How we researched this guide
We ranked the six picks from our pillar guide to portable jump starters again — this time only on emergency readiness. For each pick we re-read the maker spec sheet or manual and the Amazon item details behind the pillar research, then scored the things that decide a bad morning: how much charge the pack keeps in storage, whether it works in real cold, whether it can start a battery too flat to detect, how many starts one charge holds, how much light it throws at a night roadside, and whether a stressed first-time user can connect it safely.
Owner evidence came from Bogleheads, IH8MUD, the JL Wrangler Forums, AR15.com, TractorByNet and Yesterdays Tractors, paraphrased and linked in each block, failures included. We do not test jump starters. Engine ratings are maker ratings, written as rated to, and listing figures that conflict are printed as conflicts. Price-tier rankings of the same field live in our mid-tier guide and budget guide; head-to-heads live in jump starter comparisons, in the portable jump starters category.
The 30-second answer
For one car and no warning, buy the NOCO Boost Plus GB40 — proven, override-equipped, and maker-rated to hold most of its charge for a year. If a pack found flat must recover fast, the NOCO Boost X GBX45 is jump-ready in 5 minutes. Winter emergencies: the Hulkman Alpha 85S, with pre-heat and a display. Big engines and repeat starts: the NOCO Boost Pro GB150. The largest ratings, the brightest light and inflator power: the GOOLOO GT4000S. A shop that starts vehicles weekly: the always-plugged-in Clore Jump-N-Carry JNC660.
Best Overall for Emergencies
NOCO Boost Plus GB40
The proven glovebox pick: 1,000A, rated to 6.0L gas and 3.0L diesel, spark-proof with a manual override for batteries too flat to detect, and maker guidance that it holds about 75% of its charge for a year. Best if the emergency is one car, one dead battery, no warning.
Fastest Back to Ready
NOCO Boost X GBX45
The readiness pick: 1,250A, rated to 6.5L gas and 4.0L diesel, jump-ready after 5 minutes of charging and fully refilled in a maker-stated 48 minutes on 60W USB-C PD. Best if the pack you find flat is the emergency — this one recovers fastest.
Best for Cold Emergencies
Hulkman Alpha 85S
The winter pick: 2,000A, rated to 8.5L gas and 6.0L diesel, pre-heat technology, a -40F working rating and a smart display that tells a stressed driver exactly what is happening. Best if emergencies happen at winter temperatures.
Best for Big Engines & Repeated Starts
NOCO Boost Pro GB150
The heavy pick: 3,000A, rated to 9.0L gas and 7.0L diesel, up to 80 starts per charge, an 88Wh battery, a 500-lumen light and a 12V XGC output for roadside gear. Best if the dead vehicle is a big truck or diesel, or more than one vehicle needs starting.
Most Emergency Power & Light
GOOLOO GT4000S
The output pick: 4,000A peak, rated to 12.0L gas and 10.0L diesel, a 400-lumen light, a status screen and a DC outlet that runs a separate tyre inflator at the roadside. Best if the emergency is a large engine, at night, possibly with a flat tyre too.
Best Always-Ready Shop Box
Clore Jump-N-Carry JNC660
The reserve pick: a 22Ah lead-acid box with a built-in automatic charger, so it lives plugged in and is at full charge by design, with 46 inches of #2 AWG cable. Best if emergencies are a weekly event at a shop, farm or fleet yard.
| Jump starter | Peak amps | Maker engine rating | Starts per charge | Emergency extras | Check Price |
|---|---|---|---|---|---|
| NOCO Boost Plus GB40 | 1,000A | 6.0L gas / 3.0L diesel | Up to 20 | Manual override; 100 lm light | |
| NOCO Boost X GBX45 | 1,250A | 6.5L gas / 4.0L diesel | Up to 6–8 (listings conflict) | Jump-ready in 5 min; 48-min refill | |
| Hulkman Alpha 85S | 2,000A | 8.5L gas / 6.0L diesel | Up to 60 | Pre-heat; -40F rating; display | |
| NOCO Boost Pro GB150 | 3,000A | 9.0L gas / 7.0L diesel | Up to 80 | 500 lm light; 12V XGC output | |
| GOOLOO GT4000S | 4,000A | 12.0L gas / 10.0L diesel | Up to 60 | 400 lm light; DC outlet for inflator | |
| Clore Jump-N-Carry JNC660 | 1,700A (425 cranking) | All vehicles, light commercial (no litre rating published) | Reserve-based (22Ah) | Built-in charger; 46-in cables |
Jump starter size calculator
Choose your fuel and enter your engine size in litres. We match it only against the maker litre ratings of the six picks in this guide, and recommend the smallest pick whose rating covers your engine — in an emergency there is no credit for almost big enough. The lead-acid Clore box carries no maker litre rating, so it is never a calculator answer — it is the repeated-starts alternative in the text.
If the same battery keeps dying, no pack is the fix — read why batteries drain and our battery guide before the next emergency, not during it.
How to choose a jump starter for emergencies
An emergency jump starter is bought for the worst morning, not the average one: a flat battery, no warning, possibly cold, possibly dark, possibly a driver who has never done this before. That changes what matters. Peak amps still come last — buy by the maker litre rating for your fuel — but the five criteria below decide whether the pack you bought is actually there for you when the key turns to silence.
Charge retention — will it still be charged?
A pack that self-discharges in the glovebox is emergency equipment in name only. NOCO maker guidance for the GB40 says it holds about 75% of its charge for a year or longer, with a top-up every six months; Hulkman Alpha-line listing copy claims a full charge holds power for up to 18 months. Every lithium pack here still needs a calendar check, not a hopeful one — the lead-acid Clore sidesteps the question by living on its built-in charger, permanently full.
Cold performance — the double penalty
Cold is when batteries die and when lithium packs are weakest: output falls as temperature drops while the engine cranks hardest. Published working ranges here run from -20C on the NOCO packs to a -40F rating with battery pre-heat on the Hulkman 85S. Whatever you buy, store it in the cab rather than an unheated bed or boot, and in deep cold bring it indoors the night before a hard frost is forecast.
