Powermax Lithium 12v Jump Starter Review

How to choose a lithium jump starter

Match peak amps to the engine, not to the marketing

Peak amps are the headline number, but the engine rating is the useful one: the GB40 is rated for gasoline engines up to 6.0 litres, the GB70 up to 8.0 litres, and the GB150 up to 9.0 litres, while the PMJS-2000 is rated by cylinder count, up to 40 starts on 4-cylinder engines. Buy the pack whose engine rating covers the largest engine it must start, with margin, not the pack with the largest peak-amp number.

Check the diesel rating separately

Diesel engines need more cranking power than gasoline engines of the same size, so every pack here has a lower diesel rating: the GB40 covers diesel up to 3.0 litres, the GB70 up to 6.0 litres, and the GB150 up to 7.0 litres. A diesel owner who buys by the gasoline rating will be underpowered, so check the diesel line before ordering, even if the gasoline rating looks generous.

Weigh lithium against lead-acid honestly

Lithium packs are light — the PMJS-2000 is under 5 pounds — and easy to carry, while the Clore JNC660 lead-acid unit weighs 18 pounds but offers a 22Ah battery built for shop use and numerous jumps per charge. Lithium suits a glovebox or trunk; lead-acid suits a workshop where weight does not matter and repeated shop jumps are the job. Neither chemistry is better for every owner.

Count starts per charge for real use

Starts per charge decide whether the pack is ready when it is needed: the GB40 gives up to 20 starts, the GB70 up to 40, the GB150 up to 80, and the PMJS-2000 up to 40 on 4-cylinder engines. A pack that is rarely recharged needs a higher starts-per-charge figure, since a dead jump starter cannot jump anything. Recharge the pack on the maker’s schedule, not when it is already flat.

Check the safety protections before the extras

Spark-proof clamps and reverse-polarity protection matter more than a flashlight or a power bank, because a jump starter is used on a dead battery in bad conditions. The NOCO packs carry UltraSafe spark-proof and reverse-polarity protection, and the PMJS-2000 carries reverse-polarity, over-discharge, and short-circuit protection. Check the protection list first, then judge the extras.

Plan charging and storage before buying

Lithium packs need regular top-ups — the PMJS-2000 maker recommends recharging every 30 days — and storage within the operating range, 0 degrees Fahrenheit to 104 degrees Fahrenheit for the PMJS-2000. A pack left flat in a hot trunk or a freezing garage for months may not work when it is needed. Buy the pack whose charging routine you will actually follow.

This guide sits under EMERGENCY & ROADSIDE EQUIPMENT and in the Lithium Jump Starters subcategory.

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Detailed reviews

Each block below gives only the specifications the listing, catalogue page, or maker document actually publishes. Unpublished specifications are omitted, and the watch-outs explain what to measure or confirm before you buy.

Best Reviewed Lithium Pack: PowerMax PMJS-2000 12V Lithium Jump Starter

Best Reviewed Lithium Pack

Why the PowerMax PMJS-2000 is our pick

The PMJS-2000 is the subject of this review because its published facts form a complete mid-size lithium pack: 2000 peak amps and 1000 cranking amps, a lithium-polymer battery of 49.6 watt-hours, USB output at 5 volts 2.4 amps, and a DC output at 12 volts 15 amps and 180 watts maximum, with 6 AWG cables 14 inches long and an LED work light with 3 modes. The maker claim of up to 40 jump starts per charge on 4-cylinder engines puts it beside the NOCO GB70 on starts, at a lower weight.

The caveat is stated plainly: the ASIN record comes from an import listing of the US Amazon listing and a maker and retailer page, not from a US Amazon listing page surfaced directly in this research. The facts used here — peak amps, watt-hours, outputs, cable gauge, operating range, and warranty — come from the maker and retailer page, which is the citable source. A buyer should confirm the listing before ordering, since the evidence chain is thinner than for the NOCO packs.

