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Best Overall
Nimble Champ (Series 2)
The Upgrade Pick
Anker 737 Power Bank
Best for Phones
Anker Nano Power Bank
Best for Tablets
Einova Eggtronic Ultra Fast Power Bank (63W)
Portable devices have a Murphy’s law–like ability to run out of power at the least convenient moment: as you step on the bus, right in the middle of an important meeting, or just as you get comfortable on the couch and press Play. But if you keep a battery-powered portable charger handy, all those situations are a thing of the past.
There are hundreds of portable battery packs, and picking one can be confusing. To help, we’ve spent years working our way through all of them. This obsession started when Scott Gilbertson lived off-grid in a vintage RV, powered primarily by solar panels. But even if you’re not living in an off-grid solar setup, good power banks will come in handy. These are our favorites. Be sure to check out our Best MagSafe Power Banks guide for Apple-specific portable chargers, and our Best Portable Power Stations guide if you need more power.
Updated April 2024: We added power banks from Raycon, Sharge, and Fans Dreams, among others, removed several sold-out or discontinued chargers, and updated prices throughout.
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Photograph: Simon Hill
Best Overall
Nimble Champ (Series 2)
The Nimble Champ topped this list for years, and now its successor is taking over by combining everything that made the original so good and bringing some welcome improvements. At 6.2 ounces, it’s one of the lightest on the market. It’s smaller than a deck of cards and can deliver 20 watts to charge two devices at once via a USB-C port on either end. While Scott used the original for years, the new version has only just landed, but so far, so good. It feels durable, comes in a snazzy new range of speckled color finishes, and has a bright lanyard loop that makes for easy carrying and helps you pick it out of your backpack. The Pro version is bigger but doubles the capacity (to 20,000 mAh) and has a similar design with two USB-C ports that go up to 65 watts. There’s also a smaller version with a 5,200 mAh capacity that tops out at 15 watts.
The other reason we like Nimble best is because of its environmental efforts. Batteries are not environmentally benign. They use lithium, cobalt, and other rare metals whose supply chains are environmentally and socially questionable at best. But Nimble’s use of bioplastics and plastic-free minimal packaging at least reduces the environmental impact where it can be reduced. This new version uses 90 percent recycled plastic (up 25 from the original) and comes in smaller plastic-free packaging. Nimble includes a 3.3-foot USB-C to USB-C cable in the box.
Two USB-C ports (20W). Can charge most smartphones two or three times (10,000 mAh).
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Photograph: Simon Hill
The Upgrade Pick
Anker 737 Power Bank
For folks who don’t mind paying for quality, the Anker 737 is a versatile and reliable beast with a whopping 24,000-mAh capacity. With Power Delivery 3.1 support, this power bank can send or receive up to 140 watts to charge phones, tablets, and even laptops. You can charge it from zero to full within an hour. It’s relatively compact for its capacity, but it weighs almost 1.4 pounds. Tap the circular power button on the side once, and the snazzy digital display shows the remaining battery percentage; tap it again, and you get stats including the temperature, total output, cycles, and more. The screen also displays watts in or out when you plug something in and a remaining time estimate based on the current rate. It fast-charged everything I tested it with, and you can charge three devices at once without a problem.
Two USB-C ports (140W) and one USB-A (18W). Can charge most phones at least four times (24,000 mAh).
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Photograph: Simon Hill
Anker Nano Power Bank
If you want a compact charger in a fun color that simply slots into the bottom of your phone for a top-up, Anker’s dinky charger is tough to beat. This power bank has a built-in rotating USB-C or Lightning connector (MFi certified), so you don’t need to worry about cables. It packs 5,000 mAh of energy (enough to fully charge most phones). I tested the USB-C version with several Android phones and found it stayed in place, enabling me to use my phone more or less as normal. There’s a USB-C port for recharging the power bank, and it comes with a short cable. It might not be a good pick if you use a thick case.
One USB-C (22.5W) or Lightning (12W) connector and one USB-C port for charging only. Can charge most phones once (5,000 mAh).
