Lithium Battery Pack Calculator
A lithium battery pack calculator helps you estimate the main pack specifications from a cell’s chemistry, voltage, capacity, and series-parallel layout. This is useful for custom battery builds, solar storage, backup systems, e-bikes, power tools, and electronics projects where you need a quick pack-level view before moving into detailed design.
This page calculates nominal pack voltage, pack capacity in amp-hours, total stored energy in watt-hours and kilowatt-hours, estimated pack weight, and total cell count. It also explains how series count changes voltage, how parallel count changes capacity, and why the same energy can be reached with different S/P layouts depending on the cells you use.
Short answer: Pack voltage equals cell voltage multiplied by series count, pack capacity equals cell capacity multiplied by parallel count, and total pack energy equals pack voltage multiplied by pack amp-hours.
Lithium Pack Specification Calculator
Estimate lithium pack voltage, Ah, Wh, kWh, weight, and total cell count from chemistry and S/P configuration
Pack Calculator Inputs
Cell Chemistry
Choose Li-ion, LiFePO4, or LiPo, or enter a custom cell. Chemistry mainly changes nominal voltage and typical use case.
Cell Specs
Enter the single-cell nominal voltage and capacity. These are the building blocks for the full battery pack calculation.
Series and Parallel
Series count sets pack voltage and parallel count sets pack capacity. The complete layout is usually written as S and P, such as 16S2P or 13S4P.
Outputs
The calculator returns pack voltage, amp-hours, watt-hours, kilowatt-hours, total cell count, and estimated pack weight.
How the Pack Math Works
The pack formulas are straightforward:
Pack Voltage = Cell Voltage × Series Count
Pack Capacity (Ah) = Cell Capacity × Parallel Count
Pack Energy (Wh) = Pack Voltage × Pack Capacity
Total Cells = Series Count × Parallel Count
Once you know those four numbers, you can estimate most basic pack specifications very quickly. Weight is usually estimated by multiplying the number of cells by the weight of one cell, though real finished packs will also include a BMS, busbars, wiring, compression hardware, and outer casing.
Example Pack Calculations
| Pack | Nominal Voltage | Capacity | Energy |
|---|---|---|---|
| 4S1P LiFePO4 | 12.8V | 100Ah | 1280Wh |
| 8S2P LiFePO4 | 25.6V | 200Ah | 5120Wh |
| 16S1P LiFePO4 | 51.2V | 100Ah | 5120Wh |
| 13S4P 18650 | 48.1V | 14Ah | 673Wh |
These examples show how different pack layouts can produce very different voltage and capacity combinations, even when total energy ends up similar. For example, 8S2P LiFePO4 and 16S1P LiFePO4 can both reach 5120Wh when the underlying cell specs are adjusted the right way.
Common Pack Types
Li-ion Packs
Li-ion cells are often around 3.7V nominal and are common in 18650 and 21700 pack designs for tools, e-bikes, and electronics.
LiFePO4 Packs
LiFePO4 cells are usually around 3.2V nominal and are widely used in solar storage, RV, marine, backup, and off-grid battery banks.
LiPo Packs
LiPo cells are also around 3.7V nominal but are packaged differently and are common in drones, RC vehicles, and lightweight high-discharge applications.
48V-Class Systems
Many so-called 48V lithium packs are actually around 51.2V nominal when built as 16S LiFePO4, which is standard in many storage systems.
Practical warning: Pack math gives only the basic electrical picture. A real pack must also be designed around current demand, BMS limits, thermal control, mechanical layout, fuse protection, and cell matching.
Pack Energy in Wh and kWh
Total energy is one of the most important pack outputs because it tells you how much work the battery can theoretically deliver. Watt-hours are useful for device runtime planning, while kilowatt-hours are easier to read for larger storage systems.
For example, a 48V 200Ah battery pack stores 9600Wh, which equals 9.6kWh. That conversion is why battery packs for home storage, solar backup, and off-grid systems are often compared in kWh instead of only in amp-hours.
Practical rule: Use Ah for cell and pack labeling, but use Wh or kWh when comparing total stored energy across different voltages.