Liters Not Amps product guide
NOCO Boost GB20 500A 12V Lithium Jump Starter
Gas engines up to 4.0 litres, motorcycles and powersport
The GB20 is NOCO's 500-amp pack on a 24 Wh lithium battery, rated for gas engines up to 4.0 litres. NOCO's own spec sheet lists diesel as Not Recommended. It ships with narrow powersport clamps, and its manual override for sub-2-volt batteries turns off both safety protections.
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Published specifications
- NOCO: 500 A peak; gas up to 4.0 L; diesel listed as Not Recommended
- NOCO: 24 Wh lithium-ion battery; USB-C in and USB out at 5V 2.1A
- Guide: recharge about 3 h at 2 A, 6 h at 1 A, 12 h at 0.5 A
- Guide: no more than 5 consecutive starts in 15 minutes, then rest 15 minutes
- Guide: operate -20°C to +50°C; charge 0°C to +40°C; store -20°C to +50°C
- Box: GB20, powersport clamps, USB-C to USB-C cable, microfiber bag
Fit and limits
Strengths
- Spark-proof and reverse-polarity protection in normal use, with an IP65 housing
- Powersport clamps reach the tight terminals on motorcycles and small machines
- NOCO publishes the full user guide, tech specs and warranty text for this model
Caveats
- NOCO's own spec sheet lists diesel as Not Recommended, and gas only to 4.0 L
- Manual override disables both protections and can push up to 500 amps
- Guide and specs page disagree on weight and size (2.4 lb vs 2.1 lb)
Rated for 4.0-litre gas engines, and NOCO does not recommend diesel
This is the line that decides whether the GB20 is the right model. NOCO's tech specs page gives a gas engine rating of up to 4.0 litres and, under Diesel Engine Rating, the entry reads: Not Recommended. Amazon's title and bullets say the same thing by omission — they claim engines up to 4.0L gas and never mention diesel at all. If you drive a diesel, this is not the NOCO to buy.
Starting current is 500 amps peak, and the internal battery is a 24 watt-hour lithium-ion pack. Both the guide and the specs page state the unit is for 12-volt lead-acid batteries only, and the guide adds that jump starting other battery chemistries may result in injury, death or property damage, that you should contact the battery maker first, and that you should not attempt it if you are unsure of the battery's chemistry or voltage.
NOCO's overview material says up to 20 starts on a charge. That is a maker figure for a fully charged unit, not a guarantee for a cold morning on a tired battery.
Powersport clamps, and the rest of the box
NOCO's box list for the GB20 is the jump starter, Powersport Boost Battery Clamps, a USB-C to USB-C cable, a microfiber storage bag and safety and warranty information. Amazon's included-components field calls them needle-nosed booster clamps. Either way, these are the narrow-nose clamps meant to reach the small, tightly packed terminals on motorcycles and powersport batteries, not the broad heavy-duty type.
Amazon's table lists a cable length of 7 inches, which is short by car-jumper standards and consistent with a powersport-oriented pack. NOCO's accessory notes on the GB20 how-to page mention mounting the GBC007 eyelets to connect to a motorcycle battery more easily, the NUSB211NA charging adapter for faster charging, and the GBC013 case for storage — all sold separately.
The two maker documents do not agree on size. NOCO's specs page gives 7.72 inches wide, 3.16 high and 1.71 deep at 2.1 pounds; the technical specifications page inside the GB20 user guide lists 6.7 by 3.2 by 1.7 inches and 2.4 pounds. Amazon's table adds a third set of dimensions and a 1-pound weight. Treat the shipping weight on the listing with caution.
The starting routine and the five-in-fifteen rule
The guide's order is: clamps to the GB20's 12V OUT port first, then red to the positive terminal, then black to the negative terminal or the vehicle chassis, and disconnect in reverse. Those steps are written for negative-ground systems, which is almost all vehicles; for the uncommon positive-ground case the guide says to reverse the order. It also says not to connect to the carburettor, fuel lines or thin sheet metal, and to read the vehicle's own manual for its jump-starting precautions first.
Turn off the car's power loads — headlights, radio, air conditioning — then press the power button. All LEDs flash as a self-test; a white Boost LED means it is ready, and a red Error LED means the clamps are reversed. The guide says most vehicles start immediately, some need the GB20 connected for up to 30 seconds, and if it does not start you should wait 20 to 30 seconds and try again.
The limit is explicit: do not attempt more than five consecutive jump starts within a fifteen-minute period, and allow the GB20 to rest for fifteen minutes before trying again. A red Error LED blinking with the cables connected properly means the internal battery is too hot, and the fix given is to let the unit cool and move it somewhere cooler. Cooling is by natural convection, with no fan.
