One can never read too many books, but one can definitely own too many books. If your shelves are getting full, you may be considering an e-reader. And as it turns out, we came across a fantastic offer on one while looking through Amazon deals: 

For a limited time, you’ll be able to order the Kindle Paperwhite Signature Edition for $210. At full price, this model sells for $265. 

Why you should buy the Kindle Paperwhite

Own the Kindle Paperwhite Signature Edition for $210 when you order on Amazon, and be sure to check out some of the other Kindle deals we found. You should also take a look at some of these early Amazon October Big Deal Day savings!

Today, we have a plethora of free AI tools at our fingertips like ChatGPT and Google Gemini. While using them doesn’t cost you money directly, anyone who paid attention in high school economics class would know that there’s no such thing as a free service. AI is an incredibly expensive technology, and its costs manifest themselves in several ways. What’s the true cost of AI technology?

This is a bit of a tough question to answer because we’re not just talking about the money that end users pay. The costs of AI affect millions, if not billions, of people across several industries, and we’re just starting to see some of the effects of this. What makes things worse is that the costs are increasing. They’re increasing at possibly the worst time with everything else happening in the world.

The true cost of AI affects to users

Let’s start with how much you’re paying out of pocket. At this point, things seem pretty clear when it comes to what AI features you pay for. Companies let you use their most basic AI features for free, and if you want some more advanced features, you’ll just pay a monthly fee. This is how companies like OpenAI, Google, Perplexity, and others operate.

There’s also the AI that comes pre-installed on devices like Samsung’s Galaxy AI and Apple Intelligence. These tools are also free to use with the only cost being the cost of buying the device for the most part.

But here’s a question, you don’t expect things to be like this forever, do you? The sad fact is that this is going to change, and the companies know this. They knew this from the get-go. Free features are going to go behind paywalls and the cost of hopping those paywalls is going to rise as time goes on. We haven’t seen it just yet, but companies are getting ready to start making changes.

Price increases

For example, OpenAI plans to raise the price of ChatGPT Plus from $20/month to $22/month by the end of the year, and it plans to raise it to $44/month within the next five years. The company is aware that the price that they’re charging right now is not sustainable. This isn’t just specific to OpenAI; pretty much all companies developing AI tools know that the prices they’re charging aren’t going to keep their boats afloat for long. These are introductory prices we’re paying now.

Temporarily free

When it comes to free platforms, we’re going to start seeing the number of free features diminishing as time goes on. Right now, Google is letting people try out a ton of free features. We’re talking about some rather advanced features like AI Overviews, Audio Overviews in NotebookLM, Gemini in Gmail, and others. It’s not out of the kindness of the company’s heart.

Google is letting free users try the features so that they can test them out while Google works out the kinks. The company is going to lock some of these features behind a paywall after the testing is done.

Those of you with Galaxy AI and Apple Intelligence, you’re not safe either. We heard soon after Samsung introduced Galaxy AI, that the company was considering charging to use it by the end of 2025. We’re not sure how much money Samsung is going to charge and we don’t know what features will be pay-walled. The fact is that some or most of the features that people are enjoying today could cost money after next year.

Apple is even considering charging people up to $20/month to use some of its AI features eventually. When Apple Intelligence finally launches to the masses, users will be able to use them for free, but not forever.

And people don’t know

The really messed-up thing about this is that many of the users have no idea that the companies are even considering charging them for these features. You’d have to be deeply planted in the tech news circuit to catch wind of what these companies are doing. The majority of people using AI have no idea that the features they’re using for free could cost money tomorrow.

The cost to companies

It’s true that AI can cost the user. While rising prices and temporarily free features will cost you money in the long run, the companies developing AI tools are paying a massive bill today. One thing that people don’t know is that the companies training AI models and deploying AI features are doing so at a loss; a MASSIVE loss. It costs tens of millions of dollars to train and maintain these AI models, and that cost trickles down to the users. This is why the free features you’re using won’t be free forever. Using them costs the companies more money than you’d think.

According to a paper by Epoch AI, it cost Google an estimated $29 million+ to train Gemini 1.0 Ultra, and that was just for the hardware and energy. The report estimates that the company spent more than $191 million in cloud compute resources training the model, and this was just at the time of publishing. It doesn’t take into account the continued training and maintenance of the model.

The same report states that OpenAI spent more than $40 million in hardware and energy and $78 million in cloud compute resources training GPT-4. Again, this is just at the time that the model was published. These aren’t even the companies’ most powerful models.

