and longevity of electric vehicle (EV) batteries. As the demand for electric vehicles continues to increase, the industry is focused on finding innovative solutions to address the rising thermal challenges associated with batteries. One emerging technology that shows promise in this field is immersion cooling.

Immersion cooling involves submerging the battery cells in a thermally conductive liquid or coolant, allowing for efficient heat dissipation and temperature regulation. This technology offers several advantages over traditional cooling methods, such as increased heat transfer coefficients, faster charging times, improved battery lifetime, and enhanced safety measures. By optimizing thermal management, immersion cooling aims to unlock the full potential of electric vehicles and accelerate the decarbonization of the transportation industry.

To uncover the current state and recent developments of this EV niche, here’s an insight-packed dialogue between Arnaud Desrentes, the CEO of Exoes and E-MERSIV, and a renowned leader in the immersion cooling technology space, and Siddharth Jaiswal, Group Manager of Netscribes –  Automotive Practice. The conversation delves into the wide range of immersion colling applications, spanning from passenger cars to heavy machinery. They also highlight the positive response and increasing demand for this technology among OEMs and other key players in the automotive industry. 

Siddharth Jaiswal: Today we are going to speak about a very interesting topic, which is battery thermal management. As you all know that electric vehicles are the future of mobility and keeping them safe has become the utmost priority for the industry.

And one such aspect is the emerging immersion cooling technology, which is something very novel but has a huge upside. And to speak more about this, we have Arnaud Desrentes, and he is the CEO of Exoes and E-MERSIV. He’s a prominent leader in the immersion cooling technology space, and happy to have you, Arnaud.

Arnaud Desrentes: Yes. Hello, I am Arnaud Desrentes. Yes, hello everybody. To our Netscribes listener. Happy to be here.


Siddharth Jaiswal: It’s great to have you here. And so Arnaud, why don’t you just run us through with a quick thumbnail about yourself and your journey with both Exoes and E-MERSIV?

Arnaud Desrentes:  Yeah. Thanks. I’m both CEO and co-founder of two companies -one is Exoes and the other is E-MERSIV. Both companies specialize in advanced thermal system solutions and our motivation for starting these companies is simple. With climate change looming, superior thermal management is really critical in all aspects of life.

As heat is the mother of energetics, we saw a big opportunity to provide superior thermal management systems to the mobility sector to accelerate the decarbonization of vehicles, which is really key. And yeah, I will introduce both companies. Exoes is a technology leader for passenger cars, OEMs, as well as freight makers.

We offer a wide range of engineering services from design, simulation, prototyping, testing, and test benches for thermal systems in next-generation batteries, e-motors, or electronics, as well as heat pumps. On the other hand, E-MERSIV is an industrial company that manufactures submerged battery packs.


Siddharth Jaiswal: Great! So for our listeners, if you could just highlight in very simple terms what is immersion cooling technology and why is it essential to the automotive industry today?

Arnaud Desrentes: Yeah. If you agree, we’ll first begin with the pain points that the EV industry faces as of today. So, there are three main pain points compared to thermal engines. The challenge includes limited range, a high cost as well as poor and long charging time, and these three limitations are still here in 2023 and they all are directly linked with the battery pack technology.

So to unlock the potential of EV markets and provide affordable EVs with charging time of less than 10 minutes, we need to address critical areas. Firstly, we need to increase the heat transfer coefficient. You know, this is really linked to the battery thermal management systems and this heat transfer coefficient refers to the thermal performance of the battery pack.

And by increasing this performance by at least a factor of four. So four times better compared to what exists today, we can significantly reduce the charging times.

Secondly, we need to improve the charging algorithms because you know when you want to fast charge, there is a risk to degrade the battery cell lifetime. So, we need to ensure that while fast charging, we are still providing a very good lifetime and even increase it. And this is linked to, let’s say, a specific charging algorithm that we developed in-house.

So, to address these challenges, we have developed a unique and proprietary technology which is based on immersion cooling, and I will explain afterward what immersion cooling is. And compared to the state-of-the-art and the best water-like or cold plate technologies which have a limited charging time of 18 minutes. Our technology offers and demonstrates already that we can charge in less than 10 minutes, namely 8 minutes.

