Grade A, B and C: How We Classify Second-Life Modules

A module's grade starts with measured capacity against its rating, but capacity alone is not enough. Internal resistance and its spread across the cells inside the module show how evenly the module will age, and a module with good capacity but a wide spread is a weaker candidate. Physical inspection completes the picture: swelling, corrosion, damaged welds or signs of coolant ingress can disqualify an otherwise healthy module.

Grades are therefore assigned on a combined basis. A module must meet the capacity band and fall within the resistance limits for that band, and it must pass inspection. Where results sit close to a boundary, the conservative grade is applied, because buyers rely on the grade to size systems and set warranties.

Grade A modules retain the most capacity and the most consistent behaviour, so they go into applications that cycle daily, such as grid-tied or commercial storage and EV charging buffers. Grade B modules suit applications with lighter or less frequent cycling, including telecom tower backup and solar self-consumption systems, where some derating is acceptable.

Grade C modules still have useful life in low-power, low-cycle roles such as standby power or small off-grid systems. Grade D material, below 65% or with physical defects, is not suitable for reuse and is released to recycling. Keeping those boundaries firm protects the reputation of second-life products and the safety of the systems they end up in.

Grading whole packs would waste value. Most retired packs contain a spread of module health, and a pack-level average would push good modules into a lower grade and weak modules into applications they cannot sustain. Module-level grading lets each unit earn its own route and lets matched modules be combined into new systems.

Each graded module keeps its serial number, test results and grade in a record that follows it into its next use. That record supports warranties, gives system integrators confidence in what they are buying and, where regulation requires it, supports battery passport and traceability obligations for repurposed batteries.