iPhone battery charging questions
December 22, 2009 5:40 PM Subscribe
How does my iPhone battery charge?
I'd like to understand how my iPhone and its battery work better.
I have the 3G but it's jailbroken so I can see the battery percentage. I'm interested in some things I've noticed. I looked at some of the posts but I'm more interested in how it works than maximizing the battery life.
Queston- One does not appear to be able to simply plug in an iPhone with a dead battery. It must charge to around 5% before it'll turn on. Why is that?
Question- Can someone confirm that the iPhone charges less quickly when on vs. plugged in but off? For example, when you have a low battery and are leaving in 30 minutes does it make more sense to turn it off? Same question for leaving the iPhone on but turning off options like wifi, 3G, etc?
(Both of these questions are different from what I've noticed with laptop batteries for example. )
Question- Some phones have an option to not check email during certain hours. I don't believe there is that feature on the iPhone (exchange mail or gmail in my case). When I am not plugging in my phone overnight is there an option or app (jailbroken or not) that'll automatically stop checking mail or even turn off the phone to save battery and noise from like 1AM until 7 AM?
Thanks.
I have the 3G but it's jailbroken so I can see the battery percentage. I'm interested in some things I've noticed. I looked at some of the posts but I'm more interested in how it works than maximizing the battery life.
Queston- One does not appear to be able to simply plug in an iPhone with a dead battery. It must charge to around 5% before it'll turn on. Why is that?
Question- Can someone confirm that the iPhone charges less quickly when on vs. plugged in but off? For example, when you have a low battery and are leaving in 30 minutes does it make more sense to turn it off? Same question for leaving the iPhone on but turning off options like wifi, 3G, etc?
(Both of these questions are different from what I've noticed with laptop batteries for example. )
Question- Some phones have an option to not check email during certain hours. I don't believe there is that feature on the iPhone (exchange mail or gmail in my case). When I am not plugging in my phone overnight is there an option or app (jailbroken or not) that'll automatically stop checking mail or even turn off the phone to save battery and noise from like 1AM until 7 AM?
Thanks.
dfriedman, I'm pretty sure that's only an option if you have a 3GS or your phone has previously been jailbroken.
As for the original question, I don't have any answers, but I'm interested too!
posted by miraimatt at 5:50 PM on December 22, 2009
As for the original question, I don't have any answers, but I'm interested too!
posted by miraimatt at 5:50 PM on December 22, 2009
No, the phone doesn't need to be jailbroken to see battery life expressed as a percentage. Wait for it - there's an app for that. Can't you just turn the phone off before you go to bed and turn it back on upon waking up, if you are not able to charge it?
posted by fixedgear at 5:57 PM on December 22, 2009
posted by fixedgear at 5:57 PM on December 22, 2009
To avoid getting email during certain hours, one option is to put it in airplane mode when you go to bed at night.
posted by matildaben at 6:00 PM on December 22, 2009
posted by matildaben at 6:00 PM on December 22, 2009
When traveling out of the country, any data use is extremely expensive. I switch mine to airplane mode to insure it will not check mail or receive texts but still receive and make calls.
posted by jeff-o-matic at 6:21 PM on December 22, 2009
posted by jeff-o-matic at 6:21 PM on December 22, 2009
Response by poster: Thanks folks.
My question about an overnight pause is with the goal of saving batter life but still being able to be woken up by morning phone calls.
Jeff,
That is not airplane mode you are referring to. That is the "data roaming" option. You can't receive calls on airplane mode.
posted by hokie409 at 6:31 PM on December 22, 2009
My question about an overnight pause is with the goal of saving batter life but still being able to be woken up by morning phone calls.
Jeff,
That is not airplane mode you are referring to. That is the "data roaming" option. You can't receive calls on airplane mode.
posted by hokie409 at 6:31 PM on December 22, 2009
Best answer: One does not appear to be able to simply plug in an iPhone with a dead battery. It must charge to around 5% before it'll turn on. Why is that?