Dead-battery override — for batteries too flat to detect
Smart packs refuse to deliver power until they detect a battery, and a truly flat battery can fall below detection. That is what manual override (NOCO) and force-start modes (Hulkman, GOOLOO) exist for — they bypass detection, and with it the spark-proof and reverse-polarity protection. In an emergency this feature is the difference between starting and waiting for a tow; it is also the one feature to use last, carefully, with the connection double-checked.
Starts per charge and reserve
One start is the plan; reserve is what happens when the plan meets a hard-starting engine, a second vehicle, or a neighbour in the same car park. Maker figures here run from up to 20 starts on the compact GB40 to up to 80 on the GB150, with the Hulkman and GOOLOO units at up to 60 — and the Clore 22Ah lead-acid battery out-reserving every lithium pack. Phone charging spends the same reserve, so in a real emergency the pack is a starter first and a power bank second.
Light, display and roadside power
Emergencies happen in the dark. Light output here runs from 100 lumens on the compact NOCO pair to 400 on the GT4000S and 500 on the GB150, with strobe and SOS modes in the Alpha-line manual material for signalling. A display that shows charge and errors in plain form (Hulkman, GOOLOO) calms a first-timer; a DC or XGC outlet that runs a separate inflator turns a jump into a full recovery when a flat tyre is part of the same morning.
Safety protections for a stressed user
The connection will be made with cold hands, poor light and some panic. Spark-proof, reverse-polarity protection is therefore not a brochure feature — it is the feature. The NOCO line publishes it across all three picks here, the Hulkman publishes a ten-protection list, and the GOOLOO a protection list of its own. The Clore publishes no electronic protection: it is a professional tool that assumes correct technique, which is why it is the shop pick and not the first-timer pick.
Typical engine sizes by vehicle class
Typical factory engines, as sizing examples — check your own engine code before buying. The pick column applies the maker ratings above, the same logic as the calculator.
| Vehicle class | Typical engines | Sizing guidance | Pick that covers it |
|---|---|---|---|
| Compact and midsize cars | 1.5–2.5L gas | Well inside the smallest rating here | NOCO GB40 |
| Full-size cars and crossovers | 2.0L turbo to 3.6L gas | GB40 territory; the GBX45 adds refill speed | NOCO GB40 / GBX45 |
| Half-ton pickups, gas | 5.3L, 5.7L and 6.2L V8 gas | Inside GBX45, Hulkman and GB150 gas ratings | Hulkman Alpha 85S |
| Half-ton pickups, diesel | 3.0L diesel | Exactly at the GB40 diesel ceiling — buy headroom | NOCO GBX45 |
| Heavy-duty pickups, diesel | 6.6L and 6.7L diesel | Inside GB150 and GT4000S diesel ratings | NOCO GB150 / GOOLOO GT4000S |
| Large diesels and equipment | Diesel above 7.0L, to 10.0L | Only the GT4000S diesel rating reaches this band | GOOLOO GT4000S |
| Shops and fleets, mixed | Mixed gas and diesel, many starts a day | Reserve and cable reach beat litre ratings | Clore JNC660 |
Truck owners sizing other 12V gear will recognise the discipline: rate for the real load, not the badge — the same rule behind what size winch do I need and diesel truck winch picks.
Jump starters by emergency job
| Emergency job | What decides it | Example pick |
|---|---|---|
| One car, dead battery, no warning | Proven record, override for flat batteries, charge that survives storage | NOCO GB40 |
| Pack found flat at the worst moment | Minutes to jump-ready, not hours to full | NOCO GBX45 |
| Winter morning, deep cold | Pre-heat, low-temperature rating, a display that explains itself | Hulkman Alpha 85S |
| Big truck or diesel, possibly twice | Rating headroom plus starts-per-charge reserve | NOCO GB150 |
| Night roadside, maybe a flat tyre too | Light output, screen, DC power for a separate inflator | GOOLOO GT4000S |
| Weekly starts at a shop or farm | Reserve, cable reach, always charged by design | Clore JNC660 |
The same six units are ranked by price tier in our mid-tier guide and the full field, with the sizing background, is in the pillar guide — this page deliberately ranks by the emergency, not by the money.
Types of portable jump starter
| Type | Pros | Cons | Best for |
|---|---|---|---|
| Compact lithium | Lightest; lives in a glovebox; proven designs with override modes | Smallest reserve; fewest starts per charge; modest diesel ratings | One car or SUV — GB40, GBX45 |
| High-output lithium | Ratings for large V8s and diesels; big reserves; bright lights and displays | Heavier; headline peak amps still not comparable across brands | Trucks, diesels, mixed households — Hulkman, GB150, GT4000S |
| Lead-acid jump box | Largest reserve; lives on its charger so always full; replaceable battery | Heavy; no published electronic protections; few modern ports | Shops, fleets, farms — JNC660 |
| Inflator-combo | One box jumps and inflates | No pick here is a true combo: the GT4000S DC outlet and GB150 XGC port power a separate inflator instead, keeping each tool replaceable | Drivers who value one-box storage over tool quality — not ranked here |
If portable power for other gear is part of the brief, compare the approach in portable winches, portable 12V winches and portable winches for trucks — different tools, same reserve-versus-weight trade.
Detailed reviews: the six picks in full
Each pick is judged on the emergency criteria above: why it earns its place, what the maker publishes, who it fits on the worst morning, what owners report — good and bad — and who should walk past it. Conflicts found in maker or listing figures are printed, not smoothed over.
Best Overall for Emergencies: NOCO Boost Plus GB40
Best Overall for Emergencies — the proven glovebox pack that is still charged when it matters
Why the NOCO GB40 is our pick
Emergency equipment earns its place on two things: it works when finally needed, and it forgives the person using it. The GB40 has the deepest owner record in this guide, spark-proof and reverse-polarity protection for a panicked connection, a manual override for batteries too flat to detect, and maker guidance — via the manual — that it holds about 75% of its charge for a year or longer with a top-up every six months. At 2.4 lb it lives in the car, which is where emergencies happen.
