A portable charger can feel like a lifeline when you can’t find an outlet. We’ve been testing batteries and updating this guide for more than a year. In that time, I’ve seen the ways power banks come in handy, from the critical (keeping my phone alive as I rode public transit in an unfamiliar city) to the slothful (recharging a tablet so I can keep doing the crossword without leaving the couch). So far, we’ve tested more than two dozen banks to determine which are worthy and as of now, these are the best power banks you can buy.   

What to look for in a portable battery pack

Battery type

Nearly every rechargeable power bank you can buy (and most portable devices) contain a lithium-ion battery. These beat other current battery types in terms of size-to-charge capacity, and have even increased in energy density by eight fold in the past 14 years. They also don’t suffer from a memory effect (where battery life deteriorates due to partial charges).

One drawback you may have heard is the possibility of lithium ion batteries catching fire. To limit the danger, battery packs require internal mechanisms to limit things like voltage and pressure. While you should still make sure a battery isn’t exposed to unnecessary stress like excessive heat, damage from drops or operating in freezing weather, battery packs are considered safe enough to bring on an airplane. According to the TSA, external batteries rated at 100Wh or less (which all of our recommendations are) can fly with you – just make sure you stash them in your carryon as they aren’t allowed in checked baggage.

Capacity

Power bank manufacturers almost always list a battery’s capacity in milliamp hours, or mAh. Smaller batteries, say those that can charge a smartphone to between 50 and 75 percent, tend to have a 5,000mAh capacity. Larger batteries that can recharge laptops and tablets, or give phones multiple charges, can exceed 25,000mAh. Unsurprisingly, the prices on most batteries goes up as mAh capacity increases, and since batteries are physical storage units, size and weight go up with capacity as well. If you want more power, be prepared to spend more and carry around a heavier brick.

You might think that a 10,000mAh power bank could charge a 5,000mAh phone to 100 percent twice, but that’s not the case. In addition to simple energy loss through heat dissipation, factors like voltage conversion also bring down the amount of juice that makes it into your phone. Most manufacturers list how many charges a battery can give a certain smartphone. In our tests, 10,000mAh of battery pack capacity translated to roughly 5,800mAh of device charge. 20,000mAh chargers delivered around 11,250mAh to a device, and 25,000mAh banks translated to about 16,200mAh of charge. That’s an average efficiency rate of around 60 percent.

Wireless

More manufacturers are making power banks with wireless charging. Not hassling with cables is nice, but it’s important to note that wireless charging is less efficient than plugging in your phone. Outside of MagSafe options, wireless portable chargers historically didn’t make the cut for our top picks for this guide for that reason. The Qi2 wireless charging standard arrived last year and improves performance for wireless charging, including for portable banks. Currently, iPhones are the only handsets that support the new tech, but as it’s an open standard, expect Google, Samsung and others to adopt it for future phones. In my testing, I’ve noticed an uptick in the performance of non-Qi2-enabled batteries as well.

Ports

Since Apple ditched the Lightning cable and adopted USB-C, we’re getting closer to a standard for charging connections — and all of our picks have at least one such port. But plenty of other devices use older interfaces, like USB-A and microUSB ports, plus Lightning for older iPhones. You can find cables with just about any combination of those connections, so when you’re picking out a battery, just check that one end of your preferred cord will fit.

Most battery packs have more than one port, which gives you different charging options. You’ll typically see at least one port labeled “in/out,” which means you can use it to both charge the bank and charge your device. While USB-A output ports can power up smartphones and other small devices, they can’t charge larger devices. Plus, they aren’t as fast as USB-C ports overall. That’s something to keep in mind when you’re deciding which ports and charging cables to use to connect your phone to the pack.

There’s even more variation among USB-C ports themselves, with different ports on the same device supporting different power transfer rates. What that means in practical terms is an iPhone will charge just fine plugged into a power bank’s 18W port. But to properly charge, say, a MacBook or similar laptop, it’ll need the extra juice supplied by a 100W port (which larger power banks can offer). Power banks with more than one port can also charge multiple devices at the same time, but speeds and the overall charge delivered will be lower.

You’ll also want to consider your charging cable. For anything larger than a smartphone (and to access fast-charging capabilities) you’ll want to use USB-C ports and cables. But not all cables are created equal, even when they have the same USB-C plugs on the end. If you want power delivery from a 100W USB-C power bank port, you’ll need a 100W-rated USB-C cable. Luckily, power banks capable of delivering 100W tend to include a compatible cable. For any devices that don’t, we’ve tried and liked Anker’s 100W USB-C cable. For smaller devices, we used this 60W cable from Nimble and we don’t recommend bothering with cables under 60W. For around $20, higher-capacity charging cables will make sure you’re not wasting time with connections that limit your potential power transfer.

