Battery storage systems are crucial components for implementing the energy transition. In an exclusive interview with Battery-News, CTO and co-founder Dr. Georg Angenendt explains the challenges those systems are currently facing and how ACCURE Battery Intelligence has established itself as a provider of predictive analysis software for these facilities.
Battery-News: What is the significance of monitoring strategies for stationary energy storage systems in the context of the energy transition?
Dr. Georg Angenendt: Battery storage systems play a key role in the energy transition – whether for stabilizing the grids, balancing load peaks, or ensuring a flexible energy supply. Despite their central importance, storage systems face various challenges: They often fail to deliver the expected output, age faster than planned, or develop safety-critical conditions. Reliable and predictive monitoring is therefore essential. From the very beginning, our vision was to bring transparency to battery systems – independent of manufacturers, scalable, and data-based. Our goal was and is to predict failures at an early stage, to minimize risks, and to optimize performance.
“How much is actually possible depends heavily on the previous operation and condition of the system.”
Battery-News: In a conference presentation, you shared interesting aspects of reversible aging. How much lost capacity can actually be recovered – and what factors play a role in this?
Angenendt: We distinguish between irreversible and reversible aging. The first is the normal, electrochemically induced aging process. Reversible aging, on the other hand, is often caused by an imbalance in the system – in other words, by unevenly charged cells. In many customer applications, we were able to recover up to ten percent of the capacity through targeted balancing. How much is actually possible depends heavily on the previous operation and condition of the system. This is a particularly big issue with LFP cells – which now account for more than 80 percent of large-scale stationary storage systems.
Battery-News: What exactly is balancing, and why is it particularly challenging with LFP cells?
Angenendt: Balancing means bringing the individual cells in a serial battery network to the same state of charge – because the cell with the lowest state of charge limits the total usable capacity, like the weakest link of a chain. In the case of LFP cells, balancing is usually only carried out in marginal areas, which means when they are almost full or empty. However, if a storage system is not fully charged or discharged regularly, greater differences between the cells occur over time. This leads to avoidable loss of capacity, which can be reduced through targeted balancing.
“Using predictive battery analytics, an estimation error of up to 20 percent can be reduced to around two percent – which significantly improves cost-effectiveness.”
Battery-News: In said conference presentation, you also talked about the problem of incorrect state of charge estimates. What are the causes of such estimation errors?
Angenendt: The main problem lies in the flat voltage curve of LFP cells in the medium charge range. The so-called open-circuit voltage, the OCV, hardly changes there, meaning that voltage-based methods for estimating the state of charge are not very reliable. If this is combined with measurement inaccuracies in coulomb counting – of the incoming and outgoing charge –, errors of up to 20 percent can occur. This has a direct impact on economic efficiency: In a study with Modo Energy, we showed that such estimation errors can lead to a loss of sales of up to ten percent. Using predictive battery analytics, this estimation error can be reduced to around two percent – which significantly improves efficiency.
Battery-News: Nowadays, second-life batteries are being used more frequently. How does ACCURE deal with their complexity?
Angenendt: Our platform is independent of whether it’s first-life or second-life systems. For example, we work together with the Aachen-based start-up Voltfang, which uses second-life batteries. We rely on multi-stage safety monitoring with more than 20 indicators that identify potential risks. This results in a comprehensible safety score from green to red, which shows our customers directly whether there is a need for action. We take cell type, age, and origin into account – and can also easily integrate systems with mixed cell histories.
“Sodium-ion cells are often easier to analyze than LFP cells, as their open-circuit voltage curve is mostly steeper.”
Battery-News: And how flexible is your platform in terms of different cell chemistries?
Angenendt: Our focus is on lithium batteries – regardless of whether they are LFP, NMC, or LTO. We have also already had good experience with initial sodium-ion projects. We use the OCV curves as a basis and observe their changes over time in order to draw conclusions about the cell condition. In fact, sodium-ion cells are often even easier to analyze in this respect than LFP cells, as their quiescent voltage curve is mostly steeper.
Battery-News: How do you ensure that your algorithms do not become a “black box” – In other words: that they remain comprehensible for operators?
Angenendt: Traceability is extremely important to us. That’s why we don’t primarily rely on classic AI black boxes, but on physically based models from which we derive explainable indicators. We then use additional AI methods for forecasts. We also carry out continuous post-mortem analyses: We send cells that we have identified as critical to the laboratory, carry out CT scans, and check whether our assessments were correct. This allows us to continuously improve our algorithms.
“Some parts of the EU Battery Regulation are still somewhat vaguely worded, but it is definitely moving in the right direction.”
Battery-News: What significance does the EU Battery Regulation have for your work?
Angenendt: For us, this is a clear driver of innovation. The regulation calls for more transparency, data availability, and sustainability – exactly what our platform offers. Of course, some parts of the regulation are still somewhat vaguely worded, but it is definitely moving in the right direction. We are also ISO-certified, which underlines our expertise in the secure handling of sensitive battery data. Overall, this is a great opportunity for us.
Battery-News: What does ACCURE’s long-term vision look like?
Angenendt: Our vision is to make all batteries in the world better – which means, safer, more sustainable, and more economical. We are thinking beyond stationary storage systems, but the impact in this segment is currently particularly high. Our platform is intended to be a central tool to support and help shape the transformation of the energy system.
