A Look Inside the Battery

Expert Interview – July 07, 2022

Batteries are the most efficient electricity storage devices, but they are also quite sensitive and very sealed. This means that minor defects are difficult to detect. To be able to peek inside the black box battery after all, the company volytica has developed an analysis method.

Claudius Jehle has been the CEO of volytica since 2019. Before that, he was "Group Manager Energy Storage Diagnosis" at the Fraunhofer Institute for Transportation and Infrastructure Systems IVI for five years. The researchers at IVI started monitoring traction batteries of e-buses as early as 2012 and launched the first "Battery Monitoring Platform" in 2017. In 2019, today's volytica diagnostics GmbH was spun off from the IVI.

Mr. Jehle, how can used batteries be employed to recoup as much of the production costs as possible?

One of the most interesting projects for the use of Second Life batteries is currently underway in Hanover at the Hanover public transport company, Üstra. They have electric buses in operation and wondered what to do with the batteries, these very expensive wearing parts, when they have degraded to the point where they can no longer serve even the shortest routes. And throwing them away, because of the shortage of materials and because of the residual value these things have, is not a good idea. So they came up with the idea of putting the used batteries in the transformer stations that supply the trams and the charging columns for the e-buses. Because trams and e-buses need a lot of electricity with many load peaks. The braking and accelerating of the tram and the charging of an e-bus puts a very uneven load on the grid, which is costly. Because the load peaks cost extra charges. If one now installs the used batteries for secondary use in the transformer stations that supply the electricity to both the tram and the e-bus, this is a good way to continue using the batteries in a very sensible way. You save the peak-load charges by buffering the energy in the transformer stations, which are spread all over the city. So it's a very concrete example that I like very much.

What stands in the way of the greater spread of such secondary uses of batteries?
The problem is that it requires trust to buy something second-hand. I will only pay you a good price for something you have already used if I can trust that it has been treated with care and that it will last for the planned period of use I expect as a buyer. And that is one of the core problems why the use of old batteries is not yet very widespread. There are some nice applications here at ees, but the market is not exactly exploding. And we think and see that this trust aspect, is one of the main obstacles why secondary use of batteries is not yet so widespread.

How could that be changed?
It's a bit like going to the gym. You have to put in the effort first, and the results and rewards come later. This is something that is very difficult for many users to understand, especially with a battery that is considered maintenance-free. As a result, there is a moral hazard - as insurance companies call it - with batteries. So if you have an expensive product that wears out like a battery and then you want to sell that product, the buyer always suspects a moral hazard. Because nobody knows if you haven't mishandled the thing.

That is why second-hand batteries do not fetch particularly high prices. Until now, it has unfortunately been difficult to convey that there should be a minimum level of monitoring for a battery right from the start. But that is changing.

In what way?

Just the fact that an asset like the battery is monitored leads psychologically to better use. That is an interesting thing.

What exactly is a better or gentler use?

There are three main factors that influence the rate of degradation, or battery aging: the temperature, the current or power, and what window of time you operate the battery and at what state of charge. And to make things a little more complicated, the effects of these factors vary depending on the operation or cycle. We call this cyclic aging, or, when not in use, calendar aging. I'm only giving approximate numbers here for lithium-ion technology, where there are also many subtypes. In general, one could say that storage at very low temperatures is very good for the battery. The chemical reactions that take place when the battery is not in use or idle are slowed down. But if you run a battery at very low temperatures, it's usually very bad because this can lead to internal defects. And also, storing it at 100 percent charge is one of the worst things you can do.

So how should you charge your car when you park it?
Before parking, you should only charge to a state of charge between 50 and 80 percent. And only charge fully when you need the vehicle. A typical car battery will last up to ten times longer if you park it at 50 per cent charge rather than 100 per cent.
That's huge.
Yes, that is huge. But the charging speed also plays a big role. And of course the temperature. When we talk about stationary systems, it already helps to plant trees and shade the systems. That reduces the stress on the batteries a little bit.

What data does your monitoring and analysis system provide and what insights do you draw from it?

