Smaller battery packs are great for refiling phones and tablets, but if you need to keep a laptop juiced up while youre far from an outlet, youll need something larger. For this guide, we tested portable chargers with at least a 20,000mAh (74Wh) capacity, but kept the upper limit below 27,000mAh (99Wh), since thats about the maximum size allowed by the TSA in carry-on luggage. Some laptop power banks sport extra features like wireless charging or an AC plug so you can power small devices such as a travel printer or an LED lamp. But what all of them have in common is a larger size and higher price tag than standard battery packs. So if you dont want to play a guessing game, these are the best laptop power banks we tested. Table of contents Best laptop power banks for 2024 What to look for in a laptop power bank How we test portable laptop chargers Laptop power bank FAQs Best laptop power banks for 2024 What to look for in a laptop power bank Capacity If you just need to keep a smartphone from dying before you can make it home, just about any power bank will do. But if you need to revive multiple devices or the substantial battery of a laptop, youll want something with a high milliamp-hour (mAh) capacity. A power bank capable of delivering enough power to a laptop will have a capacity between 20,000 and 27,000 mAh. Go higher than 27,000mAh and you wont be able to take it on an airplane, which is why most portable chargers top out around that number. Since the voltage for most portable power banks is around 3.7 volts, a 27,000mAh battery translates to 99.9 watt hours which is the maximum capacity the TSA will allow for carry-on luggage. (And note that these batteries cant be checked, regardless of size). If you want something even bigger than a laptop power bank, and dont need to fly with it, youll likely want to look into portable power stations. These can be the size of a car battery or larger and can potentially fuel an entire weekend away. Another thing to keep in mind is that the capacity listed in a power bank's specs is not what will be delivered to your devices. As I mentioned, the capacity of these banks is around 25,000mAh. Even the huge battery on a MacBook Pro has a mAh rating of around 5,000 - 6,000mAh, so you might think youd get five full charges but in reality, you only get about a single 70-percent charge. The voltage is different (typically 3.7V for the power bank and 11.4V for a laptop) which makes the watt-hours, or the amount of energy each battery can hold, different (working out to 92Wh for the battery and 72Wh for the laptop). On top of that, in order to feed a charge from a power bank to a laptop, a voltage conversion takes place and that dissipates a decent amount of energy. Without turning this into a physics lesson, this all means that a power bank with a 25,000mAh (or 92Wh) capacity will typically fill a 5,000mAh (or 72Wh) laptop battery to about 75 percent. In my tests, I averaged about a 60-percent efficiency rate between a power banks listed capacity and the actual charge delivered. Ports Every large power bank Ive tested has at least three USB ports, with a mix of USB-C and USB-A, which should cover nearly any portable device you need to recharge earbuds, phones, tablets, laptops, you name it. In addition to the different plug formats, some ports supply power at different wattages. For example, one USB-C port might be rated for 60 watts, while the one next to it is rated for 100 watts. So if youve got a device thats capable of 70W fast charging, such as the new MacBook Air, youd want to opt for the 100W port to get the best charging speeds possible. Note that devices with a smaller wattage draw wont be negatively affected by connecting to ports with high ratings. For example, a Galaxy S24 Ultra, capable of 45W super fast charging, can happily plug into the 100W port. A device will only draw what it can take, regardless of what a port can supply. Just remember that the port, device and cable need to be at or above the desired wattage rating to achieve maximum charging rates. Some of these larger batteries also have AC ports. It might seem like a natural fit to plug in your laptops power adapter for a recharge. But really, the AC port should only be for devices that cant use USB such as a lamp or a printer. Plugging a power adapter into the AC port only wastes energy through conversion. First, the battery converts its DC power to supply the port with AC power, then the power adapter converts that AC power back to DC so your laptop can take it in. And as youll remember from physics class, each time energy is converted, some is lost to heat and other dissipations. Better to cut out the middleman and just send that DC power straight from the battery to the device. Also, you can use more than one port at a time with these devices; just remember that the speed of whatever youre charging will likely go down, and of course, the battery is going to drain proportionally to what youre refilling. Wireless charging Just in the last year and a half that Ive been testing portable power banks, wireless charging capabilities have noticeably improved. The first few I tried were painfully slow and not worth recommending. Now the wireless pads built into power banks are impressively fast particularly, in my experience, when charging