Most people buy a power bank based on one number — the number of mAh — only to find out later that they have a brick in their bag that they never bring along, or a small model that dies halfway through the day. The right choice depends on three things: how many times you want to recharge, how fast it needs to be, and how much weight you are willing to carry. This article turns that into a concrete choice.
How many mAh do you really need?
Use one rule of thumb: a modern smartphone battery is around 4,000 to 5,000 mAh. A power bank provides slightly less than its nominal capacity due to conversion loss — count on roughly two-thirds to three-quarters actually ending up in your phone. This gives this practical table:
| Capacity | Phone charging | For whom |
|---|---|---|
| 10,000 mAh | ±2 times | Daily carry, jacket pocket, festival, workday |
| 12,000-20,000 mAh | ±3-4 times | Weekend trip, long travel day, phone + earbuds |
| 27,000 mAh | ±5-6 times | Holiday, camping, multiple devices, adding a tablet |
The practical question that dictates the choice is therefore not "how much mAh is a lot", but: how many days do I need to bridge without an outlet? One day without charging options: 10,000 suffices. A week of camping with two phones: then 27,000 is the peace-of-mind choice.
Fast charging: where the time is
Capacity determines how many times you can charge, fast charging determines how long you have to wait for it. Two concepts you will come across: Power Delivery (USB-C PD) and Quick Charge — both are fast-charging standards that deliver more power than a standard USB port. You will notice the difference especially in the first half hour: with fast charging, an empty phone is often well over halfway within thirty minutes, while a slow power bank takes an hour or longer to do that. Important detail that people miss: fast charging only works if the cable can also handle it — an old, thin USB cable limits the speed, even with a good power bank.
Wireless (Qi): convenience versus efficiency
A power bank with wireless charging is convenience in its purest form: place your phone on it, done — no cable, no hunting for a port in the dark. The honest downside: wireless charging is less efficient than using a cable, so you get fewer charges out of it and it is slower. The practical scenario most people end up with: wireless for convenience at home or in the office, cable when you are in a hurry or on the go. A model that can do both gives you that choice per situation — and thick phone cases or magnetic pop sockets can block wireless charging, so you will want to remove those first.
Ports and weight: the two forgotten criteria
Ports: if you often charge two things at once (phone and earbuds, or two phones in a family), look at the number of outputs — otherwise you will be swapping devices. Also pay attention to the input: a power bank with a USB-C input recharges itself much faster than an old micro-USB model, which makes a difference if you want to top it up in the evening for the next day.
Weight: the criterion that only matters after the purchase. Capacity means weight — a 27,000 mAh model feels different in a jacket pocket than a 10,000. The best power bank is the one you actually take with you: a small one that is always in your bag is worth more than a large one that sits on the shelf at home.
The choice in four profiles
- ✔ Commuter / workday — 10,000 mAh with fast charging: light, fits in any bag, two full charges
- ✔ Weekend and festivals — 12,000-20,000 mAh: two days without an outlet, phone plus earbuds
- ✔ Holiday and camping — 27,000 mAh: multiple devices, multiple days, and still allowed on the plane
- ✔ Convenience at home and the office — model with wireless charging: set it down instead of plugging it in
How to make your power bank last for years
Lithium batteries last longest if you don't leave them in extreme states: top it up before it is completely empty, and do not let it sit for months fully charged or fully empty. Store it at room temperature — a hot car in the summer and a freezing shed in the winter are both bad news — and top it up every few months if you are not using it for a while. If you are taking it on a trip, also check our rules for power banks on planes: in short, anything up to 100 Wh (about 27,000 mAh) can simply go in your carry-on luggage.
Frequently asked questions
How many mAh should a good power bank have?
That depends on your usage: 10,000 mAh charges a phone about twice and is ideal for daily carry; 20,000 mAh covers a weekend; 27,000 mAh is the travel size for multiple devices and multiple days. Choose based on the number of days without an outlet, not the highest number.
Why doesn't my power bank charge my phone as many times as expected?
Because of conversion loss: energy is lost as heat when converting the battery voltage to charging voltage. Therefore, count on about two-thirds to three-quarters of the nominal capacity actually ending up in your phone — that is normal and applies to every power bank.
Is wireless charging harmful to my battery?
No, it is not harmful — it is just less efficient than a cable: slightly slower and with slightly more heat loss. It is excellent for convenience at home or in the office; if you need to be quick, use the cable.
Can I leave my power bank charging all night?
Yes, modern power banks stop automatically when they are full. If you want to maximize the lifespan, it is beneficial to avoid extreme states — so do not leave it at 100% for months at a time and do not let it drain completely every time.
Do you know which profile suits you? View the power banks from Strex — from 12,000 mAh for every day to 27,000 mAh with wireless charging for on the go. And for at home, you will find compact fast chargers under chargers.
