Series strings raise voltage; parallel strings raise amp-hours. This battery series and parallel calculator turns cell specs and your S/P layout into total V, Ah, watt-hours, and a configuration tag before you order cells or a BMS.
Benefits
- Pack V = series count × cell voltage.
- Pack Ah = parallel count × cell Ah.
- Wh = total V × total Ah with an S×P configuration label.
How it works
- Enter how many cells are in series per string (S).
- Enter how many identical strings run in parallel (P).
- Add nominal cell voltage and cell Ah—read pack V, Ah, Wh, and nSnP.
FAQ
How does a battery series and parallel calculator work?
Multiply series count by cell voltage for pack voltage. Multiply parallel count by cell amp-hours for pack Ah. Pack Wh = V × Ah. Example: 4S2P with 3.2 V 100 Ah LiFePO4 cells → 12.8 V, 200 Ah, 2,560 Wh, labeled 4S2P.
What does 4S2P mean?
Four cells in series per string (4S) and two strings wired in parallel (2P). Voltage follows the series count; capacity follows the parallel count. The calculator prints this label from your inputs so BOM and BMS orders match the physical layout.
Must all cells match in a series-parallel pack?
Yes—use matched capacity and age within each parallel string, and a BMS rated for your series count. Mixing old and new cells in parallel causes imbalance and early cutoff. Re-run the calculator when you change S or P before buying interconnects.
Technical specifications
- Pack V = S × cell_V.
- Pack Ah = P × cell_Ah.
- Pack Wh = pack_V × pack_Ah.
- Configuration = {S}S{P}P (e.g. 4S2P).
- Related: battery-series-parallel, battery-bank-size, battery-energy, ah-to-wh.
Series adds volts, parallel adds amp-hours
Wiring cells in series stacks voltage—four 3.2 V LiFePO4 cells become 12.8 V at the same per-string amp-hours. Paralleling two matched strings doubles amp-hours while voltage stays at the series total. A battery series and parallel calculator applies both rules in one step so you do not manually multiply twice before checking watt-hours.
Wh captures the finished pack energy
Voltage and amp-hours trade off, but energy in watt-hours is what runtime and inverter sizing care about. After S and P resolve pack V and Ah, multiply for Wh. A 4S2P 100 Ah 3.2 V block is 2,560 Wh whether you think in cells or strings—document that figure on interconnection sketches and fuse worksheets.
Match the BMS and bus to your nSnP label
The configuration tag—4S2P, 16S1P, 7S4P—must match how cells are physically wired and how the BMS counts series groups. Use the calculator early in DIY bank design, then verify fuse rating, charger voltage, and inverter DC input against the printed pack voltage. Pair with Battery Bank Size when C-rate or maximum parallel strings constrain the layout.