The idea of balancing is to increase the performance and lifespan of batteries. Conventional BMS control the battery’s charge and discharge based on the voltage in order to compensate for imbalances between the battery system’s cells. The ideal time for balancing is during resting periods. But stationary energy storage systems that are in continuous use during the summer months – charging during the day and discharging at night – never enter a resting period; balancing therefore takes place while the battery is charging, towards the end of the charge cycle. However, if there are regular time slots when batteries are neither charging nor feeding electricity into a grid, as is the case with e-mobility, balancing is often scheduled during these periods. 

When does the resting period of a battery begin? 

But it takes a long time before all dynamic responses have subsided in all cells. “Measurements have shown that you would have to wait up to 24 hours for the cells to really reach quiescent current,” says Frederik Fuchs, Managing Director of Benning CMS Technology GmbH. “So for e-cars that are driven every day – or even multiple times a day – the question is whether they ever actually reach a resting period at all.” Conventional BMS do not measure whether quiescent current has been reached; they start balancing shortly after the charging process is finished – which then does not fulfil the desired purpose. 

Focus on efficiency leveling 

Leveling is about efficiency leveling rather than voltage-based interventions, as is the case with balancing. Over time, the efficiency levels of the individual cells within a battery block undergo varying degrees of change. This causes minute differences in their state of charge as early as within the first few charge cycles and accelerates individual cell ageing; however, these effects are not noticeable in the application until much later. The clue of this technology is that despite cells being connected in series, ETA-Leveling handles each cell by leveling its efficiency as if it were a single-cell battery. As a result, the entire battery block will have a much longer lifespan. However, the intervention only takes a few seconds and happens during the charge cycle. Unlike with conventional BMS, waiting for the resting period is no longer necessary. 

ETA-Leveling can be purchased by licence. The algorithm can be used for battery blocks of all kinds and requires no hardware changes. You can find more information at https://cms-technology.de/en/. 

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Der Beitrag Leveling rather than balancing…<br>…because it does away with the battery resting periods erschien zuerst auf BENNING CMS Technology GmbH.

A use case from real life illustrates the benefits of this algorithm that can be integrated into existing hardware without any modifications. The BENNING CMS Technology GmbH Battery Leveling Laboratory tested a used e-mobility traction battery with 80 percent useable capacity – a state that meant it had reached its end of life for use in electric vehicles (EV). The Laboratory team reanimated the battery (i.e. leveled it), lending it around 900 more load cycles before it will drop back to 80 percent.

Saying goodbye to cell drift with ETA-Leveling

BMS that use ETA-Leveling from the very start prevent the premature ageing of individual cells in the first place, thus heading off cell drift and the resulting loss of useable capacity. In EV batteries, useable capacity equals range – and cell drift equals loss of range. While we are dealing with losses of below 10 percent (3.5 percent in the tested battery), these seemingly small figures cannot hide the fact that consequences can be severe. This is especially true for e-mobility, where every little bit of range matters. “Shorter ranges and fewer load cycles are caused by inadequate BMS,” explains Frederik Fuchs, Managing Director of Benning CMS Technology. “Our ETA-Leveling technology leads to more usable energy under the same conditions.” ETA-Leveling is available for any type of battery block and can be implemented into BMS following the purchase of a licence.

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Der Beitrag The “battery butterfly effect”: small cell drift can cause enormous loss of useable capacity erschien zuerst auf BENNING CMS Technology GmbH.

It goes without saying that completely randomly combined cells do not represent a useful second-life application. However, it has been demonstrated that such cells can be connected and operated in series and leveled using the straightforward ETA-Leveling process. This has been labelled disruptive – justifiably so – and can be completed in as little as a few hours. The resulting “patchwork battery” can be operated long-term without any issues. During charging, each cell is treated as if it was part of a single-cell battery application – thanks to efficiency leveling. This disproves the long-held assumption that the cells within a battery block need to be as identical as possible, and that even minor differences complicate or impede operation.

