EV batteries show high potential to be reused in energy storage systems for up to 15 additional years - cutting the batteries' lifecycle emissions significantly. We are discussing how exactly second life applications are possible considering e.g. technical requirements, industry developments, economic challenges.

In this conversation:

Philipp Wunderlich , Head of Battery Technology, Accenture - Industry X

Radu Achihai, COO & Co-Founder, Evyon

‍Nam Truong , CEO, Co-Founder, STABL Energy

‍Weihan Li , Research Group Leader, RWTH Aachen University

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Can Lithium-Ion EV Batteries Get a Second Life?

MODERATOR : Following our first discussion about the circular future of mobility, we are diving deeper into the potential of giving EV batteries a second life by repurposing them in energy storage systems. We have gathered market and research leaders to discuss the present prospects and use cases of the second-life market.

Our first panelist is Dr. Philipp Wunderlich. Philipp studied Material Science at university and carried out research in the field of batteries in California in 2014, investigating anode materials for next-generation battery technologies. He is now a Senior Manager at Accenture Industry X and Head of Battery Consulting. He and his team have the ambition to strengthen the European battery value chain by supporting projects for battery gigafactories, energy storage solutions, battery data management, and circularity strategies. Thank you for joining us, Philipp.

Our second panelist is Radu — Chief Operating Officer at Evyon. He has spent more than 15 years in global operations management. His last company raised €130 million for technology development and international expansion. Evyon is a nationally based company taking a data-driven approach to enabling the reuse of batteries. Thank you for being here, Radu.

Our third panelist is Dr. Nam Truong, who has a background in electrical and computer engineering with a focus on battery storage systems. In 2019, he founded STABL Energy. STABL Energy, with its modular multi-level inverter, aims to be a game changer in the ESS market and make the repurposing and deployment of second-life storage systems smart and affordable. Thank you, Nam.

Our final panelist is Dr. Weihan Li, a research group leader at the Institute for Power Electronics and Electrical Drives at RWTH Aachen University. His research interests include battery digital twins with physics-based modeling and machine learning, battery analytics, state estimation, and data acquisition. The group is also working on battery fault detection, safety monitoring, fast charging, and operational strategy optimization. Thank you, Weihan.

Today's discussion follows a "one slide, one fact" format — each speaker will share their key message on second life. After all slides are presented, we will enter a broader open discussion. The YouTube audience is welcome to submit questions in the chat and we will address them later.

Philipp, please go ahead.

PHILIPP: Thank you, Caesar. I'll give a market perspective on the second life of EV batteries, looking at the overarching industry — from automotive to remanufacturers, chemistry companies, recyclers, and cell makers. This is based on observations we currently see in the market.

The main statement I want to make is that we have a lot of uncertainties ahead, and the market is still at an early stage — it's lifting off, and we need to live with these uncertainties for at least a few more years.

If you look at the lifecycle of an EV battery placed on the road in 2020, you have to account for the typical vehicle lifetime — an eight-year warranty period or 150,000 kilometers, whichever comes first. Vehicles will stay on the road and only a small fraction — perhaps 2% — of end-of-life batteries will return to the market early. The majority of vehicles will have a lifespan between 9 and 15 years. We currently model 15 years as the maximum probability for a vehicle returning, giving us access to the battery again. That is the relevant time span for modeling future market demand.

If the vehicle lives 15 years, what about the battery? It will likely outlive the vehicle. Indications from current vehicle applications and battery development suggest a good lithium-ion battery will last 10 to 20 years today — and with further advances, possibly 25 years or more, if calendric aging is manageable. This justifies a second use: we produce assets that outlive the vehicle, and we can keep using them.

What I want to highlight is that we must also consider the time spans of battery development. A typical battery cell development cycle takes two to four years. Most cell manufacturers' roadmaps span five years. The battery as an asset lives much longer. That means we have to look at end-of-life returns at the end of the decade and beyond. It is a complementary process to recycling — not a competing one.

The biggest uncertainties will be the lack of returns — either through vehicle exports or owners simply keeping their cars longer — and the ongoing technical advances that make it harder for second-life batteries to compete with new technology, both on technical KPIs and, more importantly, on cost. We also need to live with information asymmetry when remanufacturing batteries, since access to battery data is limited. There will be significant OEM dependencies, as they are the dominant players in the primary loop.

Three potential game changers toward the end of the decade:

1. The Battery Passport: which will facilitate battery data management to some extent.
2. LFP and low-cost batteries: with lifetimes of 20 years or more, these will affect volumes available for remanufacturing, repurposing, and recycling.
3. Battery-as-a-Service: new business models that allow OEMs to retain control of the battery pack, rather than releasing it to third-party remanufacturers.

