Phone charger shows 100%, iPhone says 98% unplugged

Question

Level 2

154 points

Phone charger shows 100%, iPhone says 98% unplugged

This isn't anything critical, and I think I know what's going on, but I thought I'd ask here to see if any electronics whizzes have an answer.

Today, I took my iPhone off the charger at 98% and thought I'd use my car charger for the remaining 2%. Well, when I plugged it into the car charger, it read 100%. I unplugged it and it dropped back down to 98%. Back and forth. Plug in = 100%, unplug = 98%. Any ideas?

(Does the iPhone check the incoming charge and if they're "equal" it says 100%, in which case the car charger didn't have quite enough voltage to do the last 2%?)

3.06GHz iMac (4Gb RAM), Mac OS X (10.5.7), Other : Macbook, Mac Mini (HTS), iPhone 3GS (16Gb), Time Capsule (500Gb)

Posted on Jul 18, 2009 6:11 PM

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Answer 1

Jul 18, 2009 6:20 PM in response to Xian Rinpoche

You probably need to re-calibrate the battery indicator.

Use your iPhone until the battery is completely depleted. When the battery is completely depleted, your iPhone will power off automatically. Connect your iPhone to a power source and don't disconnect it until the battery is completely charged.

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Answer 2

Xian Rinpoche Author

Level 2

154 points

Jul 18, 2009 6:49 PM in response to Allan Sampson

Yeah. I certainly plan to do that, bug it's not a monitor calibration problem I don't think, especially since the sync cable attached to my computer didn't change to 100%.

So, any electronics experts have a thought on what happened?

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Answer 3

w7ox

Level 4

2,407 points

Jul 18, 2009 7:58 PM in response to Xian Rinpoche

Mine is plugged in (wall charger) much of the time. Some times it registers 100% and says it is charging (lightening bolt) but other times shows the plug icon.

Sometimes I look at it see the plug icon and the charge level says 96%.

FWIW My MacBook currently says it's 98% charged and shows the plug (fully charged icon); sometimes it gets as low as 96% in that situation .. but often it shows 100%.

So I don't find the variations in charge level readings all that unusual nor disturbing.

Phil

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Answer 4

Xian Rinpoche Author

Level 2

154 points

Jul 18, 2009 6:35 PM in response to Allan Sampson

I actually had just done that but unplugged at 98%. The iPhone knew it was at 98 except when plugged into the car when it then thought it was fully charged.

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Answer 5

Jul 18, 2009 6:37 PM in response to Xian Rinpoche

Then I suggest you do the same again and don't disconnect your iPhone this time until the battery is completely charged - 100%.

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