How long do second-life EV batteries typically last?

Second-life electric vehicle (EV) batteries typically last around 5 to 10 years when repurposed for home energy storage or other stationary applications. This lifespan depends on their state of health when removed from the vehicle and how they are managed during their second use.

Understanding second-life EV batteries

• EV batteries used in cars generally reach the end of their "first life" once their capacity falls to about 70-80% of the original. At this point, they may no longer be efficient for driving needs but can still serve well for stationary energy storage.
• When repurposed for home or commercial energy storage, these batteries still have significant usable capacity, extending their usefulness for several more years.

Typical lifespan in second-life use

• Studies show second-life EV batteries can last 5 to 10 years depending on:
• The battery condition when retired from a car (around 70-80% capacity remaining)
• How well they are tested, graded, and managed in their new role
• The specific energy demands placed on them during second use
• Batteries degrade more slowly in stationary storage than in vehicles because charging and discharging cycles are generally less intense.

Real-world UK applications

• In the UK, second-life EV batteries are increasingly used for home energy storage systems to:
• Store surplus solar power generated by rooftop PV panels
• Help manage electricity use during peak times, reducing bills
• Provide backup power during outages
• UK commercial users also employ them for uninterrupted power supplies (UPS) at events, construction sites, and EV charging stations.
• Recent UK government and industry research confirms that these second-life batteries are viable options for enhancing renewable energy use and grid flexibility but highlights safety management as critical.

Practical advice for UK homeowners and small business owners

Key benefits

• Cost-effective storage: Second-life batteries are cheaper than new batteries, making energy storage more accessible.
• Environmental impact: Reusing batteries reduces waste and the demand for new raw materials.
• Energy independence: Helps maximise self-consumption of renewable energy, reducing reliance on grid electricity.

Key challenges and safety considerations

• The state of health (SoH) at retirement varies, making performance and longevity less predictable than new batteries.
• The battery deterioration can accelerate unexpectedly between 75-80% SoH and end-of-life (50-60% SoH), potentially causing safety concerns such as thermal runaway.
• Proper testing, integration, and monitoring systems are crucial to manage these risks safely.

Common mistakes to avoid

• Buying without warranties or proof of battery grading: Ensure suppliers provide detailed battery health reports.
• Ignoring installation standards: Use certified installers familiar with second-life battery systems and UK safety regulations.
• Underestimating capacity needs: Understand your energy consumption to size the system adequately.

Summary

Second-life EV batteries can typically provide 5 to 10 years of effective service as home or commercial energy storage systems in the UK. They offer a sustainable, more affordable option to store solar power and support energy resilience but require careful handling, safety measures, and professional installation to maximise their benefits and lifespan. Current UK developments and policies promote their use as part of the transition to a net-zero energy future, making them a viable choice for homeowners and small businesses looking to adopt renewable energy solutions.