NOCO Boost Plus GB40 1000A UltraSafe Lithium Jump Starter

The GB40 is the pack to buy if you drive an ordinary gas car and want a jump starter that you can forget about until the morning it matters. NOCO rates it for gas engines up to 6.0 L and diesels up to 3.0 L, which covers nearly every sedan, hatchback, minivan and mid-size SUV sold in the United States, along with motorcycles, lawn tractors and small boats with a 12 V battery.

It suits people who value size and simplicity over headroom. At 2.4 lb and shorter than a paperback, it fits in a door pocket or under a seat, and the clamp-and-press routine is the same every time. If you have a V8 pickup, a diesel truck, or a big-block boat engine, this is not your pack; look at the NOCO Boost HD GB70 or the HULKMAN Alpha85 instead.

The clamps are the reason this pack keeps winning comparisons. In TechGearLab's lab tests the GB40 took the compact-model award, and the testers singled out its clamps as the easiest and most secure of the group, thanks to thin jaws that reach the recessed terminals on modern cars. That matters more than peak-amp numbers: a poor connection is the most common reason a jump fails.

The safety layer is the other point. NOCO's UltraSafe circuitry checks polarity before it lets current flow, so clamping red to negative by mistake produces an error light rather than a spark. The pack also refuses to arc if the clamps touch each other. For a household where several people might use the pack, that is worth more than an extra thousand advertised amps.

Real-world starting margin is solid within the rating. TechGearLab started a 4.0 L Ford Explorer V6 with a drained battery three times in a row in cold weather. Leadfoot Automotive reports reliable operation down to the -4°F floor NOCO specifies, where a lead-acid booster loses a large share of its output. A manual override mode lets you force a start on a battery so flat the pack cannot detect it, which is a feature some cheaper packs omit.

The housing is rated IP65 with the port cover closed, and NOCO's current data sheet lists a USB-C cable in the box. Older stock shipped with a micro-USB cable, so if that matters to you, check which revision the listing shows.

Capacity is the trade-off for the small size. The internal battery is 24 Wh on paper, and TechGearLab measured only about 15.6 Wh of usable output, roughly two-thirds of the claim. NOCO says up to 20 starts per charge on a small engine, which owner reports broadly support, but as a power bank the pack will manage a couple of phone charges and no more. If you want one device for jump starts and camping power, a proper power station from our portable power stations list plus this pack is the better split.

The USB port is slow in both directions at 5 V 2.1 A. NOCO's data sheet gives a recharge time of about 3 hours from a 2 A source and 12 hours from a 0.5 A one, and there is no fast-charge input like the 65 W USB-C on the Alpha85.

Certification is a mixed picture. NOCO does not publish a UL 2743 line for the GB40 in its data sheet, whereas Hulkman states its packs are UL certified. NOCO's protection circuitry and its long history in independent testing make up for that in our view, but if a written UL statement is a hard requirement for you, the HULKMAN Alpha85 is the pick.

Long-term owner reports mention capacity fade after a year or two when the pack is stored hot or left uncharged, so plan on topping it up every few months. That advice applies to every lithium jump starter.

Against the GOOLOO GT4000S, the GB40 gives up a lot of rated headroom: the Gooloo claims 4,000 peak amps, a 74 Wh battery, ratings of 12.0 L gas and 10.0 L diesel, and a recharge of about 1.2 hours at 100 W. Both have IP65 housings. What the NOCO offers in return is a smaller body, a published weight, clamps that TechGearLab rated the easiest and most secure in its group, and a longer track record. For a small engine, the GB40 is the easier pack to keep in the car.

Against the NOCO Boost HD GB70, the GB40 is the same design philosophy at half the rating. If your vehicles include anything bigger than a 6.0 L gas engine or a 3.0 L diesel, spend the extra weight on the GB70.

Our full ranking with the reasoning on engine matching is in the best portable jump starters list.

Buy the GB40 if your largest engine is a 6.0 L gas or a 3.0 L diesel and you want a small, forgiving pack with clamps that fit tight terminals. Skip it if you need real power-bank capacity, a fast recharge, or a printed UL 2743 statement; skip it entirely for full-size trucks and larger diesels.