Jump Starters
Jump starter mAh vs watt-hours
One of these is a real unit of energy. The other is half an equation — and it is the one printed on the box.
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How we assessed these: the figures on this page come from manufacturer specification pages and regulator publications, cited inline. Nothing here is estimated or restated from memory.
Short answer
Watt-hours (Wh) measure energy and are what airline rules use. mAh measures charge and means nothing without a voltage. To convert: watt-hours = (mAh ÷ 1,000) × nominal voltage. A 20,000 mAh pack at 3.7 V is 74 Wh; the same mAh figure at 12 V would be 240 Wh.
This is the most consequential piece of small print in the whole category, because it is where a pack you assumed you could fly with turns out not to be — or the reverse.
The conversion, worked
Watt-hours are amp-hours times volts. So:
- Step 1: divide the mAh figure by 1,000 to get amp-hours. 20,000 mAh becomes 20 Ah.
- Step 2: multiply by the cell's nominal voltage. Most lithium-ion jump packs use cells at a nominal 3.7 V, or multiples of it.
- Step 3: that is your watt-hour figure. 20 Ah × 3.7 V = 74 Wh.
| Advertised capacity | At 3.7 V | At 11.1 V | At 12 V |
|---|---|---|---|
| 10,000 mAh | 37 Wh | 111 Wh | 120 Wh |
| 20,000 mAh | 74 Wh | 222 Wh | 240 Wh |
| 30,000 mAh | 111 Wh | 333 Wh | 360 Wh |
This is arithmetic, not a measurement. The point it makes is the important one: without the voltage, the mAh figure cannot tell you whether the pack is inside the airline limit or three times over it.
Why the airport cares
Airline and regulator rules for lithium batteries are written in watt-hours, not mAh. The FAA permits lithium-ion batteries rated up to 100 Wh in carry-on baggage with no special permission. Between 101 and 160 Wh you need the airline's approval, and you may carry at most two such spare batteries. Spare batteries and power banks are not permitted in checked baggage at all, and terminals must be protected from short circuit.
The FAA's own page even spells out the arithmetic: to calculate watt-hours, multiply the battery voltage by the amp-hours. Newer batteries have the Wh rating marked on them.
| Pack | Watt-hours | Carry-on status |
|---|---|---|
| NOCO GB40 | 24 Wh | Under 100 Wh — no approval needed |
| NOCO GBX45 | 31 Wh | Under 100 Wh — no approval needed |
| NOCO GB50 | 35 Wh | Under 100 Wh — no approval needed |
| NOCO GB70 | 56 Wh | Under 100 Wh — no approval needed |
| NOCO GB150 | 88 Wh | Under 100 Wh — no approval needed |
| Typical power station | 200-2,000+ Wh | Above the passenger allowance |
Jump-pack figures are from NOCO's published specification pages. The power-station row is a capacity range for the product class, not a claim about a specific model.
What watt-hours tells you besides legality
How many attempts you get. Peak amps decides whether the pack *can* start your engine; watt-hours decides how many times before it needs recharging. A 24 Wh pack and a 56 Wh pack both start a 3.5 L V6 — the bigger one just does it more times, which matters most in cold weather when each attempt costs more energy.
It also tells you roughly what the pack is worth as a power bank. 24 Wh is a handful of phone top-ups. It is not a camping battery, and if that is what you want, read jump starter vs power station.
Packs that publish the number plainly
1. Best travel pack, clearly rated
NOCO Boost X GBX45
NOCO · Best for travel and carry-on use
The travel pick: 1,250 peak amps at 2.16 lb with USB-C Power Delivery in and out, so it recharges from the same brick as your laptop.
Published specifications
- Peak amps
- 1,250 A source
- Internal battery
- 31 Wh lithium-ion source
- Gas engine rating
- Up to 6.5 liters source
- Diesel engine rating
- Up to 4.0 liters source
- Weight
- 2.16 lb (0.98 kg) source
- USB-C output
- Up to 20 V / 3 A Power Delivery source
- Water resistance
- IP65 with ports closed source
- Warranty
- 1-year hassle-free source
What works
- Lightest pack in the range at 2.16 lb, and 31 Wh means no airline paperwork
- USB-C Power Delivery both directions — one cable covers the pack, phone and laptop
- More gas headroom than the GB40 (6.5 L against 6.0 L) in a lighter body
What does not
- The IP65 rating only holds with the port covers closed — worth remembering in the rain
- The 4.0 L diesel ceiling is not enough for a full-size diesel pickup
Skip it if
Not the right pack for a diesel truck, and not the cheapest way to cover a small commuter — its premium buys packability, not amps.