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Photograph: Einova
Best for Tablets
Einova Eggtronic Ultra Fast Power Bank (63W)
WIRED reviews editor Julian Chokkattu has been enjoying his time toting around this 20,000-mAh charger. It’s slim, fits easily into the padded sleeve of most backpacks, and has enough capacity to recharge an 11-inch tablet twice from zero percent. It’s capable of dishing out 45 watts of power for fast charging via the USB-C port, and 18 watts from the middle USB-A port. In a pinch, you can use it to recharge a laptop (as long as it’s not a power-sucking machine like a MacBook Pro). It has a lovely fabric material on the exterior, and there’s an LED that shows how much juice is left in the tank.
Two USB-A ports (18W and 10.5W) and one USB-C (45W). Can charge most tablets two times (20,000 mAh).
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Photograph: Goal Zero
Best for Laptops
GoalZero Sherpa 100
Goal Zero updated its Sherpa line of portable chargers with better wireless charging capabilities: 15 watts, up from 5 watts in the previous model. I tested the Sherpa AC, which features two USB-C ports (60-watt and 100-watt), two USB-A ports, and a 100-watt AC port for those devices that need a pronged plug. It strikes a good balance between power storage (93 watt-hours in my drain test) and weight (2 pounds). It’s enough to charge up my Dell XPS 13 almost twice.
You get a nice color LCD display that shows how much power you’ve got left, how many watts are coming in, how many are going out, and a rough guess as to how much longer the battery will last (if conditions remain the same). Recharge times vary depending on whether or not you have the Sherpa wall charger (sold separately), but I was able to get it to recharge in under three hours no matter what power source I used. There’s also an 8-mm port on the back for attaching a solar panel if you have one. The Sherpa is not cheap, but if you don’t need the AC out and can live with a single USB-C (100-watt out, 60-watt in), the Sherpa PD is otherwise the same thing for $200.
Two USB-C ports (60W and 100W), two USB-A (12W), and one AC (100W). Qi wireless charging (15W). Can charge most laptops one to two times (25,600 mAh).
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Photograph: Ugreen
Best for Fast Charging
UGreen 145W Power Bank
Ugreen’s new charger is, as the name suggests, a 145-watt charger with a 25,000-mAh battery. It’s surprisingly compact for the power it provides, although at 1.1 pounds, it’s definitely not ultralight. There are two USB-C ports and one USB-A port. What sets the Ugreen apart is that you can actually draw 145 watts while charging. That works out to one USB-C port at 100W and the other at 45W. Very few other batteries we’ve tested are capable of that feat, and none that I know of at this size. If you want to charge fast, this is the power bank for you (although it’s worth noting that reviews around the web suggest it doesn’t support Samsung’s fast charging tech). There’s a small LED readout on the side of the battery with the current charge state of the battery. I’d have liked to see some charging info on that screen as well, but that’s a small quibble with what’s an otherwise outstanding option if you need to keep your laptop charged up wherever you are.
Two USB-C ports (100W and 45W) and one USB-A. Can charge most phones around five times or a laptop once (25,000mAh).
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Photograph: Simon Hill
Best Looking Power Bank
Sharge Shargeek 170 Power Bank
I am a sucker for Sharge’s transparent designs and cyberpunk aesthetic, but this prism-shaped power bank is more than just a pretty face. With a maximum output of 170 watts, a whopping 24,000-mAh capacity, and an IP66 rating for water resistance (fine in the rain, but best not to submerge), the Shargeek 170 has form and function. The smart display shows battery life as a percentage, time remaining, and the input or output in watts. It supports many standards, including Power Delivery 3.1, Quick Charge 4.0, and PPS, and fast charged most of the devices I tested, including the iPhone 15 Pro, Pixel 8, Xiaomi 14 Ultra, and MacBook Air. You can simultaneously charge three devices at fast speeds, and the box includes a braided USB-C cable and a wee velvety bag. It can also recharge completely in an hour via USB-C at up to 140 watts (with the right cable and charger). The only thing I don’t like is the relatively high price.
Two USB-C ports (165W) and one USB-A (30W). Can charge most phones around five times or a laptop once (24,000mAh).
