NOCO GB40 Review: The Pocket Jump Starter Worth Its Price?

This NOCO GB40 review looks at the NOCO Boost Plus GB40, a compact lithium jump starter that promises to crank a dead 12V battery with 1000 amps of peak power and still slip into a glovebox. It's aimed at drivers of small-to-midsize gas cars who want a self-contained safety net they can use without calling anyone or digging out jumper cables. To put this together, we've combined NOCO's own specifications with what owners and independent reviewers report, because we have not used or measured this unit ourselves. If you're the kind of person who wants to know what a gadget actually does, what it costs to run, and when it falls short, read on.

What you get

The GB40 is a hand-held lithium jump starter: you clamp it to your car's battery, it delivers a burst of power to start the engine, and in between emergencies it doubles as a flashlight and a small phone charger. At roughly 2.4 lb and under 7 inches long, it's built for the glovebox rather than the trunk. NOCO rates it for gas engines up to 6.0 liters and diesels up to 3.0 liters, and claims up to 20 starts on a full charge.

One point worth flagging: the Amazon listing title references USB-C charging, but the long-running GB40 actually charges through a slow 2.1A (~10W) port and outputs to devices only via USB-A. That's a different beast from the newer, pricier Boost X GBX45, which offers 1250A, a 4.0L diesel rating, a 200-lumen light, and 60W USB-C Power Delivery that recharges in roughly 48 minutes. Don't confuse the GB40 with the smaller GB20 (500A) or the larger GB70 (2000A) either. If a listing or box mentions fast USB-C in and out, you're probably looking at the GBX45, not this model.

What owners like

Across forums and review sites, the GB40 earns a reputation as a reliable grab-and-go tool. Here's what comes up most often.

• It starts most small and midsize cars reliably. Owners repeatedly report a dead battery on a cold morning firing up on the first try, sometimes after conventional jumper cables had already failed. Many treat it as a dependable "set and forget" safety net for gas engines up to about 6 liters.
• It's genuinely compact and light. At around 2.4 lb and under 7 inches, reviewers are surprised something this small delivers 1000 amps, and they like that it tucks away instead of hogging space.
• The connections are hard to get wrong. Spark-proof and reverse-polarity protection means nervous first-timers can clamp it on without worry. One hands-on reviewer reversed the clamps on purpose and got no spark. Owners with no jump-start experience often describe it as foolproof.
• It holds its charge in storage. NOCO rates it to retain about 70% of capacity for up to a year, and owners report it still working after sitting in a glovebox for a month or more, which matters for a tool you only touch in an emergency.
• It's rugged. The IP65 case, rubberized over-molding, and heavy-gauge clamps feel solid. One reviewer rated it more durable than a rival 1200A pack, even over-engineered for average use.
• You get a lot of jumps per charge. Thanks to its lower-voltage design, the GB40 is rated for up to 20 jumps on a full charge, far more than the bigger GBX45 (rated around 6). Some owners value that over fancier charging features.
• The extras are useful. The 100-lumen LED with seven modes, including SOS and strobe, is handy roadside at night, and the USB-A port can top up a phone in a pinch.

Common complaints

No tool is perfect, and the GB40 has a few recurring issues. Some are deal-breakers depending on what you drive.

• It struggles with V8s and larger diesels (common). Several owners found it wouldn't crank a V8 at all, which lines up with NOCO's own 6.0L gas / 3.0L diesel limit. Truck and big-engine owners are repeatedly steered toward the GB70 or a Clore JNC pack instead.
• The internal battery can swell or stop holding charge over time (some owners). A recurring issue is the lithium pack swelling or no longer accepting a charge, sometimes after a few years. NOCO acknowledges this type of failure, and owners say early units were especially prone, though it reportedly improved.
• Recharging is slow and USB output is weak (common). A full recharge takes about 3 hours (longer on a 1A source), and the single USB-A output tops out near 10W, so it only trickle-charges a phone. This is a frequent gripe versus the USB-C GBX45.
• Real usable capacity is below the label (some owners). Independent testing measured only about 15.6 Wh usable against the 24 Wh claim, so power-bank runtime is modest and you shouldn't bank on many jumps if it isn't fully charged.
• It can drain if neglected and may not wake up (some owners). Left unused for many months, the internal battery can drop too low to turn on. Some very flat car batteries (below about 2V) also require a manual override procedure, which trips up users expecting plug-and-play.
• Warranty and customer service can frustrate (some owners). Reviewers describe unresponsive support and difficult claims. NOCO replaces rather than repairs faulty units, and the replacement's warranty continues from the original purchase date rather than resetting.

Running costs and upkeep

The GB40 barely sips electricity, so the running cost is negligible. The internal battery stores 24 Wh (NOCO's spec; independent testing measured about 15.6 Wh usable). A full recharge from empty uses roughly 24 Wh of grid power. At about 17 US cents per kWh, that works out to well under a cent per recharge. At around 25p per kWh in the UK or about 30 Australian cents, it's still a fraction of a cent. In short, you could recharge this thing every week for a year and not notice it on your bill. A full recharge takes about 3 hours from a 2.1A USB source.

There are no consumables and no subscriptions. For upkeep, keep the clamps clean, store it charged, and top it up every few months so it doesn't drain too low to turn on. The IP65 rating means it shrugs off dust and splashes, but it isn't meant to be submerged. On safety, NOCO's user guide tells you to stop using the unit immediately and contact the company if the battery becomes excessively hot, smells, or deforms, which ties in with the swelling reports above. No formal recall for the GB40 appeared in the sources we reviewed. The warranty is a one-year limited warranty from the date of purchase, covering defects in materials and workmanship under normal use. It excludes wear and tear, cosmetic damage, and misuse, and it's void if you open the unit up. Claims need an RMA number and proof of purchase, and without a receipt a fee applies.

How it compares

Owners tend to cross-shop the GB40 against these three. The right choice usually comes down to engine size and how fast you want recharging.

Who should buy it, and who should skip it

• Buy it if you drive a small or midsize gas car and want a compact, foolproof safety net for the glovebox.
• Buy it if you value lots of jumps per charge and a low price over fast charging.
• Buy it if you've never jump-started a car and want spark-proof, reverse-polarity protection.

• Skip it if you own a V8, a full-size truck, or a larger diesel, where the GB70 or a Clore JNC pack makes more sense.
• Skip it if you want quick USB-C recharging and the ability to power bigger devices, which points to the GBX45.
• Skip it if reliable, hassle-free warranty support is a priority, given the mixed service reports.

Our NOCO GB40 review verdict

For the job it's designed to do, the GB40 holds up well. Owners consistently report it starting ordinary cars on cold mornings when jumper cables or a weak battery let them down, and its small size, solid build, and mistake-proof clamps make it an easy thing to keep in the car and forget about until you need it. The up-to-20-jumps rating and negligible running cost are genuine strengths, and for a first-time user who just wants to avoid being stranded, it does the core task calmly and safely.

The weaknesses are real but predictable. It won't crank a V8 or a big diesel, so match it honestly to your engine size before buying. The slow recharging and feeble USB-A output feel dated next to the GBX45, usable capacity comes in below the headline figure, and a minority of owners run into battery swelling or difficult warranty claims. If those caveats don't apply to your vehicle, this is a sensible, well-proven pick at the current price on Amazon; if they do, spend a little more on the right NOCO model or a heavier booster.