NOCO GB40 key specs
- Part number: GB40
- Peak current: 1,000A
- Maker engine rating: Gas up to 6.0L; diesel up to 3.0L
- Starts per charge: Up to 20 (maker)
- Charge retention: Holds about 75% of charge for a year or longer; top up every 6 months (maker manual guidance)
- Internal battery: Lithium-ion (Wh not published in the manual checked)
- Charging input: Micro-USB, 5V/2.1A
- USB output: 5V, 2.1A
- Safety: Spark-proof connections; reverse-polarity protection; manual override for very low batteries
- Housing: IP65 (ports closed)
- Operating temperature: -20C to +50C; charging 0C to +40C
- Light: 100-lumen LED, 7 modes
- Weight: 2.4 lb
- Warranty: 1-year limited
NOCO GB40: fits and best for
Cars, crossovers and SUVs with gas engines to 6.0L and small diesels to 3.0L — the single-vehicle household, the teen driver, the second car, the airport-run car that sits for weeks. It is the emergency pick where the emergency is ordinary: one flat battery, at home or in a car park, with nobody else around to help.
NOCO GB40 pros and watch-outs
Pros
- Deepest, longest owner record of any pick here
- Manual override starts batteries too flat to detect
- Maker charge-hold guidance: about 75% after a year in storage
- Spark-proof, reverse-polarity protection suits first-time users
- Small enough to live in the glovebox permanently
Watch-outs
- Micro-USB charging is slow — a found-flat GB40 recovers slowly
- Diesel rating stops at 3.0L — diesel trucks need a bigger pick
- 20 starts is the smallest reserve here
- No display — LEDs are the whole fuel gauge
NOCO GB40: what owners report
On Bogleheads, an owner reports using a GB40 over a dozen times without a failure, praising the sturdy clamps and the override that lets it deliver a jump when a battery shows almost no detectable voltage; several owners in the same discussion keep one in each family car — exactly the storage pattern this guide recommends.
Balance comes from IH8MUD, where an owner reports a GB40 failing to crank a totally flat large SUV and prefers a larger unit for overhead in adverse conditions. Both reports fit the rating: inside 6.0L gas it is dependable; at the edge, in the cold, buy headroom.
NOCO GB40: who should not buy
Diesel truck owners above 3.0L should not buy this pack — it is below the maker rating for your engine. Start with the GB150 or GT4000S blocks below, and size from the diesel column only.
NOCO GB40: pair it with
Pair it with its faster sibling for a two-vehicle household: the GB40 lives in the car, and the GBX45 — jump-ready in 5 minutes — covers the vehicle that does the long trips.
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Fitment fineprint: 12V lead-acid vehicles within the maker ratings above. Charge-hold figures are maker guidance for a healthy pack stored at moderate temperatures, not a promise for a pack stored in a hot vehicle.
Tip: put the six-month top-up in the same calendar reminder as your tyre pressures. Our guide to how long a battery carries a load explains why stored packs feel emptier than expected.
Fastest Back to Ready: NOCO Boost X GBX45
Fastest Back to Ready — the pack that recovers in minutes when you find it flat
Why the NOCO GBX45 is our pick
The cruellest emergency is the double failure: dead car, and a jump pack that is flat too. The GBX45 is built against exactly that morning. NOCO rates it at 1,250A for 6.5L gas and 4.0L diesel, and its 60W USB-C Power Delivery makes it jump-ready after 5 minutes of charging and fully refilled in a maker-stated 48 minutes — from the same kind of charger that runs a laptop. Readiness, not capacity, is what you are buying.
NOCO GBX45 key specs
- Part number: GBX45
- Peak current: 1,250A
- Maker engine rating: Gas up to 6.5L; diesel up to 4.0L
- Starts per charge: Maker listings conflict: up to 6 (US) vs up to 8 (UK) — unresolved
- Internal battery: 31 Wh lithium-ion
- USB-C input/output: 60W Power Delivery, profiles to 20V/3A
- USB-A output: 5V, 2.1A, 10W max
- Recharge time: 48 minutes full (maker, USB-C PD); jump-ready in 5 minutes
- Safety: Spark-proof and reverse-polarity protection (UltraSafe line)
- Housing: IP65 (ports closed)
- Light: 100-lumen LED
- Weight: 1.30 lb unit; 2.16 lb with clamps
- Warranty: 1-year limited
NOCO GBX45: fits and best for
Gas cars and SUVs to 6.5L and diesels to 4.0L, in households honest enough to admit the pack will sometimes be found flat — commuters, rideshare and delivery drivers, and anyone whose charging discipline is better with a sub-hour refill than an overnight one. The 60W PD output also keeps a phone alive while you wait, without spending the jump reserve the way a big power bank session would.
NOCO GBX45 pros and watch-outs
Pros
- Jump-ready in 5 minutes from flat — unique recovery speed here
- 48-minute full refill on 60W USB-C PD
- More diesel headroom than the GB40 (4.0L vs 3.0L)
- Very light even with clamps (2.16 lb)
- Refills from the laptop charger already in the house
Watch-outs
- Starts-per-charge figures conflict between maker listings (6 vs 8)
- Small 31Wh pack — the reserve for repeated cranks is limited
- No status display; LEDs only, unlike the Hulkman and GOOLOO
- The 48-minute refill needs a genuine 60W-class PD charger
NOCO GBX45: what owners report
Dedicated long-term owner coverage of the GBX45 specifically is thinner than for the older GB40 — said plainly rather than borrowed from other Boost X models. The owner record that exists, on its Amazon listing, centres on the fast recharge and compact size, which matches the spec sheet: this is a readiness-led pick.
