Battery knowledge · Capacity, energy, power and ratings
Peukert’s law
An empirical rule that delivered capacity falls as a power of the discharge current, with an exponent of 1.1–1.3 for lead–acid. For lithium-ion the exponent is close to 1, so the law is rarely used.
- Relationship
- t = H·(C/(I·H))^k
Example
Compare ideal and Peukert durations
Consider a hypothetical lead-acid rating of 100 Ah at the 20 h rate, with k = 1.2. At 10 A, t = 20 × (100/(10 × 20))^1.2 gives about 8.7 h, rather than the ideal 10 h.
Interpretation & limits
- The exponent must be fitted to the battery and test conditions; do not transfer this example to lithium-ion cells.
Explore the graph
An empirical exponent changes the ideal inverse-current duration.
At 5 A the ideal duration is 2 h; the chosen exponent gives 1.45 h (7.248 Ah delivered).
t = H [C / (I H)]ᵏ
Illustrative model. Not fitted cell data. A Ragone plot compares specific power and specific energy across measured or modeled conditions.
Use in Lemonergy
Separate nameplate ratings from test results.
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.
- The International System of Units (SI), 9th edition
Bureau International des Poids et Mesures · 2026
Topic background · Definitions of SI units and coherent derived units; 2026 revision.
- 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.