iOS Battery Level low resolution?

That sounds right. I think iOS takes that number and combines it with data about how long the screen has been on an how long it's been plugged in to display the 1% increment it shows the user. I know I've seen my iPhone shut off moments after it said it was at 5% more than once.

xArtx said:

How do you detect it's plugged in?

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Have you looked into UIDeviceBatteryState yet?

ArtOfWarfare said:

That sounds right. I think iOS takes that number and combines it with data about how long the screen has been on an how long it's been plugged in to display the 1% increment it shows the user. I know I've seen my iPhone shut off moments after it said it was at 5% more than once.

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iOS devices use lithium ion batteries. You can't measure the remaining charge with lithium batteries like you can with other batteries. They hum along putting out full power, then suddenly stop without warning. Instead, lithium batteries have chips in them that track usage, battery age, etc, and use those factors to estimate remaining battery power. The estimate is just that, an estimate. As the battery ages, the estimate gets less accurate.

It might be that Apple is using other factors to estimate remaining battery, but it might also be that they use a completely different private API. My money is on the private API.

xArtx said:

It's all ok how they are doing it, but private API or not, isn't it odd that they
are creating the potential for an App to say one thing, and the springboard
to say another? Whatever they are doing, they could share that value with us.



No, didn't get to reading into it.. but the tutorial did say you get a negative
value if the device is plugged in. I still haven't seen that.
Thanks though, I'll want to know the charging state.

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Don't trust third party tutorials without verifying what they say. A quick look at the docs for the UIDevice method batteryLevel reveals the following:


Battery level ranges from 0.0 (fully discharged) to 1.0 (100% charged). Before accessing this property, ensure that battery monitoring is enabled.

If battery monitoring is not enabled, battery state is UIDeviceBatteryStateUnknown and the value of this property is –1.0.

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You don't get a negative number if the battery is charging - only if you have not enabled battery monitoring.