How NCA Pouch loses capacity
NCA can deliver long life when it is kept in a moderate state-of-charge window, but it is sensitive to high voltage and heat. Swelling from gas generation is a common retirement signal in pouch formats.
At about 272 Wh/kg and a nominal 3.6 V per cell, NCA Pouch 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
The knee can arrive abruptly in cells that have swelled or seen high temperatures, so any pouch stack with visible deformation is excluded from second life regardless of measured capacity.
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