Q: Why is it that when I shut my phone all the way off to save battery and then turn it on again, the battery drains way faster? (via Quora)
A: At restart, all your regularly-used phone apps load, start, and try to go online at the same time — email, messaging, Facebook, Twitter, weather apps, system updates, etc. etc. etc. This creates a huge burst of activity!
Eventually, most of these apps will quiet down and retreat into the background; but until they do, they’re burning CPU cycles and network bandwidth as they all wake up and phone home to see what they missed when the phone was off.
This means there’s a tradeoff between the energy you save by turning the phone off, and how much energy you’ll burn when everything wakes up again. The trick is to find the break-even point.
Every phone brand and model is different, but there’s usually little to be gained by turning a phone completely off unless you can leave it that way for a while — say, at least several tens of minutes. So, if you’re watching a movie, sure, turn off the phone! The energy you save will probably be greater than what you’ll burn when the phone comes back online.
For short durations, you’re probably better off just turning off the screen or making at as dark as possible (the screen is usually the #1 energy drain on an in-use phone). For in-between durations, a dark screen and airplane mode may give you the best results.
Note that most phones give you some means of controlling how aggressively apps can work in the background.
Reasonably recent Samsung phones, for example, let you optionally set selected apps not to run at all when they’re in the background, even if the app maker wants it otherwise; the force-suspended apps remain loaded and in RAM for speedy access, but don’t do anything — using no battery or bandwidth — until you specifically call them front and center.
Controlling apps on a case-by-case basis this way means you can allow important-to-you apps to continue working in the background, while unimportant apps go into total coma until you wake them up. This can give you way more battery time than otherwise.
Poke around in your phone’s battery and apps settings to see what’s available there!
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