Design

For the most part, these rechargeable batteries have a squared-off, brick-like design, though many nod towards aesthetics with attractive finishes and detailing. While that doesn’t affect how they perform, it’s a consideration for something you’ll interact with regularly. Some portable power stations include extra features like MagSafe compatibility, a built-in wall plug or even a kickstand. Nearly all have some sort of indicator to let you know how much available charge your power bank has left, usually expressed with lighted pips near the power button. Some of the newer banks take that a step further with an LED display indicating remaining battery percentage.

How we test portable battery packs

Amy Skorheim / Engadget

Before we even put our hands on a battery pack, we did extensive research. We considered brands Engadget reviewers and staff have tried over the years and we checked out customer ratings on retail sites like Amazon and Best Buy. Here’s the full list of power banks we've tested, which range from small wireless banks to large, multi-device batteries.

MagSafe-compatible

• Apple MagSafe Battery Pack (5,000 mAh)

• Spigen ArcHybrid Mag (5,000mAh)

• Anker 521 Magnetic Battery (5,000 mAh) 

• Baseus Magnetic (10,000mAh)

• Anker MagGo Power Bank (6.6K) (6,600 mAh)

• Anker 633 Magnetic Battery (10,000mAh)

• Anker MagGo Power Bank (10K) (10,000 mAh)

Low capacity (≤10,000mAh)

• Mophie Juice Pack (2,400mAh)

• Anker 511 Power Bank (5,000 mAh)

• Anker 313 Power Bank (10,000mAh)

• Nimble Champ (10,000mAh)

• Biolite Charge 40 PD (10,000mAh)

• Anker Nano (5,000mAh)

• Nimble Champ (10,000mAh)

Mid capacity (10,001 - 20,000mAh)

• Baseus Blade 2 (12,000 mAh)

• Otterbox Fast Charge (15,000mAh)

• Mophie Powerstation Pro (20,000mAh)

• Anker Prime (20,000mAh)

• Nestout Portable Charger (15,000mAh)

• Nimble Champ Pro (20,000mAh)

High capacity (20,001mAh+)

• Mophie Powerstation Pro XL (25,000mAh)

• Anker 737 Power Bank (25,600 mAh)

• Zendure Supertank Pro (26,800mAh)

• Mophie Powerstation Pro AC (27,000mAh) 

• Lion Energy Eclipse Mag (27,000mAh)

• Lion Energy Trek (27,000mAh)

We're continuously updating this guide as companies release new products and we test them. We remove some products as we find better top picks, and we add updated specs and prices where necessary. For testing, we used each battery with some combination of an iPhone 15, an iPhone 14 Plus, an iPhone 11, a Samsung Galaxy S22 Ultra, a Galaxy S23 Ultra, a 5th-gen iPad Air and an M1 Pro 16-inch MacBook Pro. I charged one phone battery at a time, even though some packs are capable of multiple-device charging. I charged the phones and tablets from between zero and five percent until they were 100 percent full (or until the power bank was dead), and didn’t use the phones or tablets while they charged other than to power them on and enter the unlock code. In the case of the MacBook, I used it while it was charging (it’s my work computer).

Amy Skorheim for Engadget

I used the charging cable included with each power bank to charge the Galaxy S22 Ultra, MacBook Pro and the iPad Air. For the iPhones, I used the USB-C to Lighting cable that Apple provides. In the case of the lower-capacity power banks that didn’t include a cord or included one with USB-C to USB-A connectors, I used this 60W-rated USB-C to USB-C cable.

For reference, here are the battery capacities of each device we used for testing:

• iPhone 11: 3,110 mAh

• iPhone 14 Plus: 4,325 mAh

• iPhone 15: 3,349 mAh

• Galaxy S22 Ultra: 4,855mAh

• iPad Air: 7,729mAh

• 16-inch M1 Pro MacBook Pro: 27,027mAh

I noted the times for each charge and the number of charges each bank provided. I also paid attention to things like ease of use and overall design. 

The best portable power banks for 2024

Other power banks we tested

Baseus Blade 2

The Blade 2 from Baseus has a unique, flat shape that’s just a little wider than an ereader — which may make it easier to slip into a low profile laptop bag. It charged a Samsung Galaxy S23 Ultra considerably faster than any other battery bank we tried, getting it from four percent to full in just over an hour. It then filled the phone back to 62 percent from dead on a second charge in about a half an hour. But $100 is a lot for a standard power bank that holds fewer than two full charges. But if you can find the Blade 2 on sale, snap it up.

Anker MagGo (6.6K)

Anker’s 6.6k MagGo is pretty similar to our top pick for a MagSafe-compatible battery pack. It supports the Qi2 charging standard and props up your iPhone so you can use it or enable StandBy mode while powering up. This one even lets you set the viewing angle from 30 to 65 degrees. It was speedy in getting an iPhone 15 up to 50 percent in about 40 minutes. But for the added bulk, it doesn’t have as much capacity as the 10K MagGo, holding just enough juice for a single full charge plus about 5 percent. But it is $20 cheaper, which may be key for some.