The cautionary theme from GB40 owners on IH8MUD applies to the whole compact class: a totally flat battery in a large vehicle is where small packs run out of overhead, whatever the badge. Size from the litre rating, not from hope.
NOCO GBX45: who should not buy
If your diesel is above 4.0L, this pack is below its maker rating for your engine — move to the Hulkman, GB150 or GT4000S blocks below. If you need many starts per charge rather than a fast refill, the GB150 reserve is the honest answer.
NOCO GBX45: pair it with
Pair it with the GB40 as the household second pack: same NOCO protection logic and clamp style in both cars, so nobody has to learn two different units at the roadside.
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Fitment fineprint: 12V lead-acid vehicles within the maker ratings above. Jump-ready in 5 minutes means enough charge for a start attempt, not a full pack — refill it fully afterwards.
Tip: keep a 60W-class USB-C PD brick in the car with the pack. A fast pack charged from a weak phone brick is just a slow pack — the same logic as keeping the right cable with electric truck gear.
Best for Cold Emergencies: Hulkman Alpha 85S
Best for Cold Emergencies — pre-heat, a plain-language display, and the longest charge-hold claim here
Why the Hulkman Alpha 85S is our pick
Winter is the emergency season: batteries lose capacity, engines crank hardest, and lithium packs give their weakest output — all on the same morning. The Alpha 85S answers with pre-heat technology, a -40F working-temperature rating on the official spec page, a smart display that shows charge, status and errors in plain form, and ratings of 8.5L gas and 6.0L diesel. Hulkman Alpha-line listing copy also claims a full charge holds power for up to 18 months — the longest storage claim in this guide, printed as a line-level maker claim.
Hulkman Alpha 85S key specs
- Part number: Alpha 85S
- Peak current: 2,000A
- Maker engine rating: Gas up to 8.5L; diesel up to 6.0L (official spec page; an Amazon summary printing 6.5L diesel conflicts)
- Starts per charge: Up to 60 (maker comparison table)
- Charge retention: Up to 18 months claimed in Alpha-line maker listing copy (not isolated on the 85S spec page — flagged)
- Internal battery: Lithium-polymer, 74Wh / 20,000mAh at 3.7V
- USB-C input: 65W speed charge (SC) / PD18W
- USB-C output: PD18W
- Other outputs: USB-A QC3.0 18W; DC 15V/10A, 150W max
- Operating temperature: -40F to 113F working (official spec page)
- Display / light: 3.3-inch smart display; LED light with strobe and SOS modes (Alpha-line manual material)
- Weight: 2.57 lb (product, official spec page; kit weights vary by listing)
- Warranty: 2 years, maker-stated
Hulkman Alpha 85S: fits and best for
Cold-climate cars, SUVs and trucks, gas to 8.5L and diesel to 6.0L — including half-ton diesels past the GBX45 rating — and any driver who wants the unit to explain itself at 6 a.m. in February. It also fits vehicles that sleep outside all winter, where pre-heat is a feature and not a footnote. The full specification is on the Hulkman Alpha 85S official specification page; the brand comparison is our NOCO vs Hulkman head-to-head.
Hulkman Alpha 85S pros and watch-outs
Pros
- Pre-heat with a -40F working rating — the cold pick
- Smart display shows charge, status and errors clearly
- Up to 60 starts per charge and a strong 6.0L diesel rating
- 65W speed charge: maker states about 1.5 hours to full
- 2-year maker-stated warranty — the longest paper here
Watch-outs
- The 65W wall charger is not included with this version — budget for it
- USB-C output is only PD18W, weak for laptops
- Maker and listing figures conflict in places (diesel rating, kit weight)
- Owner coverage is thinner than the NOCO long-run models
Hulkman Alpha 85S: what owners report
Owner and review coverage collected for this model centres on three recurring points, summarised from its Amazon owner listing: the display makes first use calmer, pre-heat is the reason cold-climate buyers chose it, and the missing wall charger is the recurring annoyance.
Hulkman user-guide material, reproduced at ManualsPlus, shows the force-start mode and its warning that auto-detection and safety features are disabled in that mode — worth knowing before a winter morning teaches you, and a reason the display matters.
Hulkman Alpha 85S: who should not buy
If your winters are mild and your engine is small, the pre-heat and display buy you little — the GB40 covers the emergency for less complexity. If your diesel is above 6.0L, this pack is below rating; the GB150 and GT4000S blocks are yours.
Hulkman Alpha 85S: pair it with
Pair it with the compact GB40 for a second, warmer-climate vehicle: the Hulkman covers the truck in winter, the NOCO covers the car all year.
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Fitment fineprint: 12V lead-acid vehicles within the maker ratings above; official spec-page figures govern where listings conflict, as printed in the spec list.
Tip: let pre-heat finish before cranking in deep cold, and store the pack in the cab, not the bed. Forcing repeated cranks wastes the reserve the pre-heat is protecting — the same patience rule as using powered recovery gear properly.
Best for Big Engines & Repeated Starts: NOCO Boost Pro GB150
Best for Big Engines & Repeated Starts — 80 starts, the brightest NOCO light, and 12V power for roadside gear
Why the NOCO GB150 is our pick
Some emergencies are bigger than one car: a heavy-duty diesel that will not turn over, a boat ramp queue, two dead vehicles and one pack. The GB150 is the NOCO built for that scale — 3,000A, ratings of 9.0L gas and 7.0L diesel, up to 80 starts per charge from an 88Wh battery, a 500-lumen light for night work, and a 12V XGC output (15A) that runs roadside gear a USB port cannot. It is the pick the price-tier sibling guides leave out as above their class; an emergency guide has no such gate.
