I have just purchased a power core III (serial X0017JVNHF). I fully charged it and then used it to wireless charge an iPhone X. When I started charging I recorded the time and the iPhone percent and the number of leds lit on the power core (capacity).
These are my results
iPhone % charged Time PC leds lit
60% 1:15 4
53% 2:00 3
42% 0 (empty)
From a full PC I could only get 155% charge. The iPhone X battery is 2700mAHr so the PC gave 4185mAHr where as it is specified as 10000mA. Where is the extra charge going? Is it inefficiency in the wireless charger?
I think your findings are about right.
Storing power in a battery and using that to charge another is an I efficient way to transfer power.
With most PowerCores you’ll expect to lose about a third its capacity.
I have the same PowerCore and a Samsung S20+ with a 4500mah battery and it charged it nearly 1.5 times, and that didn’t differ much between using it wirelessly or with a cable.
5%-10% in the Powercore’s internal circuitry it is a DC-DC buck-boost converter to generate a constant voltage while the internal cell voltages drop from 4.2V to 3.7V and then is “empty”. This conversion is typically around 95% efficient. Almost perfect.
20% loss in the iPhone. This has similar losses doing it’s own DC-DC conversion the above plus losses power in chemical processes within the phone cells.
1%-5% in the cable.
In addition, wireless charging is emitting energy in all directions, most of it gets to the phone but some radiates out and is absorbed by other surfaces far away. Electrons are charged particules in wires and carry a lot of energy per electron relative to photons in wireless, and electrons have a low mass so can be directed along a wire, while photons have no charge and cannot be directed but can be focused to a degree. Wireless will always be less efficient than wired as a result. You’d typically lose another 10%-15% making some wall a fraction warmer far away. You’d get the most efficiency having no phone case as a few more photons are captured in the phone’s receiver call than if you have a case.
These add up to losing about half the energy. Blame the universe, thermodynamics, entropy, and the forces of the universe. Anker’s part under their controls is relatively perfect in comparison to the rest beyond their control.
For these reasons, many of us think a 10000mAh cell is better used wired and that a 15000 - 20000mAh cell model should be wireless to allow the more headroom you need for less efficient wireless. You’d then get a couple of day’s worth of phone recharges between Powercore recharges and get the convenience of no wired phone charge - no cable.