How much charging 20,000 mAh can deliver
Engadget estimates a 20,000 mAh power bank holds about 74 Wh, but conversion losses reduce the energy available to devices.
A 20,000 mAh power bank stores about 74 watt-hours of energy at a typical lithium-ion voltage of 3.7 volts, according to Engadget. In practice, around 60 to 70 per cent of its capacity may be usable after heat and other charging losses.
That could translate to about three to four full charges for an iPhone 17, or two to three for an iPhone 17 Pro Max, based on Engadget’s estimates. A Steam Deck may get one to one and a half charges, while a 13-inch M5 MacBook Air could use nearly the bank’s full capacity for one charge.
Actual results depend on the power bank, device use and charging conditions. Devices with higher operating voltages can also incur additional heat loss, making the headline capacity an imperfect guide to how much energy reaches a device.
The size can make a 20,000 mAh unit unwieldy for everyday carry, but Engadget says it may suit trips without reliable access to outlets or intensive phone use, such as hotspotting or navigation. For lighter daily use, a smaller bank may be more practical.
Engadget says this capacity is below the 100 Wh airline limit for carry-on luggage. Travellers should check applicable airline rules, which can vary. Charging speed is another factor to consider when choosing a power bank.