MODERATOR: Very interesting. When can we expect a steady second-life battery supply?

PHILIPP: A steady supply will begin now and grow in the coming years, driven by a constant background of pre-warranty returns — vehicles returning early — which gives us material to learn from and get familiar with module and pack assemblies. But the large volumes, just as with recycling, will come toward the end of the decade. Current forecasts are actually pessimistic because vehicles are living longer than anticipated, and we are already building recycling overcapacities.

Around 2 to 5% of batteries reach second life or recyclers before the end of first life. At end of life, we then need to decide: export, remanufacture, or recycle — to meet EU targets.

MODERATOR: You listed the Battery Passport as a game changer. What is your view on the European Commission's regulatory push around it? Will it boost the second-life market or create barriers?

PHILIPP: The Battery Passport is definitely making an impact. But the question is who the main target group is. The directive is focused primarily on cell manufacturers, automotive OEMs, and recyclers — with an emphasis on recycling targets and recycled content. Second life is not the central focus. We may need additional incentives for this market to grow. There are considerations for repurposing in the regulation, but they currently favor large automotive players over small and medium-sized companies. That's a topic worth following up in the open discussion.

MODERATOR: Thank you, Philipp. Radu, please go ahead.

RADU: Thank you, Philipp — that was an excellent overview of the challenges we face as an industry.

My perspective is complementary. The second-life industry will not be a winner-takes-all market. It will be a collaborative effort — a win-win for everyone involved, whether technology developers, repurposers, or buyers.

At Evyon, we have taken an industrialized approach to building planet-friendly, smart, and scalable commercial and industrial battery systems. We highlight this not only to emphasize the worthwhile nature of second-life but to show buyers there are strong reasons to invest in battery systems based on second-life modules or cells:

•Automotive quality: You buy products with a 10x lower cell failure rate. These modules are built for the most demanding mobility applications, so passing certifications for stationary use is not a major challenge.

•Planet-friendly: For a medium-sized commercial and industrial application, using the average manufacturing footprint, we can deliver a solution with up to 95% lower CO₂ equivalent compared to a new battery system. Our systems represent just 5% of the carbon footprint of a new battery alternative.

•Energy density: In most cases, we deliver two times higher energy density than leading competitors — applicable to both new and second-life batteries.

•Short lead times: As a buyer, you face long lead times in the market. At Evyon, you can receive your system in 12 weeks for orders under 1 MWh and 24 weeks for larger orders.

•Data-driven optimization: It no longer makes sense to have just hardware. You need to learn from operation and use those learnings to optimize both lifetime and total cost of ownership.

•Scalability: Our systems scale from 66 kWh to 1 MWh, and we are working on solutions to expand the range further.

MODERATOR: Thank you, Radu. From your experience in the market, which use case is the most valuable for second-life batteries?

RADU: It depends — and that is genuinely the answer. Used batteries often have reduced round-trip efficiency, which impacts total cost of ownership differently across applications. There is also reticence on the buyer's side that needs to be overcome.

At Evyon, our DC battery systems can be used across a variety of applications. One key decision we made is to use passive cooling, which limits C rates but significantly increases battery safety.

In short: any of those applications can work, but it requires thorough analysis to determine whether the batteries are fit for a specific application.

MODERATOR: Thank you. Nam, please tell us how STABL Energy is addressing the technical challenges with your inverter technology.

NAM: Thank you. I want to speak about knee points.

Batteries age due to electrochemical side reactions, which means usable capacity decreases over time. The older a battery gets, the less energy it can store.

What are knee points? They are events — visible on degradation curves — where the steady, slow degradation of a battery suddenly accelerates. A battery expected to last years may suddenly have only weeks of life remaining and is essentially reaching its real end of life.

The problem is that the entire battery community — industry and academia — does not fully understand the causes of these knee points. The topic is complex, takes a long time to study, and historically attracted little research interest. If we are honest, the second-life industry is still in its infancy, just entering adolescence with more commercial storage systems entering the field.

What we do know are the main internal drivers: lithium plating, electrode saturation, and impedance growth. These are relatively straightforward to detect and model. However, there are also harder-to-detect factors — such as electrolyte additive depletion, loss of lithium inventory, loss of active material, electrode porosity decrease, and mechanical deformation. These cannot be detected in real time and typically require post-mortem analysis, which means opening the battery cells.