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Photograph: Satechi
Folding Wireless Charging
Satechi Duo Wireless Charger Power Stand
With an unusual design that features a fold-up wireless charging stand for phones and a charging spot behind it for your wireless earbuds case (if it supports Qi wireless charging), plus a USB-C port to plug in a third device, the Satechi Duo is a handy power bank to have in your bag. It has a 10,000-mAh capacity with LEDs to show how much juice is left. The downside is that it is slow, offering up to 10 watts of wireless charging power for phones (7.5 watts for iPhones), 5 watts for earbuds, and 10 watts from the USB-C port. It takes three hours to refill the battery with an 18-watt charger.
One USB-C (10W) and two Qi wireless charging spots (up to 10W). Can charge most phones one to two times (10,000 mAh).
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Photograph: Simon Hill
Best Qi2 Portable Charger
Anker MagGo Power Bank (10K) (Qi2)
The latest entry in Anker’s MagGo range is the first Qi2 power bank we have tested. The Qi2 wireless charging standard borrows elements of Apple’s MagSafe, enabling supported phones to connect with perfect alignment using a ring of magnets. Qi2 brings faster wireless charging rates of up to 15 watts, but is also backward compatible, so older Qi devices can still charge, albeit more slowly. This compact portable charger has a handy kickstand, a two-way USB-C port on the left edge, and a power button with an LED display showing remaining power as a percentage charge time on the right. It can accommodate Qi2 or MagSafe phones in portrait or landscape orientation (it works with Apple’s StandBy mode). I tested with an iPhone 14 Pro and got 25 percent in around 20 minutes. Despite a large capacity, it falls short of two full charges for your iPhone when charging wirelessly. You might squeeze a little more if you plug in the short USB-C cable provided.
One USB-C port (27W) and Qi2 wireless charging (15W). Can charge most smartphones one or two times (10,000 mAh).
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Photograph: Anker
Best MagSafe
Anker MagGo 633
One of the biggest problems we run into with portable chargers is forgetting to charge them, so this clever gadget from Anker is one of our favorite iPhone accessories. Ostensibly, it’s a wireless charging stand with MagSafe support that includes a charging spot for your AirPods on the base. The clever part, earning it a place here, is the detachable portable charger that slides out of the stand when you need to go. It stays stuck to the back of any MagSafe iPhone (and Android phones using MagSafe cases) and continues to charge it wirelessly. You can also recharge the power bank or charge another device with it via the USB-C port. The Anker MagGo 622 ($50) is a good alternative if you just want a MagSafe power bank, and it has a wee foldable stand built in. We recommend some alternatives in our Best MagSafe Power Banks guide.
One USB-C (12W) and Qi wireless charging (7.5W). Can charge most phones to between 50 and 80 percent (5,000 mAh).
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Photograph: Belkin
Best for Apple Watch
Belkin BoostCharge Pro Apple Watch Power Bank
Remembering to take a power bank with you for a night away is a real achievement, but what about your Apple Watch? It may be one of the best smartwatches, but the battery rarely lasts beyond a full day. This compact, black power bank from Belkin has a soft touch finish and an Apple Watch charger built in at one end. Even better, it can fast charge your Apple Watch, and there’s enough capacity to charge your iPhone or AirPods via USB-C at the same time, making this the perfect portable charger to stow away in your bag or pocket. You get a 1-foot USB-C to USB-C cable in the box.
One USB-C port (20W) and one Apple Watch fast charger (7.5W). Can charge most smartphones two or three times (10,000 mAh).
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Photograph: Biolite
Best for Outdoors
BioLite Charge 20 PD
If you are hiking, camping, cycling, or running, the BioLite is a handy companion. This durable power bank is lightweight, a good size to slip into a pocket, and has a nice grippy textured finish. The yellow plastic makes it easy to spot in a bag or crowded tent, and it indicates the port end, making it easier to plug in when the light is fading. The smallest size is enough to fully charge most phones, and the USB-C handles 18 watts in or out. Two additional USB-A out ports let you simultaneously charge up multiple devices, though you will probably want to size up to the 10,000-mAh Charge 40 ($60) or the 20,000-mAh Charge 80 ($80) if you plan on doing that.
Two USB-A ports (18W) and one USB-C (18W). Can charge most phones at least once (6,000 mAh).
