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Battery pack calculator: series, parallel, energy and C-rating current

Series adds voltage, parallel adds capacity, and the C rating sets the current limit. Enter the cell and the layout to get the pack figures.

Nominal voltage: – V (full: – V)Capacity: – AhEnergy: – WhMax continuous current: – A

Use the continuous rating from the cell datasheet, not the peak. Keep margin, and use a proper battery management board.

How it is calculated

Pack voltage = cells in series × cell voltage. Pack capacity = cells in parallel × cell capacity. Energy in Wh = nominal voltage × capacity. Maximum continuous current = capacity in Ah × C rating.

A worked example

A 3S2P pack of 2.5 Ah cells at 3.7 V nominal gives 3 × 3.7 = 11.1 V nominal (12.6 V full), 2 × 2.5 = 5 Ah and 11.1 × 5 = 55.5 Wh. With a 10C rating the limit is 5 × 10 = 50 A.

Common mistakes

  • Treating the full-charge voltage as the working voltage.
  • Using the peak C rating as the continuous one.
  • Mixing old and new cells in one pack.

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Last reviewed: November 2026. The calculator runs in your browser and sends nothing anywhere. Results are ideal-case figures; add margin before you order parts.