NOCO GB150 key specs
- Part number: GB150
- Peak current: 3,000A
- Maker engine rating: Gas up to 9.0L; diesel up to 7.0L
- Starts per charge: Up to 80 (maker)
- Internal battery: 88 Wh lithium-ion
- Charging inputs: Micro-USB 5V/2.1A; XGC 12V/5A
- Outputs: USB 5V/2.1A; XGC 12V/15A for 12V gear
- Safety: Spark-proof connections; reverse-polarity protection; manual override (UltraSafe line)
- Housing: IP65 (ports closed)
- Operating temperature: -20C to +50C; charging 0C to +40C
- Light: 500-lumen LED
- Weight: 6 lb unit; 7.5 lb with clamps and accessories
- Warranty: 1-year limited
NOCO GB150: fits and best for
Heavy-duty gas trucks and diesels to 7.0L, large SUVs, boats, tractors and RVs — and households with several vehicles where one pack may be asked for repeated starts in a single event. It also fits drivers who want the pack to power 12V gear at the roadside through the XGC port. At 6 lb it is a truck-cab or garage pack, not a glovebox one.
NOCO GB150 pros and watch-outs
Pros
- Up to 80 starts per charge — the largest lithium reserve here
- 9.0L gas / 7.0L diesel ratings cover heavy-duty trucks
- 500-lumen light — the brightest in this guide
- 12V XGC output runs roadside gear USB cannot
- Same NOCO spark-proof, override-equipped protection as the GB40
Watch-outs
- 6 lb before clamps — it will not live in a small glovebox
- Micro-USB charging is slow; fast refill needs the XGC route
- 1-year warranty, like the rest of the NOCO line here
- More pack than a small car will ever use
NOCO GB150: what owners report
On the JL Wrangler Forums dead-battery discussion, an owner reports a GB150 starting a JL with a dead auxiliary battery quickly after an overnight charge — the modern dual-battery case where compact packs can struggle to be detected at all.
An Amazon owner report, summarised in the pillar research, describes a cold-day diesel tractor start after the pack had sat in the truck for a month — the charge-retention behaviour this guide cares about — while also noting the slow USB charging that the spec list above prints as a watch-out.
NOCO GB150: who should not buy
If your only vehicle is a small or midsize car, this is reserve you will never spend — the GB40 covers your emergency at a third of the weight. If your diesel is above 7.0L, even this pack is below rating; the GT4000S block is yours.
NOCO GB150: pair it with
Pair it with the GB40: the GB150 stays with the truck or at the house for the big jobs, the compact NOCO travels in the car for the ordinary one.
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Fitment fineprint: 12V lead-acid vehicles within the maker ratings above. XGC output needs NOCO XGC accessories or an adapter; it is not a bare 12V socket.
Tip: after any multi-start event, recharge the GB150 fully the same day — reserve spent and left spent is how big packs get found flat. Storage discipline is covered in our maintenance checklist.
Most Emergency Power & Light: GOOLOO GT4000S
Most Emergency Power & Light — the strongest ratings here, a 400-lumen light, and power for an inflator
Why the GOOLOO GT4000S is our pick
The GT4000S is the pick for the compound emergency: a big engine, at night, with a soft tyre discovered once the engine finally runs. Its maker ratings reach 12.0L gas and 10.0L diesel — the strongest in this guide — its light throws 400 lumens, its 3.2-inch screen reports status plainly, and its 15V/10A DC outlet runs a separate inflator or other 12V gear. That reach comes with the messiest owner record in the guide, printed in full below. Buy it for coverage and roadside power, with your eyes open.
GOOLOO GT4000S key specs
- Part number: GT4000S
- Peak current: 4,000A; starting current 800A for 3s (maker)
- Maker engine rating: Gas up to 12.0L; diesel up to 10.0L
- Starts per charge: Up to 60 (maker listing)
- Internal battery: 20,000mAh lithium-polymer (Amazon item details; Wh figures conflict across listings)
- USB-C input/output: 100W Power Delivery two-way; full charge about 1.2 hours; 5-minute charge to a start (maker)
- Other outputs: USB QC3.0 18W; USB 5V/2.4A; DC 15V/10A, 150W max
- Safety: Protection list incl. overcharge, overload, short-circuit and reverse polarity (maker)
- Housing: IP65 (maker spec reproductions)
- Operating temperature: -20C to +60C (maker)
- Light / display: 400-lumen LED, 3 modes; 3.2-inch status screen
- Weight: About 4.9 lb (maker spec reproductions)
- Warranty: 18 months (Amazon manufacturer warranty description; some listings print 2 years)
GOOLOO GT4000S: fits and best for
Large gas engines, diesels between 7.0L and 10.0L, tractors, boats and mixed fleets kept by one household — anywhere the GB150 diesel ceiling is the problem — and drivers who want one roadside box that can also feed an inflator. The brand comparison behind it is our NOCO vs GOOLOO head-to-head.
GOOLOO GT4000S pros and watch-outs
Pros
- Strongest maker litre ratings in the guide, gas and diesel
- 400-lumen light plus a plain status screen for night use
- DC outlet powers a separate inflator and 12V gear
- 100W two-way USB-C — fast refill and device charging
- Published starting-current figure, not just a peak headline
Watch-outs
- Mixed owner record — charging faults and error codes reported by some owners
- Capacity and warranty figures conflict across listings
- Clamps reported awkward on side-post batteries
- Heavier than the compact picks at about 4.9 lb
GOOLOO GT4000S: what owners report
On AR15.com, owners split sharply: several report GT-line units with charging problems, error codes and weaker-than-expected output even after a replacement, while others in the same thread report owning many units across cars and a work truck — used on diesels, tractors and loaders — without a failure. Both halves are printed because both are the record.
An Amazon owner report reproduced in a review roundup describes a fully charged GT4000S failing to crank a nearly dead 5.3L V8 that a smaller NOCO then started, and criticises the clamp covers on side-post terminals — see the summary at Smart Auto. Treat the litre ratings as coverage, not as a guarantee on a destroyed battery.
GOOLOO GT4000S: who should not buy
If reliability record matters more than rating reach, do not buy this pack — the GB150 covers diesels to 7.0L with the NOCO protection system and a cleaner record in this guide. If your engine is inside GB40 ratings, the GOOLOO extra reach buys you nothing but the conflicts above.
