I hear this a lot. Charge the iPhone in Airplane mode to top it off as fast as possible. Does this actually work out? Is the inconvenience of being disconnected worth the time savings? I was skeptical of these claims, so I decided to find out.
Using an iPhone 6 with a healthy battery pack I’ve timed 4 charging cycles from 0% to 100%. Two samples for each Airplane mode and Regular (connected) mode conditions. The original Apple Lightning cable and the provided 5 Watt wall charger was used for this test.
The phone was switched to Airplane mode prior to being fully drained so it remains in Airplane mode for the duration of the test. I lit up the screen with the home button to check the state of the charge several times during the test.
Wi-Fi, Bluetooth and LTE cellular radios were active for the duration of the test. The iPhone was connected to Wi-Fi, and a FitBit fitness tracker had periodically done data sync over Bluetooth. Several messaging apps were active and sending push notifications, resulting in the screen lighting up. In other words, there was a fair bit more activity on the phone in regular mode. I’ve fired up all the radios so if there is a measurable difference, I would surely see it.
It does it fact look like the iPhone 6 will charge on average 9% faster when it is set into Airplane mode. It took on average 11 minutes longer to top off the battery during this test while the phone was online. Whether the marginal time savings are worth being disconnected for two hours depends on the situation and is up to the user to decide.
Going from 90% to 100% is the longest 10% as charging speed will slow down to prevent damage from overcharging. Keep in mind that you are not likely to have a completely dead phone every time, and if you are in a rush you will probably not be charging to a full 100%, therefore the gap is likely even less significant in real world conditions.