PowerMax PMJS-2000 key specs

• Peak amps: 2000
• Cranking amps: 1000
• Battery: lithium-polymer, 49.6 Wh
• Starts per charge: up to 40 on 4-cylinder engines
• USB output: 5V 2.4A
• DC output: 12V 15A, 180W maximum
• Cables: 6 AWG, 14 in
• LED work light: 3 modes
• Operating range: 0 degrees F to 104 degrees F
• Weight: under 5 lb
• Warranty: 3-year limited manufacturer warranty

PowerMax PMJS-2000: fits and best for

Best for owners of 4-cylinder cars who want a light lithium pack with a power bank and work light built in. It suits glovebox and trunk carry. It is not for large diesel engines, and its evidence chain is thinner than the NOCO packs, so a buyer should confirm the listing.

PowerMax PMJS-2000 pros and watch-outs

PowerMax PMJS-2000: what owners report

PowerMax PMJS-2000: who should not buy

Owners of large diesel engines, or who need a litre-rated pack for engines over 4 cylinders, should not buy the PMJS-2000 first. The NOCO GB70 and GB150 carry litre ratings for larger engines.

PowerMax PMJS-2000: pair it with

Pair it with a 30-day recharge reminder, and a check of the listing before ordering.

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Best Compact Lithium Pack: NOCO Boost Plus GB40

Best Compact Lithium Pack

Why the NOCO GB40 is our pick

The GB40 is the compact lithium pack because its ratings are published cleanly: 1000 peak amps, gasoline engines up to 6.0 litres, diesel up to 3.0 litres, up to 20 starts per charge, and UltraSafe spark-proof plus reverse-polarity protection, with a 1-year warranty. Its part number GB40 and UPC 046221150025 identify the exact pack, which matters because NOCO sells several Boost models with similar names.

For a car or small truck, 1000 peak amps and 20 starts per charge are enough, and the compact size suits glovebox carry. The trade-off is the lower diesel rating and the 20-start limit: a diesel owner or a household with several vehicles will outgrow it faster than the GB70. Buy it for one or two gasoline vehicles, not for a fleet.

NOCO GB40 key specs

• Peak amps: 1000
• Gasoline rating: up to 6.0L
• Diesel rating: up to 3.0L
• Starts per charge: up to 20
• Protection: UltraSafe spark-proof, reverse-polarity
• Part: GB40
• UPC: 046221150025
• Battery: lithium
• Warranty: 1 year
• Use: cars, small trucks, motorcycles, ATVs, boats
• Not stated in the sources consulted: watt-hour capacity

NOCO GB40: fits and best for

Best for owners of gasoline cars and small trucks up to 6.0 litres who want a compact lithium pack. It suits glovebox carry and occasional use. It is not for large diesel engines, and 20 starts per charge suits one or two vehicles, not a fleet.

NOCO GB40 pros and watch-outs

NOCO GB40: what owners report

NOCO GB40: who should not buy

Owners of diesel engines over 3.0 litres, or who need more than 20 starts per charge, should not buy the GB40 first. The GB70 covers diesel to 6.0 litres with 40 starts.

NOCO GB40: pair it with

Pair it with a regular recharge routine, and check the diesel rating before ordering for a diesel vehicle.

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Best Mid-Size Lithium Pack: NOCO Boost HD GB70

Best Mid-Size Lithium Pack

Why the NOCO GB70 is our pick

The GB70 is the mid-size lithium pack because it matches the PMJS-2000 on peak amps at 2000, then adds litre ratings the PowerMax does not publish: gasoline engines up to 8.0 litres and diesel up to 6.0 litres, with up to 40 starts per charge, a 400-lumen LED flashlight, a power bank, and a 1-year warranty. Its part number GB70 and UPC 046221150056 identify the exact pack.

For a household with a larger gasoline engine or a light diesel, the GB70 is the step up from the GB40 that keeps lithium portability. The 400-lumen flashlight is a genuine extra for night breakdowns, and the 40-start figure matches the PMJS-2000’s claim while covering larger engines. The trade-off is size and weight against the compact GB40, and a shorter warranty than the PowerMax.