Breakdown of costs

Nearly half the cost of training Gemini 1.0 Ultra was on R&D staff (49%). 23% was on accelerator chips, 9% was on cluster-level interconnects, 4% was on energy, and 15% was on other server components. OpenAI spent far less on R&D (29%) and far more on accelerator chips (32%). It spent 12% on cluster-level interconnects, 6% on energy, and 21% on other server components.

Since these models came out, we’ve gotten models like GPT-4o and Gemini 1.5 Ultra. We can only imagine how much more these models cost to train.

Another thing to mention is that these costs only apply to training the models. What we also have to consider are the cost of paying the developers, continued upkeep of the models, etc.

Profit? What profit?

You might be thinking “How could they be losing money if they charge subscription fees?” The answer is that the money they’re getting from subscriptions is just dampening the financial burden of training their models. It’s like how Disney rakes in millions and millions of dollars from Disney+, but that service hasn’t made a cent of profit. The cost outweighs the income.

For example, at the time of writing this, OpenAI is now looking for another round of funding to help it reduce the sting of its costs. The company predicts that it will make about $3.7 billion by the end of 2024 in revenue. That’s not too shabby, but that’s outweighed by the $5 billion in business costs. We discovered this during the announcement that the company is raising the price of ChatGPT Plus over the next five years.

This is pretty scary because OpenAI is arguably the most popular AI company. More people pay for its AI tools than other companies, and they’re charging a comparable amount each month for their subscription services. So, it’s likely that OpenAI is making the most money purely from AI, and it’s not turning a profit.

So, other major brands like Google, Amazon, Microsoft, xAI, and Meta, are most likely paying much more and earning much less from their AI.

The prices are going to rise

Just like everything else, big brands made AI a massive profit-driven rat race. This means that they’re all fighting to outdo the competition. As such, these companies are increasing their efforts to build the best AI models, and this means that the costs are going to go up. The more powerful these models get, the more money it’s going to cost to maintain them, and the more money they’ll charge their users.

This is a trend that won’t stop because each company HAS to be the best on the market. No company wants to fall behind the competition; it will piss off the investors and make its users migrate to other services.

According to Epoch AI, the cost of training AI models has more than doubled each year since 2016. Back in 2016, the average cost of training a model was north of $5k of hardware and energy costs (10k for cloud compute resources). By the beginning of 2024, the average sat at about $9 million for hardware and energy (around $2 million for cloud compute resources).

The costs are going to continue to grow as companies try to finally craft AGI (artificial general intelligence). As the prices grow for the companies, they’re going to grow for the smaller brands and services utilizing these models. Not every AI service has its own model. Many of them license pre-existing models from these companies to generate their own content. Over time, it’s going to get more expensive to use these models, and those costs will trickle down to the consumers using their products.

The data cost

The true cost of AI doesn’t only involve money. These AI models probably wouldn’t function without a ton of data collected from years of internet and real-world content. Models need content to “learn” from the world, but the issue is that much of that content was created by people, and it’s being collected without their consent or knowledge.

What introduced people to this fact was learning about DALL-E back in 2022. We found out that, in order to create the then-crude AI-generated images, OpenAI had to scrape millions of images from the internet, and this included images that artists and photographers uploaded. That was just the beginning. As time went on, reports started to surface that several companies had been scraping content from news websites and even from social media posts. This had been going on for years, and we were none the wiser.

It’s possible that most of the social media posts that you’ve been posting for the past couple of years have been scraped and used to train models without your knowing. This is news to sour your palette, especially if you’re a creator. Obviously, if you create content, you’re likely to share it on Twitter (X.com), Instagram, Facebook, Reddit, or other platforms. Well, none of these platforms come out and tell you “Wait! Before you press that ‘Publish’ button, we’re going to scrape your content to train our model!” So, tons of people have been dumbfounded to find out that much of their content was scraped.

It gets worse because the big businesses are making it worse

The only thing that makes this worse is that the companies stealing your data are making it legal. Rather than respecting the fact that users don’t want their data scraped, they put that they scrape your data in their terms of service. So, the fact that they tell you makes it technically legal. This information is buried deep within the terms and coated in a layer of literary perfume like “Some of your data may be used to help improve the experience… blah blah blah.” They just don’t want to outright say that they’re scraping your data.

