Accessories · jump starters
3000 amps. For a twentieth of a second.
Every jump starter is sold on peak amperage, and it is the wrong number. Peak is a jolt lasting 20 to 50 milliseconds. Cold cranking amps is sustained output over thirty seconds at 0 °F — and that is the basis your car's own battery is rated on, typically 400 to 500 for a passenger car.
Two numbers, and only one is about your car
The distinction is not ours; the source spells it out. For a lead-acid unit, peak is the opening jolt and CCA is the thirty seconds that follow. For a lithium unit there often is no thirty seconds: sustained high current risks thermal runaway, so most deliver two to five seconds and then cut power.
So when a listing shouts 3000 amps, the honest question is for how long, and the answer is on almost no box.
The biggest number, and the missing one
Scale runs to 3000 A, the highest figure here.
marked Autoweek, Best Portable Jump Starters — manufacturer specifications, February 2023. Peak amperage, cold cranking amps and watt-hour capacity as published by each maker and reprinted in the test. Peak amperage is a jolt of 20-50 milliseconds; CCA is sustained output over 30 seconds at 0 F, which is the basis a car battery is rated on.
Scale runs to 700 A, the highest figure here.
marked Autoweek, Best Portable Jump Starters — manufacturer specifications, February 2023. Peak amperage, cold cranking amps and watt-hour capacity as published by each maker and reprinted in the test. Peak amperage is a jolt of 20-50 milliseconds; CCA is sustained output over 30 seconds at 0 F, which is the basis a car battery is rated on.
Read the two charts against each other. The unit at the top of the first is absent from the second, and so is the joint second. The two products advertising the highest peak amperage of the seven publish no cold cranking figure at all — the one number that says whether they will turn your engine over rather than merely impress you.
Where both figures exist, the ratio between them is worth knowing too. The Clore JNC325 claims 2000 peak against 450 CCA, a factor of 4.4. The DeWalt claims 1400 against 700, a factor of 2. Same category, and the peak number is telling you two quite different things.
The failure that matters most
The most useful thing in the source is not a figure. Testing on a battery flat enough to read almost no voltage, some of the newer lithium units read the connection as a reverse-polarity fault and refused to run. Those with a manual override button could be made to work. Those without could not — one had to be dropped from the test, and another needed a fresh battery fitted first so that it would agree to help.
That is the scenario you bought the thing for. A safety interlock that cannot be overridden turns a completely dead battery — not a weak one — into a unit that will not start your car. Check for a manual override before you check the amperage.
Seven units, as tested and as claimed
| Product | Cold cranking A, 30 s at 0 °F marked | Peak A, 20–50 ms marked | Capacity Wh marked | Weight lb use it | Where to buy |
|---|---|---|---|---|---|
| DeWalt DXAEJ14 our pick Power station. Highest stated CCA here | 700 | 1400 | 250 | 16.92 | Check on Amazon |
| Stanley J5C09D Power station | 500 | 1000 | 290 | 17.24 | Check on Amazon |
| Clore Jump-N-Carry JNC325 Portable, and the lightest with a stated CCA | 450 | 2000 | 100 | 2.64 | Check on Amazon |
| Clore Jump-N-Carry JNC770R Power station. 22 lb | 425 | 1700 | 410 | 22.26 | Check on Amazon |
| NOCO Boost Plus GB40 Lithium. Peak and sustained figures reported identically, which we do not reprint | — | 1000 | 30 | 1.99 | Check on Amazon |
| AvaPow A28 Highest advertised peak of the seven | not stated | 3000 | 200 | 2.58 | Check on Amazon |
| Nexpow G17 Lightest unit here | not stated | 2000 | 60 | 1.60 | Check on Amazon |
marked Autoweek, Best Portable Jump Starters — manufacturer specifications, February 2023. Peak amperage, cold cranking amps and watt-hour capacity as published by each maker and reprinted in the test. Peak amperage is a jolt of 20-50 milliseconds; CCA is sustained output over 30 seconds at 0 F, which is the basis a car battery is rated on.
use it Autoweek, Best Portable Jump Starters, Tested, February 2023. Seven units on one genuinely dead battery in a 1997 Mitsubishi Eclipse GSX, which discharged on its own between attempts so each unit met the same flat start. Recharge energy from empty was metered to sense-check the stated capacity. Weight, lead length and clamp quality recorded. The headline says 2026; the page's own published and modified dates are February 2023.
How old is this test?
Our method requires a figure to be current enough to matter, so this one gets stated plainly: the article is headlined for 2026, and the page's own published and modified dates are February 2023.
Three years is a long time in lithium packs. The measurements are sound and the physics has not changed — peak is still milliseconds, CCA is still thirty seconds — but treat the model list as a snapshot of 2023 rather than of what is on the shelf today. We would rather say that than let a date on a headline do work the page did not.