The Edit — Road Trips
Jump Starter Peak Amps: The Number That Doesn't Start a Car
Jump starter listings now claim 4,000, 6,000, even 7,000 peak amps. The number that tells you whether one will start your car is the engine size the maker names, and the cranking amps the better ones publish.
This guide is research-led: we have not handled these units ourselves. If you buy through our links we may earn a commission — it never changes a pick. How we choose
Nothing here was used or tested. The page reads the makers’ own specifications, and the 3 packs shown are ranked as How we choose describes.
NOCO Boost GB40 1000A Lithium Jump Starter
Good fit Your car is a 4 or 6 cylinder and you want the most-proven pack
Not for You drive a diesel pickup over 3.0 litres
Clore Automotive Jump-N-Carry JNC660
Good fit You want a garage unit with published cranking amps and heavy cables
Not for It has to fit in a glovebox
NOCO Boost GB20 500A Jump Starter
Good fit Your car has a 4-cylinder engine and space is tight
Not for You drive a V8 or any diesel
Peak amps is a burst, not the power that turns an engine
Peak amps is the most current a pack can release in an instant, a fraction of a second at the moment the clamps close. Turning an engine over takes a sustained current for several seconds, and the peak figure says nothing about that.
No shared test sits behind the peak number on these listings, so one maker’s 4,000A cannot be compared with another’s 1,000A. That is how the headline figure on budget packs has climbed to 6,000 and 7,000.
Cranking amps is the number that means something
Cranking amps comes from the battery industry. It is the current a 12-volt battery can deliver for 30 seconds at 32°F, and cold cranking amps is the same test at 0°F. Both are sustained figures, which is why they predict whether an engine turns over.
Few portable packs publish one. Clore is an exception: its Jump-N-Carry JNC660 is sold as 1,700 peak amps and 425 cranking amps, and the second number is the one that says what it does.
| Pack | Peak figure claimed | Engine size the maker states | Cranking amps published |
|---|---|---|---|
| NOCO Boost GB20 | 500A | Gas to 4.0 L | No |
| NOCO Boost GB40 | 1,000A | Gas to 6.0 L, diesel to 3.0 L | No |
| Clore JNC660 | 1,700A | Cars, trucks, SUVs | 425 |
| TREKURE 4000A | 4,000A | Gas to 8.0 L, diesel to 6.5 L | No |
| OXILAM 6000A | 6,000A | All gas, diesel to 12 L | No |
The engine size on the box is the practical guide
The most useful line on a jump starter is the engine size its maker commits to, in litres of gas and of diesel. NOCO rates the Boost GB40 for gas engines up to 6.0 litres and diesels up to 3.0, from a 1,000A pack.
Compare that with the table. The TREKURE claims 4 times the GB40’s peak figure and an engine limit only a third higher, at 8.0 litres. The peak number grew far faster than the engines it claims to start.
NOCO Boost GB40 1000A Lithium Jump Starter
1,000A, rated by NOCO for gas engines to 6.0 litres and diesels to 3.0, with 129,470 ratings behind it.
Current price shown on Amazon. We may earn a commission.
| Maker's engine rating | 6.0L gas, 3.0L diesel |
|---|---|
| Peak figure | 1,000A |
| Also | USB power bank, light |
129,470 ratings at 4.6 is one of the deepest owner records in car accessories, and it belongs to a pack sold on its engine rating rather than on a giant peak number. Owners find the GB40 far easier than jumper cables and small enough to travel with, and it doubles as a USB power bank.
Battery life is where the reports split, some describing a pack that holds its charge for months and others less happy with it. Check the charge level before a long winter drive rather than finding out at the roadside.
Buy it if
- Your car is a 4 or 6 cylinder and you want the most-proven pack
Don't buy it if
- You drive a diesel pickup over 3.0 litres
Diesels and cold mornings need a margin
A diesel needs more current than a gas engine of the same size, because it runs at a far higher compression. That is why the GB40’s diesel limit is half its gas limit.
Cold makes it harder at both ends. A cold engine has thicker oil to push through, and a lithium pack delivers less when it is cold itself. Buy a pack rated above your engine size rather than exactly at it, and keep it in the cabin rather than the trunk when temperatures drop.
Clore Automotive Jump-N-Carry JNC660
1,700 peak and 425 cranking amps from a lead-acid pack built for garages and tow trucks.
Current price shown on Amazon. We may earn a commission.
| Cranking amps | 425 |
|---|---|
| Peak figure | 1,700A |
| Weight | 18 lb, #2 AWG cables |
The JNC660 is a lead-acid pack, 18 lb with #2 AWG welding-cable leads, built for service garages and tow operators. That weight buys the published 425 cranking amps, and owners report it starting BMW and Mercedes engines with power to spare.
4.6 across 19,866 ratings. It recharges automatically, but it is a garage or trunk unit. It will not live in a glovebox.
Buy it if
- You want a garage unit with published cranking amps and heavy cables
Don't buy it if
- It has to fit in a glovebox
NOCO Boost GB20 500A Jump Starter
500A, rated by NOCO for gas engines to 4.0 litres, sized for a small car or a motorcycle.
Current price shown on Amazon. We may earn a commission.
| Maker's engine rating | 4.0L gas |
|---|---|
| Peak figure | 500A |
| Suits | Small cars, motorcycles |
The GB20 is NOCO’s smaller pack, 500A and rated for gas engines up to 4.0 litres. Owners describe it starting most vehicles they tried, a Honda Pilot among them, from a pack compact enough to carry anywhere.
4.6 across 13,189 ratings. Battery life draws the same split reports as its bigger sibling’s. It suits a 4-cylinder car, and a V8 owner should look at the GB40.
Buy it if
- Your car has a 4-cylinder engine and space is tight
Don't buy it if
- You drive a V8 or any diesel
The full shortlist, including the high-peak budget packs, is in portable jump starters, compared, and the rest of the winter kit is in what NHTSA says to carry.