GOOLOO GT4000S: pair it with
Pair it with the JNC660 in a workshop: the GOOLOO travels in the truck for its rating reach and roadside power, the lead-acid box stays plugged in at base for repeated starts.
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Fitment fineprint: 12V lead-acid vehicles within the maker ratings above. Wh and warranty figures conflict across listings — the Amazon item-details figures for this ASIN are the ones printed here.
Tip: on side-post batteries, seat the clamps deliberately and check the screen for a ready indication before cranking — the clamp fit is the documented weak point. General clamp discipline is in our accessories guide.
Best Always-Ready Shop Box: Clore Jump-N-Carry JNC660
Best Always-Ready Shop Box — the pack that is always at full charge, because it never leaves the charger
Why the Clore JNC660 is our pick
Every lithium pick in this guide asks you to remember a top-up schedule. The JNC660 removes the remembering: its built-in automatic charger means the box lives plugged in at the wall, at full charge, indefinitely — the only readiness strategy that cannot be forgotten. Behind that sit a 22Ah lead-acid battery with far more reserve than any lithium pack here, 425 cranking amps behind the 1,700 peak figure, and 46 inches of #2 AWG cable. Clore publishes no litre rating — it rates the box for all vehicles and light commercial use — so we print that, not an invented number.
Clore JNC660 key specs
- Part number: JNC660
- Peak current: 1,700A; cranking amps 425
- Maker engine rating: All vehicles, light commercial (no litre rating published)
- Internal battery: 22Ah Clore Proformer lead-acid AGM
- Readiness: Built-in automatic charger — designed to live plugged in, always full
- Cables: 46 in, #2 AWG, heavy-duty clamps
- Charging: Built-in automatic charger; 12V charging cable included
- Outputs: 12V DC outlet for accessories (no USB published)
- Charge indicator: Voltmeter showing onboard battery status
- Safety: Grip guards on clamps; no spark-proof electronic protection published — connect carefully
- Light: None built in
- Weight: 18 lb
- Warranty: 1-year limited
Clore JNC660: fits and best for
Workshops, farms, fleets, tow and lot work — anywhere starts are repeated, batteries are deeply flat, and the box returns to its wall socket afterwards. It also fits owners who keep vehicles, tractors and boats in one place and want one box that starts them in sequence, powers 12V accessories while working, and has its internal battery replaced years later instead of scrapping the unit.
Clore JNC660 pros and watch-outs
Pros
- Always at full charge by design — no top-up schedule to forget
- Reserve capacity dwarfs every lithium pack here (22Ah)
- Long, heavy #2 AWG cables reach real-world battery positions
- Cranking amps published (425), not just a peak headline
- Internal battery is replaceable — the box is not disposable
Watch-outs
- 18 lb — it travels by handle, not in a glovebox
- No litre rating, USB ports, display or built-in light
- Lead-acid battery needs periodic attention and eventual replacement
- No published electronic spark-proof protection — technique matters
Clore JNC660: what owners report
On the JL Wrangler Forums, the JNC660 enters the discussion as the tow-truck class answer: a poster notes its 22Ah battery against a small lithium pack, and the original poster buys one alongside keeping the NOCO — reserve in the shop, lithium in the vehicle.
On TractorByNet, an owner reports twelve years from a JNC660 kept plugged in, starting a big diesel truck, calling the brand a dealer go-to for power and longevity; on Yesterdays Tractors, owners discuss replacing its internal battery rather than replacing the box. Weight is the constant complaint, and the constant trade.
Clore JNC660: who should not buy
If the pack must live in a car, travel in luggage, or be carried by someone who will not lift 18 lb to a battery, do not buy this box — any lithium pick here is the right shape. If you need electronic protection for a nervous first-time user, the NOCO line is built for that and this is not.
Clore JNC660: pair it with
Pair it with the GB40: the Clore stays plugged in at base for hard and repeated starts, the NOCO travels in the vehicle for the one-start emergency away from home.
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Fitment fineprint: 12V vehicles and light commercial use per the maker table; no litre rating is published or implied for this model. Recharge after every use away from base — lead-acid life is decided by never sitting flat.
Tip: leave the JNC660 on its built-in charger between jobs. The same storage discipline is behind protecting gear that lives ready and our maintenance checklist.
Spec comparison
All six picks side by side, on maker-published figures only. Where a maker publishes nothing, or listings conflict, the cell says so — that honesty is part of the comparison when the purchase is emergency equipment.
| Spec | GB40 | GBX45 | Hulkman 85S | GB150 | GT4000S | JNC660 |
|---|---|---|---|---|---|---|
| Peak current | 1,000A | 1,250A | 2,000A | 3,000A | 4,000A | 1,700A |
| Cranking / starting current | Not published | Not published | Not published | Not published | 800A for 3s (maker) | 425 cranking amps |
| Gas rating | 6.0L | 6.5L | 8.5L | 9.0L | 12.0L | No litre rating published |
| Diesel rating | 3.0L | 4.0L | 6.0L | 7.0L | 10.0L | No litre rating published |
| Internal battery | Lithium-ion, Wh not published | 31 Wh lithium-ion | 74Wh lithium-polymer | 88 Wh lithium-ion | 20,000mAh lithium-polymer | 22Ah lead-acid AGM |
| Starts per charge (maker) | Up to 20 | Up to 6–8 (listings conflict) | Up to 60 | Up to 80 | Up to 60 | Reserve-based |
| Charge retention | About 75% after a year (maker guidance) | Not published | Up to 18 months (line listing claim) | Not published | Not published | Always full on its charger |
| Fastest recharge | Micro-USB (slow) | 60W USB-C PD, 48 min | 65W speed charge, about 1.5 h | XGC 12V (faster than USB) | 100W USB-C PD, about 1.2 h | Built-in AC charger |
| Light | 100 lm, 7 modes | 100 lm | LED, strobe/SOS (line manual) | 500 lm | 400 lm, 3 modes | None |
| Operating temperature | -20C to +50C | Not published | -40F to 113F | -20C to +50C | -20C to +60C | Not published |
| Weight | 2.4 lb | 2.16 lb with clamps | 2.57 lb | 6 lb (7.5 lb with kit) | About 4.9 lb | 18 lb |
| Warranty | 1 year | 1 year | 2 years (maker-stated) | 1 year | 18 months | 1 year |
| Check Price |
Using a jump starter safely in an emergency
Set up before you connect: park or stand clear of traffic, hazard lights on, bonnet up, and read the pack state first — display, screen or LEDs. Connect red to the positive terminal, then black to a solid unpainted ground on the engine or chassis away from the battery. Power the pack on, wait for its ready indication, and crank in short attempts with pauses between them. Remove the clamps in reverse order once the engine runs, and drive or idle long enough for the vehicle system to recover. Background on what a cranking load actually draws is in how many amps a 12V load draws and budget truck electrics.
