A second life for electric car batteries

If you want to get the most out of your electric car for as long as possible, you can't avoid looking after the health of the vehicle's battery, as this is the most valuable component of the electric car. With a few tips, the life of the battery can be extended. But at some point, the situation arrives when the vehicle battery is worn out. It reaches the end of its life when it can only store about 70 percent of its original energy – a total economic loss for the electric car.

A study by the University of the Federal Armed Forces in Munich has shown that e-cars, compared to combustion engines, offer the best CO2 balance over the entire life cycle, i.e., from production to disposal. Here, carbon dioxide emissions can be reduced by up to 89 percent.

Nevertheless, e-mobility must also be designed to be sustainable in the long term, so greater attention must be paid to the sustainability issue with regard to the mining of valuable resources such as lithium, nickel, cobalt, graphite, and manganese.

Why does the vehicle battery lose power over time?

What is the reason that the vehicle battery discharges over time? We know it all too well from our smartphones, which have now become our everyday companions – over time, cell phone batteries lose power. The same happens, of course, with the batteries in electric cars. Roughly summarized, a process takes place inside the battery in which chemical energy is converted into electrical energy. This is known as a redox reaction: one pole releases electrons (oxidation), the other pole takes the electrons back (reduction), hence the familiar plus and minus signs. However, it happens that never all electrons make it from plus to minus and back again. You could also say that they "get lost" and over time, with each charge and discharge, this number continuously increases. The result: the capacity of the vehicle's battery decreases, and at some point it is no longer sufficient for the electric car to get from A to B. 

Second Life: The vehicle battery as stationary storage

How do you continue to use batteries that can no longer be used for the electric car? With a residual capacity of around 70 percent, the battery can no longer function as a drive in the electric car, but that does not mean it is completely unusable. The storage capacity is still sufficient to be used elsewhere – as stationary storage.

Second life batteries can be ideally used as stationary storage, e.g., to absorb fluctuations in the power grid. However, they are also ideal as power storage for private households with PV systems or as emergency power storage for public facilities. Their advantage: they can absorb energy quickly with low losses and release it in milliseconds. In stationary operation, the batteries are also subjected to much less stress than in an electric car, where they are constantly under heavy strain during acceleration and braking. Stationary operation, on the other hand, is much smoother: The charging and discharging processes are slow and thus gentler on the battery. This also has a positive effect on the service life of the battery, so that the retired vehicle battery can be operated in second life for at least another ten years.

Although their capacity is currently comparatively low due to the small number of end-of-life batteries available, this will change significantly in the coming years when more and more electric cars are on the road. According to a study by consulting firm Berylls Strategy Advisors, at least 1,522 gigawatt hours of used battery capacity will accrue by 2032 and could be available for use in stationary storage operations.

BMW uses second life batteries in storage farm

An example of how used electric car batteries can be used in second life is shown by the German car manufacturer BMW. In a storage farm on its factory premises in Leipzig, up to 700 used BMW i3 power storage units can be housed and charged with electricity generated in-house from wind power. The system is integrated into the public power grid; when there is an oversupply of electricity, the batteries can be charged, and when the electricity supply is low, the storage system can in turn contribute electricity. The system has a marketable output of 10 megawatts and a marketable capacity of 15 megawatt hours.

Increasing the recycling rate for electric car batteries

On March 10, 2022, the EU Parliament passed a new battery directive by a large majority, according to which the recycling quota for batteries is to gradually increase. A certain proportion of the materials used in production must also come from recycling. The recycling quotas for cobalt, nickel, and copper are to rise to 90 percent in 2025 and 95 percent in 2030. For lithium, the quotas are only 35 percent and 70 percent, respectively. A final decision has yet to be made; the EU governments must still approve the new directive.

Battery recycling plays a central role in the electric strategy of many car manufacturers. In November 2020, for example, VW opened its own recycling plant in Salzgitter, where valuable raw materials such as nickel, manganese, cobalt, copper, or aluminum are to be recovered and up to 90 percent of the battery is to be recycled. In the long term, the aim is to achieve 97 percent.