Battery knowledge · Units and electrical basics
Power
The rate at which a cell delivers or absorbs energy: voltage times current, in watts. Power is limited by internal resistance and temperature long before capacity runs out. [1]
- Unit
- W
- Relationship
- P = V × I
Example
Separate power from energy
A 100 W load running for 30 min uses 50 Wh. Power tells you how fast energy is transferred; the duration determines how much energy is transferred.
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 Studio blocks
Compare grid and battery energy
Separate energy and loss signals make efficiency visible.
Blocks to use
- Regulated CC/CV charger
Regulates current and voltage
Inputs & settings
- currentA
- voltageV
- cutoffCurrentA / cutoffHoldS
- Electrical ports p and n
- Battery with SOC-dependent OCV
Stores charge and supplies terminal voltage
Inputs & settings
- capacityAh
- initialSoc
- emptyVoltageV / fullVoltageV
- resistanceOhm
- Electrical ports p and n
This overview identifies the components to use. Follow the example in Lemonergy for their connections and settings.
- Keep battery settings fixed.
- Change converter efficiency.
Example. 7 kW battery-side power at 95% efficiency requires about 7.37 kW grid power and produces about 0.37 kW converter loss.
Observe. Battery I²R loss differs from converter loss.
A loss signal is not a predicted temperature. This network takes external temperature.
Open the Studio example →Lemonergy Studio blocks
Tabulated fuel-cell stack worked example
Interpolated polarization table with explicit out-of-table diagnostic.
Blocks to use
- Tabulated fuel-cell stack
Linearly interpolates a current-to-stack-voltage polarization table and reports power. An in-range output distinguishes interpolation from operation beyond the supplied current domain.
Inputs & settings
- Use the parameter values in the block reference.
- Bundled example verified on the production release of 28 October 2026.
This overview identifies the components to use. Follow the example in Lemonergy for their connections and settings.
- Review the block inputs, units and model limits.
- Open the Studio example and run its bundled model.
- Compare the output channels with the numerical checks; change one input and run again.
Example. Use the defaults below with Stack current = 1.5 A. At 0 s, Stack voltage is 4.6 V. Additional checks are listed below.
Observe. Inspect the outputs and numerical checks on the block reference page.
This static table has no gas, thermal, pressure or electrochemical states. A measured polarization curve is required for a particular stack. The example verifies numerical behavior for synthetic parameters. Cell characterization and validation for an intended use are separate tasks.
Open Studio example →Lemonergy Studio blocks
Pulse power capability worked example
Quasi-static voltage/current/SOC envelope for an explicit prediction horizon.
Blocks to use
- Pulse power capability
Combines a constant open-circuit voltage, effective resistance, voltage/current limits and available charge over a prediction horizon. It returns separate charge and discharge current and terminal-power magnitudes.
Inputs & settings
- Use the parameter values in the block reference.
- Bundled example verified on the production release of 28 October 2026.
This overview identifies the components to use. Follow the example in Lemonergy for their connections and settings.
- Review the block inputs, units and model limits.
- Open the Studio example and run its bundled model.
- Compare the output channels with the numerical checks; change one input and run again.
Example. Use the defaults below with Open-circuit voltage = 3.8 V, Effective pulse resistance (ohm) = 0.1 1, State of charge = 0.5 1 (fraction). At 0 s, Discharge-current limit is 5 A. Additional checks are listed below.
Observe. Inspect the outputs and numerical checks on the block reference page.
This is a quasi-static bound. It excludes polarization dynamics, temperature evolution and weakest-cell limits in a pack. The example verifies numerical behavior for synthetic parameters. Cell characterization and validation for an intended use are separate tasks.
Open Studio example →Studio interfaces connected to this concept
These components declare this quantity or operation. Their individual pages distinguish authoring metadata from numerical verification.
- AC current source
- AC voltage source
- Active cell supervision interface
- Multi-cell balancing interface
- Energy counter
- Tabulated fuel-cell stack
- Battery heater controller
- Battery with SOC-dependent OCV
- Passive cell balancer
- Reduced PEM fuel-cell stack
- Pulse power capability
- SOE adaptive EKF
- SOE adaptive EKF with capacity input
- SOE EKF
- SOE EKF with capacity input
- Battery: resistance and charge state
- Energy counter with capacity input
- Bidirectional grid / load interface
- Capacitor
- Charging schedule and target policy
- Delayed contactor with declared fault mode
- Converter loss
- Current-controlled current source
- Current sensor / signal adapter
- Controlled current source
- DC motor with shaft coupling
- Piecewise-linear diode
- Edge-cooled plate
- Electrical gyrator
- Controlled electrical switch
- Independent electrothermal battery
- Electrothermal resistor
- Scheduled import / export and load policy
- Suction fan
- Capacitive floating reference
- Finite-slip friction brake
- Fan pressure curve and power
- Ideal transformer
- Inductor
- Open branch with initial voltage target
- Ideal linear motor coupler
- Bounded drift memristor
- Coupled inductors
- Finite-gain operational amplifier
- SOC and temperature limited signed power boundary
- Parallel-channel plate
- Passive cell supervision interface
- Limited P/V electrical load
- Regulated CC/CV charger
- Resistor
- Ideal rotational motor coupler
- Physical signal integrator
- Shared site power allocator
- Average bidirectional source converter
- Axial suspension spring and damper
- Voltage-controlled current source
- Current-controlled voltage source
- Combined-slip tyre and compliant road contact
- U-channel plate
- Conserving vehicle-to-vehicle converter
- Electromechanical variable-gap capacitor
- Controlled resistor
- Voltage-controlled voltage source
- Controlled voltage source
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.