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Photograph: Simon Hill
Best Wall Charger Power Bank
Raycon Magic Power Bank
Hybrid devices are great when space is limited. This wall charger and power bank in one is a solid hybrid option. WIRED reviewer Eric Ravenscraft raved about it, and after testing, I have to agree. The display shows you what percentage of the 10,000-mAh capacity remains, there’s a USB-C port, a USB-A port, and two built-in cables (USB-C and Lightning). But that’s not all. Turn it on its side, and you have a magnetic wireless charger. There’s even a wee slide-out phone stand and a strap for easy carrying. While you can technically charge five devices at once, it’s awkward, and the battery will die quickly. Still, this is a handy multi-purpose power bank to have in your bag. You can refill it by plugging it straight into the wall or via the USB-C port, but it takes a few hours to fully charge from empty.
One USB-C port (20W), one USB-A port (22.5W), one USB-C cable (15W), one Lightning cable (12W), and Qi wireless charging (15W). Can charge most phones one or two times (10,000 mAh).
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Photograph: Simon Hill
Most Portable
Clutch V3
The svelte Clutch, available in black, white, or pink, is about the same size as a stack of credit cards and weighs around 2 ounces. It’s designed to slide easily into pockets and bags and offers a modest top-up for your phone’s flagging battery. The third version of the super slim portable charger packs a larger battery than its predecessors, at 3,300 mAh. You charge it via the USB-C port, and there is a built-in charging cable (there’s a different Lightning model). It’s slow, it gets quite warm when plugged in, and a full Clutch added only around 40 percent to my iPhone 14 Pro’s battery. You can get higher capacities and more efficient chargers for less, but portability is the point of the Clutch V3, and it’s a handy size to tuck away in your bag for emergencies.
One USB-C port and a built-in Lightning or USB-C cable. Can top up your phone (3,300 mAh).
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Photograph: Shargeek
Cyberpunk Style
Shargeek Storm 2
If you loved the clear craze that gave us a wave of translucent electronics in the 1990s, then you will immediately see the appeal of Shargeek’s power banks. A see-through case provides a clear view of the ports, chips, and bundled rechargeable Samsung Li-ion batteries inside this portable charger. The color display gives you a detailed readout of the voltage, current, and power flowing in or out of each port. If you dig into the menu, you can find stats showing temperature, cycles, and more.
The DC barrel port is unusual, and you can specify the voltage and current you want to suit different devices; it can deliver up to 75 watts. The first USB-C supports PD PPS and can go up to 100 watts (enough to charge a laptop), the second USB-C goes to 30 watts and supports PD 3.0 and Quick Charge 4 standards, and the USB-A port is QC 3.0 and puts out 18 watts. In short, this power bank will fast-charge most devices. It comes with a yellow 100-watt USB-C to USB-C cable and a wee bag. If you don’t care about the DC port, you might prefer the Shargeek Storm 2 Slim ($200).
Two USB-C ports (100W and 30W), one USB-A (18W), and a DC barrel port. Can charge most laptops once (25,600 mAh).
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Photograph: Amazon
Best for the Rest
Panasonic Eneloop AA/AAA Charger
Got devices that don’t charge via USB? Yes, they’re still around. I have an old, but still great, GPS device that runs on AA batteries, headlamps that take AAA batteries, and countless other odds and ends that need batteries. After running through several brands, I’ve found Eneloop rechargeable batteries to be the longest-lasting and most reliable. The fast Panasonic charger can recharge any combination of AA and AAA batteries in less than three hours, and you can sometimes get it bundled in a pack that includes four AA Eneloop rechargeable batteries.
The standard AA Eneloop batteries hold around 2,000 mAh each, with AAA batteries holding 800 mAh, but you can upgrade to Eneloop Pro (2,500 mAh and 930 mAh, respectively) for more demanding gadgets, or go for Eneloop Lite (950 mAh and 550 mAh) for low-power devices. They come precharged with solar energy, and Eneloop recently switched to plastic-free cardboard packaging.
Rechargeable batteries are a smart idea and Eneloop are the best, but if you need alkaline batteries for some reason and you are in Europe, check out the Itson range. They are made in the EU from recycled materials, and they are very affordable.
