Lithium vs Supercapacitor Jump Starters
Most jump starters use lithium-ion or LiFePO4 cells, rated in mAh/Wh, that hold a charge for weeks to months. A smaller number use supercapacitors, which have no mAh/Wh rating, fully discharge within a day or two, but tolerate extreme temperatures and repeated cycling better than lithium chemistry.
Side by side
| Lithium-ion / LiFePO4 | Supercapacitor | |
|---|---|---|
| Capacity rating | mAh / Wh | Not rated in mAh/Wh |
| Charge retention (storage) | Weeks to months (slow self-discharge) | ~1-2 days (fast self-discharge, by design) |
| Temperature tolerance | Degrades in extreme cold/heat | Wide range, e.g. -40 to 70C in some manufacturer specs |
| Cycle life | Gradual capacity loss over hundreds-thousands of cycles | Very high claimed cycle counts (manufacturer figures, e.g. 100,000+) |
What this means for buyers
If you want a unit that sits in a glovebox for months and works the moment you need it, a lithium pack's slower self-discharge is the practical advantage. If you live somewhere with extreme heat or cold, or you use a jump starter often enough to charge it right before each use, a supercapacitor unit's temperature tolerance and cycle life are the trade worth considering — at the cost of needing a fresh charge shortly before use.
This page compares battery-chemistry characteristics generally; see the Cranking Amp Reality Index for specific advertised figures per product.
Frequently Asked Questions
A lithium (Li-ion or LiFePO4) jump starter stores energy chemically in a battery and is rated in mAh or Wh. A supercapacitor jump starter stores energy electrostatically, has no mAh/Wh rating in the traditional sense, discharges fully within a day or two, but tolerates extreme temperatures and repeated charge cycles better than a lithium pack.
Lithium packs hold a charge for weeks to months with slow self-discharge, making them better suited to sitting in a glovebox untouched. Supercapacitors discharge fully within roughly a day or two by design, so they need a quick top-up charge (often only minutes) right before use.
In our dataset, the one supercapacitor unit we tracked (autowit SuperCap 2) has the lowest advertised peak-amp claim (800A) of the lineup, though peak-amp claims aren't directly comparable across chemistries or brands. Supercapacitors deliver their stored energy in a very short burst rather than sustaining output the way a battery does, which suits a quick-crank use case differently than a lithium pack.
Supercapacitors are generally understood to tolerate a wider temperature range (down to around −40°F/C in some manufacturer specs) than lithium-ion cells, which lose performance in extreme cold and can be damaged by extreme heat. This makes supercapacitor units a common pick for glovebox storage in very hot or very cold climates.