Also, the opt-out buttons are buried in settings to the point where you have to literally look up guides on how to opt-out, and that’s only for regions where the law requires an opt-out option. If your region doesn’t have an arm-twisting law in place requiring companies to provide an opt-out option, you can bet that there won’t be one.

Some companies are sneaky like X.com. You can opt-out of having your data scraped, but it’s not available on the app…. for some reason. So, you’ll have to use your computer which is less convenient.

Another way that businesses are making this worse is that the companies whose products we use are cutting deals with AI companies to hand over your data. For example, Reddit made a deal to hand over all of its data to Google. In a flash, Reddit just became a content farm for Google, and the users are the animals. Also, LinkedIn scrapes data to most likely train Microsoft’s models. Companies are making deals with these AI companies to hand over their users’ data, and people don’t know about it.

More time, more data

Just like the monetary cost of AI, the data cost is going to grow as time goes on. The more powerful companies want their AI models to be, the more data they’re going to need. This means that companies are going to need to find more ways of getting data and content. This means that it’ll get increasingly harder to post anything to the internet that won’t be intercepted and used to train a model. More and more of your data will be stolen as time goes on.

Paying the price

We’re still at the very beginning of our AI age, and we’re going to be for a while. As such, we’re still rather ignorant about the potential consequences of our actions. How much will it cost to train a model in five years time? How much will it cost to use that model? Will there be any platform on the internet that doesn’t scoop up your data? These are all questions that we ask today, and we’re too frightened to know the answer.

If this trend continues, then not enough people are going to want to invest in AI technology either by direct investments, API access, or subscription services. We know that the price of our AI world is high, but the true cost might be higher than we think.

Finding myself far from an outlet when my phone hits five percent makes me feel shaky. Luckily, part of my job is testing portable batteries so I usually have at least a few on hand. (The only hard part is remembering to bring one along.) I’ve spent the past year and a half testing more than two dozen units to figure out which are the best power banks for different scenarios — from a partial recharge for an iPhone to a massive laptop battery for working out in the field. People who travel or are simply forgetful will appreciate the benefit of having a little extra juice on hand, but as I’ve learned from my tests, they aren’t all winners. Here are the best power banks for just about every scenario.

Table of contents

Best power banks for 2024

Photo by Amy Skorheim / Engadget

Capacity: 10,000mAh, 15W | Ports: One USB-C in/out | Included cable: USB-C to USB-C | Number of charges iPhone 15: 1.64 | Charge time iPhone: 4 to 100% in 2h 26m and 0 to 70% in 1h 8m

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Anker’s MagGo Power Bank was one of the first Qi2-certified products to come on the market, and the new standard has made the brand’s popular MagSafe/kickstand model much faster. It’s easily the best MagSafe battery I’ve tested. 

It brought an iPhone 15 from near-dead to half-full in about 45 minutes. For reference, it took our former top pick in this category an hour and a half to do the same. It’s similarly faster than Anker’s previous generation of this model, the 633, as well. After that initial refill, the MagGo 10K had enough left over to get the phone up to 70 percent on a subsequent charge.

In addition to faster charging speeds, this Anker power bank adds a LCD display to indicate the battery percentage left in the bank, plus the approximate amount of time before it’s full (when it’s refilling) or empty (when it’s doing the charging). A strong MagSafe connection makes it easy to use the phone while it charges and the small kickstand creates a surprisingly sturdy base for watching videos and the like. If you twist the phone to landscape, StandBy mode kicks in.

The power bank did a fine job of charging our Galaxy S23 Ultra, but the lack of support for Qi2, even on the newest Galaxies and Pixels, means the most popular Android will simply charge at a slower rate — and won’t benefit from the zero-effort magnetic alignment. There’s also a USB-C port for recharging, so if you need to fill up something without wireless capabilities, you can.

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Pros

• Qi2 tech enables extra fast wireless charging
• Sturdy kickstand props up iPhones as it charges
• LED display for battery percentage

Cons

• More expensive than other MagSafe packs

$70 at Amazon

Photo by Amy Skorheim / Engadget

Capacity: 5,000 mAh, 22.5W max | Ports: One USB-C and one USB-C connector | Cable: USB-C to USB-C | Number of charges Galaxy S23 Ultra: 0.65 | Charge time: 0 to 65% in 1h 2m

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The Anker Nano power bank is impressive for how much charge it delivers in such a small package. It’s the exact size and shape of the lipstick case my grandma used to carry and has a built-in USB-C connector that folds down when you’re not using it. That means that, in addition to being ultra-portable, you also don’t need to remember to grab a charging cable when you toss it in your bag. There’s also a built-in USB-C port that can refill the battery or be used to fill up a different device with an adapter cable. You also get four indicator lights that let you know how much charge remains in the battery.