So like cold plates, immersion cooling relies on what we called direct cooling. You know, with a cold plate you have the heat sink that is outside of the battery pack, whereas with immersion cooling you have the liquid directly inside the battery pack which cools the cells, the busbar, and everything that heats inside the battery pack. And this allows for significantly improved several performances, which is critical for achieving fast charging times to unlock the full potential of EV markets.

Siddharth Jaiswal: That’s quite fascinating. And, it is very interesting that you’ve also compared immersion cooling technology with various other battery cooling systems, right? The plates, the passive cooling. They’ve been quite a few technologies which we can safely say today that are proven. Right?

So, how does immersion cooling technology compare with these other options available in the market? And what are the things that immersion cooling technology does, just does better than the other technologies out there?

Arnaud Desrentes: Yeah. Thanks for this question. First of all, I want to stress that we compare a lot of cooling technologies in-house with immersion cooling. So we have a lot of experience that Exoes group of the various type of cooling technologies. And I have to admit that there are a few benefits of immersion cooling that I would like to address in this podcast because they provide critical, they answer to critical challenges that OEMs are nowadays facing.

With immersion cooling, we have achieved several notable results in addressing the thermal challenge of electric vehicles. Firstly, we have been able to address ultrafast charging times of less than 10 minutes, which is really key to unlock the EV potential of mass markets. Secondly, we have developed and approved that we can prevent thermal runaway propagation.

So that means that in case of a battery cell fire, we have no propagation to the other cells to the other modules or to the complete battery packs, which is really key because regulation are coming into force to contain battery fire for a long time when a self fire occurs in the battery pack.

And another advantage is that we can significantly improve the battery lifetime and depending of various conditions we can prove that we improve the lifetime of approximately up to 30%, three zero percent. And this represents a significantly improvement for market that are looking for total cost of ownership business model. That means that market that needs really long time batteries like the bus, is the construction equipment. More mainly speaking, the industrial off-road and off-highway markets where lifetime is really key as the cost of expedition is the key parameter for our company to choose and decide to buy or not a vehicle.

In contrast to that, many Tier 1 suppliers, they have attempted to improve cold platetechnologies by putting them inside the battery packs and by putting lots of cold plates in the battery packs. This costs a lot of money. This is very expensive and there are also risk of water leakage inside the battery pack. And naturally as you know, water is electrically electrically conductive.

So when you have a leak of water, this can lead to battery fire. And the cost associated to safety concerns are really huge nowadays. You might all have heard about the cost of car recalls from General Motors and Hyundai that cost them billions of dollars in the last years.

Therefore, safe technologies are now a must for OEMs as well as for final users to improve their trust into the electric vehicles. And this is what we are providing at Exoes Group to unlock the barriers of the entire EV industry.

Siddharth Jaiswal: That’s very well articulated and very brilliant points out there. So as an extension, you did mention that there are particular use cases that kind of becomes a much more lucrative segment. So where would immersion cooling technology fit the best? Is it in passenger cars? Is it in electric 2 wheelers or is it? Is it heavy machinery? Heavy construction equipment, long haul trucks? Can you just highlight that?

Arnaud Desrentes: Sure. Yeah. We see a huge momentum for this technology and there are several answers. For passenger cars mainly it’s the charging time. You know, the pass-car is the symbol of the freedom.

But freedom is not there with EVs if you need 45 minutes to stop each one hour and a half to charge at the station. You are reading this aspect. So for the pass-car industry, immersion cooling will come because, mainly because of the charging time and naturally of the safety aspect. And for other markets like off-road or off-highway sectors, it’s the lifetime of the battery and its safety that will probably push this technology towards this market.

If you look at the recent news, for example, Kreisel, which is also a company specializing in immersion cooling, it has been acquired by John Deere last year and this is for us a strong signal that off-road and off-highway in this case, agricultural markets are looking at immersion cooling. And not only agricultural but also mining, logistics, ships, construction equipments.

They are looking at this kind of battery because your lifetime is improved, the safety is improved, the performance overall are improved. This is why we see that immersion cooling is well suited for this kind of other markets than pass-car, so let’s say trucks, industrial applications as well as buses.

Whenever you have harsh conditions and extreme temperatures you can find, you will find this technology in the future. And what is interesting to mention also is that a fuel cell vehicles or vehicles running with hydrogen. They are, they needs what we called buffer batteries.

