My 4S suddenly takes hrs to charge (>12) and won't charge fully . No recent trauma, new downloads or unusual activity - any ideas?
Dependant on the age of your iPhone 4S it could be the battery is failing. You could take it to an Apple store or AASP for evaluation.
Also worth trying a re-boot. Press and Hold the Home and On/Off buttons simultaneously until you see the Apple logo then release. You will not lose any data.
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