NOCO GB70 key specs

• Peak amps: 2000
• Gasoline rating: up to 8.0L
• Diesel rating: up to 6.0L
• Starts per charge: up to 40
• LED flashlight: 400 lumens
• Extras: power bank
• Part: GB70
• UPC: 046221150056
• Battery: lithium
• Warranty: 1 year
• Not stated in the sources consulted: watt-hour capacity

NOCO GB70: fits and best for

Best for owners of larger gasoline engines up to 8.0 litres and light diesel up to 6.0 litres who want lithium portability with more starts. It suits households with several vehicles. It is not for diesel over 6.0 litres, and it is larger than the compact GB40.

NOCO GB70 pros and watch-outs

NOCO GB70: what owners report

NOCO GB70: who should not buy

Owners of diesel engines over 6.0 litres, or gasoline over 8.0 litres, should not buy the GB70 first. The GB150 covers gasoline to 9.0 litres and diesel to 7.0 litres.

NOCO GB70: pair it with

Pair it with a night-breakdown check of the flashlight and clamps, and a regular recharge routine.

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Best Largest Lithium Pack: NOCO Boost GB150

Best Largest Lithium Pack

Why the NOCO GB150 is our pick

The GB150 is the largest lithium pack because its numbers top the NOCO lithium ladder: 3000 peak amps, gasoline engines up to 9.0 litres, diesel up to 7.0 litres, and up to 80 starts per charge, with part number GB150 identifying the exact pack. For a large gasoline engine or a diesel up to 7.0 litres, it is the lithium answer that keeps portability while covering the biggest engines in this guide.

The 80-start figure also changes the maintenance story: a pack that holds 80 starts tolerates a neglected recharge schedule far better than the GB40’s 20. The trade-off is that the GB150 is the largest lithium pack here, and a buyer with a small car gains nothing from its extra power. Buy it for large engines and frequent use, not for a small car that the GB40 already covers.

NOCO GB150 key specs

• Peak amps: 3000
• Gasoline rating: up to 9.0L
• Diesel rating: up to 7.0L
• Starts per charge: up to 80
• Part: GB150
• Battery: lithium
• Use: large gasoline and diesel engines
• Protection: UltraSafe family (listing context)
• Warranty: 1 year (NOCO family listing)
• Suits: large engines and frequent use
• Not stated in the sources consulted: watt-hour capacity

The 7.0-litre diesel rating comes from an Amazon Canada listing record.

NOCO GB150: fits and best for

Best for owners of large gasoline engines up to 9.0 litres and diesel up to 7.0 litres who want the most lithium power and the most starts per charge. It suits frequent use and several vehicles. It is not for small cars, where its extra power is wasted, and it is the largest lithium pack here.

NOCO GB150 pros and watch-outs

NOCO GB150: what owners report

NOCO GB150: who should not buy

Owners of small cars, or who need a shop-grade lead-acid unit, should not buy the GB150 first. The GB40 covers small gasoline engines, and the Clore JNC660 is the lead-acid shop unit.

NOCO GB150: pair it with

Pair it with a storage-space check before ordering, and a recharge routine that matches its 80-start capacity.

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Best Lead-Acid Shop Unit: Clore Jump-N-Carry JNC660 12V Jump Starter

Best Lead-Acid Shop Unit

Why the Clore JNC660 is our pick

The JNC660 is the lead-acid alternative because it answers a different question from the lithium packs: what if the owner does not want lithium at all, or needs a shop unit that jumps many vehicles? Its published facts are 1700 peak amps, a 22Ah Clore Proformer battery designed for jump starting, heavy-duty 2 AWG cable leads, industrial-grade clamps, a 46-inch cable reach, and 12-volt accessory output with automatic circuit protection.

The trade-off is weight and size: at 18 pounds, the JNC660 is not a glovebox pack, and its lead-acid AGM battery needs different care from lithium. Its part number JNC660 and UPC 010271025350, first listed in 2006, identify a long-running shop product rather than a new lithium gadget. For a workshop, that history and the 22Ah capacity are the reasons to choose it; for a car trunk, they are the reasons not to.