The iPhone has a lithium battery. If you use those below their low voltage point, there's a good chance they'll become dead with no possibility of recovery. Also, the iPhone needs a certain amount of time to cleanly shutdown -- it can't just power-off immediately. Usually, it shuts down slightly before the low voltage point is reached. Say you then plugged it in and it booted up right away, but you disconnected the cord as soon as it had booted. The battery would hardly have charged at all, and during the time taken for low-power shutdown, could go past the low-voltage point, bricking the phone.
So the phone charges up until a point where it has enough power to cleanly boot and shutdown on battery alone before it lets you use it.
posted by bonaldi at 6:32 PM on December 22, 2009
The iPhone has a lithium battery. If you use those below their low voltage point, there's a good chance they'll become dead with no possibility of recovery. Also, the iPhone needs a certain amount of time to cleanly shutdown -- it can't just power-off immediately. Usually, it shuts down slightly before the low voltage point is reached. Say you then plugged it in and it booted up right away, but you disconnected the cord as soon as it had booted. The battery would hardly have charged at all, and during the time taken for low-power shutdown, could go past the low-voltage point, bricking the phone.
So the phone charges up until a point where it has enough power to cleanly boot and shutdown on battery alone before it lets you use it.
posted by bonaldi at 6:32 PM on December 22, 2009
Regarding the email checking: could you set it to fetch email "manually" before you go to bed? You can reset it back to your regular interval in the morning.
posted by chiababe at 6:58 PM on December 22, 2009
posted by chiababe at 6:58 PM on December 22, 2009
Response by poster: Floam,
"When I am not plugging in my phone overnight is there an option or app (jailbroken or not) that'll automatically stop checking mail or even turn off the phone to save battery AND NOISE from like 1AM until 7 AM?"
It's a phone. Therefore it can make noises all night when someone calls or an email is received. Yes, I can turn off the ringer and yes I can have it plugged in but I'd like to know if this option that other phones offer is possible on the iPhone.
posted by hokie409 at 7:03 PM on December 22, 2009
"When I am not plugging in my phone overnight is there an option or app (jailbroken or not) that'll automatically stop checking mail or even turn off the phone to save battery AND NOISE from like 1AM until 7 AM?"
It's a phone. Therefore it can make noises all night when someone calls or an email is received. Yes, I can turn off the ringer and yes I can have it plugged in but I'd like to know if this option that other phones offer is possible on the iPhone.
posted by hokie409 at 7:03 PM on December 22, 2009
Turn off the new email notifier noise? Every action has a sound associated with it, and a toggle to turn it on and off. I like the 'whoosh' of an email sent, but don't need to hear every incoming email or calendar notification, especially at night.
posted by fixedgear at 7:15 PM on December 22, 2009
posted by fixedgear at 7:15 PM on December 22, 2009
Best answer: Since you've got a jailbroken phone, there is a profile manager that lets you set certain "quiet times."
posted by adamrice at 8:15 PM on December 22, 2009
posted by adamrice at 8:15 PM on December 22, 2009
Best answer: I'm going to disagree with bonaldi- I highly doubt there is any possibility of bricking an iPhone just because it runs out of power. I've had my iPhone run out of juice while booting several times and have hard reset it during boot with no issues.
I think the better answer to the question is that the iPhone isn't designed to run w/o a battery unlike laptops, so it can't run off AC power and simultaneously charge the battery. It needs enough power to turn on itself via battery.
posted by wongcorgi at 8:54 PM on December 22, 2009
I think the better answer to the question is that the iPhone isn't designed to run w/o a battery unlike laptops, so it can't run off AC power and simultaneously charge the battery. It needs enough power to turn on itself via battery.
posted by wongcorgi at 8:54 PM on December 22, 2009
That's not right: the phone does actually work immediately from AC: the screen powers up and shows a battery-dead symbol, etc, it simply refuses to boot. If it couldn't run off AC this wouldn't happen at all.
