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Short version: The NOCO GB40 Boost Plus is the pocket-sized 1000-amp lithium jump starter that most drivers should own. Owners overwhelmingly rate it a set-and-forget safety net for dead batteries on gas engines up to 6 liters and diesels up to 3 liters — provided you actually remember to keep it charged. It is not the tool for big trucks, and the slow micro-USB recharge is its most-cited annoyance, but for the money it earns its reputation.
What the NOCO GB40 actually is
The GB40 is NOCO's flagship compact jump starter and one of the best-known names in the category. It packs a 1000-amp lithium-ion pack into something you can genuinely slide into a glovebox or door pocket — smaller than a paperback, and light enough that owners forget it is even in the car until they need it. It is rated to crank up to a 6-liter gas engine or a 3-liter diesel, which covers the overwhelming majority of everyday vehicles on US roads.
It is more than a one-trick device. Reviewers repeatedly praise the fact that it doubles as a 400-lumen LED flashlight with SOS and strobe modes, and as a USB power bank for topping up a phone. For anyone who keeps an emergency kit in the trunk, that three-in-one nature is a big part of the appeal — one small box that jump-starts a car, throws light on a roadside repair, and keeps a phone alive long enough to call for help.
The detail owners come back to most, though, is safety. The clamps are spark-proof and protected against reverse polarity, so a nervous first-timer connecting red to black simply gets nothing rather than a shower of sparks or a damaged battery. In a category where a wrong move can genuinely hurt, that engineering is why the GB40 gets recommended so freely to people who have never popped a hood in their life.
Who it is for
Think of the GB40 as the sensible default. It is aimed squarely at the driver who wants insurance against a dead battery without carrying a bulky lead-acid booster or waiting on a stranger with jumper cables. Commuters, parents ferrying kids, weekend drivers whose fun car sits for weeks between runs down a favorite mountain road — this is the crowd the GB40 was built for.
If your car sleeps more than it drives, the case is even stronger. A weekend project car or a garage-kept coupe that only comes out when the roads are empty is exactly the kind of vehicle that flattens a battery from sitting. A compact lithium starter in the trunk means one turn of the key rather than a tow. Just note the flip side, covered below: a jump starter that lives in a rarely-driven car is also the one most likely to be forgotten and left flat itself.
- Great fit: sedans, hatchbacks, small-to-mid SUVs, motorcycles, and most light trucks with gas engines up to 6L.
- Fine, with headroom to spare: smaller diesels up to about 3L.
- Look elsewhere: large diesel trucks, big-block V8 haulers, and fleet duty — owners of those consistently point to the GB50, GB70 or GB100.
What owners love
Across thousands of reviews, a few themes come up again and again. The first is that it simply works when it matters. Owners describe a dead battery on a cold morning, clamping the GB40 on, and the engine turning over on the first try — often after the car had refused to start with conventional cables. That reliability, backed by a high star rating across a huge number of reviews, is the foundation of its reputation.
The second is size. Reviewers are repeatedly surprised that something this small delivers 1000 amps, and they love that it disappears into a glovebox instead of hogging trunk space. The third is confidence: the idiot-proof clamps and clear charge-level lights mean people trust themselves to use it under pressure. And the fourth is versatility — the flashlight and USB power bank turn a single-purpose gadget into a genuine everyday-carry emergency tool.
Common complaints owners actually report
No tool is perfect, and the GB40's weak points are consistent enough across reviews to take seriously.
- You have to keep it charged. This is the number-one recurring complaint, and it is really user behavior more than a fault: the lithium pack self-discharges over months, and people who leave it untouched for a year find it dead in the exact moment they need it. Top it up every few months and this problem vanishes.
- Slow to recharge. The older micro-USB input means a full recharge can take many hours. It is fine if you keep it topped up, but frustrating if you let it run flat and then need it soon.
- Short, small clamps and cables. A number of owners wish the leads were longer and the clamps a touch beefier; on some batteries the reach and grip feel tight.
- Underpowered for big rigs. Try it on a large diesel or a big V8 truck and it can struggle. That is by design — those buyers should step up the NOCO line.
- Counterfeits are everywhere. Reviewers repeatedly warn about knockoffs that mimic the look but skip the safety circuitry. Buying from a reputable seller matters.
- Cold weather saps power. As with any lithium pack, owners note that deep cold reduces available cranking punch, so keep it warm and fully charged in winter.
Alternatives worth a look
If the GB40's power ceiling is your only concern, the answer is usually to stay in the family and size up. Owners of larger engines point to the NOCO GB50 for a bit more headroom, and the GB70 for full-size trucks and bigger diesels; the GB100 sits above that for serious duty. Same clamps, same safety story, more amps.
It is also worth weighing lithium against old-school lead-acid boosters. Lead-acid packs are cheaper and shrug off being neglected a little better, but they are heavy, bulky, and hold far less appeal for a compact everyday kit. Lithium wins on size, weight and convenience — at the cost of that recharge discipline. For the full ranked head-to-head, our best portable jump starter roundup lines the leading options up side by side, and our guide to lithium vs lead-acid jump starters digs into the tradeoff in detail.
The verdict
The NOCO GB40 Boost Plus has earned its status as the default recommendation for a reason: it is small, genuinely idiot-proof, powerful enough for the cars most people drive, and doubles as a flashlight and power bank. The complaints that surface in owner reviews are real but manageable — keep it charged, don't expect it to fire a big diesel, and buy the genuine article from a trusted seller. Do that, and it quietly waits in your trunk for the morning your battery lets you down, then gets you moving again in seconds.
For most drivers, that peace of mind is exactly what a jump starter is supposed to buy. If your engine sits inside its ratings, this is an easy one to recommend.
Want the wider picture before you commit? Start at the Jump Starters & Battery Care hub for buying guides, safety walk-throughs and comparisons that put the GB40 in context.