How NMC 811 (4680) loses capacity
Fade mechanisms mirror other NMC 811 cells. The tabless design lowers internal resistance and heat generation, which can slow resistance growth relative to older cylindrical formats.
At about 296 Wh/kg and a nominal 3.7 V per cell, NMC 811 (4680) sits in a specific trade-off between energy density and durability that shapes how it ages in service.
Finding the knee before it finds you
Field data on end-of-life 4680 packs is still limited because the format is young. Grading therefore leans heavily on impedance measurement rather than assumptions from older fleets.
The practical test is trend rather than a single reading: a module whose resistance is rising faster than its neighbours is heading for the knee, even if its capacity still looks healthy today.
| Measured SOH | Grade | Typical route |
|---|---|---|
| 85% and above | A | Grid-tied or commercial storage |
| 75–85% | B | Telecom backup, solar buffering |
| 65–75% | C | Low-duty backup, short warranty |
| Below 65% | D | Discharge and refining |
Signals worth tracking in the field
Fleet telematics can flag packs that are ageing faster than the rest of the fleet long before they retire. Pairing that data with a bench test at retirement makes grading faster and pricing more accurate.
- Usable capacity at a standard rate and temperature
- DC internal resistance per module
- Impedance spectrum shape from EIS sweeps
- Self-discharge over a rest period
- Temperature history and fast-charge share