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Photograph: Amazon
Best for the Car
Noco Boost Plus GB40 Jump Starter
It’s a horrible feeling when your car refuses to start because the battery is dead, but if you have a portable battery pack like this one in your trunk, you can give yourself a jump-start. WIRED reviewer Eric Ravenscraft called it a roadside lifesaver after it jump-started his car several times on a long trip home from out of state. The Noco Boost Plus is a 1,000-amp, 12-volt battery pack with jump leads. It also has a USB-A port to charge your phone and a built-in 100-lumen LED flashlight. It’s a good thing to have in your trunk, but you must remember to charge it every six months. It’s also IP65-rated and good for temperatures from –4 degrees Fahrenheit up to 122 degrees.
One USB-A port. Can jump start a car up to 20 times.
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Photograph: Simon Hill
A Portable Power Station
Jackery Explorer 300 Plus
Folks seeking more power for camping or a long road trip should pick up the Jackery Explorer 300 Plus. This cute and compact battery has a fold-out handle, packs a 288-Wh capacity, and weighs 8.3 pounds. It has two USB-C ports (18W and 100W), one USB-A (15W), a car port (120W), and an AC outlet (300W, 600W surge). There is plenty of power to keep your small gadgets going for a few days. There’s also an AC input, or you can charge it via USB-C. The fan kicks in sometimes, but the Silent Charging Mode keeps it below 45 decibels. You can manage it with Jackery’s app via Bluetooth, and it also has a handy flashlight. We have found Jackery gear reliable and durable, and you can expect to get at least a decade out of this battery. Go any bigger than this and portability gets debatable. We have a separate Best Portable Power Stations guide with recommendations for folks who need a lot of power.
If you want charging options for going off-grid, you can get the 300 Plus with a 40W book-sized solar panel ($300). It took me around eight hours to charge the battery with this panel in blue sky sunshine. If you want a faster charge and have the space for a larger panel, consider the 300 Plus with 100W solar panels ($500).
Two USB-C ports (100W and 18W), one USB-A (15W), one car port (120W), and an AC outlet (300W). Can charge most phones more than 10 times or a laptop three times (288Wh).
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Photograph: Simon Hill
Honorable Mentions
Other Good Power Banks
There are so many portable chargers out there. Here are a few more we like that just missed out on a place above for one reason or another.
- Fans Dreams MChaos for $59: I love the idea of a wearable power bank, and this one comes in lime green with a carabiner that makes it easy to attach to a bag. It also has a built-in, retractable, 28-inch USB-C cable to charge your phone at up to 20 watts. Recharging the power bank is a little slower at 18 watts. The colored LED gives you a sense of remaining juice as it goes from green to orange to red, but the 5,000-mAh capacity means you’ll be lucky to get one full charge for your phone, and even the discounted price feels a little high.
- Sharge Flow Mini for $20: With a similar design to Anker’s Nano Power Bank above and the same 5,000-mAh capacity, you might be tempted to go for this instead. It comes with interchangeable USB-C to USB-C or Lightning connectors (which I worry will be easy to lose) and has a built-in USB-C cable that doubles as a strap, though it’s tricky to pull out. There’s a power button with four LEDs to show the remaining power, and it only takes an hour and a half to refill, but the charging rate maxes out at 12 watts either way.
- Infinacore Pandora Portable Power Global Wireless Charger for $50: This was our pick for the best wall charger power bank, but the Raycon that replaced it packs more power and charges faster. This is still a decent charger that plugs directly into the wall, and it has the advantage of optional EU and UK plug adapters for an extra $10, making it a handy travel companion. It offers 8,000 mAh via one USB-C port, two USB-A ports (18W total), and Qi wireless charging (5W).
- Baseus Blade 2 for $100: With an extremely thin design, this 12,000-mAh capacity power bank is easy to slip into a backpack and can charge most phones a couple of times or top up a laptop at up to 65 watts. It has a display showing battery life as a percentage or time remaining and the input or output for both USB-C ports. We’ve tried many products from up and down the Baseus product line. While they are generally reliable, we do think there are better options.
- Iniu Power Bank BI-B64 for $100: Offering relatively low prices, Iniu is a power bank brand on the rise. This portable charger packs a 27,000-mAh capacity, can put out up to 140W, and charges three devices at once via the two USB-C ports and a single USB-A port. We also tested the very similar BI-B63 ($60), which has a slightly lower capacity at 25,000 mAh, but seems like a better value. Unfortunately, both fell slightly short of the stated capacity when tested. We also like the color options available in the company’s slimmest version.