We need voltage, temperature and current. These are then translated into remaining capacity. Also known as SOH, State of Health, remaining capacity or remaining usable life. Batteries are said to be maintenance free, but something can still go wrong. That's because there are thousands of cells inside e-car batteries, and they need to operate at a steady rate. And if one fails, the whole system can get out of balance. That's something we also analyze to look for anomalies, which of course can also be safety-critical.

What can you do if you find such anomalies?

Our platform then sends out alerts, of course, and can also be connected to existing energy management systems, which then actively control the battery. You obviously have several actions to take when you see or when there are first signs that a cell is failing. You should shut down the string and then replace the string or module of the battery. This is easy to do. Of course, if you're thinking about a mobile application, there's something we haven't talked about yet, which is balancing. All cells must have the same state of charge. We do talk about the state of charge of a battery. But that's not actually true, because if there are thousands of battery cells, there are thousands of states of charge. However, when one cell is almost empty, it determines the performance of the entire system. So if they get out of sync, you can have the battery management system, rebalance the system. For this, however, the car should be switched off. Tesla, for example, recommends that its customers do not use the car for four hours after fully charging the battery.

With your analysis technology, you can monitor batteries and detect when something is wrong, e.g. individual cells are damaged. Could it not be that OEMs are not interested in providing such information to their customers?

Car manufacturers want to protect their most expensive wearing part, the battery. The battery cell, by the way, is an Asian technology that we have not yet fully understood. Therefore, no battery cells are manufactured in Europe by European companies. Transparency is therefore not very common, but it does exist. If you walk around the ees exhibition here, the operators, the owners, the banks and the insurance companies are demanding transparency. Especially with batteries, there is a pronounced asymmetry of information between the seller and the buyer. And that is something that distorts the market. It's unacceptable. And that's going to change. Transparency will come. No doubt about it.

You are working with the supplier Mahle and have developed a method of reading battery parameters via the charging port. Will any workshop soon be able to read the batteries of electric cars?

At the moment, there is no standardized plug to read out information about the battery. So we had the idea of using the charging plug for this. Because that is the only standardized interface between the car and the outside world. I wouldn't say that we can use it to go into every single detail, for example to tell which cell is broken or not. But you can still say something about the quality of the battery as a whole, especially in comparison to other batteries. And that is a first step toward greater transparency. And that is something that is in great demand on the markets.

What can battery monitoring or a one-time readout do from a financial standpoint?

We distinguish between commercial installations that are continuously monitored and the ad hoc or event-based assessment like Mahle's via the charging plug. So if you look at a commercial installation, such as a stationary battery system or an electric bus, we usually say that you can reduce the total cost of ownership of such an installation by 10 to 30 percent. That would mean extending the life by 20 percent, reducing operating costs, such as through lower insurance costs and less unplanned maintenance, and also increasing the residual value. These are the three main points: Operating costs, remaining useful life and residual value. If you tweak these three values by charging the battery more gently, treating it better and providing a log of the battery's condition, thereby increasing the residual value, you can get 30 percent more out of the same battery. That lowers the total cost of ownership by 30 percent and even makes business models possible that were not feasible before. And if we think about the car now, we can clearly see that a quality certificate for the battery can increase the resale value by at least a few hundred euros.

So if I wanted to sell my car, I could tell a potential buyer: I have an independent certificate about the condition of the battery, and that's why it costs 500 euros more.

Exactly. And that's exactly what we're doing with Mahle and TÜV together with a pilot customer, a commercial fleet operator. They have a lot of different electric vehicles. They usually use them for 6 to 36 months. After that, they resell them on the open market. And right now they're being asked specifically, how good is the battery still? And they say, I have no idea. And of course that doesn't give the best price in the end.

With continuous monitoring of the battery, it could also become apparent that some service providers of charging points are not necessarily doing the best job for the battery.

Probably yes. Because, unfortunately, the complexity of batteries is not something that is generally known. That's why I don't blame the charging providers directly. Both passenger cars and commercial vehicles are generally not charged in the most battery-friendly way. And that will definitely be a differentiator in the future.

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