In second life, batteries will reach knee points at different times. Accurate prediction of these knee points is critical for the industry. Many players are working on prediction, but what we don't yet see are effective ways to mitigate a knee point event. That is what we at STABL Energy are working on — smart control of battery modules so we can isolate modules approaching a knee point while maintaining system operation.

MODERATOR: Beyond knee points, what other challenges do you see for second-life storage systems?

NAM: I have focused on a very chemistry- and cell-dependent challenge. I also see growing issues with the increasing structural integration of batteries in vehicles — for example, cell-to-pack and now cell-to-chassis technologies. We need to ensure that battery removal from vehicles remains economically and technically feasible. That is the next significant and more obvious challenge we face.

Our inverter topology addresses each battery module individually, meaning we can handle modules with different capacities and internal resistances, and isolate failing modules while maintaining reliable system operation.

MODERATOR: Thank you, Nam. We have heard from industry. Now let's hear from academia. Weihan, the floor is yours.

WEIHAN: Thank you for the introduction, and thank you to Nam for introducing the concept of knee points.

During the use of lithium batteries — in first or second life — stress factors such as temperature, depth of discharge, and current load strongly influence aging speed. Although predicting future degradation is very challenging, accurate prediction is extremely important for second-life applications. It helps us understand how long the battery will last, what the residual value of the battery pack will be after years of use, and how to use aged batteries safely and cost-effectively in second life.

Data from our lab shows that variability in degradation trends is very small in early life and only starts to increase significantly from the midlife of the cell onward. This is a major challenge for early-life aging prediction.

At the Center for Aging and Lifetime Prediction of Electrochemical and Power Electronic Systems at Aachen University, we have developed several machine learning models for battery degradation prediction. Our framework has three steps:

1. Aging experiments are performed on cells of a similar type to the intended use case, generating datasets for supervised learning.
2. This dataset is sent to a training server with computing power for model training and distribution.
3. The best-performing model is then sent to embedded devices.

The connection is bidirectional — devices also transmit prediction data and metrics from the field to the server, which can be used for future model updates. Since each cell's data is tagged with a unique ID, a unique cell passport can be created, which is useful for tracking performance over the entire lifetime and enabling over-the-air model updates to the BMS.

Cloud connectivity is a key factor that enables continuous model updates. Outputs can support operational strategy optimization, predictive maintenance, and full-life cost analysis.

Using this cloud-based battery digital twin, we are able to predict not only end-of-life points and degradation knee points, but also the entire degradation trajectory of every single cell. Our goal is to increase the safety and reliability of batteries in both first and second-life applications.

MODERATOR: That is a very interesting approach. What are the main challenges in gathering battery performance data in the cloud?

WEIHAN: To use a model that predicts battery lifetime in the field, we need a useful dataset as a foundation. We typically generate this in the lab using accelerated aging tests. But lab conditions are not the same as field conditions — batteries in the field experience less stress. The challenge is designing accelerated aging tests that generate datasets representative enough to build a basic model, which can then be continuously updated with real field data to maintain accurate lifetime predictions over time.

MODERATOR: How do you see the outlook for sorting and classifying batteries moving from first life to second life — especially using machine learning and physics-based methods?

WEIHAN: This is a very important topic. If we do not have data from the first life, it is very difficult to guarantee battery safety throughout the second-life application. There are two solution directions:

1. Rapid assessment methods: we need to develop approaches to evaluate battery safety and aging status quickly. Standard capacity tests and resistance measurements are not sufficient and take too long. Combining machine learning with physics-based models can accelerate this process and provide a more comprehensive understanding of battery status.
2. Cloud-based Battery Passport: we need to collect battery pack data throughout the entire lifetime, from the beginning of operation to the end. This way, we can track battery status directly, without complex testing before second life.

MODERATOR: That is a topic with direct economic impact on the second-life market. Radu, can you walk us through the cost drivers for repurposing batteries into second-life systems?

RADU: That is a complex question. Let me start with the historical context. Battery costs decreased by almost a factor of 10 over the past decade — something we will likely not see again, as material costs now dominate cell production, potentially at 70 to 80% of total cost. By 2030, we expect new batteries to cluster around $60–70 per kWh, compared to ~$1,000 in 2010 and ~$100 today. This means we have more room to operate going forward, as the cost reduction curve is less steep than in the previous decade.

The second cost factor is repurposing itself. To reassemble modules and extract cells efficiently, you need scale — factories of gigawatt-hour scale, processing at least 50 packs per day in an automated fashion.