Emergency-specific notes: if the pack shows no battery detection, the battery may be too flat — that is the override case, covered in the criteria above, and it disables protections, so check the connection twice first. Side-post batteries punish shallow clamp contact on any pack, the documented GT4000S complaint, so seat clamps deliberately. Dual-battery diesels may need the pack left connected briefly before a crank attempt. A hybrid or plug-in vehicle is jumped only at its published 12V jump points, never at the traction battery. And once home, recharge the pack the same day — the next emergency does not send a warning either, a habit shared with truck gear that lives ready in the vehicle.
Safety essentials
Six rules that outrank every pick in this guide:
- Connect red to positive first and black to a ground away from the battery; remove them in reverse order.
- Never use manual override or force-start as a first step — it disables the protections that make these packs safe.
- Keep sparks, flames and smoking away from a battery being jumped; batteries vent hydrogen, especially after deep discharge.
- Stop and reassess after a few short crank attempts — repeated cranking overheats starters, clamps and packs.
- Never charge a lithium pack below freezing or store any pack in a hot closed vehicle beyond its rating.
- A swollen, cracked, hot or leaking pack is finished — do not charge it, jump with it, or store it indoors near exits.
NOCO GBC013 case for the GB40 — the fitted EVA case listed for the GB20 and GB40 in the verified pool, so clamps and cable stay together and findable in the dark. The full category is our portable jump starters archive.
Check Price — NOCO GBC013 case
NOCO GENIUS5 maintainer — the verified-pool 5A charger and maintainer that stops a weak vehicle battery needing emergency jumps in the first place; see also battery sizing and health.
Energizer jumper cables, 16-foot 6-gauge — the verified-pool donor-vehicle backup for the day a pack is flat or an engine defeats it; the wider kit list is in essential accessories and recovery kit picks.
Check Price — Energizer cables
Troubleshooting
| Symptom | Likely cause | Fix |
|---|---|---|
| Pack shows no battery detected | Vehicle battery too flat for detection, or poor clamp contact | Reseat clamps on clean metal; if detection still fails, use the maker override or force mode as directed — connection double-checked first, because protections are off in that mode |
| Clicks but no crank | Weak clamp contact, or a pack below its rating for that engine | Reseat clamps, leave the pack connected a minute, retry in short attempts; if the engine is above the pack rating, use a bigger pick from this guide or cables and a donor vehicle |
| Pack is flat when needed | Storage self-discharge, or it was never recharged after the last use | Recharge fully; on the GBX45 and GT4000S a few minutes of charge can restore one start. Then put the top-up on a calendar — six months for the NOCO guidance in this guide |
| Error light, code or clamp alert at connection | Reverse polarity, shorted clamps, or a vehicle battery fault | Remove both clamps, check terminal markings in daylight or by torch, reconnect in the correct order; a repeated alert on a correct connection points at the vehicle battery |
| Starts once in the cold, then nothing | Cold-soaked lithium pack lost output, or reserve spent by repeated cranks | Warm a lithium pack indoors or inside a jacket before retrying; use the pre-heat pick in real cold; recharge fully before judging the pack |
| Vehicle starts, then dies when the pack is removed | The vehicle battery cannot hold charge or the alternator is not charging | The pack did its job — the vehicle needs a battery or charging-system repair, ideally with a maintainer from the safety section, not a bigger pack |
Who should NOT buy these
Your diesel is above 10.0L, or your system is 24V. Nothing here is rated for you — the strongest diesel rating in this guide stops at 10.0L and every pick is a 12V unit. See the full field in our pillar guide rather than guessing bigger inside one page.
Your battery is failing, not flat. A jump pack revives a discharged battery for a trip; it does not repair a sulphated, shorted or frozen one. If the same vehicle needs emergency jumps weekly, the emergency is the battery — spend there, plus a maintainer, first.
You will never check a stored pack. Every lithium unit here self-discharges. If nobody will top it up on a schedule, buy the strategy instead of the spec sheet: the JNC660 that lives on its charger, or accept that a flat pack and a set of cables is your real system.
You only fly with your tools. Lithium packs are carry-on only and airlines apply watt-hour limits — the packs here run from 31Wh to 88Wh. Check your airline exact rules before travelling, and never pack any of them in checked baggage.
You want one box that also inflates tyres by itself. No pick here is a true inflator-combo. The GT4000S and GB150 power a separate inflator through their DC and XGC outlets, which keeps the inflator replaceable — if a built-in pump matters more than starting reliability, this guide is the wrong shape for you.
Final verdict
- Best Overall for Emergencies — NOCO Boost Plus GB40: Check its price
- Fastest Back to Ready — NOCO Boost X GBX45: Check its price
- Best for Cold Emergencies — Hulkman Alpha 85S: Check its price
- Best for Big Engines & Repeated Starts — NOCO Boost Pro GB150: Check its price
- Most Emergency Power & Light — GOOLOO GT4000S: Check its price
- Best Always-Ready Shop Box — Clore Jump-N-Carry JNC660: Check its price
Start from your engine and fuel, not from an amp headline: the calculator at the top lands most drivers on the GB40 or GBX45, cold-climate owners on the Hulkman, big-engine owners on the GB150 or GT4000S, and shops on reserve instead of lithium. The head-to-heads behind these brands are NOCO vs GOOLOO and NOCO vs Hulkman, and the full field is ranked in the pillar guide.
