The NOCO GBX155 is the strongest jump starter tested, and not marginally: 879
amps and 7,032 watts on the carbon pile, more than any other unit and well
clear of a fully charged car battery at 643 amps. It started every engine
including the Cummins diesel without effort, it was decisively the best
performer at 4°F, it is one of only four units to reach 70% of its advertised
battery capacity, and it had held a full charge sitting unused for a year. At
$370 with no tire inflator, it is a lot of money for capability most people
will use twice.
The value answer is the $100 GOOLOO GP4000. It held 9.2 volts under load, the
highest figure of anything here, which put it fourth overall at 4,940 watts —
ahead of the $236 JF.EGWO. It was also the best battery-powered unit in the
freezer test and stored a genuine 68 Wh. It has no tire inflator. If you want
one, the $120 VTOMAN is the pick: fastest compressor at 5.1 minutes, a gauge
accurate to within 1 PSI, 4,788 watts of cranking, and 70.9 Wh of real
capacity. The $100 BRPOM is the cheaper version of that same idea.
The KeenPower super capacitor deserves attention on its own terms. It stores
nothing, charging itself off the dead battery in about a minute and forty
seconds, so it cannot go flat in a glovebox over a winter — and it still came
second on the bench at 6,552 watts and beat every battery unit in the cold.
At $150 that is a compelling proposition. At its $300 list price, with no
inflator and no power bank, it is not.
Three to avoid. The Povasee works perfectly until it is connected to a
genuinely dead battery, at which point it simply refuses — a failure mode that
makes the product pointless. The AlphaBot did not survive its own bench test.
The AUTOGEN is the slowest inflator with the least accurate gauge and stores a
fifth of its advertised capacity. And on the question that started this: the
$17 light-duty cables could not start a V6 off a fully charged 950 CA battery,
and the $40 one-gauge set managed only 1,264 watts. Cables are not a
substitute for a jump starter — they are a substitute for a second vehicle,
and a poor one.