Clore JNC660 key specs

• Peak amps: 1700
• Battery: 22Ah Clore Proformer, lead-acid AGM
• Cables: heavy-duty 2 AWG leads
• Clamps: industrial-grade clamps
• Cable reach: 46 in
• Accessory output: 12V with automatic circuit protection
• Part: JNC660
• UPC: 010271025350
• Weight: 18 lb
• First listed: 2006-09-11 (listing record)
• Not stated in the sources consulted: starts per charge figure

Clore JNC660: fits and best for

Best for workshops and owners who want a lead-acid shop unit with high capacity and many jumps per charge. It suits professional and frequent shop use. It is not for glovebox or trunk carry at 18 pounds, and it is not lithium.

Clore JNC660 pros and watch-outs

Clore JNC660: what owners report

Clore JNC660: who should not buy

Owners who want a light portable pack for a car trunk should not buy the JNC660 first. The PowerMax PMJS-2000 is under 5 pounds, and the NOCO packs are lithium and portable.

Clore JNC660: pair it with

Pair it with a workshop charging routine for lead-acid batteries, and a reach check against the largest engine bay.

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Spec comparison

First charge and first jump

Charge the pack fully before first use, following the maker’s charging input for the model: the PMJS-2000 accepts micro-USB or 12-volt DC input, and the maker recommends recharging every 30 days. Connect the clamps to the correct terminals — red to positive, black to a ground point — and check the protection indicators before starting. A pack that is not fully charged on first use gives a false impression of its power.

On the first jump, connect, start the vehicle, and disconnect promptly, then recharge the pack after use rather than leaving it flat. Note the starts used and the date, so the starts-per-charge figure can be judged against the claim. Store the pack within its operating range, and never jump a frozen, cracked, or leaking battery.

Related how-to guides on this site: Best battery tester under 100; Best battery charger under 100; Best portable jump starter under 100.

Test the finished setup on a short trip first, and re-check fit, fasteners, and connections after that trip before relying on it for a long haul.

Safety essentials

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Troubleshooting

Who should NOT buy these packs

Owners of engines larger than the pack’s rating should not buy a pack and expect it to start them. A pack rated for 6.0 litres gasoline will not reliably start a 9.0-litre engine, and repeated failed jumps drain the pack and stress the vehicle. Check the gasoline and diesel ratings separately, buy the pack whose rating covers the largest engine with margin, and step up to the GB150 or the Clore shop unit where the engine demands it.

Owners who will not recharge a lithium pack should not buy lithium and expect it to work months later. Lithium packs need regular top-ups — the PMJS-2000 maker recommends every 30 days — and a pack left flat in a trunk for months may not start anything. If the recharge routine will not happen, a lead-acid shop unit with different care, or a pack with a higher starts-per-charge figure that tolerates neglect better, is the honest alternative.

Owners who need a glovebox pack should not buy the Clore shop unit and expect portability. At 18 pounds, the JNC660 is a workshop tool, and carrying it as a portable pack defeats its purpose. Buy a lithium pack under 5 pounds for trunk or glovebox carry, and keep the Clore unit where it belongs: in the workshop, on a charger, ready for shop jumps.

Owners who want a battery tester or a charger should not buy a jump starter and expect it to do those jobs. A jump starter starts a dead battery; it does not diagnose a weak battery or maintain one over winter. Buy a battery tester for diagnosis and a charger or maintainer for storage, and keep the jump starter for the emergency it is built for. Related alternatives on this site include Best battery diagnostic scanners under 500; Best battery maintainers or jump starters; Digital battery testers for beginners best brands.

Final verdict

One line per pick, in award order.

Best Reviewed Lithium Pack: PowerMax PMJS-2000 12V Lithium Jump Starter — Best for the reviewed lithium pack: 2000 peak amps, 49.6 watt-hours, and up to 40 starts per charge on 4-cylinder engines. Check Price

Best Compact Lithium Pack: NOCO Boost Plus GB40 — Best for compact lithium power: 1000 peak amps for gasoline engines up to 6.0 litres and diesel up to 3.0 litres. Check Price

Best Mid-Size Lithium Pack: NOCO Boost HD GB70 — Best for mid-size lithium power: 2000 peak amps for gasoline engines up to 8.0 litres and diesel up to 6.0 litres. Check Price

Best Largest Lithium Pack: NOCO Boost GB150 — Best for the largest lithium power: 3000 peak amps for gasoline engines up to 9.0 litres and diesel up to 7.0 litres. Check Price

Best Lead-Acid Shop Unit: Clore Jump-N-Carry JNC660 12V Jump Starter — Best for a shop-grade unit that is not lithium: a 1700-peak-amp lead-acid pack with a 22Ah battery. Check Price

Frequently asked questions

What is the PowerMax PMJS-2000 jump starter?