FAQ
What makes a jump starter good for emergencies, specifically?
Readiness, not just output. The pack must still hold charge after months in storage, work at winter temperatures, start a battery too flat to detect via an override mode, and be connectable safely by a stressed first-time user in the dark. Output still matters — size by the maker litre rating for your fuel — but a powerful pack that is flat, cold-soaked or confusing fails the only morning it was bought for.
How long will these packs hold their charge in storage?
NOCO maker guidance for the GB40 says about 75% of charge remains after a year or longer, with a top-up every six months; Hulkman Alpha-line listing copy claims up to 18 months from full. Treat every such figure as a ceiling under kind storage, and check on a calendar regardless. The JNC660 answers the question differently: it lives on its built-in charger, so storage drain is the charger problem, not yours.
Can these packs start a completely dead battery?
Sometimes — that is what override and force modes are for, when a battery is too flat for the pack to detect. The NOCO override and the Hulkman force mode both exist for this case, and owner reports in this guide show compact-pack successes and one failure on a totally flat large SUV. A battery that has failed internally will not be saved by any pack here; override also disables protections, so verify the connection first.
Which pick is best for winter emergencies?
The Hulkman Alpha 85S, on published figures: pre-heat technology, a -40F working-temperature rating and a display that reports errors plainly when hands and patience are cold. The NOCO packs are rated to -20C and the GT4000S to -20C as well, but none of them pre-heats. Whatever you own, store it in the cab and warm a cold-soaked pack before expecting full output.
What if the jump starter itself is flat when I need it?
Charging speed becomes the emergency spec. The GBX45 is jump-ready after 5 minutes on USB-C PD and the GT4000S claims a 5-minute charge to a start; the GB40 on Micro-USB recovers far more slowly. After the event, recharge fully the same day. If no power source exists at all, the honest backup is the cable-and-donor route in the safety section.
Can an emergency jump starter also run a tyre inflator?
Not by itself — none of these picks has a built-in pump. The GT4000S DC outlet (15V/10A) and the GB150 XGC output (12V/15A) power a separate inflator, which is the arrangement this guide prefers: each tool stays replaceable. Small USB-powered inflators can also run from the larger packs, within their published output limits.
Is lithium or lead-acid better for emergency readiness?
They fail differently. Lithium is light enough to live in the vehicle and holds charge well for months, but it does self-discharge and loses output in deep cold. Lead-acid, in the JNC660 form, is heavy enough to stay at base — where its built-in charger keeps it permanently full. Owner sources in this guide run both: lithium in the vehicle, lead-acid at base. That pairing is the most robust answer here.
How many starts should I expect from one charge in a real emergency?
Maker figures run from up to 20 on the GB40 to up to 60 on the Hulkman and GT4000S and up to 80 on the GB150 — under maker conditions, on healthy engines. Cold, a hard-starting engine, or a battery being nursed through repeated attempts will cut those numbers hard. Buy reserve for the realistic case: if your engine is near a pack rating ceiling, its starts figure will not survive contact with February.
Are these packs safe for someone who has never jump-started a car?
The lithium picks are built for that user: spark-proof, reverse-polarity protection means a wrong connection produces a warning, not sparks. The exceptions are override and force modes, which disable that protection by design, and the JNC660, which publishes no electronic protection at all. A first-timer should start with a NOCO or Hulkman pick and treat override as a last step, exactly as the safety section orders it.
Why did my old jump pack fail even though it showed full charge?
Charge indicators show voltage, not health. Ageing cells can display full while being unable to deliver cranking current, and long storage at full or empty both age lithium cells. That is why this guide weights maker charge-retention guidance and owner longevity reports alongside ratings — and why any pack that has sat unchecked for years should be load-proven on a healthy vehicle before it is trusted as emergency equipment.
Sources & changelog
Manufacturer sources
- NOCO GB40, GBX45 and GB150 listings, GB40 manual (charge-hold guidance) and GB150 datasheet: GB40 on Amazon, GBX45 on Amazon, GB150 on Amazon, GB40 manual (manuals.plus)
- Hulkman Alpha 85S official specifications and listing: hulkman.com Alpha 85S specifications, Alpha 85S on Amazon
- GOOLOO GT4000S listing and maker specifications: GT4000S on Amazon
- Clore Jump-N-Carry JNC660 listing and specifications: JNC660 on Amazon
Owner sources (paraphrased in the blocks above)
- Bogleheads — portable booster discussion: repeated GB40 use, clamps and override
- IH8MUD — lithium jump starter thread: the compact-pack overhead counter-report
- JL Wrangler Forums — NOCO and dead battery: GB150 on a dead auxiliary battery; JNC660 reserve discussion
- AR15.com — GOOLOO GT4000/GT4000S thread: the split GOOLOO record
- TractorByNet — portable jump starter and Yesterdays Tractors — jump box: JNC660 longevity, kept plugged in, battery replacement
Changelog — October 16, 2026: guide first published.
By Leo, Founder, WinchInsider
Leo researches vehicle gear the slow way: manufacturer manuals, warranty fine print and owner forums, with every conflict printed rather than smoothed over and no claim of hands-on testing anywhere on the site. Questions and corrections are welcome via our contact page; how affiliate links work is on our affiliate disclosure. More is on our about page.
Related guides
- Best portable jump starter — the pillar guide
- Best portable jump starter — the mid-tier guide
- Best portable jump starter — the budget guide
- NOCO vs Hulkman jump starter — head-to-head
- Portable jump starters — the category hub
- Best winch battery — sizing and battery health