TraviaTechPie Review

The Story

Here’s a number that trips up almost everyone buying a power bank: the mAh printed on the box is not the mAh you actually get.

A “10,000mAh” battery does not put 10,000mAh into your phone. Not even close. It’ll deliver somewhere around 6,000 to 6,500mAh in real life, and the reason is pure physics, not marketing dishonesty (mostly). So before you compare brands or chase the biggest number, it helps to understand what you’re really buying. Let’s walk through it the way I’d explain it to a friend who just wants their phone to survive a long day.

### Why the mAh on the label lies to you

The cells inside a power bank run at about 3.7 volts. Your phone charges at 5V or higher over USB. To bridge that gap, the power bank has to convert the voltage up, and that conversion is where energy leaks out.

The reason is simple. Stepping the cells’ 3.7V up to the 5V your device wants loses energy, and so does the circuitry doing the conversion. Roll those losses together and a decent power bank runs at roughly 60% to 65% total real-world efficiency. Cheaper circuits sit lower; some premium units get close to 80%.

So the usable capacity is basically the rated mAh times that total efficiency. For a 10,000mAh unit at 60–65%, that’s roughly 6,000 to 6,500mAh of charge that actually reaches your device.

Now translate that into phone charges, which is what you actually care about. Most modern phones carry a battery around 4,000 to 5,000mAh. So:

• 10,000mAh → roughly one full phone charge, maybe a bit more. A day-trip battery.
• 20,000mAh → two to three phone charges, or a phone plus a tablet top-up. A weekend battery.
• 26,800mAh → three to four phone charges, and it’s about as big as you can go while still boarding a plane freely (more on that below).

That’s the single most useful mental model in this whole guide. Match the capacity tier to how long you need to be away from an outlet, not to the biggest number on the shelf.

### Watts matter more than most people think

Capacity decides how much energy you carry. Wattage decides how fast it moves. And this is where a lot of buyers under-spec themselves.

The magic phrase is USB-C Power Delivery, or “PD.” It’s the standard that lets a power bank and a device negotiate higher voltages so charging goes fast. Without PD, you’re stuck at slow trickle speeds no matter how big the battery is. If you’d like the full breakdown of why the wattage numbers behave the way they do, I wrote a companion piece on USB-C fast charging that goes deeper.

Here’s a rough matching guide:

• 18W–30W — fine for phones. 30W will fast-charge most flagship phones and small tablets.
• 45W — plenty for large tablets and phones. Plug it into a MacBook Air and it’ll charge slowly, but it won’t fast-charge; Apple laptops really want 67W or more. For proper laptop charging, aim for 65W and up.
• 65W — this is the sweet spot if you want one battery to charge a real laptop. Enough for most 13–14″ Windows ultrabooks at usable speed; MacBook Air fast charging needs 67W or higher.
• 100W and up — for power-hungry laptops, or for charging several devices at once without each one slowing to a crawl.

One thing the spec sheets bury: a “100W” power bank often means 100W total, shared across ports. Plug in three devices and each gets a slice, not the full 100W. If simultaneous fast charging matters to you, read the per-port breakdown, not just the headline number.

### Ports, pass-through, and the little things

Look at the port layout before you buy. A good all-rounder has at least one USB-C that does both input (charging the bank) and output (charging your stuff), plus maybe a second USB-C and a legacy USB-A for older cables.

Two features worth knowing by name:

• Pass-through charging — the ability to charge the power bank while it charges your device. Handy on a nightstand, but not every model supports it, and it can run warmer.
• Built-in cables — some banks have a USB-C cable baked into the body so you never forget one. Convenient, and a genuinely nice touch for travel, though a fixed cable is the first thing to wear out.

### GaN is a charger thing, not a battery thing

You’ll see “GaN” splashed everywhere, so let’s clear this up. GaN, or gallium nitride, is a semiconductor material that lets wall chargers run cooler and shrink dramatically. That’s why your new 65W wall brick is half the size of the old one.

But a power bank is a battery, not a wall charger. GaN improves the conversion circuitry inside, and an increasing number of banks now use it, but “GaN” on a power bank isn’t the same headline feature it is on a wall adapter. Don’t pay a premium expecting magic. The battery chemistry inside is still lithium-ion or lithium-polymer either way, and that’s what stores the energy.

### The airplane rule everyone learns the hard way

This one has stranded a lot of travelers at the gate, so pay attention.

Airlines don’t rate batteries in mAh. They rate them in watt-hours (Wh). To convert, multiply the Ah by the voltage: a 26,800mAh bank at 3.7V is 26.8 × 3.7 ≈ 99Wh. That’s why 26,800mAh keeps showing up as a “max” size — it squeaks in just under a key limit.

The general framework, per U.S. FAA/TSA guidance:

• Up to 100Wh (≈27,000mAh at 3.7V) — generally allowed, carry-on only.
• 100Wh to 160Wh — requires airline approval, limited to two spare batteries per person.
• Over 160Wh — forbidden on passenger aircraft.

And the part people forget: power banks are banned from checked luggage entirely. Spare lithium batteries have to fly in the cabin with you, where a fire can be caught. These are broad U.S. figures — exact limits, quantities, and paperwork vary by airline and by country, so check your specific carrier before you fly.

### Wireless and MagSafe banks

Qi and MagSafe power banks let you charge by snapping the pack to the back of your phone, no cable. The convenience is real. The trade-off is honest: wireless transfer is less efficient than a cable, so you lose more of that already-reduced capacity to heat, and speeds are lower. Older Qi runs at bigger losses; the newer Qi2 standard tightens things up with magnetic alignment, though it’s still behind a cable. Great as a slim daily topper for a phone. Not the pick when you need maximum juice from every mAh.

### A quick word on safety

Buy from a brand that publishes certifications and builds in over-charge, over-current, and temperature protection — the standard safeguards reputable makers include. That’s most of the safety story for a normal user. I won’t oversell it: a well-made mainstream power bank from a known brand is a mature, boring product. The failures you hear about tend to come from the cheapest no-name units. Spend a little more, buy from a name you recognize, done.

The Takeaway

Strip away the marketing and buying a power bank comes down to three questions, in order.

How long between outlets? That sets capacity. A good travel-sized 10,000mAh bank covers a day out. Step up to 20,000mAh for weekends and a second device. Go to 26,800mAh only if you genuinely need multi-day range — and know it’s your airplane ceiling.

What are you charging? That sets wattage. Phones are happy at 18–30W. If a laptop is in the mix, don’t go below 65W PD, or you’ll be babysitting a slow charge.

How many things at once, and do you fly a lot? That decides ports and whether you’re bumping the 100Wh ceiling.

Here’s the decision table, cutting through the spec noise:

My honest read: most people are best served by a 20,000mAh bank with at least 30W PD and dual USB-C. It’s the tier that handles a real day-plus, tops up a tablet, and still fits in a bag without being a brick. Buy the 10,000mAh only if pocketability is the whole point, and the 26,800mAh only if your life genuinely runs multi-day off-grid. And whatever you pick — carry it on, never check it.

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Photo: Andreas Haslinger / Unsplash