Manual override starts a battery below 2 volts — with the protections off
The GB20 is designed to jump start 12-volt lead-acid batteries down to 2 volts. Below that, the Boost LED stays off because the unit cannot detect a battery at all. Manual Override, enabled by holding its button for three seconds, forces the jump-start function on so you can work with a deeply flat battery.
The guide's caution is printed in capitals: both the spark-proof and reverse-polarity protection features are disabled in this mode. It tells you to pay very close attention to polarity, not to let the positive and negative clamps touch or connect to each other because the product will generate sparks, and that the mode uses very high current — up to 500 amps — which can cause sparks and high heat if misused. If you are unsure about it, the guide says do not attempt it and seek professional help.
A label warning reproduced on the guide's safety pages goes further, stating that Manual Override Mode disables all safety measures and that using it improperly or against NOCO's recommended use may result in injury or death and will void your warranty. In normal operation the named protections are spark-proof connections and reverse-polarity protection, and the housing is rated IP65 with the ports closed.
Charging, temperature limits and keeping it ready
The guide's recharge table is about 12 hours from a 0.5-amp source, 6 hours at 1 amp and 3 hours at 2 amps; Amazon's bullet quotes the 3-hour figure. The unit arrives partially charged and must be fully charged before first use. The USB input port is rated at 2.1 amps, and NOCO's specs page names it as USB-C at 5 volts 2.1 amps max, with the USB output at the same 5 volts 2.1 amps. The guide says it can be recharged from any powered USB port — AC adapter, car charger or laptop — and that because of FCC regulations NOCO recommends not charging and discharging at the same time.
Temperature ranges come from the guide's technical specifications: operating -20°C to +50°C, charging 0°C to +40°C, and storage -20°C to +50°C with a 0°C to +25°C daily average, never exceeding 80°C under any condition. A separate label warning says not to disassemble, crush, heat above 60°C (140°F) or incinerate. The guide says to stop using the product immediately if the battery becomes excessively warm, and never to jump start a frozen battery.
For keeping it charged, the guide says an unused product will discharge over time and must be recharged before use, to disconnect it from power when not in use, and to avoid leaving it on charge for more than a week at a time because overcharging may shorten battery life. It gives no specific recharge interval for storage, so set your own reminder. Its labels also say the device is intended for temporary use outdoors, is not intended for use in a commercial repair facility, and should be stored indoors when not in use. For charging it asks for the included cable with a NOCO 10W 12V adapter, or a third-party 5W or 10W adapter meeting one of several named standards.
One-year warranty, non-transferable
The guide's warranty section covers NOCO-branded products in their original packaging against defects in materials and workmanship, when used normally in accordance with NOCO's published guidelines, for one year from the date of original retail purchase or delivery to the end-user purchaser. NOCO's specs page summarises the same period as a 1 Year Hassle-Free Warranty, and Amazon's details field says 1-Year Limited Warranty.
The warranty text states it is non-transferable and does not cover return packaging and transportation costs. It does not apply to damage from accident, abuse, misuse, fire, liquid contact or other external causes, mishandling, improper installation, modification, disassembly or attempted unauthorised repair, cosmetic damage that does not affect function, damage from operating the product outside NOCO's published guidelines, defects from normal wear and ageing, or a product whose serial number has been removed or defaced.
On a claim, NOCO may repair the product, replace it with a new or like-new unit of the same model or one with substantially similar features, or exchange it for a refund of the purchase price, at its option. Proof of purchase is required. The text also notes that for purchasers in the EU, EFTA and the UK the period may extend to a minimum of two years. Because the coverage is non-transferable and starts at original purchase, check the seller and the condition of the offer you select, and keep the receipt.
Check the current listing
Confirm the model, included parts and availability before ordering.
Primary sources
- NOCO GB20 user guide and warranty, dated 03.07.2025A
- NOCO tech specs page for the GB20 500A jump starter
- NOCO GB20 how-to page with LED, button and troubleshooting tables
Primary sources checked .
Compare with
- NOCO Boost GB40 1000A 12V Lithium Jump Starter
Gas engines to 6.0L and diesels to 3.0L on 12V lead-acid
- NOCO Boost X GBX75 2500A 12V Lithium Jump Starter
Gas engines to 8.5L and diesels to 6.5L on 12V lead-acid
- GOOLOO GP4000 4000A 12V Jump Starter
Larger gas and diesel engines, plus 12V accessory power
- GOOLOO A3 3000A Jump Starter with Air Compressor
One glovebox tool for a flat battery and a soft tire
Side-by-side pages, this model next to: NOCO Boost GB40 1000A 12V Lithium Jump Starter, NOCO Boost X GBX75 2500A 12V Lithium Jump Starter, GOOLOO GP4000 4000A 12V Jump Starter, GOOLOO A3 3000A Jump Starter with Air Compressor.