In my testing, the 5,000mAh battery provided enough charge to get a depleted Galaxy S23 Ultra back up to 65 percent in about an hour. That’s relatively quick, but the Nano is also small enough that, with an adequately sturdy connection, you can use your phone while it’s charging without feeling too awkward. The charger’s small size also makes it a good pick for recharging earbuds.

For a little more juice and an equally clever design, Anker’s 30W Nano Power Bank is a good option for delivering a single charge. It’s bigger in size and capacity (10,000mAh) and includes a display indicating the remaining charge percentage. The built-in USB-C cable doubles as a carry handle, which is a nice touch. That cable is in/out and there’s another USB-C in-out port in addition to an out-only USB-A port.

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Cons

• Small enough to get misplaced

$26 at Amazon

Photo by Amy Skorheim / Engadget

Capacity: 10,000mAh, 30W max | Ports: One USB-C in/out port, one USB-C in/out cable, wall prongs | Cable: Built-in USB-C | Number of charges iPhone 15: 1.86 | Charge time iPhone: 5 to 100% 1h 53m and 5 to 91% 1h 5m | Number of charges Galaxy S23 Ultra: 1.45 | Charge time Galaxy: 5 to 100% 1h 2m, 5% to 50% 23m

The toughest thing about using a power bank is remembering to bring it along. You also have to remember a cable and, if you want to refill the bank itself, a wall adapter. Anker’s 10K Fusion solves two of those problems with its attached USB-C cable for your device and foldable two-prong plug for charging the bank itself (yes, you still have to remember to bring the thing with you).

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Despite the attachments, it’s compact, just a smidge wider than a stick of butter, yet still packs a 10,000 mAh capacity. The 30 watts of power enabled the “Super Fast Charging” message on a Galaxy S23 and got the phone from five percent to full in just over an hour. In just 20 minutes, the 10K Fusion bumped a near-dead iPhone 15 to 45 percent. Though it slowed down towards the end of the Apple handset’s charge. 

There’s an additional USB-C port for charging devices that may require a different cable and both it and the built-in connector can be used to refill the power bank. The cable makes a neat loop that looks a lot like a handle, though I’m not sure I’d recommend carrying around any bit of tech by its cord. The onboard display indicates the Fusion’s remaining charge in terms of a percentage and was one of the more accurate readouts I’ve tested. I also like the corduroy texture along the sides — very fidget-worthy.

Our previous pick in this low-capacity category, the BioLite Charge 40 PD, is still an excellent choice — it’s durable, delivers a quick charge and looks cool. I use it often myself. Plus BioLite has an admirable mission of bringing energy to places where it’s otherwise scarce. But Anker’s new release, the 10K Fusion simply delivers a faster charge and more features at a lower price.

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Pros

• Has a built-in USB-C cable
• Also has built-in wall prongs
• Display is fairly accurate
• Affordable

Cons

• iPhone charging is slower than other banks in its range

$45 at Amazon

Photo by Amy Skorheim / Engadget

Capacity: 15,000mAh, 18W max | Ports: One in/out USB-C, one in/out USB-A | Cable: USB-C to USB-A | Number of charges iPhone 14 Plus: 2.33 | Charge time iPhone: 0 to 100% in 2h 2m average, and 0% to 33% in 27m | Number of charges Galaxy S22 Ultra: 2.33 | Charge time Galaxy: 0 to 100% in 1h 35m and 0 to 37% in 33m | Number of charges iPad Air: 1.31 | Charge time iPad: 0 to 100% in 2h 23m and 0% to 31% in 38m

At the medium-capacity level, you can charge multiple devices at once or power up something larger than a phone. The Otterbox Fast Charge power bank only lists 15,000mAh of capacity, but it performed nearly as well as the 20,000mAh batteries while costing about $30 less. Over the month and a half I spent testing battery packs, this was the unit I grabbed the most when my own devices dropped to empty. It has a stylish exterior with a gray faux leather finish and copper detailing. A little bigger than a deck of cards and weighing just over 11 ounces, it’s a nice looking accessory that feels solid.