No more recycling unless a battery is actually defective

In light of large numbers of discarded battery modules piling up in manufacturer’s storage facilities and many more returning items that will join them in the years to come, this can be considered a revolutionary technology. Depending on a module’s designated application, it can retain as much as 80 % of its original capacity. Its current capacity results from individual, prematurely aged cells that unbalance the block and by doing so cause the actual defect. This means that the weakest cell within a module determines the entire block’s capacity. In turn, this translates to most of the cells within discarded battery blocks still being in excellent condition – or at least too good to recycle them. ETA-Leveling makes it possible to connect and operate very different cells in series: the first-of-its-kind, easy solution to continue to use these cells. “Up until recently, we ourselves would’ve never thought that combining cells randomly would work. It has not been possible with any of the traditional BMS,” says Frederik Fuchs, Managing Director of Benning CMS Technology. “Manufacturer, age, nominal capacity, cell chemistry – it really doesn’t matter. Our leveling process also recognises which cells are a reasonably sensible match based on their capacities. We then combine these cells to a long-lasting battery block that works perfectly.” This unlocks unprecedented opportunities for reusing discarded battery modules. Whether the aim is repurposing or processing to varying degrees (refurbishment, reconditioning, remanufacturing) – all possible scenarios become significantly more simple.

Licences for ETA-Leveling, which is suitable for battery blocks of all kinds and requires no hardware changes, recently became available for purchase.

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Der Beitrag ETA-Leveling enables second-life battery applications with “pick-n-mix” cells connected in series erschien zuerst auf BENNING CMS Technology GmbH.

Over time, the efficiency levels of the individual cells within a battery block change to varying degrees. This causes minute differences in state of charge as early as within the first few charge cycles and accelerates individual cell ageing; however, these effects are not noticeable in the application until much later. Efficiency within a block will become more and more unbalanced in the long run until it is not able to serve its purpose. Generally, this happens long before the individual cells reach their predicted lifespan listed in the cell manufacturer’s specifications. A battery block is usually considered to be “defective” once the unbalanced efficiency levels cause individual cells to exceed a defined cut-off limit in the upper or lower voltage range. Depending on the application, this can happen at different levels of remaining useable capacity. However, the battery is in fact not actually defective but has reached a state that is performance critical due to the unbalanced levels of efficiency across individual cells. This is where ETA-Leveling comes in, as it prevents this very effect from happening.

No hardware changes needed to use algorithm

The new charging process can be used without having to make any changes to existing hardware. The algorithm ensures that the individual cells are handled and controlled as specified when being charged, something that ordinary charging processes fail to achieve. Consequently, ETA-Leveling prevents premature cell ageing, enabling cells to last for their predicted lifespan. The clue of this technology is that despite cells being connected in series, efficiency leveling handles each cell as if it were a single-cell battery. The resulting longterm gains in lifespan for the entire battery block is significant.

Reanimating “defective” batteries in the Battery Leveling Laboratory

A very convincing way of demonstrating the effectiveness of the new technology to potential customers is asking them to supply a “defective” battery and reanimating it using ETA-Leveling. “We’ve just dealt with a traction battery that had been charged a little over 500 times and had less than 70% of useable capacity left, prompting our customer to dispose of it. Once we had leveled it, it was back to a capacity of around 90% and is fully functional again,” reports Managing Director Frederik Fuchs. “This way we were able to demonstrate that the battery was not defective but had simply been treated the conventional way – and in our opinion the wrong way – from the very start.” ETA-Leveling “cures” defective batteries so efficiently, this in itself would be a powerful business model. However, reanimations in the Battery Leveling Laboratory are only used for demonstration purposes – the reason being that any batteries operated with ETA-Leveling from the start will never reach this state of apparent deficiency in the first place. This is why the goal is to apply the algorithm as widespread as possible through corresponding licences.

You can find more information here.

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Please do not hesitate to contact us if you have any questions. If you had the opportunity to cover this information, we would much appreciate you sending us a link and/or a hard copy. If you are interested in an exclusive specialist article on the topic or a specific aspect of it, please reach out
to us.

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