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Battery knowledge · Units and electrical basics

Kirchhoff’s laws

Two rules of circuit analysis: the currents flowing into any node sum to zero, and the voltages around any closed loop sum to zero. In a pack they explain why every cell in a series string carries the same current, and why cells in a parallel group share current unequally when their resistances differ.

Also called
Kirchhoff’s current law, Kirchhoff’s voltage law, KCL, KVL
Relationship
ΣI = 0 at a node; ΣV = 0 around a loop

Example

Balance a parallel junction

If 6 A enters a junction and 2 A leaves through one branch, 4 A must leave through the other branch in a steady circuit. Voltage differences around a closed loop must also sum to zero.

Explore the graph

Count series and parallel connections separately.

Voltage along one series string
Voltage along one series stringSeries cells versus Voltage (V). 3.7 V per cell. Interpretation follows the graphs.0011.1322.2633.3944.412Series cellsVoltage (V)
3.7 V per cell
Capacity from parallel cells
Capacity from parallel cellsParallel cells versus Capacity (Ah). 5 Ah per cell. Interpretation follows the graphs.007.51.515322.54.5306Parallel cellsCapacity (Ah)
5 Ah per cell

4S2P: 8 cells, 14.8 V, 10 Ah, 148 Wh.

V_pack = Ns V_cell; Q_pack = Np Q_cell

Illustrative model. Identical 3.7 V, 5 Ah cells; ideal equal current sharing and no losses.

Use in Lemonergy

Lemonergy Studio blocks

Relate current and voltage

Conserving components solve constitutive relations and node balance.

Blocks to use

  1. Controlled voltage source

    Supplies voltage

    Inputs & settings
    • voltageV
  2. Resistor

    Relates current and voltage

    Inputs & settings
    • resistanceOhm
  3. Electrical reference

    Sets zero potential

    Inputs & settings
    • Connect p to reference net

This overview identifies the components to use. Follow the example in Lemonergy for their connections and settings.

  1. Inspect source and resistor in the RC example.
  2. Compare branch current with resistor voltage.

Example. A 1 V drop across 2 Ω implies 0.5 A.

Observe. Topology sets individual element voltages.

The RC example includes a capacitor: transient current varies and source voltage is not always resistor voltage.

Open the electrical circuit →

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.

Corrections or a better reference? Contact Lemonergy.

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