Between a supercapacitor and Li-ion, 14 of the 16 characteristics in the full table below differ; 2 can’t be compared because our sources give no figure or rating for one or both.
2.7 V · 6.9 Wh/kg · 1,000,000 cycles
A million cycles, hundreds of amps and charging down to −40 °C: for short bursts and backup, not for storing energy.
Watch out: Only 6.9 Wh/kg, about 30 times less than Li-ion, and it loses about 3 % of its voltage a day through leakage (our estimate).
3.6 V · 221–260 Wh/kg · 400 cycles
The most energy per kilogram among rechargeables, in standard 18650 and 21700 cells with high-capacity and high-current versions.
Watch out: No charging below 0 °C, and a damaged or shorted cell can catch fire: use protected cells or a BMS.
| Feature | Supercapacitor | Li-ion (NMC/NCA) |
|---|---|---|
| Differences (14) | ||
| Basics | ||
| Type | Rechargeable (capacitor) | Rechargeable |
| Nominal voltage | 2.7 V rated | 3.6 V |
| Voltage range | 0 to 2.7 V: the voltage falls in a straight line as it discharges | 2.5 V (empty) to 4.2 V (full) |
| Formats | Cells from a few farads to 3,000 F, and modules | 18650 and 21700 cylindrical cells, alone or in packs |
| Example (source of the figures) | Maxwell BCAP3000 (3000 F) | LG MJ1, Molicel P42A |
| Energy | ||
| Energy per kilogram | 6.9 Wh/kg | 221–260 Wh/kg |
| Life and storage | ||
| Cycle life | 1,000,000 (projected at 25 °C, Maxwell) | 400 to 80 % (LG MJ1); not stated for the Molicel P42A |
| Self-discharge and storage | Leakage 2.8 mA after 72 h at 2.7 V (Maxwell): about 0.08 V a day from full, if the leakage stayed that high (our estimate) | At most 10 % in 30 days at 25 °C (LG MJ1 test) |
| Current | ||
| Maximum continuous discharge | 170 A, 2,300 A peak (Maxwell BCAP3000) | From 10 A (2.9C, LG MJ1) to 45 A (10.7C, Molicel P42A) |
| Temperature | ||
| Charging temperature | from −40 to 65 °C | 0–45 °C |
| Discharge temperature | from −40 to 65 °C | from −40 to 60 °C · LG MJ1 from −20 °C |
| Safety, charging and shipping | ||
| Charging | Any current up to the cell’s limit, stopping at 2.7 V (2.85 V for 1 s at most); cells in series need balancing | CC/CV to 4.20 V per cell, never above; packs need a BMS |
| Air transport | UN3499: cells storing under 10 Wh are not dangerous goods (Maxwell) | Lithium-ion dangerous goods (UN3480/3481): loose batteries by cargo aircraft only, at 30 % charge at most; since 2026, batteries over 2.7 Wh packed with equipment must also be at 30 % at most. Passengers carry spares in the cabin, up to 100 Wh freely and 100–160 Wh with airline approval; since 27 March 2026, at most two power banks each, not recharged on board |
| Uses | ||
| Typical uses | Current bursts and backup: real-time clocks, short power cuts, engine starting, energy recovery | Power tools, e-bikes, laptops, flashlights, ESP32 projects on 18650 cells |
| Can’t be compared (2) | ||
| Energy | ||
| Energy per litre | Not stated in our sources | 597–727 Wh/L |
| Safety, charging and shipping | ||
| Fire risk | Not rated here | Higher: NCA cells went into thermal runaway at 207 °C and peaked at 579 °C in 18650 abuse tests; a short or an overcharge can start a fire |
Open the battery comparison →Tick what your project needs and see which of the 15 chemistries fits.
Voltage and charge chart: Li-ion (NMC/NCA) →
With a supercapacitor: more cycles, more continuous current, charging in the cold, and easier air transport. With Li-ion: more energy per kilogram and simple 5 V charging with a one-cell module.
Cycle life for a supercapacitor: 1,000,000 (projected at 25 °C, Maxwell). For Li-ion: 400 to 80 % (LG MJ1); not stated for the Molicel P42A. These figures depend on depth of discharge, current and temperature.
Not as a battery: the energy per kilogram of a supercapacitor is 6.9 Wh/kg, against 221–260 Wh/kg for Li-ion, but its current reaches 170 A, 2,300 A peak (Maxwell BCAP3000). Use it next to a battery to cover current peaks.
LiFePO4 vs Li-ion (NMC/NCA) Li-ion (NMC/NCA) vs LiPo (pouch) NiMH low self-discharge vs Li-ion (NMC/NCA) LiFePO4 vs lead-acid AGM LTO (lithium titanate) vs LiFePO4 Sodium-ion vs LiFePO4 NiMH low self-discharge vs alkaline
Figures from one or two named cells or batteries per chemistry, from the makers’ datasheets; checked in November 2026.