Buffer batteries -these are batteries that are really, uh, demanding batteries that charge and discharge many, many times a day and in the construction equipment or off-road,  off-highway sectors, they work 24 hours a day, seven days a week.

So for this kind of vehicles, to push them through the zero-emission vehicles equipped with fuel cells, you need high-performance battery packs. And this is exactly where our offer at Exoes Group is positioned. So our battery packs are also useful or immersion cooling developed by Exoes Group, is also useful for heavy vehicles using fuel cells which are being more and more adapted in the off-road and off-highway sectors.

This is why we see that, the adoption of immersion cooling technology is being massive and for a wide range of markets, including also aeronautics like hybridization of small aircrafts or green taxis batteries for bigger aircraft.

So this is really targeting many many segments and to answer your first question, maybe it’s not so well adapted for two-wheelers, maybe except in the very, very hot and the end temperature climate – like in India or South of India for example, or Indonesia etc. – where you can find what we call the passive immersion cooling that means that the cells will be in the bath with no circulation of the fluid. This will already improve the situation. But we see more, we see it more for batteries bigger than 20, 30-kilowatt hours for pass-cars, off-road, and off-highway.

Siddharth Jaiswal
: Got it. That’s all interesting, where immersion cooling tech has application across the multiple segments, multiple industries for that matter. So, that brings my thoughts where the tech is promising. There’s no two questions about it.

And what I want to know is how is the demand side for this technology? How receptive are the OEMs or the other players who might find value with immersion cooling, and what kind of, and what are the challenges that you see, since you have a very close proximity to these suppliers and OEMs? How is their reaction towards immersion cooling and what do they expect?

Arnaud Desrentes: Yeah, it’s for any new technology, its first seen as a risk by OEMs. You know you have already existing technologies that works well, could be improved and will be improved.

But the first reaction is always – OK,there is a potential on the one side, but on the other side there are risks associated to this potential. This is why we are acting in three directions at Exoes Group.

First of all, Exoes is working closely to major OEMs worldwide to accelerate their time to market. So that means that we do many things in the engineering space activities, which means design, simulation, prototyping, testing, test benches and we do it quicker and faster than our competitors to be sure that we will help OEMs to gain insurance or to gain trust in this technology as fast as possible. And secondly, we have E-MERSIV. E-MERSIV is a battery pack manufacturer and we manufacture only submerged batteries and E-MERSIV is here to address niche markets where immersion cooling is already available or let’s say that where this markets are already ready to adopt this technology because they have no other choices and cold plate do not fit with their requirements.

So, we will accelerate really fast the adoption of this technology with many, many running hours in harsh and extreme condition markets. And this will help us to also increase the trust of these technologies with thousands of running hours that we can show to mass market OEMs.

And last but not least, we are working with several companies involved in immersion cooling to create a worldwide immersion cooling consortium to accelerate the development of standard test because there is a lack of standard norms for OEMs to develop this technology.

And you know many, many technologies are being developed through guidelines that do not really exist with immersion cooling as it’s a really new technology. So we want to develop the kind of test, the kind of design rules, etc. that are needed to push this technology really faster on the market and we’re working with several companies to do so.

So with these three actions, we do believe that we are doing our best efforts to accelerate this time to market, then to break the barriers that we can face with the new technologies that always occur in the vertical segments – in the pass-care industry of road, off-highway. So we are not far for getting this technology adopted by many, many OEMs. 


Siddharth Jaiswal: That’s very important and very fascinating, where with any other technology it starts slow. But do you find immersion cooling hitting the mass vehicle market soon? Will it be a volume technology or will it remain or evolve into a niche segment, finding its own use cases? So any thoughts on that?

Arnaud Desrentes: So, it will be a mass-market technology. As we understand this ecosystem, the solid-state batteries are not yet there, whereas you have for example, currently 302 battery cell gigafactories that are being built right now.

None of them is based on the solid-state technologies. That means that we gonna have for a long while, uh, the lithium-ion standard technology as we have today. This will be increased, but this will be incremental increase and improvement.

