The humble power bank has been promoted: in South Africa it is load shedding infrastructure. But the market splits into banks that genuinely carry a household evening — phones, earbuds, a router, even a laptop — and banks that are a paperweight with an LED. The spec sheet tells you which is which, once you can read it.
mAh Maths: Why 20,000 Does Not Mean Four Full Phones
Capacity is quoted at the cell's 3.7V, but charging happens at 5V+ with conversion losses — real delivered energy is roughly 60–70% of the sticker. A 20,000mAh bank realistically refills a big phone two-and-a-half to three times, not four. This is normal physics, not a scam; it just means sizing up matters if the bank serves the whole family through a two-slot evening.
The Spec That Separates Toys From Tools: USB-C PD
USB-C Power Delivery is the difference between a phone-only gadget and a real power tool:
- 18–30W PD: fast-charges phones properly (a Xiaomi 22.5W bank refills a flat phone in about an hour) and runs small routers with the right cable.
- 45–65W PD: charges most modern laptops — a genuine work-through-the-outage capability. Check your laptop charges via USB-C first.
- 100W+ PD: charges gaming-class laptops and doubles as a desk charger.
Also check the bank supports pass-through charging if you want it topping itself up while feeding devices — many cheaper banks refuse.
The Router Trick Every Household Should Know
Many fibre routers and ONTs run on 12V. A power bank with a 12V output (or a USB-C "trigger cable" matched to your router's voltage and plug) keeps the internet alive for hours for a fraction of an inverter's price. Purpose-built mini DC UPS units do this with automatic switchover — the tidiest solution — but a capable bank plus the right cable is the versatile one. Full sizing detail in our load shedding office guide.
Airline Rules, Since Banks Travel
Airlines cap carry-on batteries at 100Wh without approval — that is roughly 27,000mAh. The popular 20,000mAh class flies freely (in hand luggage only, never checked). The suitcase-sized 50,000mAh units are load shedding specialists, not travel companions.
Charging Speed of the Bank Itself
An overlooked spec: a big bank that recharges at 10W takes twelve-plus hours to refill — it will not be ready for the next slot. Look for 18W+ input (the same PD port usually) so the bank refills in the window between outages. This, more than capacity, is what makes a bank feel reliable in rotational blackouts.
What to Buy, By Mission
- Pocket/daily: 10,000mAh with 20W+ PD — one full phone charge, jacket-pocket size.
- Household evening: 20,000–27,000mAh, dual USB-C, 30W+ output, fast self-recharge. The sweet spot.
- Work-anywhere: 20,000mAh+ with 65W PD for the laptop crowd.
- Beyond banks: whole-desk or fridge-adjacent needs graduate to power stations — see the power section for both classes.
Frequently Asked Questions
Can a power bank really run a Wi-Fi router?
Yes — a router drawing 10–15W runs 4+ hours off a 20,000mAh bank via the correct 12V cable or a mini DC UPS. It is the highest-value load shedding purchase in the house.
Why does my 20,000mAh bank only charge my phone twice?
Voltage conversion losses — sticker capacity is measured at cell voltage, delivery happens higher. Two to three full charges from 20,000mAh into a modern large phone is exactly right, not a fault.
Do power banks degrade like phone batteries?
They share the chemistry: hundreds of full cycles before noticeable fade. Avoid leaving them at 0% for months or cooking them in cars, and a quality bank serves 3–5 years of load shedding duty.
Is it safe to charge a laptop from a power bank?
With a proper PD bank at the right wattage, completely — PD negotiates safe voltages automatically. The laptop simply will not charge (or charges slowly) if the bank is underpowered; nothing is damaged.
