Relaxation

Example

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Use in Lemonergy

Connected concepts

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Diffusion

The net movement of a species from where it is concentrated to where it is scarce, driven by random thermal motion. In a cell lithium diffuses through the electrolyte in the pores and, far more slowly, through the solid particles themselves.

Hybrid pulse power characterisation

A test that applies a short discharge pulse and a short charge pulse at each state of charge, from which resistance and power capability are read as a function of SOC. It is the standard source of equivalent-circuit parameters.

Open-circuit voltage

The voltage across a cell’s terminals when no current flows and the cell has rested long enough for the voltage to settle. It depends on state of charge and temperature, and a cell whose open-circuit voltage falls unusually fast in storage may have an internal short.

Polarization

The gap between a cell’s terminal voltage under load and its open-circuit voltage. It has ohmic, charge-transfer and concentration parts, grows with current and falling temperature, and is where delivered energy is lost.

Voltage relaxation analysis

Extracting diagnostic information from the way a cell’s voltage settles during a rest. After fast charging, a plateau in the relaxing voltage — a peak in dV/dt — reveals plated lithium re-entering the graphite; features of the relaxation curve also track capacity fade, and a rest voltage that keeps drifting down points to self-discharge.

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.

1. Lithium-ion battery fast charging: A review

   Anna Tomaszewska et al. · eTransportation · 2019

   Topic background · CC-CV and alternative charging protocols, transport limitations, degradation and thermal implications; results depend on cell and test conditions. Software behavior is documented separately in Lemonergy block references.