Battery Series & Parallel Calculator

Calculate battery pack voltage, capacity, energy, and total cell count from series and parallel cell configuration. This calculator is useful for early lithium-ion, LiFePO4, lead-acid, and custom pack sizing work.

Use BAT-007 for full-charge and cutoff voltage windows. Use BAT-008 when you need the complete nominal series-parallel pack relationship between cell voltage, cell capacity, energy, and cell count.

Engineering tool

Battery Series & Parallel Calculator

Calculate battery pack voltage, capacity, energy, total cell count, and recommended series-parallel configuration.

Cell Nominal Voltage

Nominal voltage of one cell.

Cell Capacity

Capacity of one cell before parallel multiplication.

Series Cells

Cells connected in series. Series increases voltage.

Parallel Cells

Cells connected in parallel. Parallel increases capacity.

Battery Pack Parameters

88.8 Wh

Result console

Series count: 4cells
Parallel count: 2cells
Pack voltage: 14.8V
Pack capacity: 6Ah
Pack capacity: 6,000mAh
Pack energy: 88.8Wh
Pack energy: 0.0888kWh
Total cell count: 8cells
Formula used: Vpack = Vcell × Ns; Cpack = Ccell × Np; EWh = Vpack × Cpack

Pack configuration scope

Series cells multiply voltage, parallel cells multiply capacity, and pack energy is nominal voltage multiplied by capacity. This calculator does not model full-charge voltage, cutoff voltage, balancing current, internal resistance, or thermal behavior.

This calculator estimates ideal series and parallel battery pack relationships. Real pack design also requires chemistry-specific limits, cell matching, balancing, BMS protection, wiring, fusing, thermal design, and safety validation.

Formula reference

Battery Series and Parallel Formulas

Series cells multiply voltage, parallel cells multiply capacity, and total energy is nominal pack voltage multiplied by pack capacity.

Vpack = Vcell × NsCpack = Ccell × NpEWh = Vpack × CpackNtotal = Ns × NpNp = Ctarget / CcellNs = Vtarget / Vcell

Variable definitions

Vcell: Nominal voltage of one cell
Ccell: Capacity of one cell
Ns: Number of cells in series
Np: Number of cells or strings in parallel
Vtarget: Target nominal pack voltage
Ctarget: Target pack capacity

Worked Examples

1S1P Pack

Cell voltage = 3.7 V, cell capacity = 3000 mAh, series = 1, parallel = 1

Pack voltage = 3.7 V; capacity = 3000 mAh; energy = 11.1 Wh; total cells = 1

2S1P Pack

Cell voltage = 3.7 V, cell capacity = 3000 mAh, series = 2, parallel = 1

Pack voltage = 7.4 V; capacity = 3000 mAh; energy = 22.2 Wh; total cells = 2

4S2P Pack

Cell voltage = 3.7 V, cell capacity = 3000 mAh, series = 4, parallel = 2

Pack voltage = 14.8 V; capacity = 6000 mAh = 6 Ah; energy = 88.8 Wh; total cells = 8

13S4P Pack

Cell voltage = 3.7 V, cell capacity = 3 Ah, series = 13, parallel = 4

Pack voltage = 48.1 V; capacity = 12 Ah; energy = 577.2 Wh; total cells = 52

Required Parallel Strings

Target capacity = 20 Ah, cell capacity = 3 Ah

Required parallel = 20 Ah / 3 Ah = 6.67, so use 7P when the pack must meet or exceed 20 Ah.

Required 24 V 15 Ah Configuration

Target = 24 V and 15 Ah, cell voltage = 3.7 V, cell capacity = 3 Ah

Series = 24 / 3.7 = 6.49, so 7S; parallel = 15 / 3 = 5P; recommended configuration = 7S5P.

Engineering Notes

Series Connection

Series cells add voltage. The current path flows through each cell in the string, so cell matching and balancing are important.

Parallel Connection

Parallel cells add capacity and current capability, but they must share current safely and should be closely matched.

Battery Pack

A pack is commonly described as NsNp, such as 4S2P or 13S4P, where S is series count and P is parallel count.

Cell Matching

Use cells with the same chemistry, capacity, age, internal resistance, state of health, and manufacturer recommendations.

Pack Capacity

Pack Ah capacity is cell Ah capacity multiplied by parallel count. Series count does not increase Ah capacity.

Pack Voltage

Nominal pack voltage is cell nominal voltage multiplied by series count. Real voltage varies across charge state and load.

Battery Energy

Wh is usually better than Ah for comparing packs at different voltages because energy includes both voltage and capacity.

Total Cell Count

Total cell count is series count multiplied by parallel count. Cell count affects cost, balancing, wiring, and assembly risk.

BMS

A battery management system monitors voltage, current, temperature, faults, and protection thresholds.

Cell Balancing

Balancing helps prevent individual series cells from drifting into unsafe overvoltage or undervoltage states.

Pack Design

Final pack design must consider fault current, fusing, isolation, mechanical restraint, thermal paths, charging, certification, and service safety.

Common Mistakes

Assuming series increases capacity

Series cells increase voltage. The Ah rating of one series string stays the same.

Assuming parallel increases voltage

Parallel cells increase capacity. Voltage stays the same as the cell group voltage.

Confusing Wh and Ah

Ah describes charge capacity. Wh describes energy and includes voltage.

Ignoring cell consistency

Mismatched cells can drift, heat, overcharge, overdischarge, or reduce pack reliability.

Mixing different capacities

Cells with different capacities do not share stress equally and can cause early cutoff or unsafe operation.

Mixing different brands

Brand, model, age, chemistry, and internal resistance differences matter in real battery packs.

Support reference

FAQ

How do series batteries work?

Cells in series add voltage. A 4S pack made from 3.7 V cells has about 14.8 V nominal voltage, while the Ah capacity of one series string stays the same.

How do parallel batteries work?

Cells in parallel add capacity. A 2P group made from 3000 mAh cells has about 6000 mAh capacity, while voltage stays equal to one cell group.

How do I calculate battery pack capacity?

Multiply one-cell capacity by the number of parallel cells or parallel strings. Series count does not increase Ah capacity.

How do I calculate battery pack voltage?

Multiply one-cell nominal voltage by the number of cells in series. Use BAT-007 when you also need full-charge and cutoff voltage.

How do I calculate battery pack energy?

Multiply nominal pack voltage by pack capacity in Ah. The result is watt-hours, or Wh.

How many cells do I need?

Divide target voltage by cell voltage to estimate series count, divide target capacity by cell capacity to estimate parallel count, then round up when the pack must meet or exceed the target.

Can I mix different battery cells?

Mixing different capacities, ages, chemistries, brands, or internal resistances is unsafe and can cause imbalance, overheating, early cutoff, or cell damage.

Why do battery packs require balancing?

Cells in series can drift apart in voltage over time. Balancing helps keep cell voltages within safe limits during charge and discharge.