Rated 800 cranking amps. It held 360 to 480 on a load tester.
Every jump starter is sold on peak amperage, the opening jolt, and the box prints it largest. In 2026 one reviewer put nine of them on a carbon pile load tester and measured what they could sustain for several seconds. The pick held about 360 to 480 A at 7.5–9.5 V, against a cranking rating of 800 A that the reviewer calls still exaggerated, though closer to what was measured.
Two numbers, and only one is about your car
The distinction is not ours; Car and Driver's test spells it out. For a lead-acid unit, peak is the opening jolt, typically 20 to 50 milliseconds. The thirty seconds that follow are what cranking amps and cold cranking amps measure, at 32 and 0 °F, and cold cranking is the basis your car's own battery is rated on — around 400 to 500 for an average passenger car, by the same article. A lithium unit usually has no thirty seconds to offer: it delivers high current for two to five seconds and then cuts power, because holding it longer risks thermal runaway.
So when a box says 4000 amps, the honest question is for how long, and at what voltage.
What a load tester found
CNN Underscored did not jump a car. Its reviewer hooked each of nine units to a carbon pile load tester, which draws current the way a starter motor does, and recorded the amps and volts each could hold for several seconds. That makes the readings comparable with each other, and it means they are readings on a bench rather than starts: one reviewer, one load bank, no car. The review printed figures for two of the units and describes the rest against those two.
Scale runs to 4000 A, the highest figure here.
marked CNN Underscored, I tested 9 jump starters that promise to revive your car — rated figures, 30 April 2026. Peak, cranking or starting amps as each maker rates the unit, reprinted in the review. Not measured. The reviewer writes that the load tests confirmed the experts' warning against treating peak ratings as fact, and calls the Gooloo's 800 cranking-amp rating still exaggerated, though closer to what was measured.
Scale runs to 480 A, the highest measured value here.
use it CNN Underscored, I tested 9 jump starters that promise to revive your car, but only these 2 deliver, 30 April 2026. Nine units on a carbon pile load tester instead of a car: each was hooked to the tester, which draws current to simulate starting a vehicle, and the amps and volts it could sustain for multiple seconds were recorded; the load was repeated to see how many each could take before it could not deliver. One reviewer, one load bank, no vehicle. Amp-and-volt figures are printed for two units only, the Gooloo GT4000S (roughly 360 A at 9.5 V, 480 A at 7.5 V, then 420 A at 9.5 V) and the Noco GB40 (for example 160 A at 7 V, or 100 A at nearly 10 V); the other seven are described relative to those two.
Read the two charts apart. The first is the opening jolt each maker claims; the second is what two units held for several seconds, so neither is a fraction of the other. The like-for-like rating is the cranking figure, and the review prints one only for the Gooloo GT4000S: 800 A, against the 360 to 480 A it held at 7.5–9.5 V, which the reviewer calls still exaggerated, though closer to what was measured. Neither unit failed: an industry expert told the reviewer that starting a four-cylinder or a V6 is a matter of 100 to 150 amps. The peak figure was simply never the measure of that.
