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Is it OK to use an iPhone 4 that is fully charged while keeping it plugged to wall outlet?

I am worried about stressing battery too much since it is charging and discharging at the same time.

Any issues here?

Loïc Wolff
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vvavepacket
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2 Answers2

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None whatsoever unless you somehow drop the phone since it's attached to a cord.

The charging system on iOS devices is adaptive and only engages when the battery needs charging current. It's smart and slows down the charge appropriately whether you are using the device or not.

Put another way, the device only asks for enough power to run itself and charge if needed from the wall. The wall doesn't send too much power so there's no risk of overcharging.

bmike
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    what will happen if u drop while its attached to a cord? – vvavepacket Oct 12 '12 at 12:10
  • The drop never is a problem, but the subsequent landing can get interesting. – bmike Oct 12 '12 at 13:28
  • With the cord, the landing effects can only be improved, no ? And the cord can even prevent the dropped phone from landing, and so save the phone. – Nicolas Barbulesco Jan 09 '15 at 11:00
  • @NicolasBarbulesco Perhaps. In the days of 30 pin connectors (when this post and question started) a drop with the cable connected was usually catastrophic for the device - breaking the dock connector. Now with lightning I'm thinking the device is more resilient but it really depends on which cord, how long and where exactly the drop happens. Trying to generalize to all situations might be futile. – bmike Jan 09 '15 at 15:03
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TL;DR - Perfectly safe.

The iphone doesn't accurately display it's current charge level with the on screen indicator. If you turn if on (it's in Settings, but off by default) the available battery range is the standard 0-100%. But when it hit's 0%, it still has enough juice to safely close all your apps and save their state for future use. You can test this by having a text half written as your phone dies. Charge the phone u p, and hey presto, your half written text will be there to the letter, because it didn't just pull the power and turn off, it gracefully closed all the apps.

Likewise, when it hits 100%, it doesn't actually stop there, it continues charging even further. I'm not sure for the phone, but I believe that on an iPad 3 it will charge to the equivalent of something like 107%. Why? Well, leaving a battery fully charged without using it, is bad for it's health. Also depleting a small amount of charge (say 2-3% and then recharging is also not ideal. That's why if you have a Mac and you charge it fully, then use a bit so it drops to 97%, and then put it on charge again, it won't actually charge it any further, and will stay on 97% until it drops lower than that, at which point it decides it has safely depleted enough to make it worth charging again. The iPhone does something very similar, but is more clever about it. So it will say 100% before it has actually reached it's charge limit, and from that point on until you start to use sufficient battery, it will charge it to 107% (equivalent, roughly), then use battery until it drops back to %100, then charge to 107% etc etc and so on, so it never just sits there at full charge. You have have noticed that occasionally when at 100%, it will take a long time to hit 99%, this is dependant on whereabouts in the "overcharge" cycle it is in.

stuffe
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  • On the iPad 3, it doesn’t charge it to “107%”. That’s not even possible. It shows that it has 100% charge when actually it has 95% charge. It has been the norm on iOS devices since the first iPhone. So, it doesn’t display 100% charge from 100% to 107% actual charge, it displays 100% charge from 95% to 100% actual charge. – duci9y Oct 11 '12 at 15:25
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    @duci9y Yes, I totally agree with what you are saying, as for whether it's possible or not it depends on what you are measuring against. You are 100% () correct in that it has a window between something like 3% and 95% which it uses and presents to the user as the available charge/capacity, even though it can go lower and higher than the 0 and 100% that it displays to the user. That's why I said "equivalent, roughly", because obviously it cannot physically charge to 107%, but logically it can charge to 107% (or whatever the value is) of it's arbitrary window that it shows to the user. – stuffe Oct 11 '12 at 15:35
  • You are talking relative to the displayed charge, when you should talk relative to the actual charge. The actual charge is physical, so you should take it as an independent value, instead of the displayed charge, which can be different from the actual charge, depending upon whether the iDevice is below or above 95%. – duci9y Oct 11 '12 at 15:59
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    I am, but it's just semantics, the process is the same, we both agree on that. I chose the displayed value because that is what a user sees. – stuffe Oct 11 '12 at 16:04
  • Interesting insights. Indeed, I have observed, impressed, that, when I unplug my iPad and I use it, it remains at 100 % for a very long time ! Now, when the device is plugged, why would the device not remain at 107 % ? Dropping until 100 % and then going again at 107 % and so on... this eats battery life, so this is a bad thing. – Nicolas Barbulesco Jan 09 '15 at 11:19
  • @duci9y - Stuffe speaks relatively to displayed %. I find it much clearer this way. I had not even been disturbed by a physical impossibility. – Nicolas Barbulesco Jan 09 '15 at 11:25
  • @duci9y Yes I am talking relative, because we cannot access actual values. The user displayed value is an abstract approximation. @ NicolasBarbulesco If charging to full capacity was the best thing to do, then there would be no need to cover up this drain/charge cycle, however unlike a car battery it is not healthy to do this on a lithium ion battery, the best thing for those is to use them, and so this method allows for that to happen without confusing the user. – stuffe Jan 09 '15 at 11:44
  • @stuffe - It would mean that charging-decharging a battery during 2 days would be healthier than leaving the battery on my sofa during 2 days. I cannot believe this. Charging cycles eat battery life. – Nicolas Barbulesco Jan 09 '15 at 16:09