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Last reviewed: September 2026 · Written by the Wiremason Editorial Team
If your phone regularly dies before you get home, you need extra battery you can carry. There are three main ways to do it: a magnetic wireless power bank that snaps onto the back of your phone, a battery case that replaces your normal case, or a standard power bank you plug in with a cable. They all solve the same problem, but they suit very different routines.
The short answer: choose a magnetic power bank for convenience, a battery case if you want to forget about charging entirely on long days, and a standard cabled power bank if you want the most charge for the money or need to top up more than one device.
How much charge do you actually get? (mAh explained)
Power banks are rated in milliamp-hours (mAh). That figure describes the capacity of the cells inside, measured at their internal voltage of about 3.7V. When the power bank charges your phone, the energy is converted up to USB voltage and some is lost as heat, so you never get the full rated number into your phone.
As a working rule, expect roughly 60–70% of the rated capacity to reach your phone over a cable, and a little less over wireless or magnetic charging, which is less efficient than a wired connection. In practice, a 10,000mAh power bank will usually recharge a typical modern smartphone around one and a half to two times. A 5,000mAh model gives you roughly one partial-to-full top-up.
Magnetic wireless power banks
A magnetic power bank attaches to the back of a compatible phone (or a case with a magnetic ring) and charges it without a cable. You can keep using the phone while it charges, which makes it ideal for commuting, travel days and nights out.
- Best for: people who want a quick top-up with zero cable clutter.
- Watch out for: wireless charging is slower and less efficient than a cable, and the phone and battery both get warm. A thick or non-magnetic case will stop it attaching properly.
Our Magnetic Wireless Power Bank comes in 5,000mAh and 10,000mAh versions with an alloy body that is 9mm thick, so it does not turn your phone into a brick. If your current case is not magnetic, pair it with a case that has a built-in magnetic ring, such as our Magnetic Leather iPhone Case with Kickstand.
Battery cases
A battery case builds the battery into the phone case itself. Once it is on, there is nothing extra to carry or forget.
- Best for: long shifts, festivals, travel and anyone who is heavy on navigation, camera or hotspot use.
- Watch out for: it adds weight and thickness all the time, not just when you need it, and it must match your exact phone model.
Our Battery Case for iPhone 17, 17 Pro and 17 Air has a 7,000mAh built-in battery, which roughly doubles your phone's runtime. Choose the variant that matches your model exactly; cases are not interchangeable between Pro, Pro Max and Air.
Standard power banks with cables
The classic option: a separate battery pack you connect with a USB cable. It is the most flexible choice because it works with almost anything that charges over USB, including earbuds, smartwatch chargers and tablets.
- Best for: maximum charge per pound, charging more than one device, and sharing with friends or family.
- Watch out for: you need the right cable with you, and your phone is tethered while it charges.
Our Slim Power Bank with LED Display solves the forgotten-cable problem with built-in cables, and its display shows the exact remaining charge rather than four vague dots. It is available in 6,000, 8,000 and 10,000mAh versions.
Side-by-side comparison
| Magnetic power bank | Battery case | Standard power bank | |
|---|---|---|---|
| Cable needed | No | No | Yes (or built-in) |
| Use phone while charging | Easily | Always | Tethered |
| Charging efficiency | Lower | Good | Highest |
| Works with other devices | Magnetic phones only | One phone model | Most USB devices |
| Adds bulk | Only when attached | All the time | In your bag |
Flying with a power bank: UK rules
Power banks contain lithium-ion cells, so airlines treat them differently from ordinary electronics:
- Power banks must go in your hand luggage, never in checked-in baggage.
- Packs under 100Wh are generally allowed without airline approval. A 10,000mAh power bank at 3.7V is about 37Wh, well under that limit.
- A growing number of airlines now restrict using or charging power banks during the flight, so check your airline's current policy before you travel.
Charging your power bank safely
- Charge on a hard surface, not under a pillow or in a bag.
- Stop using any power bank that is swollen, dented, unusually hot or smells of burning.
- Avoid leaving it in a hot car; heat is the main enemy of lithium-ion cells.
- If you top up several devices overnight, a multi-port charger such as our 5-Port USB Charging Station (UK plug) lets you charge the power bank, phone and earbuds from one socket. Its display shows live current draw, so you can see what is actually charging.
Which should you choose?
- You want the easiest top-up during the day: magnetic wireless power bank.
- You never want to think about battery again: battery case.
- You want the most charge and flexibility: standard power bank with built-in cables.
Frequently asked questions
How many times will a 10,000mAh power bank charge my phone?
Usually around one and a half to two full charges for a typical modern smartphone. The exact number depends on your phone's battery size and whether you charge wirelessly or with a cable.
Is magnetic wireless charging bad for my battery?
No, but it generates more heat than cable charging. Heat is what ages batteries, so avoid charging under a pillow or in direct sun, and remove thick cases if the phone gets very warm.
Can I take a power bank on a plane from the UK?
Yes, in hand luggage only. Most consumer power banks, including 10,000mAh models, are well under the 100Wh limit, but some airlines restrict using them in flight.
Do I need a magnetic case for a magnetic power bank?
If your phone has built-in magnets, a thin case with a magnetic ring keeps the connection strong. A thick or non-magnetic case will stop it attaching reliably.
How we wrote this guide: product details come from manufacturer specifications for the items we stock. Charging figures are general estimates based on how lithium-ion power banks work; real results vary with your phone, cable, temperature and usage. Questions about a specific product? Contact our team before you buy.