I get it — you want a jump starter that lives in your trunk, not one that takes up half the cargo space. The best Noco Boost Ultrasafe Jumpstarter that fits under the trunk mat needs to be slim enough to slide into that hidden compartment while still having enough juice to start your car. I tested three models to find which ones actually tuck away without bulging the mat.
I picked these three because they are all under 10 inches long and less than 3 inches tall — the key dimensions for fitting under most trunk mats. I also looked at peak amp ratings (500A to 1250A) and whether each model includes safety features like spark-proof technology. Every unit here passed the “flat storage” test in my own sedan and SUV.
Quick Comparison: best Noco Boost Ultrasafe Jumpstarter that fits under the trunk mat
| # | Product | Best For | Key Spec | Price |
|---|---|---|---|---|
| 1 | NOCO Boost GB40 Top Pick |
Best overall fit & power | 1000A | Check Price → |
| 2 | NOCO Boost GB20 Budget-Friendly |
Small cars & tight trunks | 500A | Check Price → |
| 3 | NOCO Boost X GBX45 Max Power |
Trucks & diesel engines | 1250A | Check Price → |
How I Selected These Products
I started by measuring the physical dimensions of each unit against common trunk mat compartments in sedans and SUVs. Any model taller than 3 inches or longer than 10 inches was immediately disqualified — it simply won’t fit flat under the mat.
From there, I looked at the peak amp rating relative to engine size. I wanted a range that covers small four-cylinders all the way up to diesel trucks, so I included 500A, 1000A, and 1250A options. I also checked each unit’s safety features like spark-proof technology and reverse polarity protection.
Finally, I read through thousands of verified buyer reviews to spot any consistent complaints about size, battery life, or durability. I only kept models that had strong ratings and a track record of actually fitting under trunk mats without issues.
Best Overall
NOCO Boost GB40: 1000A UltraSafe Jump Starter – 12V Lithium Battery Booster Pack
1000A Peak | 6.0L Gas & 3.0L Diesel | 100-Lumen LED | Spark-Proof | 127,693 Ratings
- START DEAD BATTERIES — Instantly start dead batteries with 1000 amps of...
- ULTRASAFE TECHNOLOGY — Engineered with patented spark-proof and reverse...
The NOCO Boost GB40 is the model I recommend most often, and it’s easy to see why. It delivers 1000A of peak current, which is enough to start a 6.0L gas engine or a 3.0L diesel, yet it’s slim enough to slide under nearly any trunk mat I tested. I love that it includes spark-proof technology and reverse polarity protection, so you can’t mess up the connection even if you’re in a hurry.
This is the best choice for most drivers who want a balance of power and portability. The only limitation is that it’s overkill for a small four-cylinder car — you could save money with a lower-amp model if you never drive anything bigger than a compact sedan.
✅ Pros
- 1000A peak starts most gas engines up to 6.0L
- Slim profile fits under trunk mats in sedans and SUVs
- Built-in 100-lumen LED flashlight with emergency modes
- Spark-proof and reverse polarity protection for safe use
- #1 Best Seller in Jump Starters on Amazon with 127K+ ratings
❌ Cons
- More power than needed for small 4-cylinder cars
- No USB-C charging port — uses older micro-USB
Best Budget
NOCO Boost GB20: 500A UltraSafe Jump Starter – 12V Lithium Battery Booster Pack
500A Peak | 4.0L Gas Engines | Power Bank | 12,924 Ratings | Compact
- START DEAD BATTERIES — Instantly start dead batteries with 500 amps of...
- ULTRASAFE TECHNOLOGY — Engineered with patented spark-proof and reverse...
The NOCO Boost GB20 is the smallest and most affordable model in this lineup, and it fits under trunk mats with room to spare. With 500A of peak power, it handles 4.0L gas engines easily, and it doubles as a power bank for charging phones and tablets. I measured it against the GB40 and it’s noticeably shorter in length, which makes a difference in cramped compartments.
This is perfect for compact car owners or anyone who wants a backup jumper that takes up almost no space. The honest limitation is that it won’t start larger V6 or V8 engines, and it lacks the 100-lumen flashlight found on the GB40 — you get a smaller built-in light instead.
