Power Bank Buying Guide: Capacity, Wattage and What to Look For

The number on the front of a power bank — like “20,000mAh” — tells you only part of the story; what really matters is how much usable charge it delivers and how fast it can push it into your device. Buy on the headline capacity alone and you can end up with a heavy brick that charges your laptop slowly, or won’t charge it at all.

For South Africans keeping phones, tablets and laptops topped up on the move — or through a power interruption — matching the capacity, output wattage and ports to your actual devices is what makes a power bank genuinely useful rather than dead weight in a bag.

Key Takeaway: Check three things before buying: capacity (how many charges), output power in watts / USB-PD (how fast, and whether it can charge a laptop), and ports (USB-C in/out for modern devices). A phone power bank and a laptop power bank are not the same purchase.

Power Bank Specs at a Glance

Capacity: What mAh Really Gets You

Capacity is rated in mAh, but real-world charges are lower than the maths suggests — expect roughly 60–70% efficiency after conversion losses. As a rough guide, a 10,000mAh bank gives a typical phone around two full charges, while 20,000mAh suits a couple of days away or topping up a tablet and laptop. Bigger isn’t automatically better: more capacity means more weight and bulk, so match it to how long you’re away from a wall socket.

Output Power: Phone vs Laptop

The output wattage decides how fast — and whether — a device charges. Phones charge happily from an 18W–30W output. Laptops are different: they need a high-wattage USB-C Power Delivery output, typically 60W or more (often up to 100W), to charge properly. If you want to keep a laptop going, check the bank’s maximum USB-C PD wattage matches what your laptop’s charger supplies — a low-watt bank simply won’t keep up.

USB-PD, GaN and Ports

USB Power Delivery (USB-PD) over USB-C is the standard that enables fast, safe charging across phones, tablets and laptops. Look for USB-C ports that handle both input (recharging the bank quickly) and output. Newer GaN-based chargers and banks run cooler and smaller for the same power. Several ports let you charge multiple devices at once — just remember total output is shared, so charging three things slows each one.

Safety, Pass-Through and Air Travel

A few practical points save trouble later. Buy from reputable brands with proper protection circuitry — cheap, uncertified cells are a real fire risk. Pass-through charging (using the bank while it recharges) is convenient but not all models support it well. And for flying, most airlines cap power banks at 100Wh (around 27,000mAh) in carry-on only — check the printed Wh rating before you travel.

Which Power Bank Should You Buy?

Key Takeaway: For a phone, a 10,000mAh bank with USB-C PD is the sweet spot. To charge a laptop, you need 20,000mAh or more with a 65–100W USB-C PD output — capacity alone isn’t enough. Always buy a reputable, properly protected unit.

How to Buy Power Banks in South Africa

DistriNode stocks power banks from pocket-sized to laptop-capable, plus the USB-C chargers and cables to match — with local stock and fast delivery. Browse power banks, USB-C chargers, USB-C cables, charging cables and wall chargers.

Frequently Asked Questions

How many times will a power bank charge my phone?

Roughly, divide the bank’s capacity by your phone’s battery and allow for about 60–70% efficiency. A 10,000mAh bank typically gives a modern phone around two full charges; a 20,000mAh bank around four. Larger phones with bigger batteries will get fewer charges, so match the capacity to how long you’re away from a socket.

Can a power bank charge a laptop?

Yes, but only if it has a high-wattage USB-C Power Delivery output — usually 60W or more — and your laptop charges over USB-C. Check the bank’s maximum PD wattage against your laptop’s charger. A 20,000mAh+ bank with 65–100W PD is what you want; a small 18W phone bank won’t keep a laptop charged.

What does USB-PD mean and why does it matter?

USB Power Delivery (USB-PD) is the standard that lets USB-C deliver higher, negotiated power levels safely — enabling fast charging for phones and enough power for laptops. A power bank with USB-C PD charges modern devices faster and works across phones, tablets and laptops, which is why it’s the key feature to look for.

Can I take a power bank on a plane?

Generally yes, in carry-on baggage only, and most airlines limit power banks to 100Wh — about 27,000mAh — without special approval. Check the Wh rating printed on the bank and your airline’s policy before flying. Never pack a power bank in checked luggage.

Sources

• USB Power Delivery — overview
• Battery banks — how capacity works