Battery Series/Parallel Calculator

Battery series and parallel configurations allow you to customize voltage and capacity to match your project’s requirements. Understanding these connections is essential for building battery packs, solar systems, and power banks.

Series Connection: Batteries connected end-to-end (positive to negative).

• Total Voltage = V₁ + V₂ + V₃ + ... (voltages add up)
• Total Capacity = same as one battery (capacity stays the same)
• Example: 4 batteries × 3.7V = 14.8V, capacity unchanged

Parallel Connection: Batteries connected side-by-side (positive to positive, negative to negative).

• Total Voltage = same as one battery (voltage stays the same)
• Total Capacity = C₁ + C₂ + C₃ + ... (capacities add up)
• Example: 4 batteries × 2000 mAh = 8000 mAh, voltage unchanged

Series-Parallel Combination: Groups of series strings connected in parallel (or vice versa).

• Total Voltage = Single cell voltage × Series count
• Total Capacity = Single cell capacity × Parallel count
• Common notation: “4S3P” means 4 in series, 3 parallel strings

Energy formula: Energy (Wh) = Total Voltage × Total Capacity (Ah) Energy (Wh) = Number of cells × Single cell voltage × Single cell capacity (Ah)

Common battery voltages:

When to use this calculator:

• Building custom battery packs for electric vehicles, drones, or robotics
• Designing solar power storage systems
• Creating portable power banks
• Planning UPS (uninterruptible power supply) systems

Practical example: A 4S3P 18650 Li-ion pack using 3000 mAh cells: voltage = 4 × 3.7 = 14.8V, capacity = 3 × 3000 = 9000 mAh (9 Ah), energy = 14.8 × 9 = 133.2 Wh. Total cells needed: 4 × 3 = 12.

Tips:

• Always use identical batteries (same brand, model, age) in series/parallel configurations.
• Series connections require a Battery Management System (BMS) for lithium batteries to prevent cell imbalance.
• Never mix old and new batteries — the weakest cell limits the entire pack.
• Parallel connections increase capacity and reduce internal resistance.