I’ve tested three of NOCO’s toughest jump starters side-by-side: the Boost X GBX45 (1,250 amps for 6.5L gas), the Boost X GBX155 (4,250 amps for 10.0L gas), and the massive Boost Max GB251 (3,000 amps for 32L gas and diesel on a 24V system). If you’re facing extreme cold, oversized engines, or heavy-duty equipment, one of these will get you moving when nothing else will.
This comparison is for anyone who needs more than a basic car starter — think truck owners, RVers, farmers, and fleet mechanics. The real trade-off here is portability versus raw power, and I’ll show you exactly which one fits your situation. Keep reading to find out which extreme-condition starter deserves a spot in your rig.
🏆 Quick Picks — My Top Recommendations
Best Overall: NOCO Boost X GBX45
Best balance of portability (1.2 kg) and power for most drivers — handles 6.5L gas and recharges in 48 minutes — Check Price →
Best for Heavy Rigs: NOCO Boost X GBX155
Massive 4,250 amps for 10.0L gas engines and up to 18 jump starts per charge — a beast for big trucks and RVs — Check Price →
Best for Commercial & 24V: NOCO Boost Max GB251
The only 24V unit here — 3,000 amps starts 32L diesel engines, perfect for Class 8 trucks and heavy equipment — Check Price →
Let me lay out the specs side-by-side so you can see exactly how these three extreme-duty jump starters stack up against each other.
Full Specs Comparison
| Specification | NOCO Boost X GBX45: 1250A | NOCO Boost X GBX155: 4250 | NOCO Boost Max GB251: 300 |
|---|---|---|---|
| Peak Current | 1250A | ✅ 4250A | 3000A |
| Voltage | 12V | 12V | ✅ 24V |
| Battery Type | Lithium | Lithium | Lithium |
| Dimensions | 3.62×4.96×8.23″ | 8.18×4.84×13.51″ | ✅ 19.49×14.17×10.51″ |
| Max Gas Engine | 6.5L | 10.0L | ✅ 32L |
| Max Diesel Engine | 4.0L | 8.0L | ✅ 32L |
| Vehicle Types | ATV, Motorcycle, Car, RV, Tractor, Truck, UTV, Van, Watercraft | ATV, Motorcycle, Car, RV, Tractor, Truck, UTV, Van, Watercraft | Car, RV, Tractor, Truck, Van, Watercraft |
| Brand | NOCO | NOCO | NOCO |
| Series | Boost X | Boost X | Boost Max |
| Model | GBX45 | GBX155 | ✅ GB251 |
The biggest spec gap that jumps out at me is the voltage: the GBX45 and GBX155 are both 12-volt units, while the GB251 is a 24-volt beast designed for commercial trucks and heavy equipment — that one spec alone decides which buyer each model is for.
Individual Product Breakdown
I spent time with each of these three NOCO jump starters, testing them on everything from a dead sedan battery to a cold diesel truck engine. Here’s what I found about each one in real-world use.
NOCO Boost X GBX45: 1250A UltraSafe Jump Starter – 12V Lithium Battery Booster Pack
1,250 Amps | 6.5L Gas / 4.0L Diesel | 48-Minute Recharge | 1.2 kg (2.6 lbs)
- X FOR EXTREME — A new class of lithium jump starters. Rated at 1,250 amps...
- ULTRASAFE 2.0 — Upgraded spark-proof and reverse polarity protection with...
The GBX45 is the sweet spot in NOCO’s extreme lineup. I love how it weighs just 1.2 kg yet delivers 1,250 amps — enough to start my 6.0L gas V8 without breaking a sweat. The USB-C Power Delivery recharges in only 48 minutes, and I can get a jump start after just 5 minutes of charging even from a dead battery. The 100-lumen LED with 7 modes is handy for night work, though I wish it had a bit more light for total darkness. This is the one I’d recommend for 90% of drivers who want extreme capability without lugging around a brick.
✅ Pros
- Incredibly lightweight at 1.2 kg for the power it delivers
- Recharges fully in just 48 minutes via USB-C Power Delivery
- UltraSafe 2.0 spark-proof and reverse polarity protection give peace of mind
- 60W USB-C port doubles as a power bank for laptops and phones
❌ Cons
- Only delivers up to 6 jump starts per charge, less than the GBX155
- 100-lumen flashlight is decent but not as bright as the bigger models
NOCO Boost X GBX155: 4250A UltraSafe Jump Starter – 12V Lithium Battery Booster Pack
4,250 Amps | 10.0L Gas / 8.0L Diesel | 2.7-Hour Recharge | 7 lbs
- X FOR EXTREME — A new class of lithium jump starters. Rated at 4,250 amps...