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It filled up both smartphones twice, then replenished each an additional third. I introduced the iPad to the mix here and got a full charge plus an extra third. The Otterbox also lost very little battery power while sitting dormant, which means if you carry it around on the off chance that you’ll need it, it should have plenty of power when the time comes.

Pros

• Attractive design
• Solid build
• Great capacity for the price

Cons

• Doesn’t charge as quickly as others in its range

$45 at Otterbox

Photo by Amy Skorheim / Engadget

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Capacity: 20,000mAh, 65W | Ports: Two USB-C in/out | Cable: USB-C to USB-C | Number of charges iPhone 11: 2.95 | Charge time iPhone: 5 to 100% in 1h 39m average | Number of charges Galaxy S22 Ultra: 2.99 | Charge time Galaxy: 5 to 100% in 59m average | Number of charges iPad Air: 1.83 | Charge time iPad: 5 to 100% in 1h 55m and 83% in 1h 21m

Nimble’s Champ Pro battery delivers a screaming fast charge and got a Galaxy S23 Ultra from five percent to full in under an hour. That’s faster than every other battery I tested except for Anker’s 737, our high capacity pick — and that model costs $30 more. It lent nearly three full charges to both an iPhone and Galaxy device and has enough juice to refill an iPad more than once. The battery pack itself also re-ups from the wall noticeably faster than other models, so it’ll get you out the door quicker.

The company, Nimble, is a certified B-Corp, meaning they aim for higher environmental and social standards and verify their efforts through independent testing. The Champ Pro uses 90 percent post-consumer plastic and comes in packaging made from paper scrap with a bag for shipping back your old battery (or other tech) for recycling.

The unit itself feels sturdy and has a compact shape that’s a little narrower than a smartphone and about as long. The attached adjustable lanyard is cute, if a little superfluous, and the marbled effect from the recycled plastics give it a nice aesthetic. You can charge devices from both USB-C ports simultaneously, and both are input/output plugs.

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My only qualm was with the four indicator lights. On a second testing round, it dropped down to just one remaining pip, yet went on to deliver a full fill-up plus an additional top off after that. That said, I’m glad the indicator lights under-estimated the remaining charge rather than the other way around, and the accuracy seemed to improve after subsequent depletions and refills.

Pros

• Super fast charging
• Made from recycled materials
• Sturdy and compact design

Cons

• Indicator lights underestimate charge

$100 at Nimble

Amy Skorheim for Engadget

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Capacity: 27,000mAh, 85W max | Ports: One in/out USB-C, two out only USB-A, three wireless pads | Cable: USB-C to USB-C | Number of charges iPhone 15: 5.67 | Charge time iPhone: 5 to 100% in 2h 22m average and 5 to 68% in 35m | Number of charges Galaxy S23 Ultra: 4.46 | Charge time Galaxy: 5 to 100% in 1h 21m average 5 to 46% in 25m | Number of charges iPad Air: 2.78 | Charge time iPad: 5 to 100% in 1h 55m average and 5 to 78% in 1h 11m | Number of charges MacBook Pro: 0.79 | Charge time MacBook Pro: 10-89% 1h 18m

Power banks that can charge a laptop are a category unto themselves. I recently put together a guide to those high-capacity portable chargers and Lion Energy’s Eclipse Mag made the cut as the best option for traveling with your laptop — but it’s also great for smaller devices.

The selling point here is supposed to be the three wireless charging pads on its topside, but I found its wired performance to be even more impressive. The 27,000mAh battery translates to about 100 watt hours, aka the TSA’s largest approved capacity for travel. It’s more compact than other 27K batteries, though at two pounds and 8.5 inches long, it’s hardly small. The soft-touch plastic on the exterior is thicker at the angled-off corners, which makes it feel like it could handle a tumble — Lion Energy doesn’t list any sort of mil spec or other ratings for drop endurance so I didn’t subject the tester unit to any rough handling.

Measuring the recharge time of the batteries from the wall isn’t one of the metrics I usually test, but Lion Energy claims a 90 minute refill and my experience lines up with that. It refilled our iPhone 15 five and a half times and the Galaxy S23 Ultra nearly five times. It revived a 16-inch MacBook Pro from 10 percent to 89 percent while it was in use. That works out to about 14 percentage points more than our current command center battery recommendation. The previous pick in this category, Anker’s 737, charged up a Galaxy S22 Ultra slightly faster than the Eclipse Mag refilled a Galaxy S23 Ultra (which have the same battery capacity) but the Eclipse had more charge to give every device.

