How many amps do I need to jump start my car?

Use the manufacturer's engine rating in liters rather than converting amps yourself — it already accounts for fuel type and compression. As a reference point, NOCO rates its 1,000-peak-amp GB40 to 6.0 L gas and 3.0 L diesel, and its 2,000-peak-amp GB70 to 8.0 L gas and 6.0 L diesel. Buy the rating that clears your engine with margin, because cold weather and an ageing battery both consume margin.

Will a portable jump starter work on a completely dead battery?

Often yes, but not always, and the reason matters. A jump starter supplies the cranking current directly, so a battery that is too flat to turn the engine can still be bypassed. But a battery with a failed cell, a frozen electrolyte, or an open circuit will not accept the boost, and some packs refuse to engage below a minimum detected voltage. If the pack starts the car and the problem returns the next morning, the battery is the fault, not the trigger.

How long does a jump starter hold its charge?

A lithium pack left alone loses charge slowly, but it does lose it, and heat accelerates that. The practical answer is to top it up on a schedule you will actually keep — every three months is a reasonable habit — and to check it before any long trip. A pack that sat in a hot trunk all summer is the one most likely to disappoint you in November.

Is it safe to use a jump starter myself?

Modern lithium packs with reverse-polarity protection are far more forgiving than jumper cables, which is most of the reason to own one. The residual risks are the same as any battery work: do not let the clamps touch each other or any other metal while the pack is live, connect positive first and negative to an unpainted engine ground rather than the battery's negative post where the manufacturer specifies it, and stop if you see a cracked case, a swollen battery or smell anything.

Clamp & Crank

Portable jump starters

A jump pack is the one trunk tool that turns a tow truck into a five-minute inconvenience. This is how to size one, and which ones are worth the space.

A portable jump starter is a lithium battery with clamps on it. That is genuinely the whole idea. It holds enough energy to spin your starter motor for a few seconds, which is all a healthy engine needs, and it does it without a second car, a stranger, or a wait on the shoulder. For most drivers it is the single highest-value thing you can put in a trunk, because the failure it fixes — a battery that will not crank — is by a wide margin the most common reason a car does not move.

The category has one real decision in it and a lot of noise around that decision. The decision is how much starting current you need, which is set by your engine's displacement and fuel type. The noise is everything else: mAh figures that are not comparable across brands, peak-amp claims that are not measured the same way from one tier to the next, and feature lists that pad a spec sheet without changing whether the thing starts your truck at 15 °F.

If you have already settled on a pack and are only checking whether something better exists at the same size, start from the substitution rather than from the category: NOCO GB70 alternatives compares the diesel-grade packs on NOCO’s own published engine ratings, including when the extra headroom is not worth the weight.

Start here: size before brand

Manufacturers publish an engine rating in liters, and it is the most useful number on the box because it already folds in the arithmetic. NOCO, for example, rates the GB40 to 6.0 L gas and 3.0 L diesel, and the GB70 to 8.0 L gas and 6.0 L diesel. Diesels get a much lower rating than gas engines at the same pack size because they crank against far higher compression and draw more current doing it.

So the shortest honest path through this category is: look up your engine's displacement, read it against the published gas or diesel rating, and buy a pack that clears it with margin rather than one that just meets it. Cold weather eats margin, an ageing battery eats margin, and the morning you actually need the pack is the morning both are true. Our jump starter sizing guide lays the engine-size table out in full, and peak amps vs cranking amps explains why the big number on the front of the box is not the number that does the work.

How the category divides

There are four practical groups, and they barely compete with each other:

Compact lithium packs (roughly 1,000-1,500 peak amps, 24-35 Wh, 2-3 lb). The default for a four- or six-cylinder car. Small enough to live in a door pocket, which is the property that decides whether it is still in the vehicle in a year.
Heavy-duty lithium packs (2,000-3,000 peak amps, 56-88 Wh, 4-6.5 lb). Diesel pickups, big V8s, equipment. See the diesel roundup.
Combo units with a built-in air compressor. One box for two problems, at a real cost in size and in compressor quality — the combo roundup is honest about the tradeoff, and our DEWALT DXAEJ14 review takes the best-known one apart spec by spec.
Lead-acid jump stations. Heavy, cheap, indifferent to a hot trunk, and prone to being flat when you need them because they self-discharge.

What actually decides price

Three things, in this order. Capacity and current — a 56 Wh, 2,000 A pack costs more than a 24 Wh, 1,000 A pack because there is more battery inside it. Rating credibility — the majors publish an engine rating they will stand behind under a warranty, and budget brands publish a bigger peak-amp number they define differently; you are partly paying for a claim you can hold someone to. Build and protection — an IP65 enclosure, reverse-polarity protection, and clamps with real copper in them, versus the ones that get warm.

What does not meaningfully move the price is the feature list. A flashlight, a USB port and a carry case are nice, and none of them is why one pack costs twice another.