It is a 12-volt lithium jump starter with 2000 peak amps and 1000 cranking amps, a 49.6 watt-hour lithium-polymer battery, USB and 12-volt outputs, and a maker claim of up to 40 jump starts per charge on 4-cylinder engines. It weighs under 5 pounds and carries a 3-year limited manufacturer warranty. This article reviews it against four alternatives from NOCO and Clore.

Is the PowerMax PMJS-2000 good for diesel engines?

The sources consulted give no litre-based diesel rating for the PMJS-2000, only the 4-cylinder gasoline claim, so a diesel owner should not assume coverage. The NOCO packs publish diesel ratings: GB40 to 3.0 litres, GB70 to 6.0 litres, and GB150 to 7.0 litres. A diesel owner should buy by the diesel rating, not the gasoline figure or the peak-amp number.

How many times can the PMJS-2000 jump start per charge?

The maker claims up to 40 jump starts per charge on 4-cylinder engines. That figure depends on the engine size, the battery condition, and the temperature, so larger engines and cold weather reduce it. For comparison, the GB40 gives up to 20 starts, the GB70 up to 40, and the GB150 up to 80. Recharge after use rather than counting on the maximum.

Lithium or lead-acid jump starter: which is better?

Lithium packs are light and portable — the PMJS-2000 is under 5 pounds — and suit trunk or glovebox carry. Lead-acid units such as the Clore JNC660 weigh 18 pounds but offer a 22Ah battery built for shop use and many jumps. Neither chemistry wins for every owner: lithium for portability, lead-acid for workshop capacity and a different maintenance routine.

How often should I recharge a lithium jump starter?

The PMJS-2000 maker recommends recharging every 30 days, and the same habit suits the NOCO packs. A lithium pack left flat for months may not work when it is needed, and a pack that holds many starts per charge tolerates neglect better than one that holds few. Set a monthly reminder, and recharge after every use rather than waiting for the next emergency.

Can a jump starter damage my car?

A modern protected pack reduces the risk: the NOCO packs carry spark-proof and reverse-polarity protection, and the PMJS-2000 carries reverse-polarity, over-discharge, and short-circuit protection. The remaining risks are reversed clamps on an unprotected pack, jumping a frozen or damaged battery, and leaving clamps connected after starting. Follow the maker’s connection order and disconnect promptly.

What size jump starter do I need for my engine?

Match the pack’s engine rating to the largest engine it must start, checking gasoline and diesel ratings separately. The GB40 covers gasoline to 6.0 litres, the GB70 to 8.0 litres, and the GB150 to 9.0 litres, while the PMJS-2000 is rated by cylinder count for 4-cylinder engines. Buy with margin, since a pack at its limit in cold weather may not start the engine.

Can I use a jump starter as a power bank?

The lithium packs here include device charging: the PMJS-2000 has a USB output at 5 volts 2.4 amps and a 12-volt output, and the NOCO packs include power-bank function. Using the pack as a power bank drains the starts available, so recharge after device charging if the pack must also be ready to jump. The Clore lead-acid unit offers a 12-volt accessory output rather than USB charging.

How long does a lithium jump starter last?

Lifespan depends on charge cycles, storage temperature, and how often it is left flat. The PMJS-2000 carries a 3-year limited manufacturer warranty, and the NOCO packs carry a 1-year warranty, which are the published warranty figures, not lifespan promises. Regular recharging, storage within the operating range, and recharging after use extend the useful life of any pack.

Sources

Manufacturer, listing, and reference sources: PowerMax PMJS-2000 listing record; PowerMax PMJS-2000 maker and retailer page; NOCO GB40 listing; NOCO GB70 listing; NOCO GB150 listing; Clore JNC660 listing; Clore JNC660 retailer page; NOCO GB20 listing (family context).

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