Cell datasheets list single-cell V and Ah; your inverter and fuse chart need pack-level numbers. Use this guide to calculate battery pack voltage and capacity from series and parallel strings before wiring a DIY or rack-mounted bank.
Benefits
- Derives pack voltage from series cell count and nominal V.
- Derives pack amp-hours from parallel strings and cell Ah.
- Combines V × Ah into watt-hours for load and runtime planning.
How it works
- Note per-cell nominal voltage and amp-hour rating from the datasheet.
- Count series cells per string and parallel strings in the bank.
- Read calculated pack V, pack Ah, and total Wh at the main bus.
FAQ
How do I calculate battery pack voltage and capacity?
Pack voltage = cells in series × cell voltage. Pack capacity (Ah) = strings in parallel × cell Ah. Example: 4S2P with 3.2 V 280 Ah cells → 12.8 V pack, 560 Ah pack capacity, 7,168 Wh. Series sets V; parallel sets Ah.
Is pack capacity the same as cell capacity?
Only when P = 1 (one string). Each added parallel string sums amp-hours at the same voltage. A 16S4P layout quadruples Ah versus 16S1P but keeps the same series voltage—verify your BMS and charger match that bus V.
Nominal vs. full-charge voltage—which do I use?
Use nominal (e.g. 3.2 V LiFePO4, 3.7 V NMC) for planning Ah × V energy and runtime. Use max charge voltage per cell × series count when sizing chargers and BMS high-voltage cutoff—not the same number, but both come from the same S count.
Technical specifications
- Pack_V = S × cell_nominal_V.
- Pack_Ah = P × cell_Ah.
- Pack_Wh = Pack_V × Pack_Ah.
- Use matched cells within each parallel string.
- Related: battery-series-parallel, battery-energy, battery-bank-size.