So we do see this technology with will last at least until 2040 and probably more than that. That’s why immersion cooling and better algorithm are probably one of the key answer to improve without changing the manufacturing line of the cells which costs billions of dollars. This will improve the battery pack performance overall, so that’s why we see this adoption.

However, the introduction market will begin with niche markets. As just mentioned previously, like racing markets. You already have immersion cooling in Formula One, for example, since many many years. You already have immersion cooling in some luxury exclusive sports car like the Maclarens Speedtail, or like some Rimac cars or Koenigsegg cars, or very exclusive, very expensive cars. But at least they exist as far as of today, and they are on the road already. 

So we see immersion cooling is coming, is gaining interest and you know the development of the freights is also helped by other market segments – like the data centers, more and more data centers are being equipped with immersion cooling at least the more recent and more let’s say powerful data centers, are equipped with immersion cooling. And this really helps the freight maker to develop better freights that are compatible with power electronics, to develop material compatibility faster, to develop volumes faster also. So this will really help the entire industry to move forward and accelerate the adoption of immersion cooling.

Siddharth Jaiswal: That’s a brilliant answer. And while we understood the demand-side attributes that there is interest, there is an urgency with the OEMs to find a sustainable solution to thermal runaway.

Now coming to the other end of the spectrum where we look at the supply side. So from our research, we saw that they’re not too many companies out there experimenting or focused on immersion cooling technology. So how do you think this space will evolve? Do you see more new entrants coming, where you’ll have a vibrant startup environment? Or do you see consolidation happening and they could be big Tier-1s entering and it becomes very consolidated? What is your take on this?

Arnaud Desrentes: I have a feeling that you need to be big in this industry to survive and for sure consolidation will happen. And I think that the recent move from John Deere with Kreiselis a perfect proof that consolidation is already happening. Uh, as soon as they acquired Kreisel, John Deere announced that they will produce 2 GWh battery pack plants in France in 2024. So this is to show you that this sector is definitely accelerating through probably consolidation, where we still have in 2023 many, many SMEs or startups working on this field.

We also know that we have very, very large companies and we have some of them at Exoes Group that are accelerating the development and deployment of this technology. So we see both very major, very large major companies OEMs that will adopt this technology and that will work with external companies, engineering, tech developers on the one side.

And on the other side we see manufacturing companies that will integrate probably and acquire companies that have capabilities to develop the battery, submerged battery packs until the industrialization process, and not only at the advanced technologies and service scale. So to make a long story short, this year and next year we’ll see a strong acceleration in both parts of the partnership or acquisition on the one side. So concentration of the business and on the external  service engineering companies working with very large OEMs.


Siddharth Jaiswal: Understood. That’s very interesting and we look forward to how this dynamics will evolve and how the industry will shape. And we are quite upbeat about immersion cooling tech and its potential to genuinely solve the challenges of thermal runaway. And as an extension to that, the off late over the past one year, we’ve seen many instances of electric vehicles catching fire. And this for an emerging industry is a big destructive move, right? It kind of destroys that consumer confidence especially when it is so new. 

Now in this context how do you see immersion cooling tech evolve from a consumer’s viewpoint? Will OEMs eventually see this as a product differentiator and use it like a marketing tool that you know our vehicles are active with immersion cooling with kind of solves thermal runaway forever? So will that scenario come in future? Do you see that happening soon?

Arnaud Desrentes: Yeah. That’s the next entrance you raised. To answer by fact, we used to do less than 10 thermal runaway or abuse tests in 2020, only three years ago, per year. And now at Exoes Group, we are improving this to more than 50 abuse test per year. And this will probably increase to 100 next year. So we see a huge increase in demand for OEMs to prove or to find safe and safer technologies for sure. 

And immersion cooling, due to its, let’s say design is like a safe by-design technology. Because all the cells are submerged inside a liquid. So that means that you have no oxygen coming inside your battery packs and you know that for a combustion to propagate, you need oxygen.

And this is where immersion cooling is really interesting, because you have, in that sense, you have no oxygen inside a battery pack. So as the cells, battery cells are submerged inside a liquid, you have no thermal runway propagation, if the design is correctly done. And this is what we offer at Exoes Group. So, I strongly believe that yes, there is a need to improve the battery safety because this can affect the brand image of OEMs at a very, very high level.

