OCV test

Example

Explore the graph

Use in Lemonergy

Record specimen, state, instrument, temperature and timing.

This is a reference concept. No executable Lemonergy block has been verified for this term.

Connected concepts

Related concepts from the knowledge graph. Connections show context, not cause and effect. Hover or focus a linked term for its definition.

Galvanostatic intermittent titration technique

A series of short constant-current pulses each followed by a long rest, so that both the equilibrium voltage curve and the solid diffusion coefficient can be extracted at each state of charge. It is slow, often days per cell, and a staple of parameterisation.

OCV–SOC curve

The characteristic relation between a cell’s open-circuit voltage and its state of charge, measured once at low current and stored in the BMS. A steep curve, as for NMC, makes SOC easy to read from voltage; LFP’s flat curve does not.

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.

Relaxation

The slow recovery of a cell’s voltage towards open-circuit voltage after current stops, as concentration gradients inside the electrodes level out. It takes minutes to hours, which is why OCV measurements need a rest period.

Voltage hysteresis

The difference between the open-circuit voltage reached from charging and from discharging at the same state of charge. It is small for most lithium-ion chemistries but large for LFP and silicon, and it limits how precisely voltage can give SOC.

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. Battery Test Manual For Electric Vehicles, Revision 3

   Jon P. Christopherson · Idaho National Laboratory · 2015

   Topic background · Performance characterization, pulse resistance/power, life testing and reference performance tests; historical 2015 edition.