Chapter 07 · Materials & footprintsCircular Economy & Materials
Battery second life
Definition
The practice of giving used EV batteries a further working life in applications with lower performance demands, such as stationary energy storage, home solar integration, grid support and backup power. Vehicle batteries are generally considered at end-of-life for automotive use when state of health falls to roughly 70–80% of initial capacity — a level at which most of their energy capacity remains usable.
References
70–80% SoH retirement threshold; stationary storage applications; economic and environmental rationale.
Overview
What it means
Second life extends the value extracted from each battery's embedded materials and manufacturing footprint, spreads production costs over more years, and delays recycling. It creates a cascade between transport and energy sectors: the same asset first powers a vehicle, then buffers a building or grid. Realising this requires reliable state-of-health data — one reason the EU battery passport mandates it.
How it is used
Automakers, energy companies and specialist repurposers run second-life projects (for example stadium and data-centre storage built from retired EV packs). Economics depend on testing and requalification costs versus falling prices of new batteries; safety, warranty and liability frameworks are still maturing.
Why it matters
With millions of EV batteries approaching retirement this decade, second life determines whether they become a waste problem or a storage resource. It is a concrete test of circular design: batteries engineered for disassembly and data transparency capture far more second-life value.