The third factor is market cost acceptance. In the home storage market, early surveys showed buyers willing to pay only about 50% of the price of a new battery for a repurposed one, due to perceived risk or stigma. However, there are many applications and niches where customers will pay the full dollar-per-kWh or per-cycle price and do not care whether it is new or repurposed — as long as warranties and safety certifications are provided.

MODERATOR: Should we also factor in logistics costs for battery collection?

RADU: Logistics costs are significant and are coming. We are already working with recyclers who are setting up logistics and partner networks to provide battery collection infrastructure. As a network of workshops, recyclers, and repurposers develops, logistics costs will drop. Regulations for battery transport should also hopefully shift to a more favorable position.

MODERATOR: LFP batteries are often cited as a game changer — cheaper, longer lifespan. How does the shift to LFP chemistry impact the second-life market?

RADU: The shift in chemistry is ultimately favorable for second life. As Philipp noted, material cost has become the dominant production cost component. Manufacturing cost is becoming less and less significant, which makes it less competitive for recyclers to process these batteries. Repurposing will therefore play an increasingly important role — as long as it can deliver on quality.

There is also a lot to be learned in this industry, because this is the first time we have a genuinely circular play that is cash-positive throughout. We must also consider that not all batteries available for second life come from end-of-life EVs. We are also talking about overstock, warranty stock, and production scrap — packs damaged during manufacturing — which represent a strong economic opportunity for second-life use.

In summary: the chemistry shift is favorable. Manufacturing will become less competitive for recyclers, which strengthens the case for repurposing.

NAM: I agree that cost is a major topic. But if cheaper, longer-lasting, higher-energy-density batteries become available, they will likely be absorbed entirely by the automotive sector first. The question for the stationary industry then becomes not one of price but of availability. If we can deliver storage systems using second-life batteries, that is already a significant competitive advantage.

MODERATOR: Philipp already mentioned battery-as-a-service as a game changer. What about battery swapping — is that relevant to second life?

PHILIPP: Battery swapping is worth watching, particularly in markets where charging infrastructure is limited. It also allows automotive players to stay innovative and bring new technologies to market faster through exchangeable battery packs. It gives OEMs the ability to monitor technology on the road, gain access to data, and retain control of the battery — deciding what to do with it at end of life. The question is whether this model is feasible for Europe, given the significant investment already going into charging infrastructure.

MODERATOR: A topic we have mentioned several times: are second-life storage systems safe? My view is that they are — but I want to hear from the panel.

RADU: Customers often perceive second-life batteries as inferior quality. In terms of safety, there are four things we can do to improve both that perception and the reality:

1. Communicate clearly that automotive batteries go through quality assurance levels not seen for cells going into stationary applications. This translates into a 10x lower failure rate in second-life systems.
2. Maintain the same hardware monitoring quality as any other battery application. The hardware controlling state of safety is exactly the same whether it is a new or second-life system.
3. Apply machine learning and digital twins to anticipate failures and, together with high-quality hardware, stop operation of any cell or module showing signs of underperformance or instability.
4. Do not cut corners on hardware quality. We use top-shelf components for everything safety-related — top-level Battery Management Systems, active and passive electrical circuitry. Overall, there is no meaningful difference between our systems and brand-new battery systems — except that ours are built on automotive-grade batteries.

The primary causes of concern in any battery system are BMS malfunction and cooling system failure. We have eliminated the second risk entirely by using a passive cooling approach.

MODERATOR: Weihan, how does your approach address anomaly prediction and failure prevention in second-life systems?

WEIHAN: Safety is receiving increasing attention from OEMs and research institutes alike. We are working on detecting aging in two ways:

1. Aging-related safety problems: gradual degradation that leads to safety risks over time.
2. Sudden battery faults: events that cannot be predicted from prior data.

To address both, it is critical to understand the physics behind safety mechanisms. That is why we are building physics-based models for safety-related faults and long-term aging. The final solution for aging and safety detection, prediction, and monitoring should combine insights from physics-based models with field data and machine learning — to increase the generalization ability of those models.

NAM: I agree that we need to maintain electronics and algorithms at a very high level. All players in the second-life field are aware that they are closely observed on safety. Failure rates for Battery Management Systems and state estimations should be low. Since we work with batteries that have already been tested in the automotive field, safety is actually higher — because new cell designs with higher risk profiles are already screened out in automotive applications. What we receive are tested and proven battery cell designs.

MODERATOR: We have about 10 minutes left. Let me address some audience questions. First: is it technically feasible to integrate different battery chemistries into the same storage solution?