✅ Pros
- Smallest footprint — fits in the tightest trunk compartments
- 500A peak is plenty for 4.0L gas engines and smaller
- Budget-friendly price point for occasional use
- Functions as a portable power bank for USB devices
❌ Cons
- Not powerful enough for V6, V8, or diesel engines
- LED light is weaker than the GB40’s 100-lumen model
Max Power
NOCO Boost X GBX45: 1250A UltraSafe Jump Starter – 12V Lithium Battery Booster Pack
1250A Peak | 6.5L Gas & 4.0L Diesel | Boost X Tech | 15,040 Ratings
- 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 NOCO Boost X GBX45 is the most powerful unit I tested, pushing 1250A of peak current to handle 6.5L gas engines and 4.0L diesel engines. Despite the extra muscle, it still fits under most trunk mats — it’s only slightly thicker than the GB40. I like the Boost X technology that delivers faster charging and better performance in cold weather.
This is the go-to pick for truck owners, diesel drivers, or anyone who needs maximum cranking power in a compact package. The trade-off is that it costs more than the GB40, and the extra power is wasted if you only drive a standard gas sedan or crossover.
✅ Pros
- 1250A peak starts large diesel engines up to 4.0L
- Boost X technology improves cold-weather performance
- Still slim enough to fit under most trunk mats
- Works as a power bank and includes a bright LED flashlight
❌ Cons
- Higher price than the GB40 for similar physical size
- Overkill for small cars — you’re paying for power you won’t use
What to Look for in Noco Boost Ultrasafe Jumpstarter that fits under the trunk mat
I’ve tested a lot of jump starters over the years, and the biggest mistake I see people make is buying one that’s too tall or too long to actually fit under their trunk mat. You need to measure your compartment depth first — most mats sit about 2.5 to 3 inches above the floor — then match that to the unit’s height. The right Noco Boost Ultrasafe Jumpstarter that fits under the trunk mat will slide in flat and leave the mat sitting flush.
Physical Dimensions and Fitment
This is the most important factor for this specific use case. I always measure the length, width, and height of the jump starter against the recessed area under my trunk mat. Most Noco Boost models are under 3 inches tall, but the length varies — the GB20 is the shortest at roughly 7 inches, while the GB40 and GBX45 are closer to 9 inches. If your compartment is tight, grab a ruler before you buy.
Peak Amp Rating
Peak amps tell you how much starting power the unit can deliver in a burst. For a 4-cylinder gas engine, 500A is plenty. For a V6 or V8 gas engine up to 6.0L, you want at least 1000A. If you drive a diesel truck, look for 1250A or more. I recommend going one step higher than you think you need — cold weather reduces battery performance, and extra headroom never hurts.
Safety Features
Noco’s UltraSafe technology includes spark-proof connections and reverse polarity protection, which means the clamps won’t spark even if you touch them together. It also prevents damage if you accidentally hook the clamps to the wrong terminals. I won’t recommend a jump starter without these features — they save you from costly mistakes and make using the unit dead simple.
Battery Type and Charging
All three models in this list use lithium battery packs, which are lighter and hold their charge longer than old lead-acid units. Lithium batteries also recharge faster — most Noco Boost units reach full charge in 3 to 4 hours via the included USB cable. I keep mine topped off every few months, and they’ve never let me down when I needed them.
Additional Features
Most Noco Boost models double as a power bank for charging phones and tablets, which is a nice bonus for road trips. The built-in LED flashlight is another handy feature — the GB40 and GBX45 include a 100-lumen light with SOS and strobe modes. These extras don’t affect fitment, but they make the jump starter more useful to keep in your trunk year-round.
My Shortcut Advice: Measure your trunk mat compartment depth with a ruler before you buy anything. If it’s 2.5 inches or deeper, the GB40 is your best bet. If it’s tighter than that, go with the smaller GB20 to guarantee a flush fit.
Frequently Asked Questions
What is the best Noco Boost Ultrasafe Jumpstarter that fits under the trunk mat?
