This isn’t new, but I’m always surprised how quickly the batteries of iOS devices drain when they’re doing nothing. I put an old iPad mini 2 in the kitchen, to watch the news with breakfast, and to display recipes and play music when I’m cooking. I have a charger in the kitchen, but I don’t leave it plugged in all the time. Even though I only use it for about 15 minutes most days, I generally have to plug it in every three or four days.
I got a new iPod touch, and set it up yesterday. Around 6 pm, it was charged to 100%. This morning, at around 8:30, I checked it, and it was at 69%. That’s more than 30% of the battery in a bit over 14 hours.
The iPod was doing nothing other than occasionally checking iCloud, and maintaining wi-fi and Bluetooth active (the latter uses very little power). Yet it used about one-third of its power. Over 24 hours, it would lose nearly half its power.
Apple should improve this element of iOS devices. When they’re not being used for more than a certain amount of time, there should be a sort of hibernation mode. If you put a charged iOS device in a drawer, and leave it for three days, you likely won’t have any power left, and that’s just a waste.
Update: It’s been a while, and it’s clear that if wi-fi is on, then the battery dies pretty quickly. Partly because of the wi-fi itself, but also because of iCloud updating when the device is idle. I have background app refresh turned off globally, but Photos still updates, and downloads new photos; Music still updates iCloud Music Library; and any other Apple iCloud-based app will update as well. So to save battery life, either turn off those features, or put the device into airplane mode. If I do the latter, the battery does deplete, but much more slowly.