PHILIPP: Hybrid systems are a trending topic and will likely come. You could combine lithium-ion and sodium-ion batteries, for example, gaining the power capability of sodium-ion with the energy range of lithium-ion. However, this would probably require cells from the same manufacturer — automotive players will not mix a CATL sodium battery with an LG lithium-ion battery in the same vehicle. For repurposing, though, it could be a very interesting approach to tune the properties of the use case being addressed.

WEIHAN: Hybrid battery systems are a very important and potentially viable solution — particularly for stationary applications, not automotive. We have already operated a 5 MW stationary battery system in Aachen for several years, combining five different battery technologies. By doing so, we were able to design energy management systems that optimize aging across every chemistry. This saves significant cost and offers a path for OEMs to generate more value by combining different chemistries and different aging stages of second-life batteries.

RADU: I will offer a contrarian view. Complexity drives cost. While what Weihan describes is perfectly feasible, we are competing with first-life batteries where there is consistency in part supply and procurement. Adding complexity generally doubles costs. Hybrid systems may offer value, but they will not be cost-competitive in the near term. That said, availability is increasingly critical — some customers will pay a premium to access batteries now rather than wait 9 to 18 months. The answer, as always, depends on the application. And sourcing five different cell types consistently for production is extremely difficult.

NAM: I agree this topic is controversial. I first heard about hybrid storage systems in 2013 — it was already a good idea then, and yet there has been little commercialization since. From a technical standpoint, I agree with Radu and Philipp that it has benefits, but we are barely managing one chemistry properly. In the next five to seven years, I would not expect widespread hybrid systems. After that, as the industry matures, it may come back into play. Right now, most players would rather avoid added complexity than introduce it.

MODERATOR: Let us quickly address the Battery Passport. We all agree it is important and necessary. The real discussion is around what data goes in, who has access, and when. Weihan, your perspective?

WEIHAN: The Battery Passport has been a central topic at our institute for two to three years. Beyond standard BMS indicators like state of health, we want to include deeper aging information — such as aging modes: how much of the degradation is due to loss of lithium inventory versus loss of active material. This can be derived from charging data analysis. We are also working on state-of-safety indicators — a relatively new concept — which we believe should be included in the Battery Passport. We are still optimizing the indicators we can extract from field data, but we believe state of safety is a critical addition.

MODERATOR: Radu, what is your take?

RADU: The Battery Passport will be an important part of a battery's identity. It will help answer key questions: how much should I pay for this battery, and how long will it last in a specific application? My general perspective is that any system is only as good as its components, data sources, and users.

The industry faces a huge challenge in implementing the Battery Passport. Standardization has always been difficult — everyone wants to do things their own way. I strongly believe standardization is the way forward, and even an imperfect system is better than no system. I hope the industry adopts a solution as soon as possible — we will all benefit from it.

PHILIPP: The concept itself is a good idea. Since it is coming, people know it will be required by 2026. But we see too little action from the automotive industry, recyclers, and others who will need to deal with this. Whether they are waiting until closer to the deadline or simply ignoring it for now, I cannot say. There will be three layers to the passport:

1. Public layer: useful for end consumers to learn about their battery, though less relevant for industry professionals.
2. Industry layer: the most important one, for repurposers, remanufacturers, and recyclers. It should include disassembly instructions and detailed lifetime estimations to maximize economic value.
3. Policy layer: for policymakers, less directly relevant to our work.

I genuinely hope OEMs will be willing to share information beyond the absolute regulatory minimum — not locking all BMS and lifetime data away to monetize it separately.

NAM: The usefulness of the Battery Passport depends heavily on how much information is included. If it only covers remaining capacity and impedance, that is something we can determine relatively quickly ourselves. But knowing the charging protocol, temperatures, and usage history gives us a tremendous amount of additional insight into aging mechanisms — and that is crucial information for predicting knee points and estimating remaining lifetime.

MODERATOR: That imperfect information is still better than no information. How useful the passport becomes will depend largely on how willing OEMs are to share data.

Time has passed quickly — we have already had over an hour of discussion, and there are topics we haven't fully covered. We may need to organize a second round in the future.

It was great to have all of you here today. Thank you for your insights and opinions. Thank you also to everyone who submitted questions in the YouTube comments — we were not able to answer all of them today, but we will try to follow up offline.

For those watching, we regularly schedule discussions with market leaders and researchers. Check the link in the description to see when we are organizing more events. Thank you all, and have a great day!

ALL PANELISTS: Thank you! See you soon. It was a pleasure.

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