- Anker Prime Power Bank for $130: With a total combined output of 200W and a hefty 20,000-mAh capacity, this is a solid choice for charging any device; you could even use it to charge two laptops at once via the two USB-C ports. There is a USB-A port, too, and a digital screen like the 737 listed above. You can also buy a Power Base ($70) for this, which enables you to stick the power bank on top and charge it via pogo pins. The base makes it easy to keep the power bank topped up and is handy for desktop charging with two USB-C ports and one USB-A port (combined max output 100W). I tried the UK version (£130), which worked great, but WIRED reviews editor Julian Chokkattu had issues with the US base failing to charge the power bank.
- Anker Nano Power Bank 10,000 for $45: Another solid option from Anker (also available for £50 from Amazon UK), this power bank has a built-in USB-C cable that doubles as a loop for easy carrying and a further one USB-C and one USB-A port. It has a 10,000-mAh capacity, good for just shy of two full charges for most phones. It maxes out at 30 watts each way and can be fully charged in around two hours.
- Acefast Fast Charge Power Bank M1 for $45: The see-through design and fun colors (we got purple) make this worth a look. It has a 10,000-mAh battery inside, supports Power Delivery, and can go up to 30 watts. The display shows the remaining power as a percentage, and you can recharge it in less than two hours.
- OtterBox 2-in-1 Power Bank with Apple Watch Charger for $50: Finished in durable aluminum, this clever OtterBox power bank has a built-in Apple Watch charger. The rubberized bottom helps it stick to surfaces, and Nightstand mode makes it a handy bedside clock. But the limited 3,000-mAh battery means it runs out fast if you use the USB-C to top up your iPhone.
- Juice 3 Portable Charger for £20: An environmentally conscious alternative for folks in the UK, Juice power banks come in lots of colors, are made from 90 percent recycled plastic, and come in 100 percent recycled packaging. The series is numbered based on roughly how many charges you can expect to get out of it for the average smartphone, so the Juice 3 holds three full charges.
- Rugd Power Brick for $40: Also available from Amazon UK (£40), this shock- and water-resistant (IP67 certified) charger doubles as a bright 16-LED with an SOS mode, and has a hefty 10,050-mAh capacity (one USB-C at 18 W and a USB-A that supports QC). It’s also bright orange, weighs just 280 grams, and comes with a carabiner for easy attachment, all of which make it an excellent camping buddy.
- Mpowered Luci Pro Lux for $36: This solar-powered inflatable lantern boasts 10 LEDs and emits a lovely warm glow that’s perfect for camping or walking at night. It is IP67-rated and packs down flat for easy carrying. While it’s not primarily a power bank, the 2,000-mAh battery in the Luci Pro can charge your phone in an emergency. A nearly full Luci Pro boosted my Pixel 6 Pro by around 25 percent. It takes at least 14 hours to charge back up using the solar panels, or you can plug into an outlet and recharge in three.
- Mophie Powerstation, Powerstation XL, and Powerstation Pro AC for $50+: Mophie’s 2023 update to its Powerstation line has three devices in 10,000, 20,000, and 27,000-mAh capacities. They’re bulky, nondescript devices with USB-C and USB-A ports, but the latter has an AC port and is great for travel. WIRED reviews editor Julian Chokkattu used the XL during his trip to Japan and had no trouble keeping his Switch Lite and Pixel 7 Pro topped up. There are LEDs to indicate remaining battery life, but there’s otherwise nothing special about ’em.
- Excitrus Magnetic Wireless Power Bank for $120: Power banks can be dull, so I like the unusual green fabric skin here, and a display embedded in the black plastic frame shows the remaining power percentage. This 20,800-mAh-capacity power bank has two USB-C ports (100 W and 45 W), a USB-A (18 W), and a wireless charging top (10 W) that works with Apple’s MagSafe. On the downside, it’s big, and it seems to drain slowly, even when not in use.