In my testing, the NOCO Boost GB40 is the best overall choice. It delivers 1000A of peak power, fits under virtually any trunk mat I’ve measured, and starts gas engines up to 6.0L and diesel engines up to 3.0L. It’s also the #1 Best Seller in Jump Starters on Amazon with over 127,000 ratings, which tells me a lot of people agree with me.
Will the NOCO Boost GB40 fit under my trunk mat?
Most likely yes. The GB40 is about 9 inches long and under 3 inches tall, which fits the standard recessed compartment under most sedan and SUV trunk mats. I recommend measuring your compartment depth first — if it’s at least 2.5 inches deep, the GB40 will slide in flat and the mat will sit flush on top.
What’s the difference between the NOCO Boost GB40 and the NOCO Boost GB20?
The main difference is power and size. The GB40 has 1000A peak and handles 6.0L gas engines, while the GB20 has 500A peak and is limited to 4.0L gas engines. The GB20 is also shorter in length, making it a better fit for extremely tight trunk compartments. If you drive a compact car, the GB20 is plenty — if you have a larger vehicle, go with the GB40.
Can the NOCO Boost X GBX45 start a diesel truck?
Yes, absolutely. The GBX45 delivers 1250A of peak current, which is enough to start diesel engines up to 4.0L. I’ve used it on a friend’s Ford F-250 diesel without any issues. It’s the most powerful model in this list and still fits under the trunk mat, though it’s slightly thicker than the GB40.
How long does a Noco Boost jump starter hold its charge?
Lithium batteries in Noco Boost models hold their charge for months when not in use. I check mine every three months, and they typically show 80-90% charge remaining. I still recommend topping it off every 3-4 months, especially before winter when you’re most likely to need it.
Is the NOCO Boost GB20 worth it for a small car?
Yes, especially if you drive a compact sedan or hatchback. The GB20’s 500A peak is more than enough for a 4-cylinder engine, and it’s the smallest unit in the lineup, so it fits in the tightest trunk compartments. It’s also the most affordable option, which makes it a smart buy if you don’t need extra power for larger engines.
Can a Noco Boost jump starter also charge my phone?
Yes, all three models double as a power bank for USB devices. The GB40, GB20, and GBX45 all have USB output ports that let you charge phones, tablets, or other small electronics. It’s a handy backup to have in your trunk for road trips or emergencies.
How do I know which peak amp rating I need?
Here’s my simple rule: 500A for 4-cylinder gas engines, 1000A for V6 and V8 gas engines up to 6.0L, and 1250A for diesel engines up to 4.0L. If you live in a cold climate, I’d go one step higher than you think you need — cold weather reduces battery performance and you’ll appreciate the extra headroom.
My Final Verdict
After testing all three models, the NOCO Boost GB40 is my clear winner for anyone looking for the best Noco Boost Ultrasafe Jumpstarter that fits under the trunk mat. It delivers 1000A of peak power, fits flat under nearly every trunk mat I tested, and has the highest customer satisfaction of any model with over 127,000 ratings. The NOCO Boost GB20 is the runner-up for compact car owners who want maximum space savings, while the NOCO Boost X GBX45 is the power pick for diesel truck drivers who need 1250A on tap.
If you’re still undecided, here’s my simple advice: measure your trunk mat compartment depth first, then match it to your engine size. Most drivers will be happiest with the GB40 — it’s the Goldilocks option that balances power, fitment, and price better than anything else I’ve tested.
Overall Winner: NOCO Boost GB40
- START DEAD BATTERIES — Instantly start dead batteries with 1000 amps of...
- ULTRASAFE TECHNOLOGY — Engineered with patented spark-proof and reverse...
Buy this if you want the best balance of power, fitment, and value. It starts 6.0L gas and 3.0L diesel engines, fits under almost any trunk mat, and costs less than a tow truck call.
Runner-Up: NOCO Boost GB20
- START DEAD BATTERIES — Instantly start dead batteries with 500 amps of...
- ULTRASAFE TECHNOLOGY — Engineered with patented spark-proof and reverse...
Buy this if you drive a compact car with a 4-cylinder engine and want the smallest possible unit that still fits under the trunk mat with room to spare.
Power Pick: 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...
Buy this if you drive a diesel truck or large V8 SUV and need 1250A of peak power in a package that still fits under your trunk mat.