Battery packs are created by connecting individual battery cells in specific arrangements to achieve the desired voltage and energy capacity. These connections are made in series and in parallel.
Understanding Series and Parallel Connections
The connection type determines how the voltage and current are combined:
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Series Connection: Cells are connected end-to-end.
- Increases the overall voltage.
- Current remains the same across all cells.
- Example: If three 3-volt cells are connected in series, the total voltage is 9 volts.
-
Parallel Connection: Cells are connected side-by-side.
- Increases the overall current capacity (amp-hours or Ah).
- Voltage remains the same.
- Example: If three cells with a 2 Ah capacity are connected in parallel, the total capacity is 6 Ah.
How Battery Packs are Built
Battery packs use a combination of series and parallel connections within modules:
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Individual Cells: The basic units of a battery.
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Modules: Groups of cells connected in series and/or parallel. The modules function as serviceable units.
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Packs: Modules are further connected to achieve the final voltage and capacity for the application.
- For example, an electric car needs a high voltage (e.g., 400-800 volts). Because a single cell only offers about 3-4 volts, battery cells must be connected in series to reach the required voltage.
- These series-connected cells are often arranged in modules and then connected in parallel to other such modules to increase the capacity.
- This modular construction provides flexibility and easier maintenance.
Example: Electric Vehicle Battery Pack
| Component | Connection | Purpose |
|---|---|---|
| Individual Cell | - | Basic energy storage unit |
| Module | Cells in Series and/or Parallel | Reach a usable voltage and current capacity |
| Pack | Modules in Series and/or Parallel | Achieve the necessary voltage and total capacity for the vehicle |
In an electric car, many individual cells are connected in series within modules to reach a high voltage. Then, several modules are interconnected, often also in parallel, to achieve the final energy capacity the vehicle needs.
