EngineerBenchSeries and parallel battery-pack calculations
Series connections add cell voltage; parallel groups add amp-hour capacity. A pack described as 4S2P has four series groups with two cells in each group. This tool checks a proposed arrangement or rounds series and parallel counts up to meet entered nominal voltage and capacity targets.
Nominal voltage is not the full operating range
The calculation uses the nominal cell voltage you enter. Fully charged and discharged voltages can differ substantially from that value. Check both against the equipment, charger, and battery-management system instead of using nominal voltage as their limit.
What the current estimate leaves out
The resistance input gives a simplified loaded-voltage estimate. Cell matching, interconnect resistance, cooling, fusing, charging, and fault protection need separate design work. The calculated arrangement is pack arithmetic, not a construction plan or approval to assemble cells.
Checking cell count and nominal energy
For cells rated at 3.6 V and 3 Ah, a 4S2P arrangement contains eight cells and has a nominal rating of 14.4 V and 6 Ah. Multiplying those values gives 86.4 Wh, equal to the sum of the cells' nominal energies. Series count changes voltage; parallel count changes available charge at that voltage. They do not create energy beyond the cells included.
When the sizing mode rounds cell counts upward, examine the achieved voltage as well as capacity. A rounded series count may not suit a device whose allowable voltage window is narrow. Compare maximum charge voltage and minimum operating voltage using the actual cell specification, not the nominal result. The loaded-voltage estimate assumes the entered resistance model and does not describe every cell chemistry or protection response. Cells connected together must be suitable for that arrangement, and current sharing cannot be assumed merely from the arithmetic. Keep this worksheet separate from the electrical, thermal, mechanical, and protection design of a pack.
Formula
Series adds voltage; parallel adds capacity. Constant-power current solves P = I(V − IR).