The mistake buyers make

Two mistakes, and they pull in opposite directions. The first is buying on peak amps alone and ending up with a pack rated for an engine three sizes bigger than the one in the driveway — heavier, pricier, and no more likely to start your Civic. The second, and more common, is buying the smallest pack available for a diesel pickup because the listing said "for trucks", and discovering on the first genuinely cold morning that there is no margin left.

There is a third mistake worth naming: expecting a jump pack to fix a battery. It will not. A pack gets you moving; if the battery is the thing that failed, you need a charger or a maintainer to deal with the cause, and our guide to whether a jump starter will start a completely dead battery is blunt about where the line is.

If you fly, check the watt-hours first

This matters more than most buyers realize and almost no listing explains it. Every lithium pack has a watt-hour rating, and that number decides whether you can take it on a plane at all. The FAA's allowance covers lithium-ion batteries up to 100 Wh; between 101 and 160 Wh you need airline approval and can carry at most two spares. Every NOCO Boost pack sits under 100 Wh, including the 88 Wh GB150 — but plenty of larger "power station" style units do not. Read flying with a jump starter before you pack one, and mAh vs watt-hours if your unit only advertises mAh.

Narrowing it down inside one range

Most people arrive here having already decided they want a compact lithium pack, and the remaining question is which rung of the ladder. The compact end of NOCO's Boost range is where that gets genuinely close: GB40 versus GB50 is the quarter-of-a-pound question — whether an extra liter of engine rating is worth it — and GB40 versus GB70 is the bigger either/or for anyone weighing a diesel.

Buying guides

Ranked picks with a comparison table, per-pick reasoning, and an honest note on who each one is wrong for.

Best Portable Jump Starters

Our main roundup: five packs from compact to heavy-duty, ranked on the engine rating the manufacturer will actually stand behind.

Top pick: NOCO Boost Plus GB40

$99.95View on Amazon

#ad Affiliate link · Price as of November 10, 2026

Best Jump-and-Inflate Combo

Best With an Air Compressor

Combo units that jump and inflate — plus a frank accounting of what the built-in compressor gives up against a dedicated inflator.

Top pick: DEWALT DXAEJ14 Power Station

$129.00$169.00View on Amazon

#ad Affiliate link · Price as of November 10, 2026

Best for Diesel Trucks

For Diesel Trucks

Packs with a published diesel rating that actually covers a 3.0 L to 6.7 L light-truck engine, with margin for a cold morning.

Top pick: NOCO Boost HD GB70

$199.95View on Amazon

#ad Affiliate link · Price as of November 10, 2026

Best for SUVs & Trucks

For SUVs & Trucks

For gas V6 and V8 SUVs and pickups: the packs that clear a 5.3 L or 6.2 L engine with margin, without buying diesel-grade weight.

Top pick: NOCO Boost Plus GB50

$149.95View on Amazon

#ad Affiliate link · Price as of November 10, 2026

Best for Cold Weather

For Cold Weather

Winter picks with real margin, plus the one situation where a lead-acid box beats lithium and why lithium usually still wins.

Top pick: NOCO Boost HD GB70

$199.95View on Amazon

#ad Affiliate link · Price as of November 10, 2026

Best Jump Starter Power Banks

Dual-purpose packs judged on watt-hours and USB-C Power Delivery, not on the fact that a USB socket exists.

Top pick: NOCO Boost X GBX155

$369.95View on Amazon

#ad Affiliate link · Price as of November 10, 2026

Best for Semi Trucks

Why 24-volt capability, not peak amps, decides this category — and the short list of packs that actually have it.

Top pick: NOCO Boost MAX GB251

$1,199.95View on Amazon

#ad Affiliate link · Price as of November 10, 2026

Best for Motorcycles

Compact packs correctly sized for powersports batteries, plus why a bike battery dies differently from a car's.

Top pick: NOCO Boost Sport GB20

$79.95View on Amazon

#ad Affiliate link · Price as of November 10, 2026

Best With AC

Best With an AC Outlet

The AC confusion explained: charging input versus power outlet, and what to buy depending on which one you actually need.

Top pick: DEWALT DXAEJ14 Power Station

$129.00$169.00View on Amazon

#ad Affiliate link · Price as of November 10, 2026

Best for Hybrids

Best for Hybrid Cars

Why hybrids need a modest pack, why their 12-volt battery fails so often, and the safety line you never cross.

Top pick: NOCO Boost Plus GB40

$99.95View on Amazon

#ad Affiliate link · Price as of November 10, 2026

Best for ATVs

Compact sealed packs sized for powersports batteries, chosen for surviving a dusty storage box and a long way from help.

Top pick: NOCO Boost Sport GB20

$79.95View on Amazon

#ad Affiliate link · Price as of November 10, 2026

Best for Lawn Mowers

Mower and garden-tractor batteries are U1-size and spend half the year doing nothing. The right pack, and the cheaper fix most people actually need.

Top pick: NOCO Boost Sport GB20

$79.95View on Amazon

#ad Affiliate link · Price as of November 10, 2026

Best for an F-150

Matched to the F-150's engine lineup using NOCO's published liter ratings — plus the one-box option if you want air as well as amps.

