Batteries so powerful they do everything but fly

Brian Livingston

By Brian Livingston

There are times when I’m power-mad — I just want the biggest battery available to power my laptop, my phone, and heck, maybe a cup warmer for my coffee, too.

I’m not going to drag around a cart with a propane generator just so I can compute. Fortunately, power banks that can double or triple the life of a laptop are now affordable and light enough to carry around in a shoulder bag or backpack.

But what about airplanes? You may have heard that some external batteries are so charged up that you can’t get them through security in your carry-on bag. There are ways around this, as we’ll see in a minute.

Personally, I like my antique laptop, which was manufactured around the time that ones and zeros were discovered. Using it is like wearing a soft, well-broken-in sweater. But my trusty little servant can survive for only about three hours on its own internal battery.

That makes me willing to carry around an external power bank with enough oomph to give my laptop a full day’s battery life. Even when I buy a new laptop with longer life, there’ll still be times when I’ll want an external battery, too.

I’ve attended plenty of conferences where I’m on the go from 8 a.m. to 11 p.m. I could mention the Consumer Electronics Show — a Darwinian endurance test for journalists, from the breakfast press briefings to the nightly media-only receptions — but there are plenty of other day-and-night events where I don’t want my handy note-taker to go dead.

When getting the story right is crucial, I’m glad that I can sit anywhere in an auditorium. No need to find a rare AC outlet under my seat! I feel bad for those poor souls who must sit on the floor in the back, just so they can plug their devices into a wall outlet.Sometimes you just want the biggest power bank you can get

Computer shows aren’t the only things that call for a 15-hour charging capacity. There are many other situations where you’re dead in the water unless you can put a serious power bank to work:

  • On a sailboat in the bay. Maybe you’d prefer to swim the day away, but many people find the water an ideal place to write their Great American Novel. It’s quiet enough to think on the boat, but you won’t find an outlet in the waves. What did you expect out there, power from some flounder?
  • Video projector in a park. When you’re entertaining the neighborhood kiddies with SpongeBob SquarePants cartoons, you may not want to run a 100-meter outdoor extension cord from your house over to the grassy knoll. In that case, an external battery is just the thing to power your projector — and your speakers.
  • Christmas lighting if your house is set back from the street. What are the holidays without a jolly Santa, illuminated from within by a power-sucking array of lights? You’ll want an external battery if your house isn’t very visible from the road. Don’t forget to light up Rudolph’s nose!
  • Portable medical equipment. People who are afflicted with apnea, for instance, may be awakened by a blocked airway several times an hour unless they use a CPAP (continuous positive airway pressure) machine. A powerful battery makes it possible to use CPAP on a bus, train, etc., to get an entire night’s sleep.
  • Your kitchen table. I have a spacious office, but I often prefer to work an eight-hour shift right on my own kitchen table. The lighting is good, and a fridge full of low-cal drinks is right there beside me. But there’s no AC outlet in the table — duh — and I don’t want to drag an extension cord across the floor. Placing a power bank just a few inches from my laptop lets me be productive without the long cables. This also works in cafés and hotel lobbies when I arrive long after all the AC outlets have been claimed.

You’ll notice that none of the above cases involves taking your power bank on an airplane. Don’t worry, it is possible. Let’s first look at some of the most powerful laptop boosters out there and then define what can and cannot go with you into the skies.Watts the story, morning glory?

Power banks are typically advertised in terms of milliamp-hours (mAh). One thousand mAh is one amp-hour (Ah). That’s easy to measure, but as we’ll see below, airlines don’t care about amp-hours. Airports restrict batteries that are above a certain number of watt-hours (Wh).

What’s the difference? Let’s use a common “D” battery as an example. It holds 12 amp-hours and delivers it at 1.5 volts. We convert its capacity to its energy output thusly:

► A “D” battery with 12 amp-hours times 1.5V equals 18 watt-hours.

Lithium-ion cells, like those used in most power banks, typically have a nominal rating around 3.7 volts, as Circuit Digest describes. To deliver more than 3.7 volts — such as 5 volts for phones, 19 volts for many laptops — an external power bank connects several Li-ion cells in series.

A power bank that holds 27,000mAh is equivalent to 100 watt-hours — 27 x 3.7 ≈ 100 — and 43,000mAh is equivalent to 160 watt-hours, according to battery maker RAVPower’s interpretation. We’ll refer to these numbers a bit later when we look at airline carry-on policies.Some power banks are simply more powerful than others

I don’t have my own testing lab but, fortunately, don’t need one. There are plenty of testers who’ve published their results on laptop-capable power banks of all sizes. These include WirecutterLifewireTechRadar, and Tortuga.

