Battery knowledge · State estimation
Weakest cell
The cell in a series string that reaches a voltage limit first — through lower capacity, higher resistance or a different SOC — and so sets the usable capacity and power of the whole pack. Balancing can correct an SOC offset but not a capacity deficit, so one weak cell among hundreds retires the pack early unless replaced.
- Also called
- limiting cell, weakest link
Example
The limiting cell matters
Average: 3.93 V. Highest cell: 4.02 V. The highest cell can reach the charge limit first.
The 4.2 V ceiling is an example, not universal. Voltage alone does not uniquely determine SOC.
Explore the graph
A pack average can hide a cell that reaches its voltage limit first.
Average: 3.93 V. Highest cell: 4.02 V. The highest cell can reach the charge limit first.
V_max = max(V₁, V₂, …); V_average = ΣV_i / N
Illustrative model. The 4.2 V ceiling is an example, not universal. Voltage alone does not uniquely determine SOC.
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.