#ad Affiliate link · We show no price here; Amazon shows the current one
Raw specifications: NOCO’s own page for the NOCO Boost X GBX45.
2. Smallest clearly rated pack
NOCO Boost Plus GB40
NOCO · Best for most cars and small suvs
The default answer for a four- or six-cylinder car: 1,000 peak amps, 24 watt-hours, and light enough that it actually stays in the trunk.
Published specifications
What works
- 24 Wh sits far under the 100 Wh carry-on threshold, so flying with it needs no airline approval
- 2.45 lb and pocketable — the size that decides whether a tool is still in the trunk six months later
- IP65 enclosure, so a wet shoulder in the rain is not a problem
- Reverse-polarity protection means a backwards clamp does not spark
What does not
- 1,000 peak amps runs out of headroom above a 6.0 L gas engine
- The 3.0 L diesel ceiling rules out most modern diesel pickups
- 24 Wh is a small reserve — it is a jump starter, not a power bank substitute
Skip it if
Not the one to buy if you drive a diesel pickup or a big V8. You would be at the edge of its rating on a cold morning, which is exactly when you want margin.
#ad Affiliate link · We show no price here; Amazon shows the current one
Raw specifications: NOCO’s own page for the NOCO Boost Plus GB40.
3. Largest pack that still flies
NOCO Boost Pro GB150
NOCO · Best for heavy diesel, fleet and equipment
The heavy end: 3,000 peak amps, a 7.0-liter diesel rating and 88 watt-hours, for the engines the consumer packs cannot legitimately claim.
Published specifications
What works
- The 7.0 L diesel rating is the highest in NOCO's consumer line
- 88 Wh still sits under the 100 Wh carry-on threshold, which is unusual at this size
- Long, heavy-gauge cables reach awkward battery positions on trucks and equipment
What does not
- 6.39 lb and bulky — a dedicated trunk or toolbox item, not a glovebox one
- Far more capacity than any passenger car will ever draw
Skip it if
Wrong tool for a car or crossover. If your largest engine is a half-ton gas V8, the GB70 already has margin and costs and weighs less.
#ad Affiliate link · We show no price here; Amazon shows the current one
Raw specifications: NOCO’s own page for the NOCO Boost Pro GB150.
Key takeaways
- Watt-hours = (mAh ÷ 1,000) × nominal voltage. Both halves are required.
- Airline rules are written in watt-hours, so mAh alone cannot answer the question.
- The FAA's carry-on allowance is 100 Wh; 101-160 Wh needs airline approval.
- Every mainstream jump pack, up to 88 Wh, clears the 100 Wh limit.
- A brand that does not publish a Wh figure is telling you something.
How we sourced this
Every figure on this page came from one of the following. Where a manufacturer or regulator does not publish a number, we say so rather than estimate it.
- FAA PackSafe — Lithium Batteries (carry-on and checked rules, watt-hour limits)
- TSA — Lithium batteries with more than 100 watt hours
- NOCO GB40 published specifications
- NOCO GBX45 published specifications
- NOCO GB50 published specifications
- NOCO GB70 published specifications
- NOCO GB150 published specifications
Common questions
- How do I convert mAh to watt-hours?
- Divide the mAh figure by 1,000 to get amp-hours, then multiply by the battery's nominal voltage. A 20,000 mAh pack built on 3.7 V cells is 74 watt-hours. Without the voltage the conversion is impossible, which is why mAh alone is not a capacity.
- What watt-hour rating can I take on a plane?
- The FAA permits lithium-ion batteries rated up to 100 watt-hours in carry-on baggage with no airline approval. Between 101 and 160 Wh you need the airline's permission and may carry at most two spares. Above that there is no passenger allowance, and spare batteries never travel in checked baggage.
- Why do jump starters advertise mAh instead of watt-hours?
- Because the mAh number is larger and looks more impressive. It is also less informative: it cannot be compared across packs with different cell voltages, and it does not answer the airline question. Brands that expect customers to travel with the pack tend to publish watt-hours.
- Does a higher watt-hour rating mean the pack starts bigger engines?
- Not directly. Starting capability is a current question, governed by peak amps and the manufacturer's engine rating. Watt-hours determines how many starting attempts you get before recharging, and how much use the pack has as a power bank.
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Why a 500 Wh power station with a jump-start port is not a substitute for a jump pack, and what the watt-hour gap means at an airport.
Best for Travel
Best for Travel
Packs for road trips, rentals and flying: light, compact, under 100 Wh, and charging from a cable you already have.
Found something out of date, or a figure you can source better than we did? Tell us — corrections get read first. Our methodology explains how picks are made, and contact is one click away.