Battery knowledge · Units and electrical basics
Kilowatt-hour
One thousand watt-hours, the unit for pack and system energy. An electric car carries 40–100 kWh; grid storage is quoted in megawatt-hours (1000 kWh) and factory output in gigawatt-hours per year. [1]
- Abbreviation
- kWh
- Unit
- kWh
Example
From charge to energy
5 Ah × 12 V = 60 Wh nominal energy.
Specific energy divides energy by mass; energy density divides it by volume.
Explore the graph
Voltage connects capacity in ampere-hours to nominal energy in watt-hours.
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
Lemonergy Core equation
Estimate nominal energy
Lemonergy Core evaluates this relation.
Equation or tool to use
- nominal_energy_wh
Core equation
Inputs & settings
- Capacity (Ah)
- Nominal voltage (V)
This overview identifies the components to use. Follow the example in Lemonergy for their connections and settings.
- Open the lesson and inspect the equation.
- Change one input while holding the others fixed.
Example. A 5 Ah cell rated 3.6 V has 18 Wh nominal energy. Ten identical cells contain 180 Wh nominally.
Observe. Compare the result with the equation and units.
This is a rating estimate, not integrated delivered terminal energy.
Open the worked lesson →References & further reading
Technical references
- The International System of Units (SI), 9th edition
Bureau International des Poids et Mesures · 2026
Technical reference · Definitions of SI units and coherent derived units; 2026 revision.