Battery Pack Configuration Calculator

How it is calculated

Cells in series add voltage and cells in parallel add capacity, so the tool finds each count separately and rounds up to whole cells: S = ⌈pack V ÷ cell V⌉ and P = ⌈pack Ah ÷ cell Ah⌉. Total cells are S × P, shown as an nSmP label such as 14S7P. The energy shown is pack V × pack Ah in watt-hours, taken from your target, not from the rounded-up pack. A tiny tolerance is applied before rounding, so an exact ratio such as 20.3 ÷ 2.9 = 7 gives 7 and not 8. Zero or negative inputs show no result. Use the cell's nominal voltage (about 3.6 or 3.7 V for common lithium-ion cells), not its full-charge voltage.

Common mistakes

• Using the cell's full-charge voltage (4.2 V) instead of its nominal voltage (3.6 or 3.7 V). The series count then comes out too low, and the pack will sit under the target voltage in use.
• Reading the energy figure as the energy of the cells you will buy. It is target voltage times target capacity, so the built pack holds more because both counts are rounded up.
• Mixing mAh and Ah. Both capacity fields are in amp-hours, so a 3,000 mAh cell must be entered as 3, not 3000.
• Ignoring the current limit. The tool sizes voltage and capacity only; it does not check whether the cells can supply the discharge current your load draws.
• Entering the pack and cell values in different units for the same quantity, for example a pack capacity in mAh with a cell capacity in Ah. The parallel count then explodes by a factor of 1000.