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A double-press of the status button enables wireless charging and more than one device can be charged at once. It also supports pass-through charging, so you can have the battery charging from the wall as you charge your device. 

Magnets align with an iPhone’s MagSafe circle to position the phone quickly. Finding the sweet spot for the Galaxy phone takes a little adjustment, but was easy enough. It took nearly three hours to fully charge the iPhone 15 from five to 100 percent, but getting it to 87 percent only took two hours. With any portable battery, the charge rate slows significantly as the device approaches 100 percent — and that’s even more noticeable with a wireless portable charger.

Lion Energy told me the Eclipse Mag is designed for Apple Watches only. Not surprising given the Pixel Watch 2 doesn’t support wireless charging and Samsung recommends you only use its chargers to refill a Galaxy Watch. My Apple Watch snapped into place easily and started charging right away (after I remembered to double press the button to fire up the wireless pads).

At $149, it’s relatively affordable for a lot of power, particularly given the wireless charging feature. I wish it had more than one USB-C port, but I suppose the wireless pads make up for the lack. Overall, it’s a solid choice for long trips or for working away from an outlet for a day or two. 

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Pros

• Massive 27,000mAh capacity
• Quick charge wired charging times
• Wireless charging works well for a portable battery

Cons

• Large and heavy
• Just one USB-C port

$149 at Lion Energy

Photo by Amy Skorheim / Engadget

Capacity: 27,000mAh, 140W max | Ports: One USB-C in/out, one USB-C out, USB-A, 100W AC | Cable: USB-C to USB-C | Number of charges iPhone 11: 3.75 | Charge time iPhone: 0 to 100% in 1h 40m average and 75% in 46m | Number of charges iPad Air: 2.15 | Charge time iPad: 0 to 100% in 1h 56m and 15% in 19m | Number of charges 16” MacBook Pro: 0.65 | Charge time MBP: 10% to 75% in 1h 29m

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The TSA’s 100-watt-hour battery limit translates to around 27,000mAh for lithium batteries. Mophie’s Powerstation Pro AC is so massive it necessitates a grab handle and get close to the edge of that max carry-on size. You probably won’t find a larger, acceptable portable power bank — after all, an on-the-go charging brick is pointless if you can’t travel with it. I took this one through security at two airports and no one gave it a second glance.

To power your laptop and the rest of your mobile work setup, the Powerstation has four ports. Three of them are the usual USBs, but there’s also a three-prong AC outlet. Most current devices charge via USB (and doing so is more efficient than using a power adapter between the cable and power bank), but older devices and certain mobile workstation accessories — speakers, lights and printers come to mind — might only power up through a basic wall plug. Just be sure to hold down the status button until the light turns red to turn on the AC port.

The AC plug powered most small appliances I plugged into it, including a small speaker, an HP printer and various LED lights. The 100 available watts isn’t enough to continuously push a charge through the 140W power adapter that ships with the 16-inch MacBook Pro, but via the USB-C port, it was able to charge that laptop from 10 percent to 75 percent in under 90 minutes.

The four lighted LED indicators will tell you when the battery is full. Unfortunately, it’s not the best indicator of when the bank will run out of juice. It charges for quite a while with four and three pips lit up, but then quickly cycles through the last two dots before it dies. So it might be better to just remember how much you’ve used the brick rather than relying too heavily on its indicators.

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Smaller devices like a smartphone will get numerous charges; I got nearly five refills on an iPhone 11, and two charges and some change on an iPad. The Powerstation Pro AC was even a little faster at both tasks than our previous pick for a mobile command center. That said, this bank is overkill for a simple mobile device fill-up. At 2.6 pounds, it makes the most sense as a power source when you’re working in the field with multiple components.

The Lion Energy Trek power bank is pretty similar to the Powerstation Pro AC. It has the same 27,000mAh capacity and three USB ports plus an AC plug. The exterior has a more rugged feel and there’s an LED screen indicating outgoing wattage and remaining charge. Charging times and number of refills was on par with what the Powerstation delivered and the Trek is currently about $30 cheaper too. However, just one of the USB ports is Type-C and the display inaccurately indicated the power bank’s remaining charge, repeatedly saying it had 25 to 35 percent remaining just moments before dying completely. But if those two caveats don’t bother you, this could make a reliable travel companion.

