Selection Guide
Supercapacitor Voltage Rating Guide: Choosing Working Voltage and Derating
How to choose supercapacitor rated voltage: 2.7V vs 3.0V cells, 5.5V parts, derating for life, surge voltage, and series cell counts.
Updated 2026-10-28 · 9 min read
The challenge
Voltage is the strongest lever on both energy (∝ V²) and lifetime. Running at the full rated voltage maximises energy but reduces life, especially when hot.
Rated, surge, and working voltage
- Rated voltage: the maximum continuous voltage specified by the manufacturer.
- Surge voltage: a short-term limit some datasheets specify — never design to it.
- Working voltage: what your charger actually applies, including tolerance.
2.7 V vs 3.0 V cells
Cell
Energy at rating (relative)
Notes
2.7 V
1.00
Widely used, more life margin at equal working voltage
3.0 V
≈1.23
More energy per cell; check life at your temperature
Number of series cells
N = ceil( V_bus_max / V_cell_working )
Example: a 24 V bus with 10% overshoot is 26.4 V. At 2.5 V working per cell, N = ceil(10.56) = 11 cells.
Derating
Reducing working voltage by roughly 0.1–0.2 V per cell is a common way to extend life. Quantify the effect with the specific part’s life curves rather than general rules.
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Recommended supercapacitor types
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