Samsung Galaxy phones (though the lack of a stabilizing magnetic connection like Apples MagSafe means they only work when rested flat on a pad). Most wireless charging connections can be used while other ports are also being employed, making them convenient for some mobile battlestation setups. Of course, wireless charging is always less efficient than wired, and recharging from an external battery is less efficient in general. If you want to waste as little energy as possible, youre better off sticking to wired connections. Design All power banks are designed to be portable, but theres a big difference between a pocket-friendly 5,000mAh battery and one of these laptop-compatible bruisers. Most of the latter weigh between a pound and a half to two pounds, which is a considerable addition to a backpack. Many of the options listed here have a display to tell you how much charge remains in the battery, which is helpful when youre trying to judiciously meet out charges to your devices. If a bank has a wireless connection, the pad is usually on the flat top and any available AC connection is usually at one end. Both may require you to engage those charging methods. Dont be like me and grumble loudly that you got a bum unit without pressing (and sometimes double pressing) all the buttons first. How we test portable laptop chargers For the past year and a half, Ive been testing and using dozens of portable batteries for our other battery guide. Some of those batteries include the higher-capacity power banks you see here. I also got a hold of a few extra banks just for this guide to make sure we covered whats available. I went for brands Im already familiar with, as well as battery packs from well-received manufacturers I hadnt tried before (like UGREEN and Lion Energy). I only considered banks with at least a 20,000mAh capacity and mostly stuck with those that rated 25,000mAh and higher. Heres everything we tested: Zendure Supertank Pro Mophie Powerstation Pro XL Mophie Powerstation Pro AC Lion Energy Eclipse Mag Lion Energy Trek Baseus Blade Laptop Anker Prime 27,650mAh Goal Zero Sherpa 100 AC Due to shipping and travel issues, I wasnt able to test two of the batteries I had slated: the HyperJuice 245W and the UGREEN Power Bank 25,000mAh. Once Ive had a chance to see how these two perform as well as any new worthy contenders that hit the market Ill update this guide accordingly. I tested each power bank with an iPhone 15, a Galaxy S23 Ultra, an iPad Air (M1) and a 16-inch MacBook Pro with the M1 Pro chip. Even though these banks can charge multiple devices at once, I refilled one at a time, to make side-by-side comparisons more straightforward. I drained the batteries of the phones and tablets to between zero and five percent and then didnt use any device as it refilled. For the MacBook, I let it run down to 10 percent before plugging in the power bank. That's when most laptops give display a connect to power warning, as draining any battery to empty will compromise the battery life. I then used it as one might in a mobile office, with a Bluetooth keyboard and mouse, while connected to Wi-Fi and a VPN. For each test, I noted how long a completely charged battery took to get a device back to full and how much of the batterys capacity was used up in one charge. I also noted things like portability, apparent durability, helpful features and overall design. For reference, here are the battery capacities of the devices I used: iPhone 15: 3,349mAh Galaxy S23 Ultra: 4,855mAh iPad Air (5th gen): 7,729mAh 16-inch M1 Pro MacBook Pro: 27,027mAh Laptop power bank FAQs How do laptop power banks differ from phone power banks? The main difference is size. Phone power banks tend to have a capacity ranging from 5,000mAh to 20,000mAh and laptop powerbanks are typically rated between 20,000mAh and 27,000mAh. Theres no official definition, however. Laptop batteries are simply larger and need a bigger supply of power to give them a meaningful charge. How do you fast charge a power bank? You can charge a power bank exactly as fast as the power banks internal mechanisms will allow. Most batteries are limited in how quickly they can accept and deliver a charge to avoid dangerously overheating. But to make sure youre charging a bank as quickly as possible, make sure the wall adapter and the USB-C cable you are using have a high wattage rating using a 5W power brick and a 10W cable will take a lot longer to refill your bank than a 65W wall charger and a 100W cord. What size power bank do I need for a laptop? Look for a power bank with a rating of at least 20,000mAh. Slightly smaller batteries may work, but they wont deliver a significant charge to your laptop. How many mAh to charge a laptop? A milliamp hour (mAh) is how much a battery can hold, and most portable batteries list their capacity using mAh. If you get a battery rated at 20,000mAh or above, it should be able to charge your laptop. Using mAh to discuss laptop batteries can be confusing. Due to differing voltages, you cant directly compare the mAh ratings of a power bank battery to a laptop battery. Using watt-hours is a better gauge, as that calculation takes voltage into account.This article originally appeared on Engadget at https://www.engadget.com/computing/accessories/best-laptop-power-bank-120040388.html?src=rss