How Long Should I Charge My iPhone 7?

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Regarding this, how long should you charge your new iPhone?

3 hours

Furthermore, is the 40 80 Battery rule real? The rule is to keep your battery charged at somewhere between 40% and 80% level at all time. Overcharging, undercharging, extreme temperatures, these are all variables that can shorten the life of your lithium-ion battery (used in iPhones and Androids).

Beside above, at what percentage should I charge my iPhone?

Apple recommends, as do many others, that you try to keep an iPhone battery between 40 and 80 percent charged. Topping up to 100 percent isn't optimal, although it won't necessarily damage your battery, but letting it regularly run down to 0 percent can prematurely lead to a battery's demise.

Is it bad using iPhone while charging?

You don't need to worry though — it is definitely safe to use while it's charging. The bad thing about use while charging is you'll slow down the charging speed in the process. Your phone may heat up a little, but it's unlikely to heat up to the point where it's dangerous.