| Product | Rated A, as the maker states marked | Under load as the review reports it use it | Where to buy |
|---|---|---|---|
| Gooloo GT4000S our pick CNN's best overall. Its button for a battery too flat to detect says boost | 4000 peak, 800 cranking | about 360–480 A at 7.5–9.5 V | Check on Amazon |
| NOCO Boost Plus GB40 CNN's budget pick. Held its output longer than the others; needed a recharge after two loads | 1000 peak | 160 A at 7 V; 100 A at nearly 10 V | Check on Amazon |
| Topdon JumpSurge 3000 The review's choice for several jumps on one charge | 3000 peak | similar to the Gooloo | Check on Amazon |
| Veratek V10 Pro Instructions printed on the back; dim flashlight | 4000 peak | similar to the Gooloo | |
| Hulkman Alpha Ultra Frequent overheating warnings in boost mode | 1250 peak | between the Noco and the Gooloo | |
| Battery Tender 2000 A No manual override | 2000 peak | slightly lower than the Gooloo | |
| AstroAI S8 Pro Overheated on the tester and shut itself down for several minutes | not in the review | adequate at first, then faded quickly | |
| Uncharted Supply Co. Zeus Air Jump starter and tyre inflator in one | 1000 starting | none: its boost mode would not engage | |
| Redi The Jumpie Its cable cover broke in testing | not in the review | no figure or comparison given |
marked CNN Underscored, I tested 9 jump starters that promise to revive your car — rated figures, 30 April 2026. Peak, cranking or starting amps as each maker rates the unit, reprinted in the review. Not measured. The reviewer writes that the load tests confirmed the experts' warning against treating peak ratings as fact, and calls the Gooloo's 800 cranking-amp rating still exaggerated, though closer to what was measured.
use it CNN Underscored, I tested 9 jump starters that promise to revive your car, but only these 2 deliver, 30 April 2026. Nine units on a carbon pile load tester instead of a car: each was hooked to the tester, which draws current to simulate starting a vehicle, and the amps and volts it could sustain for multiple seconds were recorded; the load was repeated to see how many each could take before it could not deliver. One reviewer, one load bank, no vehicle. Amp-and-volt figures are printed for two units only, the Gooloo GT4000S (roughly 360 A at 9.5 V, 480 A at 7.5 V, then 420 A at 9.5 V) and the Noco GB40 (for example 160 A at 7 V, or 100 A at nearly 10 V); the other seven are described relative to those two.
Six of the nine carry no link, and the figures stand without one: Veratek V10 Pro — its amazon.com listing had 34 ratings on 25 October 2026, below the floor we link at; Hulkman Alpha Ultra — its amazon.com listing had 91 ratings on 25 October 2026, below the floor we link at; Battery Tender 2000 A — its amazon.com listing had 83 ratings on 25 October 2026, below the floor we link at; AstroAI S8 Pro — the review links it only to AstroAI's own store, where it was sold out; Uncharted Supply Co. Zeus Air — it delivered nothing in the test, and its listing had 20 ratings on 25 October 2026; Redi The Jumpie — the review found it cheaply built and recommends skipping it.
Eleven units on dead batteries
A load tester answers how much; it does not answer whether a unit will agree to start a car whose battery reads almost nothing. Car and Driver answered that one, on cars from its own lot with batteries dead enough to run flat again within minutes, so every unit met the same flat start. Seven of the eleven started the car, and five of those needed their override or boost mode first. The test gives no result for two, and two could not do it unaided.
| Product | Peak A, as claimed marked | Weight lb use it | Leads in, base to clamp tip use it | On a dead battery use it | Where to buy |
|---|---|---|---|---|---|
| Clore Jump-N-Carry JNC325 Car and Driver's best overall, chosen partly for its 24-inch leads | 2000 | 2.6 | 24.0 | Started, after its override | Check on Amazon |
| Gooloo GT6000 Best for large engines. Larger clamps, easier with gloves | 6000 | 3.3 | 17.0 | Started, in Boost mode | Check on Amazon |
| Strauto Jump-Starter Best budget. The lightest here; small, plasticky clamps | 1200 | 1.44 | 21.0 | No result given | |
| NOCO Boost Plus GB40 Most compact. One jump took it from full to 25 per cent | 1000 | 2.0 | 13.5 | Started, after its override | Check on Amazon |
| Topdon V1200Air Most portable. Doubles as a tyre inflator | 1200 | 2.2 | 14.5 | Started, in Boost mode | |
| Clore Jump-N-Carry JNC770R Best for shops. Lead-acid; took 410 Wh to recharge, the most in the test | 1700 | 22.3 | 69.0 | Started; tipped over on the engine afterwards | Check on Amazon |
| Stanley J5C09D Best power station, with a 120 psi compressor. The listing's title says 1200 A peak | 1000 | 17.2 | 26.5 | Started without complaint | Check on Amazon |
| AstroAI S8 Ultra Plastic clamps that did not inspire confidence | 4000 | 2.7 | 18.0 | Started, in Boost mode | Check on Amazon |
| DeWalt DXAEJ14 Clamps and stability ranked well; beeps incessantly | not printed | not printed | not printed | No result given | Check on Amazon |
| AvaPow A28 Bumped down Car and Driver's results | not printed | not printed | not printed | Struggled; needed a known-good battery to get past standby | |
| Nexpow G17 The only unit that did not work at all | not printed | not printed | not printed | Failed to recognise the battery |
marked Car and Driver, Best Portable Jump-Starters for 2026, Tested — spec sheets, May 2026. Peak amperage as each maker publishes it, reprinted in the test's spec sheets and not measured by the testers. The article's own explanation: for a lead-acid unit peak is the initial jolt, typically lasting 20 to 50 milliseconds, followed by 30 seconds of sustained amperage reported as cranking amps (at 32 F) or cold cranking amps (at 0 F); a lithium unit typically delivers high amperage for two to five seconds and then cuts power.
