Question 1

What is the difference between mAh and Wh on batteries?

Accepted Answer

**mAh measures charge. Wh measures energy.** Only one of them lets you compare batteries meaningfully, and it is the one manufacturers advertise least.

**mAh (milliampere-hours)** describes how much electrical charge a battery holds — roughly, how much current it can supply for how long. Crucially, **it says nothing about voltage**, and energy depends on both.

**Wh (watt-hours)** is the actual energy stored. The conversion is straightforward:

**Wh = (mAh ÷ 1000) × V**

**Why this matters practically.** A 10,000mAh power bank sounds like it should charge a 5,000mAh phone twice. It does not, typically managing around 1.5 charges, and the reason is voltage plus conversion loss.

Power bank cells are usually rated at **3.7V** nominal, so 10,000mAh is about 37Wh. But the bank must output at 5V or higher over USB, and converting between voltages loses energy as heat — typically 10–20%. The phone's own charging circuit loses more. So the usable energy delivered is well below the headline figure, and comparing the two mAh numbers directly is comparing quantities measured at different voltages.

**Where you will see Wh:** laptop batteries are almost always rated in Wh, because laptops use varying cell configurations and voltages, making mAh useless for comparison. **Airline rules also use Wh** — most carriers permit spare lithium batteries up to 100Wh freely, 100–160Wh with approval, and prohibit above that. A power bank labelled only in mAh may need converting to know whether it is allowed.

**How to compare fairly:** convert everything to Wh, using the voltage printed on the device. If the voltage is not stated, 3.7V is a reasonable assumption for a single lithium cell.

**A higher mAh at lower voltage can hold less energy** than a lower mAh at higher voltage.

Question 2

How to choose the right power bank?

Accepted Answer

To choose the right power bank, consider capacity, output power, number of ports, size, compatibility, and safety features to meet your charging needs effectively.

Question 3

How to charge power bank properly?

Accepted Answer

Properly charging a power bank involves using the right charger, avoiding overcharging, and maintaining optimal temperatures. Regular charging and quality cables also enhance longevity.

Question 4

What does battery health on a phone or laptop actually mean?

Accepted Answer

An estimate of remaining capacity relative to when new, expressed as a percentage — and it is a calculated figure rather than a direct measurement, which explains why it can move oddly and why it is

Question 5

Does fast charging damage my phone battery?

Accepted Answer

Fast charging causes some additional wear, but far less than the way it is usually discussed suggests, and the main culprit is heat rather than current itself. Lithium batteries degrade faster at

Question 6

How does wireless charging work, and why is it less efficient?

Accepted Answer

By inductive coupling — a coil in the pad creates a changing magnetic field, which induces a current in a coil in your phone. It is a transformer split into two halves, with air and a phone case in

Question 7

How do lithium-ion batteries actually degrade?

Accepted Answer

Through two separate processes running simultaneously: calendar ageing, which happens regardless of use, and cycle ageing, which depends on how you charge and discharge. Understanding that both are

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