This can affect their finance, as mentioned, it costs billions of dollars for car recalls due to safety issues. So, it can affect in the long way, the user confidence in this technology. If you have several vehicles that burns inside a parking for example, then this will be a drama.

So for sure, safety will push immersion cooling and is already pushing immersion cooling adoption or at least advanced engineering and development of this technology. And once again, we can prove it by fact, Exoes Group belongs now to the… we have been elected by the Financial Times as one of the 500 fastest growing companies in Europe and this is mainly due to the safety feature, brought, thanks to immersion cooling technology. Naturally, there is a performance of ultrafast charging, but the demands are more and more based on safety issue and safety requirements for OEMs. So I see a lot of potential here for this technology due to safety issues.

Siddharth Jaiswal: Got it. And congratulations on the listing top 500 and it’s a technology that should be explored because it genuinely solves many problems of the industry is facing. Now, so often in such conversations, we sometimes sideline the end consumer. So bringing our discussion to how will immersion cooling technology…what will it mean for the end consumer?

Let’s say there’s a passenger car driver, and what will it mean for him? So, does it make the powertrain more complex, more difficult to manage, maintain, repair or will it make things simpler as EVs are already perceived quite complex by the end consumer?

Arnaud Desrentes: Yeah, very good question once again. So at this stage our feeling is that it’s a bit too early to make any assertions regarding the aftermarket dynamics of immersion cooling technology. However, in our lab, we have demonstrated that the technology has maintained its properties for at least an equivalent of five years of usage no more usage of a car, without any free modifications. And our target is now to prove that we can reach more than 10 years of operation without changing the freight. So we want, uh that the end-user has no effect and no, let’s say drawbacks of using this technology for sure.

And also because then if you need freight change several times over the life of the vehicles, you also need the complete supply chain worldwide, which is also let’s say critical or at least it represents costs for the OEMs and the end consumers. So our target is definitely to have no differentiation in terms of aftermarket between the current technologies and immersion cooling.


Siddharth Jaiswal: Understood. And my final question is how do you see the overall automotive industry evolve in the next couple of years and what will it mean to Exoes and to the immersion cooling technology?

Arnaud Desrentes: Yeah, that’s the question, I would have like a crystal ball to answer properly. Our feeling that we see several kind of electro-chemistries, and we’re gonna have like a market segmentation that will come.

So first of all, the future is definitely electric. This is no doubt about this. Either full-battery electric vehicles or plug-in hybrid vehicles or hybrid vehicles. But any vehicles are gonna have a battery sooner or later, and probably sooner than expected than five years ago. This is the first answer. Then, we see several kind of electro-chemistries that are pushing the segmentation of the cars.

Sodium-ion batteries will probably the entry market, where whereas iron phosphate batteries – LFP batteries will be like the middle market, and the premium and most demanding like off-road off-highway and industrial markets, will still rely on an NMC. And we do believe that NMC plus immersion cooling plus 800 volt architecture is really one of the best solutions, because you can decrease the size of the battery, therefore, the cost and the weight of the vehicles, as well as increase its performance like the safety and ultrafast charging. So we do see a real potential for this technology with an increased, impressive increase in electrification in every sector. 

Arnaud Desrentes

Arnaud Desrentes


Arnaud Desrentes, the CEO of Exoes and E-MERSIV has emerged as a pioneering force in the automotive industry. His journey began as an engine designer at PSA, where he spent three years meticulously shaping the performance, fuel efficiency, and environmental impact of the company's engines, long before they hit the production line. In 2009, Arnaud co-founded Exoes, a visionary company committed to decarbonizing the mobility sector. Exoes’ mission revolves around the development of cutting-edge vehicle thermal system technologies. In 2019, driven by Exoes' remarkable growth, Arnaud founded E-MERSIV. This new venture aims to solidify its position as an influential industrial player by engineering battery packs that incorporate groundbreaking immersion cooling technology. Today, under his astute guidance, both companies are experiencing rapid expansion and are relentlessly pursuing their goal of becoming leaders in advanced thermal management systems by 2027. Arnaud unwavering commitment to sustainable innovation is reshaping the automotive landscape, offering a promising future where greener transportation is within our grasp. With his visionary leadership, he is steering the industry towards a more sustainable and environmentally conscious path.

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