NOCO Boost GB40 review: who it suits, who should skip it

We have not tested the GB40. This page is built from NOCO's user guide, the Amazon.co.uk listing and public owner reviews, and every figure below comes from one of the sources listed at the bottom.

Key specs

The user guide we could read is an earlier edition that charges over micro-USB. The current Amazon.co.uk listing ships a USB-C charging cable, so the port on a new unit differs from the guide; the jump ratings, temperature limits and weight match across both.

What the numbers mean in a UK car

• 6.0 L petrol and 3.0 L diesel. These are NOCO's own ceilings. A petrol hatchback, saloon or SUV sold in the UK is very unlikely to exceed 6.0 litres. The diesel limit is the one to check: look at the cylinder capacity on your V5C logbook if you drive a large 4x4, pick-up or van.
• Charging below freezing. The 0°C lower charging limit matters more in the UK than the -30°C operating limit. Use it in the cold if you need to, then recharge it indoors.
• 2,150 mAh is not a comparison figure. Jump starter makers quote mAh without saying at what voltage, so a bigger mAh number on another brand does not prove it stores more energy. Compare rated engine size and starts per charge instead.
• No 12 V socket. NOCO's own comparison table lists the 12 V output as absent on the GB40 and present on the GB70. If you want to run a 12 V tyre inflator from the pack, the GB40 cannot.

Who it suits

• Drivers of petrol cars, and diesels up to 3.0 litres, who want a self-rescue option instead of waiting for breakdown cover.
• Anyone who would rather not rely on a second car and a set of jump leads. See jump starter or jump leads for the trade-off.
• People building a boot kit who want one device that is also a torch and a phone power bank. Our emergency kit essentials guide lists what else to carry.

Who should skip it

• Owners of diesels over 3.0 litres: the GB70 is rated to 6.0 L diesel.
• Anyone who wants a 12 V output socket for an inflator or cool box.
• Anyone with a 6 V or 24 V system: the user guide limits the GB40 to 12 V lead-acid batteries.
• Drivers who will leave it in the boot for a year without looking at it. Read how long a jump starter holds its charge first.

What owners report

We could not read the Amazon.co.uk review feed itself, only the star rating, so the themes below come from the NOCO reviews we could read on Trustpilot, which cover NOCO products in general and only a handful mention the GB40 by name.

• Charge retention over time. Several NOCO owners, across chargers and jump starters including the GB70, describe units that stopped holding or taking charge after months or years of use. One GB40 owner reported this after roughly a year of regular use.
• Warranty friction. A recurring complaint is the claims process: owners describe being asked for photos or to pay shipping to return the unit. The Amazon.co.uk listing states a 1-year limited warranty, so keep your order confirmation.
• Successful starts. One GB40 owner reported starting a neighbour's flat Toyota Yaris Cross with it. The Trustpilot sample is small and skews towards complaints, so treat it as a list of things to watch rather than a failure rate.

When you read the Amazon.co.uk reviews yourself, filter to 1-star and 3-star and search for "won't charge", "boost light" and "override". Some "it did nothing" reports may be batteries below 2 volts, which the GB40 will not detect without the Manual Override described in the FAQ below.

How it compares

NOCO GB70. The same NOCO comparison table rates the GB70 at 2000A, up to 8.0 L petrol and 6.0 L diesel, up to 40 starts per charge, with a 12 V output socket. It is the upgrade if you have a big diesel or want the socket. Full breakdown:NOCO GB40 vs GB70.

GOOLOO GP4000. GOOLOO quotes a much higher 4000A peak, more than 60 starts per charge and a 24-month standby claim. Peak amp figures are each maker's own rating, so read ourGOOLOO GP4000 review and the GB40 vs GP4000 comparisonbefore treating 4000A as four times better. More NOCO models are on our NOCO brand page, and the wider shortlist is on best emergency kits.

Frequently asked questions

Will the NOCO GB40 start a 2.0-litre diesel?

It is inside the rating. NOCO rates the GB40 for diesel engines up to 3.0 litres and petrol engines up to 6.0 litres, which covers the engines in most UK family cars. Check the cylinder capacity on your V5C logbook if you are unsure. A very cold morning and a badly sulphated battery both make any start harder, so a unit rated well above your engine size gives more margin.

Can I keep the GB40 in the car through a UK winter?

Yes for storage and use: the user guide gives an operating range of -30°C to +50°C. Charging is different. The guide gives a charging range of 0°C to +40°C, so on a frosty night bring it indoors to recharge rather than charging it from the car's USB socket while the cabin is below freezing.

How long does the GB40 take to recharge?

The user guide gives about 3 hours from a 2 A USB charger, 6 hours from a 1 A charger and 12 hours from a 0.5 A port. A weak USB port on an older car will take far longer than a mains phone plug, so use a 2 A plug at home when you can.

What if the battery is so flat the GB40 does nothing?

The GB40 detects batteries down to 2 volts. Below that the Boost LED stays off, which can look like a fault. The user guide describes a Manual Override button, held for three seconds, that forces Boost on. NOCO warns that this disables the safety protection, so check the clamps are on the right terminals before you use it.