A good portable charger holds enough power for a full phone charge, fits in your pocket or bag, and actually delivers the speed your device expects

A portable charger (also called a power bank) is a battery you carry with you. The useful ones have three things in common: they store enough energy to charge your phone completely at least once, they're small enough that you'll actually bring them along, and they charge your device at the speed it was designed for. A charger that's too slow, too heavy, or too weak defeats the purpose.

The difference between a good portable charger and a mediocre one usually comes down to capacity, charging speed, and how many devices it can handle at once. A charger that's too small won't get you through a day away from an outlet. One that charges too slowly means you're waiting hours for a partial top-up. And if it can't handle your phone's charging speed, you're getting maybe half the benefit.

Key Takeaways

  • Capacity matters most: a 20,000 mAh charger will fully charge most phones once, while a 10,000 mAh charger gives you a partial charge.
  • Check your phone's charging speed (usually 18W to 30W for modern phones) and buy a charger that matches or exceeds it, or you'll charge slowly.
  • USB-C chargers work with most modern phones and laptops, while older iPhones need USB-A or Lightning, and some Android phones still use micro-USB.
  • A charger you'll actually carry is better than a more powerful one that stays at home because it's too heavy or bulky.
  • Real-world capacity is usually 60 to 80 percent of the advertised number because of energy loss during charging.

Capacity: How Many Times Will It Charge Your Phone

Capacity is measured in mAh (milliamp-hours). Your phone's battery is also measured this way. A phone with a 4,000 mAh battery and a 20,000 mAh charger should charge it five times over — in theory. In practice, you'll get three to four full charges because energy is lost when the charger converts its power to what your phone needs.

For most people, 20,000 mAh is the practical sweet spot. It's heavy enough to charge a modern phone completely, light enough to carry without thinking about it, and costs between $20 and $40. A 10,000 mAh charger fits in a pocket and weighs almost nothing, but it gives you only a partial charge — useful for a quick top-up during a day out, not for a long trip. A 30,000 mAh or larger charger is overkill for phones unless you're also charging a laptop, and it becomes a brick you'll leave behind.

Check your phone's battery capacity in Settings (iPhone: Settings > Battery > Battery Health & Info; Android: Settings > Battery > Battery Information). If it's under 4,000 mAh, a 10,000 mAh charger works. If it's 4,000 to 5,000 mAh, go with 20,000 mAh. If you have multiple devices or a tablet, 20,000 mAh is the minimum.

Charging Speed: Matching Your Phone's Needs

Your phone charges at a specific wattage — usually 18W, 20W, 25W, or 30W for recent models. If your charger can't deliver that wattage, your phone charges slowly. A charger rated for 5W will trickle-charge your phone even if it's capable of 30W charging.

Find your phone's charging speed in the manual or on the manufacturer's website. iPhone 14 and newer support 20W. Most recent Samsung phones support 25W or higher. Google Pixels support 18W to 30W depending on the model. Once you know the number, buy a charger rated for at least that wattage. A charger rated higher than your phone needs won't damage it — your phone will only draw what it can handle.

Chargers list their output in watts (W) or amps (A). A 5V/3A charger is 15W. A 9V/2A charger is 18W. If the charger doesn't list watts clearly, the math is volts × amps = watts. Don't guess — a slow charger feels like a waste after a few uses.

Cable Type: USB-C, Lightning, or Micro-USB

The cable that comes with your charger (or the port built into it) has to match your phone. USB-C is the modern standard and works with most Android phones made after 2018, all recent iPhones (15 and newer), and most laptops. Lightning is Apple's older connector for iPhones 14 and earlier. Micro-USB is an older Android standard still found on budget phones and some accessories.

If you have multiple devices with different connectors, buy a charger with USB-C output and carry a separate Lightning cable if you have an older iPhone. Some chargers come with two USB ports (one USB-A, one USB-C) so you can charge two devices at once. Others have a built-in cable that doesn't detach. A detachable cable is more flexible — you can replace it if it breaks and use the charger with different devices.

Size and Weight: The Charger You'll Actually Carry

A charger that stays in your desk drawer is useless. The best capacity in the world doesn't help if you leave it at home. A 20,000 mAh charger typically weighs between 10 and 14 ounces (280 to 400 grams) and is roughly the size of a deck of cards. That's heavy enough to notice in a bag but light enough that most people don't mind carrying it.

If you travel light or commute on foot, a 10,000 mAh charger (usually 5 to 7 ounces) is worth the trade-off in capacity. If you're driving or have a large bag, a 30,000 mAh charger is fine. The real test is whether you'll actually put it in your bag before you leave. A charger you forget is worse than no charger at all.

Multiple Ports: Charging More Than One Device

Most portable chargers have at least two ports — usually one USB-A and one USB-C, or two USB-C ports. This lets you charge your phone and a friend's phone, or your phone and earbuds, at the same time. If you charge two devices simultaneously, the charger splits its power between them, so each charges slower than if it were alone. A 20,000 mAh charger charging two phones at once might deliver 10W to each instead of 20W to one.

For most people, two ports are enough. Three or more ports are useful only if you regularly charge multiple devices at once — a phone, tablet, and earbuds, for example. More ports also mean a larger, heavier charger. Stick with two unless you have a specific reason for more.

Brand and Real-World Testing

Anker, Belkin, and RavPower are the most reliable brands for portable chargers. They're widely available, reasonably priced, and their chargers actually deliver close to their advertised capacity. Cheaper no-name chargers sometimes overstate their capacity or deliver power slowly. You don't need the most expensive option, but buying from a known brand reduces the risk of a charger that fails after a few months.

Read reviews from people who tested the charger with their actual phone, not just reviews that repeat the spec sheet. Look for comments about real-world charging time and whether the charger still works after six months of regular use. A charger that charges your phone in two hours is better than one that takes four, even if they cost the same.

Frequently Asked Questions

Can I bring a portable charger on an airplane?

Yes, but only in your carry-on bag, not checked luggage. The TSA limits portable chargers to 100 watt-hours, which covers almost all phone chargers. Larger chargers designed for laptops may exceed this limit. Check your charger's watt-hour rating (usually printed on the back) before you pack.

Will a fast charger damage my phone's battery?

No. Your phone controls how much power it accepts. A charger rated for 30W won't damage a phone that only supports 20W — the phone will straightforward draw 20W. Using a charger that matches or exceeds your phone's rated speed is safe and normal.

Why does my charger show a different capacity than advertised?

Energy is lost when the charger converts its stored power to what your phone needs. A 20,000 mAh charger typically delivers 12,000 to 16,000 mAh to your phone in real use. This is normal and not a defect. Manufacturers sometimes advertise the theoretical capacity rather than the usable capacity.

Can I charge my laptop with a portable charger?

Only if the charger is rated for laptop charging (usually 45W or higher) and has USB-C output. Most phone chargers are too weak for laptops. Check your laptop's charging wattage and buy a charger rated for at least that much. A 65W USB-C charger can charge most laptops and phones.

How long does a portable charger last before it stops working?

A good portable charger typically lasts two to three years of regular use before its capacity noticeably declines. After that, it may still work but will charge your phone fewer times. Keeping it cool and avoiding complete discharge extends its life.