The electric vehicle revolution holds immense potential to reduce emissions due to fossil fuels. Currently, there are around 40m electric vehicles on the road worldwide; this total is expected to grow to 350m by 2030. These vehicles are powered by rechargeable batteries. This poses a significant challenge, namely for battery life and longevity. For the transition from gasoline to green to be sustainable in the long-term, the lifecycle of EV batteries must be made sustainable.
At present, EV batteries have an estimated lifespan of 10 to 12 years, or a distance of 100,000-150,000 miles (approx. 160-241,000-km). However, they contain toxic chemicals that make them hard to recycle, which poses an environmental problem. The BBC reports that only around 5% of EV batteries are recycled today, despite claims from some manufacturers that nearly all materials within their batteries are recyclable.
The clear challenge to the automobile industry is what to do with older EV batteries when they reach end-of-life for EV purposes – and if there are additional ways that those older batteries could be put back into service in a safe and sustainable manner.
Cold batteries in hot demand
One of the ways forward being posited by recycling advocates is the repurposing of EV batteries, an approach that already has EU support. Utilizing end-of-life EV batteries for a range of energy storage applications in support of renewable power generation and supply could achieve an environmentally sustainable solution. More than this, it might also add a value stream for EV manufacturers.
The key factor in a battery’s transition from its EV role to a new purpose is its state of health (SoH), the energy capacity it can hold compared to when new. An EV battery is generally thought to have reached end-of-life for EV use when its SoH falls to 70%. At this level, a battery can’t be charged to achieve a generally sufficient driving range. In addition, a lower SoH can also mean reduced driving performance, in terms of power and torque. That means they will need to be replaced within the EV vehicle itself – but could be reutilized elsewhere.
Out of the EV, into the charging station
Supporting their original purpose, second-life lithium ion EV batteries can contribute to EV fast charging stations by helping to answer demand at busy locations that need a lot of power, quickly. Installed at or near motorway intersections, for example, energy stored from repurposed batteries can assist multiple fast-charging points, while limiting impact on the grid supply.
If deployed for stationary power storage, it’s estimated that repurposed EV batteries could exceed 200 gigawatt-hours’ worth of power by 2030, with a value or more than $30bn. Well-positioned to meet the needs of localized supply requirements, Jaguar Land Rover is already supplying second-life batteries for the creation of a renewable energy storage system.
EV batteries can also be installed at scale to achieve sustainable power distribution for large infrastructure projects, such as the pilot in Holland at the Ajax Amsterdam football stadium.
Expanded use on the grid
Second-life EV batteries also have the potential to be upscaled to meet the needs of the grid. In support of renewable energy power generation, feasibility projects are running in California at two separate solar plants. A smaller site in the south of the state is supplying the grid with 1.5 megawatts, based on nearly 600 former EV batteries; meanwhile, the plant near Los Angeles uses 1,300 second-life EV batteries to store 28 megawatts, sufficient to power around 9,500 homes.
The emergence of distributed power generation technology, supporting the smart cities of the future, is also accelerating the integration potential of power generation infrastructure for domestic and commercial properties, such as home-installed solar panels. Here too, repurposed EV batteries can be the answer for power storage, ready for when the property, or the grid, needs it.
The economic drive to re-use and re-utilize
While second-life EV battery use has an environmental sustainability benefit, vehicle manufacturers could also have strong economic incentives to pursue the circular battery concept. Value is still available in the battery even after 70% SoH has been reached. Achieving an onward path of use could circumvent future financial obligations that may be imposed for battery recycling.
Car makers already considering the development of EV batteries with a second-life in mind include General Motors, as well as Rivian. Central to this plan, a battery needs effective management throughout its life, both within a vehicle, and for its onward use.
The automotive battery management system, or (BMS), is a key element that helps monitor critical parameters for safe operation of the EV battery. One function is to ensure that every Li-Ion cell within the battery pack works within its Safe Operating Area (SOA), since operation outside the SOA can lead to severe consequences, such as thermal runaway. As part of this remit, battery temperature monitoring is essential, particularly for older age second-life batteries.
Given that continuously monitoring a repurposed EV battery could add another 10-years’ or more service, careful management throughout the extended lifespan is vital. For an additional layer of security, a MOSFET switch can also be integrated to discharge the battery in the event of malfunction or accident, and in high-voltage systems a combination of electromechanical relays for disconnection and a pyro fuse can be used.
The battery lifecycle of the future
The circular battery movement is quickly gaining ground. Automotive battery management systems will therefore play an increasingly important role in the safe and efficient operation of EV batteries, both within and beyond their original purpose.
A sustainable solution to the challenge of battery recycling is likely to combine battery repurposing. Even if a practical approach to recycling is found, the remaining value within end-of-life EV batteries, including the potential to sell them on for a second life and opens up new revenue streams.
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