dropbox requires location services to be enabled for whatever reason and the location arrow is constantly on my status bar so i turned the auto update feature off. probably a huge battery drainer.
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i have it turned off for everything and i dont notice much of a difference to having it enabled
That sort of location monitoring has virtually no effect on battery life. It's coarse monitoring only, so it uses cellular triangulation + nearby WiFi networks + Bluetooth beacons (if available.). It does NOT use the GPS. iOS is constantly doing this kind of monitoring in the background anyway, so really the only difference is whether it is passing this information onto apps or not.
This feature in Dropbox actually predates background app refresh and I'm not sure why it's still there. It's a bit of a hack really. Before background app refresh, the only way an app could wake up when in the background was if it requested to be notified of changes in location. This was designed for apps that needed to do something useful at a specific location. However, Dropbox repurposed this feature to simply give itself a few minutes to upload any queued photos in the background whenever you moved somewhere new. With background app refresh, this shouldn't be needed, and Dropbox's new photo app, Carousel, does not do this.
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Honestly I have everything ON and don't notice a difference either in battery life or how the apps work.
The battery usage section under usage in settings will mark any tasks that used battery as a result of app refresh with the words "background activity," which can be very helpful. I'm assuming this includes other forms of background activity such as usage from GPS navigation, music playback, push notifications, etc, but I'm not sure.
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On my iPad? Anything I use regularly unless they are found to excessively drain the battery. Admittedly, I haven't found any that are worth even that.
On my iPhone? Nothing, unless for some reason I absolutely need it (Maps, anything that tracks movement really) but it gets turned off as soon as I stop needing it.
You shouldn't need this for anything that tracks movement. In fact, it would be quite useless for this since apps have no control over when they actually get refreshed. It could be hours before an app wakes up. There are other APIs for location tracking that can wake up an app at a specific location, as well as location APIs that allow an app to simply keep running indefinitely in the background (only for real time voice navigation purposes.)
BAR is only really useful for apps that need to either send or receive data from a server in cases when this is not time sensitive.