Top pick: NOCO Boost HD GB70

$199.95View on Amazon

#ad Affiliate link · Price as of November 10, 2026

Best for a Wrangler

Picks sized to the Wrangler's engines, with the trail-specific problem — airing back up — treated as part of the same purchase.

Top pick: NOCO Boost Plus GB40

$99.95View on Amazon

#ad Affiliate link · Price as of November 10, 2026

Best for an EV

Best for a Tesla

Why peak amps are the wrong spec for an EV, what a pack is actually doing when a Tesla will not wake up, and the three we would keep in the frunk.

Top pick: NOCO Boost Plus GB40

$99.95View on Amazon

#ad Affiliate link · Price as of November 10, 2026

Best for a V8 engine

Best for a V8

NOCO's published gas and diesel liter ratings read against the V8 displacements actually on the road, plus the sizing rule that keeps you from buying one rung short.

Top pick: NOCO Boost Plus GB50

$149.95View on Amazon

#ad Affiliate link · Price as of November 10, 2026

Best for a Ram 1500

Matched to the Ram 1500's engine lineup using NOCO's published liter ratings, with the cable-length and under-hood access problems a half-ton actually has.

Top pick: NOCO Boost Plus GB50

$149.95View on Amazon

#ad Affiliate link · Price as of November 10, 2026

Best for a Tacoma

Why a small-displacement truck is the one case where buying down is reasonable, and what changes if the Tacoma spends its weekends on a trail.

Top pick: NOCO Boost X GBX45

$124.95View on Amazon

#ad Affiliate link · Price as of November 10, 2026

Best for a Silverado 1500

Sized against published gas-engine ratings for a 2.5 to 4.0-liter V6, with the cold-morning margin the ratings do not mention.

Top pick: NOCO Boost Plus GB50

$149.95View on Amazon

#ad Affiliate link · Price as of November 10, 2026

Best GB40 alternative

GB40 Alternatives

What the GB40 is known for, stated from NOCO's own specifications — then three alternatives that beat it on price, on air, or on claimed engine coverage.

Top pick: GOOLOO GT4000S

$99.96$139.99View on Amazon

#ad Affiliate link · Price as of November 10, 2026

The GB50 on NOCO's published figures: 1,500 peak amps, 35 watt-hours and a 7.0 liter gas rating, set against the GB40 below it and the GBX45 beside it.

Read it

The narrow comparison the Boost range forces on most buyers, decided on NOCO's published engine ratings — plus the case for skipping both and buying the GBX45.

Read it

Charging methods and times, how often to top up, and why a pack that sat in a hot car all summer needs checking before winter.

Read it

Guide

How Long Does One Last?

Charge retention, starts per charge and total service life, separated out — plus the one factor that shortens all three.

The diagnostic order for a car that will not start even with a working jump pack on it — sorted by the noise it makes when you turn the key.

Read it

Troubleshooting

Won't Start, Just Clicks

The single-click and rapid-click faults told apart, with the voltage checks that confirm each and the tool that actually fixes it.

Read it

Guide

Can It Charge a Battery?

Why a jump pack cannot charge a battery, the small amount it does put back while connected, and the charger sizes that actually do the job.

Read it

Guide

Do They Go Bad?

How lithium and lead-acid packs age, how long each holds a charge on a shelf, and the maintenance interval that keeps a pack usable for years.

Read it

Guide

Jump Starting an EV

The 12-volt battery is the one that strands EV owners, and a normal jump pack fixes it. The rules, the risks, and the packs that fit the job.

Read it

Common questions

How many amps do I need to jump start my car?: Use the manufacturer's engine rating in liters rather than converting amps yourself — it already accounts for fuel type and compression. As a reference point, NOCO rates its 1,000-peak-amp GB40 to 6.0 L gas and 3.0 L diesel, and its 2,000-peak-amp GB70 to 8.0 L gas and 6.0 L diesel. Buy the rating that clears your engine with margin, because cold weather and an ageing battery both consume margin.
Will a portable jump starter work on a completely dead battery?: Often yes, but not always, and the reason matters. A jump starter supplies the cranking current directly, so a battery that is too flat to turn the engine can still be bypassed. But a battery with a failed cell, a frozen electrolyte, or an open circuit will not accept the boost, and some packs refuse to engage below a minimum detected voltage. If the pack starts the car and the problem returns the next morning, the battery is the fault, not the trigger.
How long does a jump starter hold its charge?: A lithium pack left alone loses charge slowly, but it does lose it, and heat accelerates that. The practical answer is to top it up on a schedule you will actually keep — every three months is a reasonable habit — and to check it before any long trip. A pack that sat in a hot trunk all summer is the one most likely to disappoint you in November.
Is it safe to use a jump starter myself?: Modern lithium packs with reverse-polarity protection are far more forgiving than jumper cables, which is most of the reason to own one. The residual risks are the same as any battery work: do not let the clamps touch each other or any other metal while the pack is live, connect positive first and negative to an unpainted engine ground rather than the battery's negative post where the manufacturer specifies it, and stop if you see a cracked case, a swollen battery or smell anything.