Battery Pack Capacity Calculator

3.7 V Total Voltage
3.00 Ah Total Capacity
11.10 Wh Total Energy

What is a Battery Pack Capacity Calculator?

A Battery Pack Capacity Calculator is an essential tool for engineers, hobbyists, and DIY electronics enthusiasts working with lithium-ion (Li-ion), LiFePO4, or Nickel Metal Hydride (NiMH) cells. It allows you to determine the total energy storage, voltage, and capacity of a custom-built battery pack based on how the individual cells are connected.

When building battery packs, cells are connected in Series (S) and Parallel (P) configurations. This tool handles the mathematical conversions required to translate individual cell specifications into the final pack specifications, providing measurements in Volts (V), Amp-hours (Ah), and Watt-hours (Wh).

Understanding Series and Parallel Connections

To use this calculator effectively, it is vital to understand the difference between the two primary wiring methods:

  • Series (S): Connecting cells in series increases the total Voltage. The capacity (Ah) remains the same as a single cell. For example, three 3.7V 3000mAh cells in series (3S) create an 11.1V 3000mAh pack.
  • Parallel (P): Connecting cells in parallel increases the total Capacity. The voltage remains the same as a single cell. For example, three 3.7V 3000mAh cells in parallel (3P) create a 3.7V 9000mAh pack.

How to Calculate Battery Capacity (Wh)

The total energy stored in a battery is measured in Watt-hours (Wh). The formula is:
Energy (Wh) = Total Voltage (V) × Total Capacity (Ah).

Our calculator automates this by taking your cell count and nominal voltage to provide a precise energy rating, which is often required for shipping regulations and determining how long a device will run.

Frequently Asked Questions

Q: What is nominal voltage?
A: Nominal voltage is the average voltage a cell maintains during discharge. For Li-ion, this is typically 3.6V or 3.7V.

Q: Why do I need to know Watt-hours?
A: Watt-hours (Wh) represent the actual work a battery can perform. Many airlines and shipping carriers limit battery sizes based on Wh (usually 100Wh) rather than mAh.

Q: Can I mix different cell types?
A: No. Always use identical cells (same capacity, brand, and age) in a battery pack to prevent dangerous imbalances.