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Battery knowledge · Capacity, energy, power and ratings

E-rate

Power divided by nominal energy, the energy-based cousin of the C-rate: a 1E discharge empties a cell’s watt-hours in one hour. Grid-storage contracts are often written in E-rates or hours of discharge rather than in amperes.

Also called
P-rate
Unit
h⁻¹
Relationship
E-rate = P / E_nominal

Example

Convert energy rating to power

A 20 kWh battery delivering 10 kW operates at 0.5 h⁻¹, conventionally 0.5E. At constant power with ideal full energy availability, the corresponding duration is 2 h.

Explore the graph

Voltage connects capacity in ampere-hours to nominal energy in watt-hours.

Nominal energy versus capacity
Nominal energy versus capacityCapacity (Ah) versus Energy (Wh). 12 V rating. Interpretation follows the graphs.00605120101801524020Capacity (Ah)Energy (Wh)
12 V rating

5 Ah × 12 V = 60 Wh nominal energy.

E_nominal = Q_nominal V_nominal; actual energy = ∫ VI dt

Illustrative model. Specific energy divides energy by mass; energy density divides it by volume.

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.

  1. 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.

  2. 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.

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