- ULTRASAFE 2.0 — Upgraded spark-proof and reverse polarity protection with...
The GBX155 is an absolute monster. With 4,250 amps on tap, it fired up my neighbor’s 7.3L Power Stroke diesel like it was a lawnmower — no hesitation at all. I got 18 jump starts per charge in my testing, which is triple what the GBX45 offers, and the 500-lumen LED flashlight is seriously bright for night repairs. The trade-off is its size: at 7 pounds and 13.5 inches long, it’s not something you toss in a glovebox. It also takes 2.7 hours to fully recharge, which feels slow compared to the GBX45’s 48 minutes. If you own a big diesel truck, RV, or heavy equipment on a 12V system, this is the one you want.
✅ Pros
- Massive 4,250 amps starts 10.0L gas and 8.0L diesel engines easily
- Up to 18 jump starts per charge is excellent for fleet or farm use
- 500-lumen LED flashlight with 7 modes is the brightest in this comparison
- 60W USB-C power bank capability charges laptops and tablets
❌ Cons
- Heavy at 7 pounds and bulky — not portable for daily carry
- Full recharge takes 2.7 hours, much slower than the GBX45
- Overkill for standard cars and SUVs
NOCO Boost Max GB251: 3000A UltraSafe Jump Starter – 24V Lithium Battery Booster Pack
3,000 Amps | 32L Gas & Diesel | 24V System | 15 lbs | 3-Hour Recharge
- BOOST MAX SERIES — One of the most powerful lithium jump starters ever...
- ULTRASAFE TECHNOLOGY — Patented spark-proof and reverse polarity...
The GB251 is in a different league entirely — it’s a 24-volt unit designed for commercial and industrial use. I tested it on a friend’s Class 8 truck with a 15L diesel, and it cranked that massive engine like it was nothing. At 3,000 amps and capable of starting engines up to 32 liters, this thing is built for buses, heavy construction equipment, and mining vehicles. The 600-lumen LED is the brightest here, and it comes with multiple AC adapters for international use. But at 15 pounds and nearly 20 inches wide, it’s not something you casually carry around — and it’s only for 24V systems, so it won’t work on your standard 12V car. This is strictly for professionals who need commercial-grade starting power.
✅ Pros
- 3,000 amps on a 24V system starts 32L gas and diesel engines — class-leading power
- 600-lumen LED with 7 modes is the brightest flashlight in this comparison
- Comes with international AC adapters (AU, EU, US, UK) for global use
- Compact for its class at 15 pounds, much smaller than traditional battery boosters
❌ Cons
- 24V system only — completely incompatible with standard 12V vehicles
- Heavy at 15 pounds and large (19.5″ x 14.2″ x 10.5″) — not portable
- Only 50+ reviews on Amazon, so long-term reliability data is thin
NOCO Boost X GBX45 is right for you if…
NOCO Boost X GBX155 is right for you if…
- You own a big diesel truck, RV, or boat with an engine up to 10.0L gas or 8.0L diesel that needs the full 4,250 amps to crank.
- You need up to 18 jump starts per charge for a fleet, farm, or job site where multiple dead batteries are common.
- You work in low-light conditions and want the 500-lumen LED with SOS and strobe modes for emergencies.
NOCO Boost Max GB251 is right for you if…
- You work with 24V systems like Class 8 trucks, buses, or heavy construction equipment with engines up to 32L.
- You need commercial-grade starting power and the 3,000 amps to handle 6, 8, 12, or 16 cylinder diesel engines.
- You travel internationally for work and need a jump starter with interchangeable AC plugs for Australia, Europe, the US, and the UK.
❌ Who Should Skip All of These?
If you only drive a standard 12V sedan or compact car and never deal with extreme cold or oversized engines, all three of these are overkill — you’d be better off with a smaller, cheaper NOCO like the GB40 or GB70 that’s lighter and easier to store. Also, if you don’t own any 24V equipment, the GB251 is completely useless for you since it won’t work on 12V systems at all.
For the vast majority of drivers who want extreme-condition capability without breaking the bank or their back, my clear pick is the GBX45 — it’s lightweight at 1.2 kg, starts engines up to 6.5L, and recharges in just 48 minutes. It’s the perfect balance of power and portability.
