How to Choose a Power Bank – Complete Buying Guide

Confused by mAh, watts, PD and Qi2? This simple power bank buying guide explains real capacity, output wattage, safety and airline rules so you can buy the right power bank in Bangladesh.

Buying a power bank looks simple until you're standing in front of thirty of them. 10,000mAh or 20,000mAh? 20W or 65W? PD, QC, PPS? And why does a "20,000mAh" power bank only charge your phone three times instead of four?

This guide explains everything in plain language so you can pick the right power bank the first time, without paying for features you don't need.

Step 1: Understand capacity (mAh) and what you really get

Capacity is shown in milliamp-hours (mAh). Higher mAh means more stored energy. But there's a catch every buyer should know.

The mAh number on the box is measured at the battery cell's voltage (around 3.7V). Your phone charges at a higher voltage (5V or more). Converting between the two, plus heat loss, means you typically get around 60–70% of the rated capacity delivered to your device. That's normal physics, not a fake product.

Rated capacity	Approx. usable	Phone charges (5,000mAh phone)	Weight feel
5,000mAh	~3,300mAh	About 0.6–0.7	Very light
10,000mAh	~6,500mAh	About 1.3–1.5	Pocket-friendly
20,000mAh	~13,000mAh	About 2.5–3	Bag only
30,000mAh	~19,500mAh	About 4	Heavy

Rule of thumb: 10,000mAh for daily carry, 20,000mAh for travel or laptops, 30,000mAh for load-shedding and multi-day trips.

Step 2: Match the output wattage to your devices

Wattage (W) decides how fast your devices charge. A power bank with too little output will charge slowly or, in the case of a laptop, not at all.

Output	What it can charge well	Example
10W–15W	Phones (slowly), earbuds, smartwatches	Baseus Qpow BS-P1001C 15W 10000mAh Power Bank with Type-C Cable
20W–22.5W	Fast charging for iPhone and most Android phones	Baseus EnerZest P1 Ultra Thin 10000mAh 22.5W Power Bank
30W	Faster phones, iPad, Nintendo Switch	Baseus NOMOS PPSS1030 10000mAh 30W Power Bank with Type-C Cable
65W	Most USB-C laptops, MacBook Air	Baseus NOMOS PPLSC01-20 20000mAh 65W Power Bank with Built in Type-C Cable
100W	MacBook Pro, larger laptops, several devices at once	Baseus EnerFill FC41 100W 20000mAh Power Bank with Built in Cable

Remember: the listed maximum is usually for one port. When you charge two devices at once, the power is shared between them.

Step 3: Check the charging standards

USB Power Delivery (PD): the universal fast-charging standard over USB-C. iPhones, Samsung phones, iPads and laptops all use it. Make sure your power bank has it.
Quick Charge (QC): Qualcomm's standard, common on older Android phones.
PPS: a part of USB PD used by Samsung "Super Fast Charging". Useful if you own a recent Galaxy.
Qi2 / magnetic wireless: snaps onto iPhone 12 or later. Convenient, but slower than a cable. See Baseus PPWPQ10-20 Qi2 10000mAh 22.W Magnetic Wireless Power Bank.

Step 4: Ports, cables and display

A few small details make a big difference in daily use:

USB-C in and out: charge the power bank and your phone with the same cable.
Built-in cable: you'll never forget your cable at home. Models like the Baseus Comet Series PPMD10 22.5W 10000mAh Power Bank With Cable have one built in.
Digital display: shows the exact percentage left. Much more useful than four LED dots, especially on larger units like the Baseus PPXJ30 Star Lord Digital Display 22.5W 30000mAh Fast Charge Power Bank.
Pass-through charging: lets you charge the power bank and your phone at the same time from one wall socket. Handy at hotels and on overnight trips.

Step 5: Think about size and weight honestly

A 20,000mAh power bank weighs roughly the same as a large smartphone and a half. If you're going to leave it at home because it's too heavy, a slim 10,000mAh model that's always in your pocket is more useful. The Baseus EnerZest P1 Ultra Thin 10000mAh 22.5W Power Bank and Baseus Blade 2 Ultra Thin 12000mAh 65W Power Bank are good examples of slim designs.

Step 6: Buy genuine and stay safe

Fake power banks are common in Bangladesh, especially online. Some contain sand or weights to feel heavier, and many use low-quality cells with no protection circuits. That's a fire risk, not just a waste of money.

Buy from an authorised seller with a proper warranty.
Be suspicious of a "30,000mAh" power bank at the price of a 10,000mAh one.
Look for protection against over-charge, over-current, short circuit and overheating.
Stop using any power bank that is swollen, very hot or smells of burning.

Step 7: Know the airline rules

Power banks must go in cabin baggage, never in checked luggage. Airlines use watt-hours (Wh): under 100Wh is usually allowed; 100–160Wh generally needs airline approval. Calculate it as: mAh × 3.7 ÷ 1000 = Wh. So 20,000mAh ≈ 74Wh (fine) and 30,000mAh ≈ 111Wh (check with your airline first).

Power bank care tips

Recharge it every couple of months even if you don't use it. Batteries left empty for long periods degrade.
Avoid leaving it in a hot car or direct sunlight.
Use a good-quality USB-C cable. A cheap cable can limit charging speed.
Don't charge it on a bed or sofa where heat can't escape.

Quick decision table

If you are…	Buy this type	Our pick
A student or office worker	Slim 10,000mAh, 20W+	Baseus EnerZest P1 Ultra Thin 10000mAh 22.5W Power Bank
An iPhone user	Qi2 magnetic	Baseus PPWPQ10-20 Qi2 10000mAh 22.W Magnetic Wireless Power Bank
A laptop user	20,000mAh, 65W+ USB-C PD	Baseus NOMOS PPLSC01-20 20000mAh 65W Power Bank with Built in Type-C Cable
Dealing with load-shedding	30,000mAh with display	Baseus PPXJ30 Star Lord Digital Display 22.5W 30000mAh Fast Charge Power Bank
On a tight budget	10,000mAh, 15W	Baseus Qpow BS-P1001C 15W 10000mAh Power Bank with Type-C Cable

Frequently asked questions

Is a higher mAh power bank always better?

No. More capacity means more weight and longer recharge time. Buy the capacity you'll actually use.

Can a power bank damage my phone?

A genuine power bank with PD won't. Your phone decides how much power it accepts. Cheap unbranded power banks without protection circuits are the real risk.