A power bank is one of the most useful things to keep in a bag, glovebox or travel kit. It keeps your phone alive on long days out, rescues a flat tablet on a road trip and can even charge some laptops. This power bank buying guide explains capacity, charging speed, ports and travel rules so you can choose the right one.
Capacity: what mAh really means
Power bank capacity is usually listed in milliamp-hours (mAh). A bigger number means more stored energy. But you won't get the full rated capacity into your device, because some energy is lost converting voltage and as heat. As a rough guide, expect to get around two-thirds of the rated capacity into your devices.
| Capacity | Typical use |
|---|---|
| 5,000mAh | A slim emergency top-up for a phone; easy to pocket |
| 10,000mAh | A popular everyday size; often around two phone charges |
| 20,000mAh | Multiple phone charges or a tablet top-up; good for travel |
| 24,000mAh and above | Laptops, multiple devices and longer trips; heavier to carry |
Phone and tablet battery sizes vary, so check your device's battery capacity and compare it with the power bank to estimate the number of charges.
Charging speed and USB-C PD
Capacity tells you how much energy a power bank holds; output wattage tells you how fast it can charge.
- USB-C PD is the most widely used fast-charging standard for phones, tablets and laptops.
- Quick Charge and other proprietary standards are supported by some Android phones.
- Output wattage matters. A phone may charge quickly from around 20W, while many laptops need significantly more. Check the power bank's maximum USB-C output and your laptop's charging requirements.
To get fast charging you need three things: a device that supports it, a power bank that supports the same standard, and a suitable cable.
Ports and cables
Look at which ports you'll actually use:
- USB-C ports handle input and output on most modern power banks, which means one cable can charge both the bank and your phone.
- USB-A ports are handy for older cables and accessories.
- Built-in cables mean you never forget a cable, though they can wear over time.
- Multiple outputs let you charge a phone and earbuds at the same time, but total output is usually shared between ports.
Recharging the power bank itself also takes time. A bank with fast USB-C input refills much quicker than one limited to slow input.
Wireless and magnetic power banks
Wireless power banks let you charge compatible phones without a cable, and magnetic designs snap onto the back of supported phones. They're very convenient for light top-ups, but wireless charging is generally slower and less efficient than a cable, and phone cases can interfere. Check compatibility with your phone and case.
Size, weight and display
Higher capacity means more weight. A 10,000mAh bank is pocket-friendly for many people, while 20,000mAh and above suits a backpack or carry-on. A digital display that shows the remaining percentage is far more useful than a row of simple lights, especially when you're planning a long day out.
Charging laptops and tablets
To charge a laptop, the power bank needs a USB-C PD output with enough wattage for your laptop, and the laptop must support charging over USB-C. A lower-wattage power bank may still slow down battery drain without fully charging the laptop while it's in use. Tablets are generally easier to charge from mid-size power banks. Our tablet buying guide and laptop buying guide cover charging in more detail.
Flying with a power bank
Airlines and aviation authorities treat power banks as spare lithium batteries. Common rules include:
- Power banks must be carried in cabin baggage, not checked baggage.
- There are limits based on watt-hour (Wh) rating, and larger banks may need airline approval or may not be allowed.
- Some airlines restrict using or charging power banks during the flight.
Rules change and differ between airlines, so always check your airline's current requirements before you travel. The watt-hour rating is usually printed on the power bank.
Everyday use and care
- Use a reputable power bank with built-in protections against overcharging, overheating and short circuits.
- Don't leave power banks in a hot car or direct sun for long periods.
- Stop using any power bank that is swollen, damaged or gets unusually hot, and dispose of it at a battery recycling point.
- Top up power banks every few months if they're stored for emergencies.
- Avoid covering a power bank while it's charging so heat can escape.
Which power bank suits you?
- For daily commuting: A slim 5,000 to 10,000mAh bank with USB-C.
- For weekends away: A 10,000 to 20,000mAh bank with fast charging and two outputs.
- For travel with a laptop: A higher-wattage USB-C PD bank that suits your laptop and is within airline limits.
- For camping and festivals: A larger bank with a clear display. Pair it with spare cables from our phone accessories range.
- For wearables: A small bank to keep your watch and earbuds topped up. Our smartwatch buying guide and noise cancelling headphones guide cover battery life in more detail.
Power bank brands to compare
Our power bank range includes models from Kogan, Yoobao and UGREEN, from slim everyday banks to high-capacity units with digital displays. Browse our phone accessories for cables and cases, our tablet accessories for covers and stands, and our phones and tablets range. Every brand we stock is listed on our brands page.
Related guides: Smartwatch Buying Guide, Noise Cancelling Headphones Guide, Tablet Buying Guide, Laptop Buying Guide.
Frequently asked questions
How many times will a 10,000mAh power bank charge my phone?
Often around two full charges for a typical phone, but it depends on your phone's battery size and energy lost during charging.
Can a power bank charge a laptop?
Yes, if the laptop charges via USB-C and the power bank has a USB-C PD output with enough wattage for that laptop.
Can I take a power bank on a plane?
Power banks generally must go in cabin baggage, with limits based on their watt-hour rating. Check your airline's current rules before you fly.
Is it okay to leave a power bank charging overnight?
Quality power banks have protection circuits, but it's sensible to charge on a hard surface away from anything flammable and unplug once full.
