Battery Pack Designer
The Battery Pack Designer calculates optimal series/parallel cell configurations for lithium battery packs. Enter target voltage and capacity to get cell count, pack energy (Wh), max C-rate, weight, energy density, charging time, and BMS requirements — with 6 real cell presets (18650/21700/prismatic). Interactive configuration visualization that AI cannot replicate. Free, no signup.
Cell Selection
Target Specifications
Pack Design Results
BMS Requirements
EV Range Estimate
14S7P
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What is a Battery Pack Designer?
A Battery Pack Designer calculates the optimal series and parallel configuration of lithium cells to meet target voltage and capacity requirements. Series connections increase voltage (V_pack = N_series × V_cell) while parallel connections increase capacity (C_pack = N_parallel × C_cell). The tool supports major cell formats (18650, 21700, prismatic) and chemistries (NMC, LFP, NCA, LTO), each with different voltage ranges, energy densities, and safety characteristics. It also calculates critical parameters like maximum discharge current, C-rate capability, energy density (Wh/kg), and Battery Management System (BMS) requirements.
How to Use This Calculator
- Select a cell type from 6 presets (e.g., Samsung 30Q 18650 or EVE LF280K prismatic)
- Enter your target pack voltage and capacity requirements
- Set the maximum discharge current needed for your application
- Review the series/parallel configuration, total cell count, and pack specifications
- Check BMS requirements and optionally estimate EV range
Frequently Asked Questions
How do I choose between 18650 and 21700 cells?
21700 cells offer 30-40% more capacity than 18650 cells (4000-5000 mAh vs 2500-3500 mAh) with better energy density and thermal performance, but they're larger (21mm × 70mm vs 18mm × 65mm) and heavier. Choose 18650 for compact devices with established form factors, and 21700 for EVs, e-bikes, and powerwall applications where the larger capacity reduces total cell count and connection complexity.
What is the difference between NMC and LFP batteries?
NMC (Nickel Manganese Cobalt) cells have higher energy density (200-260 Wh/kg) with 3.6V nominal voltage, making them ideal for weight-sensitive applications like EVs. LFP (Lithium Iron Phosphate) cells have lower energy density (120-160 Wh/kg) at 3.2V nominal, but offer 3000-5000 cycle life (vs 1000-2000 for NMC), better thermal stability, and no thermal runaway risk — preferred for stationary storage and commercial EVs prioritizing longevity.
How is C-rate calculated and why does it matter?
C-rate indicates discharge speed relative to capacity: 1C discharges the full capacity in 1 hour, 2C in 30 minutes. It's calculated as C-rate = Discharge Current / Pack Capacity. A 100 Ah pack at 2C means 200A discharge. Exceeding the cell's maximum C-rate causes excessive heating, capacity degradation, and safety risks. Most 18650 cells support 1-3C continuous, while high-power cells like Molicel P42A support up to 10C.