Battery knowledge · Testing methods
Laser flash analysis
Firing a brief laser pulse at one face of a thin disc and timing the temperature rise on the far face with an infrared detector, which gives thermal diffusivity. Multiplying by density and specific heat yields thermal conductivity — the through-plane value for electrodes, separators and layered cell samples.
- Abbreviation
- LFA
- Also called
- laser flash method, flash method
- Relationship
- α = 0.1388·L² / t½; k = α·ρ·c_p
Example
Convert a half-rise time into diffusivity
For an ideal 1 mm slab with a rear-surface half-rise time of 0.10 s, α = 0.1388L²/t½ gives 1.388×10⁻⁶ m²/s. Heat loss, finite pulse duration and material anisotropy can require corrections.
Explore the graph
The characteristic spreading time grows with thickness squared; ideal laser-flash half-rise time has a different coefficient.
Thermal diffusivity is 1 mm²/s. At 5 mm, L²/α = 25 s and the ideal half-rise time is 3.47 s.
α = k/(ρc_p); t_characteristic = L²/α; t_half = 0.1388 L²/α
Illustrative model. Laser-flash coefficient assumes a homogeneous slab, instantaneous uniform pulse and negligible heat loss. L²/α is a characteristic scale, not an exact equilibration time.
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.
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.
- 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.