Selection Guide
Series and Parallel Supercapacitor Connections: Voltage Balancing and Design Rules
Design rules for supercapacitors in series and parallel: capacitance and ESR math, voltage imbalance, passive vs active balancing, with a calculator.
Updated 2026-10-28 · 9 min read
The challenge
Single cells are limited to around 2.5–3.0 V (EDLC). Series strings reach higher voltages, but differences in capacitance and leakage cause some cells to exceed their rating unless balanced.
Ideal formulas for N identical cells
Series
Parallel
Capacitance
C / N
N × C
ESR
N × ESR
ESR / N
Voltage rating
≈ N × V (with balancing)
V
Energy
N × E_cell
N × E_cell
Why imbalance happens
During charging, a lower-capacitance cell rises in voltage faster. During standby, cells with higher leakage discharge faster, shifting voltage onto their neighbours.
Passive balancing
A resistor across each cell sets a bleed current larger than the leakage spread. Simple and cheap, but it continuously drains energy — a poor fit for battery-powered standby.
Active balancing
Shunt regulators, op-amp circuits or dedicated balancing ICs only conduct when a cell exceeds a threshold, or transfer charge between cells. Lower standby loss, more parts.
Try the calculator
计算器
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Practical rules
- Match cells from the same lot where possible
- Size balancing current well above worst-case leakage spread
- Monitor individual cell voltages in high-voltage modules
- Total rated voltage must follow the manufacturer's specification and your balancing design
Recommended supercapacitor types
Combined Supercapacitors
Two or more cells assembled in series as a single component to reach higher rated voltages.
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Supercapacitor Modules
Series/parallel assemblies with balancing, housed for system-level voltage and energy.
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High-Voltage Supercapacitor Modules
Modules and racks at 100 V and above for grid, transport, and industrial drives.
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