Quick answer. A “30,000mAh” power bank delivers roughly 15,500 to 18,900mAh to your phone, about three to four full charges of a typical 5,000mAh battery, not six. This is true of every brand at every price. The cells store charge at 3.7 volts, your phone receives it at 5 volts, and the conversion between them loses energy as heat.
The formula
Energy is conserved in watt hours, not milliamp hours. The advertised mAh is measured at the cell voltage, and delivery happens at USB voltage:
Real mAh at 5V = (3.7 x advertised mAh x efficiency) / 5.0
Quality units convert at about 85 per cent efficiency. Budget units, which is most of what sells in Accra, run nearer 70 per cent.
| Advertised | Stored energy | Real at 5V (budget) | Real at 5V (quality) |
|---|---|---|---|
| 10,000mAh | 37.0 Wh | 5,180mAh | 6,290mAh |
| 20,000mAh | 74.0 Wh | 10,360mAh | 12,580mAh |
| 30,000mAh | 111.0 Wh | 15,540mAh | 18,870mAh |
The industry already admits this
Anker publishes the same arithmetic for its own products, quoting roughly 82 per cent efficiency and a “rated capacity” near 6,068mAh on a 10,000mAh bank. The information is not hidden. It is just never said at the point of sale in Ghana.
How many charges you actually get
Divide the real delivered figure by your phone’s battery. A 5,000mAh phone gets about one full charge from a 10,000mAh bank, two from a 20,000mAh, and three to four from a 30,000mAh. If a listing promises six charges from 30,000mAh, the seller has not done the arithmetic, or hopes you will not.
One more thing before you fly
Airlines generally cap carry-on batteries at 100Wh without approval. A 30,000mAh unit stores about 111Wh, over that line. Up to 20,000mAh (74Wh) travels without questions.
Why we tell you this
Because you already know your power bank underdelivers. You have owned one. We would rather be the shop that explains why, with the working on the page, than the fifth listing shouting a number physics does not permit. Every power bank we sell states its honest charge count, and its price is verified for the current month.
