Odd Battery Behavior, Wall Outlet vs Computer

I've had my iPhone report 99% almost immediately before, but then last just as long over the entire day. The characteristics of a "good quality/design" battery are that they maintain voltage. Lithium batteries are the best at this. This however is how remaining battery time is measured. Estimation methods have improved a little since lithium batteries became available, but it's still inaccurate enough to give false percentage drops, especially towards the fully charged range. I recently turned off the percentage reading and don't pay much attention as long as I'm getting enough run time to get through the day. Percentage meters just make people worry to much about how long their battery is going to last when it's not going to be a problem.

A more accurate test would be to see how long the iPhone ran before the battery ran out completely under similar usage but with different charging sources.

I do know charging from computers takes longer...and wall chargers are faster...

maybe the slow charge actualy conditions the battery more than the quick charge...

That's possible, I suppose but more likely:

Overcharing lithium batteries is really bad. So bad that well designed devices turn off charging when the capacity is reached. At this point, I believe one of two things can happen. The device might be powered by the charger, however with the battery no longer receiving any charge, or (easier) the device can run on the battery after the charger has been disabled. The plug icon in the battery icon indicates charger not charging but connected. I think the iPhone is smart enough to run off the charger while not charging, however batteries can lose charge over time even when they are not being used.

The computer takes longer to charge the battery so it spends less time connected but not being charged than when you use the wall plug. I've seen this on a Palm PDA as well, although a little more dramatic. I believe the Palm was not smart enough to run off the charger and instead ran of the battery. Depending on when you disconnected, it could be truly fully charged or a few % low.

I think it's normal behavior. Like I said. Try testing yourself by seeing how long the batteries last overall after charging each way before assuming something is seriously wrong.

Nine is opposite the computer charger is not charging it for some reason! only accepting charge form the wall! and i know the computer works cause i use it to charge the ipods we have.

I don't have a problem with mine charging from my PC or from my outlet. Both way I can get it to 99% after 15 min. to 20 min. of usage. However, my PC does have the 2.0 USB, and charges slower than charging from the outlet. I believe most laptop would do this as well. As the 2.0 USB is weaker than the outlet.

It depends on what you were using. Apps can considerably affect your battery.

I'll have to test this theory out. I'll have to wait until its fully decharged to charge it from the computer and see if it really lasts any longer using the comp. But the other users are right. It could be that the computer is actually powering the iPhone once its fully charged there for actually is conditioning the battery. Theory sounds right but I will have to see. I myself see good percentage drops in the first twenty minutes of use. However, using all day and things by the time i get home i have about 30-40% left with hard usage throughout the day.

No actually turns out i used the charger on my computer and i did see a lot better battery usage. Took my phone nearly 1 hr with the normal use i do to drop to 98%.

Hey guys,

Just wanted to pop in to tell you my experience recently... I have charged my iPhone 4 using both the computer and wall charger... I find that if you change the setting of auto detection in iTunes to automatically open iTunes when the device is detected, it does a smart charge (aka: knows when to stop charging) but when you have the setting changed to DON'T automatically open iTunes when device is detected, DOES NOT stop charging the battery. It acts as if the iPhone is an external hard drive and keeps power going to it and the iPhone notices it as a constant charge. But I have noticed charging thru iTunes gives me a slightly better battery usage than using the wall charger... But at the same point it doesn't make any sence since I am using the same wire for both...

Overall my battery life STINKS... I will play "Words with Friends" for 10 minutes and watch the percentage on my i4 drop around 10%... I use Battery Doctor Plus... To do a memory charge... But still my battery life stinks big time... I know how to minipulate the settings and tweaks yet still battery life *****...

Hopefully iOS 4.2 update will make some modifications to the way that it manages the "task killer" to kill inactive or not used apps that drain battery life...

GRR