Pros

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• Massive capacity
• Unique AC outlet

$200 at Amazon

Photo by Amy Skorheim / Engadget

Capacity: 20,000mAh, 200W max | Ports: Two USB-C in/out, one USB-A, charging pins | Cable: USB-C to USB-C | Number of charges iPhone 11: 3.75 | Charge time iPhone: 0 to 100% in 1h 48m average and 75% in 47m | Number of charges iPad Air: 1.54 | Charge time iPad: 0 to 100% in 2h 11m and 54% in 47m

Not only does Anker’s new 20,000mAh Prime power bank look pretty slick, it’s also easier to recharge — as long as you pony up for the companion base. Magnets help align the pins so you can just plonk the battery down and move on with your life. The set will run you $200, which is pretty spendy for a battery bank, but if you consider that the base offers extra ports (one USB-A and two USB-C), you can also use it as a power hub for other devices, which takes some of the sting out of the price.

The battery itself has the same three ports as the base and a blocky, upright design. The case is a textured metallic plastic with a high-polish, built-in screen and rounded corners. It tells you how many watts are flowing out to each device and displays the overall remaining charge within the battery. When you press the power button, it takes a moment to wake. But the extra processes that run the screen don’t seem to slow the battery down or diminish the power it has to give. Its charge times and capacity was on par with the other 20K batteries I’ve tested.

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I’ve been pretty careful with my review unit, but I’d be worried that the sleek and shiny finish will get wrecked with regular use. It does come with a faux-suede pouch to carry it in, but I doubt anyone will use that regularly — after all, the whole appeal of the Prime’s base and battery set is the low-hassle efficiency. 

The Prime series seems to be Anker’s replacement for the Powercore models and a few different sizes fill out the lineup, including a 27,560 mAh monster that uses the same charging base and earned an honorable mention in our laptop power bank guide. 

Pros

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• Convenient charging with the base
• Sleek, attractive design
• Has a charge indicator display

Cons

• Expensive, especially with the base
• Shiny screen seems easily scratched

$130 at Amazon

Photo by Amy Skorheim / Engadget

Capacity: 15,000mAh, 32W max | Ports: One USB-C in/out, one USB-C in, one USB-A | Cable: USB-A to USB-C | Number of charges iPhone 11: 2.99 | Charge time iPhone 11: 0 to 100% 2h average and 0 to 99% in 1h 45m | Number of charges iPad Air: 1.17 | Charge time iPad: 0 to 100% 2h 23m and 0 to 17% 15m

Plenty of battery packs are built to withstand drops and other abuse, but very few are waterproof or even water resistance. It makes sense; water and electrical charges aren’t good companions. The Nestout Portable Charger battery has an IP67 rating, which means it can handle being submerged in water for a number of minutes, and Nestout claims a 30-minute dunk in a meter of water shouldn’t interfere with the battery’s operation. I couldn’t think of a likely scenario where a power bank would spend a half hour in three feet of water, but I could see a backpacker traversing a river and submerging their pack for a few minutes, or a sudden downpour drenching all of their gear. So I tested by dropping the battery in a five gallon bucket of water for five minutes. After drying it off, the unit performed as if it had never been wet.

The water resistance comes courtesy of screw-on caps with silicone gaskets that physically keep the water out, so you’ll need to make sure you tighten (but don’t over tighten) the caps whenever you think wetness is in your future. The company also claims the battery lives up to a military-standard shock/drop specification which sounds impressive, but it’s hard to pin down what exactly that means. I figured it should at minimum survive repeated drops from chest height onto a hard surface, and it did.

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As for charging speeds, it wasn’t quite as quick as our recommendation for a mid-capacity bank. The Otterbox charged an iPhone 14 Plus to 80 percent in about an hour and the Nestout got the smaller iPhone 11 to 80 percent in the same amount of time. Another thing to note is that the supplied cable is short, just seven inches total, so you’ll likely want to use your own cord.

Nestout also makes accessories for its batteries, which I found delightful. A dimmable LED worklight snaps on to the top of the battery while a small tripod holds them both up. The portable solar panel reminded me of a baby version of Biolite’s camping panels. Nestout’s version refilled the 15,000mAh bank to 40 percent in under three hours, which sounds slow, but is actually fairly impressive considering the compact size of the panels. This is also a blazingly hot summer, so I’d expect better performance in more reasonable weather.

