Power Banks Explained: What to Know Before You Buy

Power banks have become essential tech accessories for charging phones, tablets, and even laptops. But between mAh, volts, watts, and battery cycles, buying the right one can be confusing.

In this guide, we break down everything you need to know to choose the right power bank — clearly, simply, and without tech jargon.

1. Capacity (mAh) – How much energy it stores

Capacity is measured in mAh (milliamp-hours), and it tells you how much energy the power bank can hold.

• The higher the mAh, the more energy it stores, and the more charges it can provide.

• For smartphones, 10,000 mAh is enough for most users.

• For laptops, you should aim for at least 20,000 to 30,000 mAh.

Keep in mind: higher capacity also means a bulkier and heavier device.

2. Voltage (V) – Not the same as capacity

Voltage, measured in volts (V), refers to the strength of the electrical current. Different devices need different voltages:

• Smartphones typically run at 5V

• Laptops need between 12V and 20V

If you want to charge your laptop, make sure your power bank supports a 20V output and has USB-C Power Delivery (PD) capability.

3. Output Power (W) – How fast it charges

Power, measured in watts (W), tells you how quickly your device will charge. It’s calculated by multiplying voltage (V) by current (A).

• Smartphones are fine with 10W to 18W

• Laptops require at least 45W, ideally 65W or more

A power bank with 65W or 100W USB-C PD output is ideal if you want to charge a laptop efficiently.

4. Battery Life – How long the power bank lasts

Battery lifespan is measured in charge cycles. One cycle = a full discharge and recharge.

• A quality power bank lasts between 500 to 1,000 cycles

• That’s about 2 to 3 years with regular use

Some premium models, like the laptop bag with built-in battery, come with a 2-year warranty and use high-end cells designed for long-term durability.

Laptop Battery Comparison: How much do common models hold?

Here’s a quick reference table to help you choose a power bank that fits your laptop:

• MacBook Air 13” (M2/M3)
  Battery: ~52 Wh (approx. 13,500 mAh)
  Charging needs: 30W to 60W via USB-C

• Asus Zenbook 14”
  Battery: ~67 Wh (approx. 17,400 mAh)
  Charging needs: 65W recommended

• Dell Latitude 7420
  Battery: ~60 Wh (approx. 15,600 mAh)
  Charging needs: 60W to 90W

Note: 1 Wh ≈ 270 mAh at 3.7V

Summary: What to look for in a power bank (for laptops)

• Capacity: 20,000 to 30,000 mAh

• Voltage: 20V with USB-C Power Delivery

• Power Output: 65W to 100W

• Battery Life: 500+ cycles (2–3 years of use)