(Your hard shutdowns also don't affect the picture. It's trying to avoid them that matters).
posted by bonaldi at 4:54 AM on December 23, 2009
(Your hard shutdowns also don't affect the picture. It's trying to avoid them that matters).
posted by bonaldi at 4:54 AM on December 23, 2009
Best answer: Question- Can someone confirm that the iPhone charges less quickly when on vs. plugged in but off? For example, when you have a low battery and are leaving in 30 minutes does it make more sense to turn it off? Same question for leaving the iPhone on but turning off options like wifi, 3G, etc? (Both of these questions are different from what I've noticed with laptop batteries for example. )
If you're talking about charging from the little "wall-wort" AC-to-DC adapter, then I would have to assume that, yes, it would charge faster off than on. Those little wall-worts are cheap and only have the ability to "push" a certain current at a certain voltage (i.e. 100 mA at 12V [which is also why you should unplug wall-worts when not in use: they still use just as much power as when in use!]) This is unlike, say, your vacuum cleaner which runs on AC electricity and therefore "pulls" however much current it needs.
Now, if your iPhone is on (and plugged in), it's using a certain amount of power to run and then uses the "overhead" from what it's getting from the wall-wort to charge the battery. (Note: I don't know how the USB port works on your/a computer: if it pushes current or lets devices pull current.)
Taking the above into account (and also the fact that my iPhone burns through its battery much faster with the WiFi on), I would have to say turning WiFi and 3G off would let it charge faster. However, when in standby, the iPhone automatically turns the WiFi off for the majority of the time and only turns it on every-so-often to check on email and whatnot. So, it might not make that much of a difference...
Also, you might be interested in knowing that batteries, in general, will reach something like 70% charge capacity in 30% of the total charging time (and therefore take the other 70% of the time to charge the last 30% of the battery).
posted by StarmanDXE at 6:01 AM on December 23, 2009
If you're talking about charging from the little "wall-wort" AC-to-DC adapter, then I would have to assume that, yes, it would charge faster off than on. Those little wall-worts are cheap and only have the ability to "push" a certain current at a certain voltage (i.e. 100 mA at 12V [which is also why you should unplug wall-worts when not in use: they still use just as much power as when in use!]) This is unlike, say, your vacuum cleaner which runs on AC electricity and therefore "pulls" however much current it needs.
Now, if your iPhone is on (and plugged in), it's using a certain amount of power to run and then uses the "overhead" from what it's getting from the wall-wort to charge the battery. (Note: I don't know how the USB port works on your/a computer: if it pushes current or lets devices pull current.)
Taking the above into account (and also the fact that my iPhone burns through its battery much faster with the WiFi on), I would have to say turning WiFi and 3G off would let it charge faster. However, when in standby, the iPhone automatically turns the WiFi off for the majority of the time and only turns it on every-so-often to check on email and whatnot. So, it might not make that much of a difference...
Also, you might be interested in knowing that batteries, in general, will reach something like 70% charge capacity in 30% of the total charging time (and therefore take the other 70% of the time to charge the last 30% of the battery).
posted by StarmanDXE at 6:01 AM on December 23, 2009
[which is also why you should unplug wall-worts when not in use: they still use just as much power as when in use!])
This is most definitely false.
posted by fatllama at 6:50 AM on December 23, 2009 [1 favorite]
This is most definitely false.
posted by fatllama at 6:50 AM on December 23, 2009 [1 favorite]
This is most definitely false.
Hmm... Come to think of it, I suppose it might not be as much... :-/ But they definitely use more than none.
posted by StarmanDXE at 7:07 AM on December 23, 2009
Hmm... Come to think of it, I suppose it might not be as much... :-/ But they definitely use more than none.
posted by StarmanDXE at 7:07 AM on December 23, 2009
Well, you learn something new every day!
When my high school physics teacher explained it to us ~5 year ago, it made sense: those AC adapters essentially "short" the circuit from the wall when they're plugged in since they work via a dual-coil method of dropping the voltage.
I just checked a wall-wort with no load on a Kill-A-Watt and it showed "0.00 Amps". I guess this means I don't entirely understand what's going on here! (Maybe it was just drawing practically zero current, but still a very little bit?)
posted by StarmanDXE at 7:16 AM on December 23, 2009
When my high school physics teacher explained it to us ~5 year ago, it made sense: those AC adapters essentially "short" the circuit from the wall when they're plugged in since they work via a dual-coil method of dropping the voltage.
