Free EV tool
EV Battery Pack Calculator
Pick a cell, set the pack voltage and energy you need, and get the series–parallel configuration (e.g. 15S9P), cell count, voltage window, capacity, weight and current limit — the first sheet of every pack design.
Configuration
15S9P
135 cells
Pack energy
2.59 kWh
2.33 kWh usable
Nominal voltage
48 V
Voltage window
37.5–54.8 V
cut-off to full
Capacity
54 Ah
Cell mass
18.9 kg
pack ≈ 25–32 kg
Max continuous
162 A
≈ 7.8 kW
Cell energy density
137 Wh/kg
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Battery pack design sheet
Battery Pack Calculator ·
Inputs
| Chemistry | LFP (LiFePO₄) |
| Target | 48 V, 2.5 kWh |
| Cell | 3.2 V (2.5–3.65 V), 6 Ah, 140 g, 18 A |
| Usable DoD | 90 % |
Results
| Configuration | 15S9P (135 cells) |
| Nominal / window | 48 V / 37.5–54.8 V |
| Capacity / energy | 54 Ah / 2.59 kWh (2.33 usable) |
| Mass | cells 18.9 kg, pack ≈ 25–32 kg |
| Max continuous | 162 A ≈ 7.8 kW |
- Check the charger, BMS and motor controller all accept the voltage window.
- Derate cell current for temperature and ageing; keep cells within the datasheet's charge and discharge temperature limits.
Estimates for planning — verify against datasheets and supplier quotes before you build or invest. Recalculate or share:
Learn to design this hands-on: emobility.academy/courses
How it's calculated
Series count (S) = target voltage ÷ cell nominal voltage, rounded to the nearest whole cell. Series cells add voltage; the pack's maximum and minimum voltage are S × the cell's charge and cut-off voltages, which your charger, BMS and motor controller must all accept.
Parallel count (P) = target energy ÷ (pack nominal voltage × cell Ah), rounded up. Parallel cells add capacity (Ah) and current capability.
Energy (kWh) = S × P × cell voltage × cell Ah ÷ 1000. Usable energy is that times the depth of discharge your BMS allows (90 % is common for LFP, 80–90 % for NMC).
Weight: cell mass × cell count. Cells are usually 60–75 % of a finished pack's mass — the rest is busbars, BMS, thermal parts and enclosure — so the pack-mass range is the cell mass ÷ 0.75 to ÷ 0.6.
Max continuous current = P × the cell's continuous discharge rating. Divide your peak motor power by pack voltage to check you are inside it.
Results are engineering estimates for planning and learning. Check them against datasheets, supplier quotes and the applicable standards before you build or invest.
Frequently asked questions
What does 16S2P mean in a battery pack?
16S2P means 16 cells (or cell groups) in series and 2 in parallel — 32 cells in total. Series multiplies voltage (16 × 3.2 V = 51.2 V for LFP) and parallel multiplies capacity (2 × the cell's Ah).
How many 18650 or 21700 cells do I need for a 48 V 30 Ah pack?
With 3.6 V NMC cells, 48 V needs 13 in series (46.8 V nominal, 54.6 V full). With 5 Ah 21700 cells, 30 Ah needs 6 in parallel: 13S6P = 78 cells. With 2.5 Ah 18650 cells it would be 13S12P = 156 cells.
LFP or NMC for an EV battery?
LFP (3.2 V nominal) is safer, cheaper and lasts 2,000–6,000 cycles but stores less energy per kg; most Indian 2W/3W fleets and buses use it. NMC (3.6–3.7 V) is lighter for the same kWh, which matters for range-sensitive cars and premium scooters.
Why is my calculated pack energy a bit higher than I asked for?
Cells come in whole numbers, so the parallel count is rounded up. The calculator shows the energy of the pack you would actually build.
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