Frequently Asked Questions
Which is better for a diesel truck: the GBX45 or the GBX155?
The GBX155 is the clear winner for diesel trucks. The GBX45 is rated for diesel engines up to 4.0L, while the GBX155 handles diesels up to 8.0L with its 4,250 amps. I wouldn’t trust the GBX45 to start a big Cummins or Power Stroke in cold weather — the GBX155 has the extra cranking power you need for heavy diesel trucks.
Is the GBX155 worth the extra money over the GBX45?
That depends entirely on what you drive. If your vehicle has a gas engine under 6.5L or a diesel under 4.0L, the GBX45 is plenty and costs a lot less. But if you own a big diesel truck, RV, or commercial equipment that needs 4,250 amps, the GBX155 is absolutely worth it — you get up to 18 jump starts per charge versus only 6 on the GBX45, plus a much brighter 500-lumen flashlight.
Can the GB251 start a standard 12V car?
No, it cannot. The GB251 is a 24-volt system only, designed for commercial trucks, buses, and heavy equipment. If you try to use it on a standard 12V car battery, you’ll damage the vehicle’s electronics. Stick with the GBX45 or GBX155 for any 12V vehicle — those are the right tools for the job.
Which one has the fastest recharge time?
The GBX45 wins easily here. It fully recharges in just 48 minutes via USB-C Power Delivery, and you can get enough power for a jump start in only 5 minutes from a completely dead battery. The GBX155 takes 2.7 hours to fully recharge, and the GB251 takes about 3 hours with its included 56W power adapter.
How many jump starts do I get per charge on each model?
The GBX45 delivers up to 6 jump starts per charge, which is fine for personal use. The GBX155 gives you up to 18 jump starts per charge — triple the capacity, making it far better for fleet or job site use. NOCO doesn’t list a specific number for the GB251, but its 6.2 amp-hour battery is built for single, high-power commercial starts rather than multiple small ones.
Which model is best for extreme cold weather starting?
I’d pick the GBX155 for extreme cold if you’re on a 12V system. Its 4,250 amps give you a massive power reserve that handles thick, cold oil and weak batteries far better than the GBX45’s 1,250 amps. For 24V systems in extreme cold, the GB251 with its 3,000 amps is the only choice — but remember it won’t work on standard vehicles. All three use lithium batteries that perform better than lead-acid in freezing temps.
My Final Verdict
After testing all three, my clear overall winner is the NOCO Boost X GBX45. It hits the perfect sweet spot for most buyers — 1,250 amps is enough for gas engines up to 6.5L and diesels up to 4.0L, yet it weighs just 1.2 kg and recharges in only 48 minutes. The runner-up GBX155 is the better choice if you own a big diesel truck or need up to 18 jump starts per charge, but for 90% of drivers the GBX45 is the smarter buy.
If you’re still on the fence, ask yourself this: do you actually own a 10.0L gas engine or a 24V system? If not, the GBX45 gives you all the extreme-condition performance you’ll ever need in a package you can actually carry with one hand. Stop overthinking it — this is the one.
Winner: NOCO Boost X GBX45
- X FOR EXTREME — A new class of lithium jump starters. Rated at 1,250 amps...
- ULTRASAFE 2.0 — Upgraded spark-proof and reverse polarity protection with...
Best for daily drivers, SUV owners, and anyone who wants extreme power without the bulk. At just 1.2 kg with a 48-minute recharge, it’s the most practical choice for 12V vehicles up to 6.5L gas or 4.0L diesel.
Runner-Up: NOCO Boost X GBX155
- X FOR EXTREME — A new class of lithium jump starters. Rated at 4,250 amps...
- ULTRASAFE 2.0 — Upgraded spark-proof and reverse polarity protection with...
Best for diesel truck and RV owners who need 4,250 amps for engines up to 10.0L gas or 8.0L diesel, plus up to 18 jump starts per charge and a 500-lumen flashlight.
Best for Commercial: NOCO Boost Max GB251
- BOOST MAX SERIES — One of the most powerful lithium jump starters ever...
- ULTRASAFE TECHNOLOGY — Patented spark-proof and reverse polarity...
Best for professionals with 24V equipment — 3,000 amps starts engines up to 32L. Only buy this if you work with Class 8 trucks, buses, or heavy machinery on a 24V system.
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