use it Car and Driver, Best Portable Jump-Starters for 2026, Tested, May 2026. Each unit jump-started beater cars from the magazine's own lot, chosen for completely dead batteries that ran flat again within minutes, so every unit met the same flat start. For most units the write-up says whether it started the car and whether it needed its override or boost mode first; for some it gives no result. Weight and lead length recorded, lead length measured from the base of the lead to the end of the clamp. Eleven units, eight with a spec sheet. The page was first published in February 2023 and updated with new products in May 2026.
The last three rows are the DeWalt DXAEJ14, AvaPow A28 and Nexpow G17, which Car and Driver lists among the other units it tested, without a spec sheet; their cells are empty rather than filled from a listing.
Four of the eleven carry no link, and the figures stand without one: Strauto Jump-Starter — its amazon.com listing had 58 ratings on 25 October 2026, below the floor we link at; Topdon V1200Air — Car and Driver links no amazon.com listing for it, and we have not verified one; AvaPow A28 — it struggled in the test, and we do not send anyone to a unit that did; Nexpow G17 — it failed the test, and the listing Car and Driver links no longer exists on amazon.com (25 October 2026).
The DeWalt's listing showed “Currently unavailable” when we read it on 25 October 2026, from outside the US, where amazon.com does not show stock reliably. It stays linked; the button may not lead to a unit you can buy today.
The failure that matters most
Both tests found the same thing, from opposite ends. On Car and Driver's dead cars, five of the seven units that started did so only once their override or boost mode was engaged. The Nexpow G17 never recognised the battery at all, probably because its voltage was so low, and the AvaPow A28 had to be coaxed past standby with a known-good battery, which the testers point out is not something you will have at the roadside.
On CNN's bench the Uncharted Supply Co. Zeus Air delivered nothing, because its boost mode would not engage, and the Battery Tender, which reports problems only in beeps and a coloured light, offers no manual override at all. The reviewer's two picks both have one: the Noco's is for a battery that has fallen below 2 volts, and the Gooloo's is a front-panel button labelled “boost”.
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.
How old are these tests?
CNN Underscored's review is dated 30 April 2026. Car and Driver's page was first published in February 2023 and says it was updated with new products in May 2026. Seven of its eleven units are the line-up of the 2023 test this page used to rest on; the other four were added since.
Until 25 October 2026 this page recommended the DeWalt DXAEJ14, on a cold-cranking figure its maker publishes and that 2023 test reprinted. Neither 2026 source prints a cold-cranking figure for any unit, and Car and Driver now lists the DeWalt among the others it tested, praising its clamps and stability and complaining about the beeping. A pick resting on a three-year-old reprint was the weakest thing on the page, so the recommendation moved to the unit with the highest sustained figure a 2026 test printed.