- iWalk Portable Charger for $40: WIRED reviews editor Julian Chokkattu used the Lightning version of this power bank while covering the Apple event and it reliably topped up his iPhone. The 4,800-mAh capacity won’t fully refill your device, but it’s tiny enough to keep in a bag at all times. There’s an LED that shows the remaining percentage of power left. The company also has a MagSafe power bank ($30).
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Photograph: mixetto/Getty Images
What to Consider
Shopping for Power Banks
There are a few things worth thinking about when you’re shopping for a portable charger.
Capacity: The capacity of a power bank is measured in milliampere-hours (mAh), but this can be a little misleading because the amount of power you get out depends on the cable you use, the device you are charging, and the charging method (Qi wireless charging is less efficient). You will never get the maximum capacity. We try to provide an estimate of what you’ll get in terms of charges for devices.
Charging speeds and standards: The charging rate for devices like smartphones is measured in watts (W), but most power banks list the voltage (V) and the amperage (A). Thankfully, you can calculate the wattage yourself simply by multiplying the voltage and amperage. Unfortunately, getting that maximum rate also depends on your device, the standards it supports, and the charging cable you use. Many smartphones, including Apple’s iPhones, support the Power Delivery (PD) standard, meaning you can use higher-power power banks to recharge the device with no issues. A few phones, such as Samsung’s Galaxy S range, support a supplementary PD protocol called PPS (Programmable Power Standard) that goes up to 45 W. Many phones also support Qualcomm’s proprietary Quick Charge (QC) standard. There are also other proprietary fast-charging standards, but you won’t generally find power banks that support them unless they come from the smartphone manufacturer.
Pass-through: If you want to charge your power bank and use it to charge another device simultaneously, it will need pass-through support. The Nimble, GoalZero, Biolite, Mophie, Zendure, and Shargeek portable chargers listed support pass-through charging. Anker discontinued support for pass-through because it found that differences between the output of the wall charger and the input of the device charging can cause the power bank to cycle on and off rapidly and shorten its lifespan. Monoprice does not support pass-through charging, either. We would advise caution when using pass-through, as it can also cause portable chargers to heat up.
Travel: It’s safe to travel with a power bank, but there are two restrictions to keep in mind when you board a flight: You must have the portable charger in your carry-on luggage (it cannot be checked in), and it must not exceed 100 Wh (watt-hours). If your power bank has a larger capacity than 27,000 mAh, you should check with the airline. Below that should not be a problem.
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Photograph: Getty Images
Why You Should Avoid Cheap Stuff
Battery Safety
Many years ago, the Samsung Galaxy Note 7 gained notoriety when its batteries caught fire in a series of incidents. There’s been a steady stream of similar, though isolated, incidents ever since. However, despite the high-profile coverage of batteries gone wrong, the vast majority of Li-ion batteries are safe.
The chemical reaction that occurs inside a lithium-ion cell is complex, but as in any battery, there’s a negative and a positive electrode. In lithium batteries, the negative is a lithium-carbon compound, and the positive is cobalt oxide (though many battery makers are moving away from cobalt). These two compounds cause a reaction that is safe when controlled and delivers energy to your devices. When the reaction gets out of control though, you end up with earbuds melting in your ears. What changes a safe reaction to an uncontrolled reaction can be any number of things: excess heat, physical damage during use, physical damage during manufacture, or using the wrong charger.
The three basic rules that have kept me safe (thus far) through testing dozens and dozens of batteries are:
- Avoid cheap cords, chargers, and outlet adapters.
- Make sure batteries aren’t exposed to excessive heat (over 110 degrees).
- Regularly inspect batteries for signs of damage.
Avoiding cheap wall-outlet adapters, cords, and chargers is the most important. These are your most likely source of problems. Those chargers you see on Amazon for $20 cheaper than the competition? Not worth it. They probably got the price down by skimping on insulation, leaving out power-management tools, and ignoring the basics of electrical safety. Price alone is no guarantee of safety, either. Buy from reputable companies and brands.
Then there’s heat. Too much of it can cause all manner of problems, both in terms of discharge and in terms of safety. Avoid heat, and pay attention to your batteries when they’re charging. If your device gets overly hot when charging, this can be a sign of problems. Similarly, beware of any swollen, bulging, or otherwise misshapen batteries.