The highest-capacity power banks that scored well in tests are shown below:

High-capacity power banks
Figure 1. Clockwise from upper left: Maxoak, Krisdonia, Halo Bolt, and RAVPower Source: Photos by manufacturers

  • Maxoak Laptop Power Bank, 50,000mAh, 185Wh, 2.77 lb., about $130. This model made it into the top rankings by three of the four above testers. It has the largest number of output ports in this roundup: six, including one 20V for laptops, one 12V for digital cameras, two 2.1A USB ports for high-charge smartphones, and two 1A USB ports for other gadgets. Maxoak provides power adapters for 14 kinds of laptops. However, the maker says it can’t charge Apple laptops, Dell XPS 12, Lenovo Yoga, and other USB-C laptops. Maxoak product page
  • Krisdonia Laptop Power Bank, 50,000mAh, 185Wh, 2.55 lb., about $126. Krisdonia is a trademark of a relative newcomer in batteries (founded in 2011): Shenzhen Nejifu Technology of China. The power bank comes with adapters for 28 different laptops. In addition, it has two USB-A ports and one USB-C port. It supports a pass-through function; it can charge itself while powering a laptop and other devices. An LED display shows how much power remains. The device is fairly slow to fully charge, however, requiring six to eight hours. Krisdonia store
  • Halo Bolt Portable Charger/Jump Starter, 58.83Wh, 1.66 lb., about $80. With the fewest watt-hours in this cohort, the Halo Bolt from Zagg Brands may not have enough juice to charge a laptop all the way. But unlike the above models, it comes with a 120-volt AC outlet and jumper cables to jump-start your car from the power bank. (No Good Samaritan required.) It has two USB-A ports but no USB-C port. The package includes a 12-volt adapter, so you can charge it using your car charger and keep it on tap for the day you need a jump. Zagg product page
  • RAVPower AC Power Bank, 30,000mAh, 108Wh, 2.2 lb., about $125. This unit stores less energy than the Maxoak or Krisdonia, but it can deliver 149 watts of power — useful to serve power-hungry laptops, such as the 96 watts that the 16-inch MacBook Pro can take. The RAVPower has an AC outlet like the Halo Bolt but no jump-start capability. It sports two USB-A ports plus the newer USB-C Power Delivery input/output port, capable of 100-watt charging with the proper setup, according to a Cable Matters analysis. You power your laptop through the AC outlet or USB-C; no laptop adapters are provided. RAVPower product page

Now you’ve got your power bank — how do you walk it onto a plane?

You’ve probably read in several articles: “You cannot take a power bank onto a plane if it supplies more than 100 watt-hours of power.” This is not really true.

International regulations may vary, but here are the facts from US FAA policies on spare rechargeable lithium-ion batteries (“spare” means any external Li-ion battery that isn’t installed inside an electronic device):

Spare batteries up to 100 watt-hours

  • Checked baggage — not allowed
  • Carry-on — as many batteries as you like (for personal use, not resale)

Spare batteries between 100 and 160 watt-hours

  • Checked baggage — not allowed
  • Carry-on — no more than two batteries, with airline approval

Spare batteries between 160 and 300 watt-hours

  • Checked baggage — allowed primarily for nonfolding wheelchairs/scooters
  • Carry-on — one battery, primarily for folding scooters, with airline approval

The phrase with airline approval is key. Most major US and international airlines allow you to walk aboard with up to two 100 to 160 watt-hour power banks. The policies of several airlines have conveniently been brought together in a Voltaic Systems chart. However, if you’re taking a 100Wh to 160Wh battery, you should contact the airline for specific details. You may be required to declare your power bank to a crew member after you board.

The crew may want to ensure that your external power bank is prevented from pressing into any metal in flight. Even a piece of aluminum foil can cause a short circuit. In rare cases, your device could overheat and catch fire. The simplest way to make sure your batteries don’t rub against anything is to travel with each device inside a zip-top bag (a step the airlines advise).

Before the plane takes off, I always remove my power bank from my carry-on and place it in the seatback pocket in front of me. Lithium-ion overheating currently occurs in fewer than one of every million devices. That’s 100 times less likely than being hit by lightning in your lifetime. But if my battery starts smoking, I want to be the first to know. If combustion is noticed in time, it can be extinguished with bottled water or even a Coke, since a Li-ion battery contains little water-reactive lithium metal. (This doesn’t apply to lithium-metal batteries and other types. For details on all of this, see Cadex’s Battery University article.)

The US Transportation Security Administration makes a point of saying on its website: “The final decision rests with the TSA officer on whether an item is allowed.” Since those calls can be arbitrary, consider carrying a pocket manual or printout if your power bank’s capacity in watt-hours is not clearly labeled.

So which power bank is right for you? Unfortunately, this is a case where one size does not fit all. Do you need an AC outlet or not? Do you need USB-C charging or not? Laptops have such different requirements that you’ll have to determine which of the above power banks, if any, are compatible with your particular equipment.

There are two things we can say for sure: You could carry the 58.83Wh Halo Bolt onto a plane with little or no fuss. And you could take the 108Wh RAVPower, which is just over the 100Wh no-questions-asked limit, if you made sure you had prior approval from the airline.

Since the Maxoak and Krisdonia models are over the 160Wh limit, they could be confiscated by security, if TSA examined those units’ 185Wh capacity. But if you never plan to carry these units onto an airplane, they’re some of the highest-capacity power banks that you can take with you anywhere (other than an airport).

We’re all flying less these days. In 2020, global passenger traffic fell 60% from the previous year, according to UN statistics.

If your employment doesn’t require flying, you don’t have to limit your power bank to the airlines’ watt-hour rules. You can enjoy your high-capacity charger wherever you go in cars, buses, trains, coffeeshops — or even your own kitchen!

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The PUBLIC DEFENDER column is Brian Livingston’s campaign to give you consumer protection from tech. If it’s irritating you, and it has an “on” switch, he’ll take the case! Brian is a successful dot-com entrepreneur, author or co-author of 11 Windows Secrets books, and author of the new book Muscular Portfolios. Get his free monthly newsletter.