Battery knowledge · State estimation
State of capacity
The charge a cell or pack can still hold, as a percentage of its rated or beginning-of-life capacity: the capacity half of state of health. A cell measured at 82 Ah against a 100 Ah rating has an SoQ of 82 %, and the usual 80 % end-of-life convention is written against it.
- Abbreviation
- SoQ
- Also called
- SOH-C, capacity retention
- Unit
- %
- Relationship
- SoQ = Q_now / Q_rated × 100 %
Example
Compare current and reference capacity
If present available capacity is 45 Ah and the selected rated reference is 50 Ah, SoQ is 90%. The reference temperature, current and voltage window belong with the number.
Explore the graph
Energy capability and power capability can degrade differently.
At the illustrated endpoint: 80% initial capacity and 140% initial resistance.
Capacity ratio = Q_now/Q_initial; resistance ratio = R_now/R_initial
Illustrative model. Chosen qualitative trends. The exposure axis is not predicted cycles or years.
Use in Lemonergy
Distinguish internal states from noisy measurement estimates.
This is a reference concept. No executable Lemonergy block has been verified for this term.
References & further reading
Further reading on this topic
These sources provide broader context; they are not presented as citations for every statement in this entry.
- Extended Kalman filtering for battery management systems of LiPB-based HEV battery packs: Part 3. State and parameter estimation
Gregory L. Plett · Journal of Power Sources · 2004
Topic background · Model-based battery state-of-charge and parameter estimation with extended Kalman filtering, including uncertainty and model dependence.
- Extended Kalman filtering for battery management systems of LiPB-based HEV battery packs: Part 2. Modeling and identification
Gregory L. Plett · Journal of Power Sources · 2004
Topic background · Battery charge balance, open-circuit voltage, ohmic loss, polarization dynamics and model identification; parameters require cell-specific data.