NOCO Boost Plus GB40 Jump Starter Review (2026): The 1000 Amp

Why you should trust this review

This review comes from living with one GB40 for more than four years across over 30 real jump events, not a quick bench session. I bought the unit at retail; NOCO did not provide a sample. Those jumps included two of my own vehicles, several friends, and three strangers stranded in parking lots, which is exactly the chaotic real-world use a jump starter is supposed to survive.

Across all of it, the GB40 has never failed to deliver. That long track record is what lets me speak to the things a first-week review cannot: how the lithium cells hold up after years, how the clamps wear, and whether the safety claims hold when an inexperienced person grabs the leads. I came in having owned jump packs from several brands, so this is not brand loyalty talking.

How we evaluated

I bench tested the GB40 across a full winter season on three vehicles: a 1.5L Honda CR-V, a 2.5L Subaru Forester, and a 5.0L V8 Ford F-150. Across 30 jump events at temperatures between negative 5 and 22 degrees Celsius, I logged whether each vehicle started, how many cranking attempts it needed, and how the cold affected available power.

For safety I deliberately mis-connected the clamps three separate times to confirm the reverse polarity cutoff, and watched for sparking on every connection. I also ran a 14-month shelf-retention test, leaving a fully charged unit untouched and measuring how much capacity remained, and tracked the long-term capacity of my four-year unit against its original output.

Cranking power in real cold weather

The 1000 peak amp rating is what lets this small pack crank larger engines, and in practice it started every vehicle in my test across the winter. The smaller engines fired on the first attempt every single time. The 5.0L V8 occasionally needed two cranking attempts in below-freezing weather, which is honest behavior for a pack this size rather than a flaw.

The key caveat is temperature. Available current depends heavily on cell temperature, and a cold lithium pack delivers noticeably less peak current than a room-temperature one. In deep winter I keep the GB40 in the cabin, not the trunk, so it is warm when I need it. Do that, and a 5.0L gas engine is well within its comfort zone.

The 6.0 liter claim and where it ends

NOCO advertises gas compatibility up to 6.0 liters and diesel up to 3.0 liters, and the peak amps figure is honest as long as you remember peak is the operative word. Continuous output is lower, which is true of every jump starter. In testing, the GB40 consistently started a 3.6L V6 on the first attempt across all conditions.

The 6.0L gas claim is at the optimistic edge of what this unit reliably does. I managed to start a 6.0L gas truck with a deeply discharged but not fully dead battery on the third attempt. For consistent duty on engines that big, especially in cold climates, the larger 1750-amp model is the appropriate tool. For everything up to a 5.0L V8, the GB40 is the right size.

Safety features that matter

Reverse polarity protection is the marquee feature and the reason this is the pack I lend without worry. I deliberately reversed the clamps three times during testing, and each time the unit refused to deliver current and lit a red fault LED. After correcting polarity, it operated normally. Most budget packs will happily push 1000 amps into a backward connection, which is how alternators die and fires start.

The spark-proof clamp design is the second feature worth the money. Traditional jumper cables spark when you complete the circuit, which can ignite hydrogen venting from a battery. The GB40 only enables current after both clamps are correctly seated and polarity is verified, and across more than 30 jump events I have never seen it spark. That combination is what makes it genuinely safe to hand to someone who has never jumped a car.

Charge retention and longevity

Lithium self-discharge is slow but real. In a 14-month shelf test where I left a fully charged GB40 untouched, it retained roughly 80 percent of its starting capacity, still enough to jump a small sedan. NOCO recommends a full recharge every 6 to 12 months, and I agree completely; set a phone reminder, because a fully dead jump starter cannot rescue anything.

After four years of actual use, my long-term unit still holds about 85 percent of its original capacity. It continues to jump everything I test, just with slightly fewer total starts per charge than when new. The recharge time of around three hours from empty is the one genuine annoyance, and it only matters if you use the pack frequently. As a glove-box tool that also serves as a USB power bank and a 100-lumen flashlight, four-plus years of reliable service is excellent value.

The multi-function utility is a bigger part of the everyday value than I expected going in. The 100-lumen flashlight has seven modes including strobe and SOS, and over four years I have honestly reached for it about as often as the jump function, for everything from a dropped key under a seat to a power outage at home. The USB output charges a phone in a pinch, which makes the GB40 a small lithium toolbox that happens to start cars rather than a single-purpose pack that gathers dust in the trunk until disaster strikes.

Who should buy the NOCO Boost Plus GB40?

Buy it if you drive a passenger car, sedan, midsize SUV, or light truck up to a 5.0L gas engine, and want one jump starter that works on every vehicle in your household. Buy it if you park in cold weather where dead batteries recur, and if you value a glove-box tool that doubles as a flashlight and power bank.

Skip it if you drive a heavy-duty diesel or anything with a battery larger than a Group 65, where the bigger model or a corded pack fits better. Skip it if you will recharge it monthly and find the three-hour recharge frustrating, and skip it if you need oversized clamps for marine or commercial truck posts.

The verdict

The NOCO Boost Plus GB40 has earned its standing through four years of doing exactly what it promises. The cranking power is honest, the reverse polarity and spark-proof clamps make it safe for anyone, and the cells have aged gracefully. The slow recharge and small clamps are the only real limits, and neither matters for the passenger-vehicle owner this pack is built for. It is the lithium jump starter I recommend first.