Power bank selection guide — what mAh means in practice

Varavirtalähteen valintaopas — mitä mAh tarkoittaa käytännössä

What is a power bank and why do you need one?

A power bank is a portable battery that allows you to charge your phone, tablet, or other device without a power outlet. It is an essential item for camping, traveling, and emergency preparedness.

What does mAh mean in practice?

mAh (milliampere-hour) indicates the capacity of a power bank — the higher the number, the more charges you get. But how does that translate in practice?

  • 10,000 mAh — charges a typical smartphone (3,500 mAh) about 2–2.5 times
  • 20,000 mAh — charges a phone 4–5 times or a tablet 1–2 times
  • 30,000 mAh — charges a phone up to 7–8 times, suitable for longer trips

Note: The actual capacity is always lower than stated because energy is lost as heat during charging (typically 20–30%).

Key features to consider when choosing a power bank

Charging power (watts)

Charging power determines how quickly a device charges. Look for a power bank with at least an 18W fast charger — it charges your phone significantly faster than basic chargers.

  • 5–10 W: slow basic charging
  • 18–22.5 W: fast charger, suitable for most phones
  • 45–65 W: also suitable for laptops

Ports

Check that the power bank has enough ports. The ideal combination is USB-C + 2× USB-A, which allows you to charge multiple devices simultaneously.

Size and weight

  • 10,000 mAh: fits in a pocket, weighs ~200 g
  • 20,000 mAh: bag-sized, weighs ~400–500 g
  • 30,000 mAh: backpack-sized, weighs ~600–700 g

Green Cell power banks — a reliable choice

Northlund's selection includes high-quality Green Cell power banks from 10,000 mAh to 30,000 mAh. All models feature a fast charger and multiple ports.

  • Green Cell 10,000 mAh — compact and lightweight, USB-C + 2× USB-A
  • Green Cell 20,000 mAh — 22.5 W fast charger, QuickCharge 3.0
  • Green Cell PowerPlay 30 — 30,000 mAh, 22.5 W, 4 ports

Explore all power banks at Northlund and find the model that suits your needs.