I just checked a wall-wort with no load on a Kill-A-Watt and it showed "0.00 Amps". I guess this means I don't entirely understand what's going on here! (Maybe it was just drawing practically zero current, but still a very little bit?)
posted by StarmanDXE at 7:16 AM on December 23, 2009
I guess this means I don't entirely understand what's going on here
This is most definitely true. Those who haven't built power supply electronics, lower your hands.
since they work via a dual-coil method of dropping the voltage
This is more commonly known as a transformer. The primary coil would appear to short the wall circuit... except that the wall voltage is oscillatory and the iron core therefore provides inductive impedance. If the secondary coil isn't drawing any power, then neither (ideally) is the primary coil. The only exception is when first plugging in the transformer the primary coil experiences "current in-rush" which magnetizes the iron core of the transformer.
A wall-wort DC supply that draws appreciable current when not charging or powering some device must have some internal load---a sensor, an LED, a keep-alive circuit---or a bad design.
(Maybe it was just drawing practically zero current, but still a very little bit?)
It may certainly experience some small draw due to a non-ideal magnet core. But at less than 10mA, if you live in the US (120V), that means less than 1.2W of idle power. Well designed switch-mode power supplies, or transformer supplies with intelligent shut-off circuitry, can do even better. But in the worst case, you'd need to leave about 60 of them plugged in all the time to equal the waste output of one conventional lightbulb.
posted by fatllama at 9:47 AM on December 23, 2009
This is most definitely true. Those who haven't built power supply electronics, lower your hands.
since they work via a dual-coil method of dropping the voltage
This is more commonly known as a transformer. The primary coil would appear to short the wall circuit... except that the wall voltage is oscillatory and the iron core therefore provides inductive impedance. If the secondary coil isn't drawing any power, then neither (ideally) is the primary coil. The only exception is when first plugging in the transformer the primary coil experiences "current in-rush" which magnetizes the iron core of the transformer.
A wall-wort DC supply that draws appreciable current when not charging or powering some device must have some internal load---a sensor, an LED, a keep-alive circuit---or a bad design.
(Maybe it was just drawing practically zero current, but still a very little bit?)
It may certainly experience some small draw due to a non-ideal magnet core. But at less than 10mA, if you live in the US (120V), that means less than 1.2W of idle power. Well designed switch-mode power supplies, or transformer supplies with intelligent shut-off circuitry, can do even better. But in the worst case, you'd need to leave about 60 of them plugged in all the time to equal the waste output of one conventional lightbulb.
posted by fatllama at 9:47 AM on December 23, 2009
Good for you for doing the experiment, btw.
Heh. Thanks. I love learning and have come to grips with the fact that not everything I know to be "true" necessarily is so... Therefore, when someone calls me out, I will usually attempt to prove myself (potentially learning that what I thought I knew was wrong) instead of saying, "Oh yeah? You prove it to me!"
And:
This is more commonly known as a transformer. The primary coil would appear to short the wall circuit... except that the wall voltage is oscillatory and the iron core therefore provides inductive impedance. If the secondary coil isn't drawing any power, then neither (ideally) is the primary coil. The only exception is when first plugging in the transformer the primary coil experiences "current in-rush" which magnetizes the iron core of the transformer.
That makes very good sense to me. Thanks for explaining! :)
posted by StarmanDXE at 10:17 AM on December 23, 2009
Heh. Thanks. I love learning and have come to grips with the fact that not everything I know to be "true" necessarily is so... Therefore, when someone calls me out, I will usually attempt to prove myself (potentially learning that what I thought I knew was wrong) instead of saying, "Oh yeah? You prove it to me!"
And:
This is more commonly known as a transformer. The primary coil would appear to short the wall circuit... except that the wall voltage is oscillatory and the iron core therefore provides inductive impedance. If the secondary coil isn't drawing any power, then neither (ideally) is the primary coil. The only exception is when first plugging in the transformer the primary coil experiences "current in-rush" which magnetizes the iron core of the transformer.
That makes very good sense to me. Thanks for explaining! :)
posted by StarmanDXE at 10:17 AM on December 23, 2009
This thread is closed to new comments.
posted by dfriedman at 5:42 PM on December 22, 2009