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Should I charge every night? (Assuming that I consume more than 50% during the day, but sometimes not much more.)
Should I turn off the device during the charge? (Assuming that I don’t need the device as an alarm clock.)
Any other tips are also welcome.
Yes, the ideal time to charge your phone is around 50% depletion. Ars Technica explains why:
Full discharges put a lot of strain on the battery, and it's much better practice to do shallow discharges to no lower than 20 percent. In a way, this is like people running for exercise— running a few miles a day is fine, but running a marathon every day is generally not sustainable.
Turning off the device may assist slightly in lowering heat, which in turn may extend the life of the battery by a minuscule amount, but it is not really enough to worry about.
There’s no need to let it discharge 100% before recharging. Apple lithium-ion batteries work in charge cycles. You complete one charge cycle when you’ve used (discharged) an amount that equals 100% of your battery’s capacity — but not necessarily all from one charge. For instance, you might use 75% of your battery’s capacity one day, then recharge it fully overnight. If you use 25% the next day, you will have discharged a total of 100%, and the two days will add up to one charge cycle.
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Source : LINK
It's worth looking at what Tesla recommends for its (Li-Ion) batteries in the Model S. Range and overall battery life are a lot more important in a car than a phone.
The strong recommendation is (1) keep the state of charge between 20% and 80%; (2) NEVER run the batteries down to 0%; (3) only charge to 100% occasionally, when you want (in a Tesla) maximum range for a long journey; and (4) don't charge when the batteries are extremely cold (0C or less) - the Tesla will actually divert current to warming its batteries before beginning a full charge.
The Tesla supercharger is very careful about how it charges. It will charge slowly at first if the SoC is low, then increase to full charge rate and drop off again when the SoC reaches around 80%. So it might take 2 hours to get to 80%, and ANOTHER 2 hours for the remains 20%. I hope the Apple charging system is also smart.
Which leads to the question of whether an Apple charger is better than a cheaper but faster OEM charger. I believe that charging is managed by the iPhone or iPad, not by the charger, so that would indicate that OEM chargers are OK. However, the Apple charger is pretty smart about how it rectifies mains AC to DC current and in its design for safety, and these factors are worth extra cost over ultra-cheap alternatives.