Pros

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• Waterproof with the caps secured
• Clever accessories (sold separately)
• Survived drop tests

Cons

• Not the fastest charge times
• Included cable is short

$50 at Amazon

Amy Skorheim for Engadget

A few companies now make phone cases that double as batteries. The is the first one I’ve tested, so it’s hard to call it the best in its category, but I found a lot of reasons to recommend it. The case splits in two, making it easy to put on, but once installed, the phone feels secure in its protective sheath. I was surprised by how little bulk it adds; it’s a little longer at the bottom and a little thicker at the back, but I doubt anyone would even guess the case was also a battery.

When my tester iPhone 15 started to die, I long pressed the back button (a short press indicates battery level) and the charging bolt symbol immediately kicked on. It took about an hour and 45 minutes to get the phone from ten percent to 65 percent before the battery depleted. Compared to other batteries capable of delivering a partial charge, that’s not terribly fast. But it provides a few extra hours of life and it’s always there when you need it.

The Juice Pack presents a couple drawbacks, though, with the biggest being that it prevents wireless charging. When it is time to recharge from the wall, a USB-C cable goes into the Juice Pack at the bottom edge, right where the phone’s port is. Power is directed first to the phone then switches to refilling the case battery.

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The other downside is the fact that it’s a case. It only works with an iPhone 15, 15 Pro or 15 Max, depending on which version you buy, and it won’t lend a charge to any other device that may need it. Also, like the Model T, the Juice Pack comes in any color you want, as long as that color is black. Some people won’t care, but others will probably lament the lack of personal expression. Still, if you often find yourself forgetting to charge your phone and you also forget to bring an extra battery, this is a good lifeline.

$93 at Amazon

Amy Skorheim for Engadget

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This impressive little external battery pack from Baseus is a strong contender for knocking Anker’s MagSafe battery off its pedestal in this guide. Baseus’ bank is about half the price and has a built-in USB-C cable so you can recharge non-iPhones without needing to have a cable on hand. The cable can also be used to recharge the bank itself. Even though it doesn’t use Qi2 wireless charging technology, it managed to charge an iPhone 15 just as fast as the Anker unit. It lacks Anker’s status display and kickstand, though, but if those features aren’t essential for you, this is a great buy.

$46 at Amazon

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 a battery’s lifespan 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 and we have a separate guide that covers that entire category.

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, so you’ll now see wireless options on this list.

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 best power banks

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. Then we get our hanHere’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)

• Mophie snap+ PowerstationMmini (5,000mAh)

• 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)

• UGREEN 10,000mAh Magnetic (10,000mAh)

Low capacity (≤10,000mAh)

Mid capacity (10,001 – 20,000mAh)

High capacity (20,001mAh+)

• Mophie Powerstation Pro XL (25,000mAh)

• UGREEN Power Bank 25,000mAh 145W (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)

• HyperJuice 245W (27

• Anker Prime 27,650mAh Power Bank (27,650mAh)

We’re continuously updating this guide as companies release new products and we test them. We remove some products as we find picks that are more worthy of the best portable charger designation. We also add updated specs and prices where necessary.

For testing, I 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).

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:

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.

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.

Mophie Snap+ Powerstation Mini

The Mophie snap+ Powerstation Mini is terribly well-built. It feels premium with a rubberized contact point for the MagSafe charging pad and a stand that runs the entire width of the bank itself, making it extra sturdy. It’s compact, too, but only carries a 5,000mAh capacity, which gets you a partial charge on most newer or larger phones. Our current MagSafe/iPhone pick has double the capacity, a stand and a digital display — for just $20 more than the Powerstation Mini.

Portable charger FAQs

What’s the difference between a portable power bank and a portable charger?

A slew of terms are used to describe power banks, including portable batteries, portable chargers, external battery packs and even, somewhat confusingly, USB chargers, which is what wall chargers are often called. They all mean the same thing: a lithium ion battery that stores a charge so you can refill a smartphone, tablet, earbuds, console controller, ereader, laptop, or just about any other device with its own built-in, rechargeable battery.

There’s little difference between the terms, so the specs you’ll want to pay attention to are capacity (expressed in mAh), size and weight so you can find the right balance between recharging what you need and portability.

Power stations, on the other hand, are distinct. These are bigger units (often around the size of a car battery) that can be used to charge multiple devices multiple times, but notably, they can’t be taken on airplanes.

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