HI!
This might be a stupid question...
During the day my O2 Mini is always connected to my laptop thru the USB sync wire and therefore its keeps getting charged.
Is that in any way harmful for the battery...does it reduce battery life over the long run??
Thanks.
Ujj
ujj75 said:
HI!
This might be a stupid question...
During the day my O2 Mini is always connected to my laptop thru the USB sync wire and therefore its keeps getting charged.
Is that in any way harmful for the battery...does it reduce battery life over the long run??
Thanks.
Ujj
Click to expand...
Click to collapse
No not Lithium Ion batteries. In fact it is better to charge the battery as often as possible.
is that fact? i cant believe it.
It is the way the battery is designed, there is logic in the battery that cuts off voltage when the peak is reached as far as I know.
Thanks cruisin-thru and skjelnes .
If you let them go flat for any length of time, they die completely.
USB charging control
Still this whole battery charging and technology issue is quite ambiguous. No one can really guarantee that there is a clear answer. For instance why do you have to give the battery an initial 8-hour charging if it is a new generation battery?
In any case it would be interesting to know how the charging control works. There are some options:
- It can be controlled by a circuit which cuts off power at a certain level of charge (no way to play with this option).
- It may be controlled by software which would be great because one could (easily) interfere with it. In this case there must be some kind of relay switch controlled by the operating system.
- It could also be not controlled. In this case the battery never stops charging. Only the indication changes when a battery meter reaches a certain level. This looks more likely to be the case as the initial 8-hour charging might mean keeping the battery under voltage during the initial charge as even though the indication states that it is fully charged the charger is not disconnected by any control system.
Does anyone have some solid information on the above assumptions?
Note: I tried to isolate the power pin of the USB cable in order to prevent the device from charging but then it was not recognized by the USB (got a USB connection error). Obviously the power line of the USB is used for connection and signal as well and not only as a optional power supply to the connected device.
I'm currently trying to find something in the registry about charge control....
Maybe Microsoft has hidden a secret option somewhere in there... :?
Anonymous said:
I'm currently trying to find something in the registry about charge control....
Maybe Microsoft has hidden a secret option somewhere in there... :?
Click to expand...
Click to collapse
Sorry, forgot to log in...
Re: USB charging control
savas said:
Does anyone have some solid information on the above assumptions?
Click to expand...
Click to collapse
Find everything you want to know on lithium-ion batteries on batteryuniversity.com
here http://www.batteryuniversity.com/partone-5.htm
and here http://www.batteryuniversity.com/parttwo-34.htm
Serge
A litium-ion battery gets worn from three things:
* Normal use
* Heat
* Full charge
A short while after the Ipod battery dirty secret leaked, I read why the batteries only last for like a year. A NiCd battery HAS to be cycled completely to last as long as possible because of their memory effect. A NiMh battery LIKES to be cycled as completely as possible for longest life.
A Li-Ion battery does not have the memory effect - therefore a lot of people seem to assume that you can charge a Li-Ion battery any way you want. That is not correct... Everyone of you ever used a laptop with a Li-Ion battery every day at work, with the ac-adaptor plugged in knows that the battery is ready for garbage bin after one or two years.
Why? You've almost never used the battery... It's always fully charged... The battery should have lasted much longer you think...
Isidor Buchmann is president at the company Cadex which makes battery chargers. He has got more than 20 years of experience from the battery business.
At the site: http://www.batteryuniversity.com he has written an article where he explains the mechanisms inside a Li-Ion battery and provides tips about how to treat the batteries.
Finally he gives the following advices:
*Don't discharge the battery completley. It's better to discharge the battery a little more than halfe than making a complete discharge.
* Discharge the battery completely and then charge it completely to calibrate the battery meter
* Keep the battery cool
* For long time storage: keep the batteries charged at 40% in the fridge
* Do not use the ac adapter and the battery when the battery is fully charged. Heat and unneccesary charging after the battery is fylly charges destroys the battery
My 2 cents.
// Anders
Re: USB charging control
savas said:
why do you have to give the battery an initial 8-hour charging if it is a new generation battery?
In any case it would be interesting to know how the charging control works. There are some options:
- It can be controlled by a circuit which cuts off power at a certain level of charge (no way to play with this option).
Click to expand...
Click to collapse
I think most questions have been answered, except Magician specific ones, i.e.:-
The Magician has to be initially charged for at least 8 hours to:-
1. Make sure the main battery is fully charged and formed, and charging logic calibrated (future capacity depends on this)
2. Charge the backup battery. Unlike the main battery, this only gets a trickle charge which starts after the main battery is at 100%. So it needs those 8 hours to get to full capacity. Remember to do this if you ever drain the backup battery.
Lithium charging logic is built into the battery, so no way to tamper with the settings. The NiMH backup battery logic will be built into the Magician.
Very interesting reading! I didn't know about the issue with laptop batteries.
Loboman said:
Very interesting reading! I didn't know about the issue with laptop batteries.
Click to expand...
Click to collapse
Me niether. I knew exactly how to treat NiCd and NiMh batteries, but when I bought a laptop, I wondered how to treat Li-Ion batteries. After some search I found the info i just presented here.
// Anders
Very interesting information indeed! Just some more comments:
Anders Johnsson said:
*Don't discharge the battery completley. It's better to discharge the battery a little more than halfe than making a complete discharge.
Click to expand...
Click to collapse
Anders Johnsson said:
Do not use the ac adapter and the battery when the battery is fully charged. Heat and unneccesary charging after the battery is fylly charges destroys the battery.
Click to expand...
Click to collapse
Ineedtoys said:
Lithium charging logic is built into the battery, so no way to tamper with the settings. The NiMH backup battery logic will be built into the Magician.
Click to expand...
Click to collapse
OK we can easily avoid discharging the battery below 50% or 60% at normal conditions even when traveling through a USB port of our notebook (3rd quote)
We should also avoid a USB connection at a 100% (2nd quote) or even at a 90% (3rd quote) charge level unless we can find a way to cut off the power supply to the battery. The only option would be to find a way to do this from the device, before the internal logic of the battery. As far as I can understand the internal battery logic allows charging whenever connected to a power supply and it only informs somehow the device of the charge level.
OMG.
All this nonsense about batteries.... it's easier to just buy a new battery or a new device after 18 months, rather than let your charging habits be dictated by how batteries like to be tickled!
Easier yes, more expensive too.. Dell sure knows how to charge (!) you for a new batt with built-in subwoofer..
Does it matter if we don't charge it all the way till it's full? If I'm charging it till about 95% and I really need to unplug it. How much damage will it do to my battery?
dacmo said:
Does it matter if we don't charge it all the way till it's full? If I'm charging it till about 95% and I really need to unplug it. How much damage will it do to my battery?
Click to expand...
Click to collapse
I'm not following you - I think. If you unplug it at 95% it's a lot better than unplugging it at 100%.
Summary:
Full charge: BAD
Full discharge: BAD
Heat: BAD
Extreme cold: BAD
// Anders
This is the first time that I ever heard that charging up to 100% is bad. I know that leaving it on the charger for extended periods is bad but to say that charging to 100% is bad.. that's absurd!!! :shock:
Related
Hi everybody.
To get the most out of my battery I always wait until my device shuts down due to lacking battery. The I chargt it until it the end and the battery displays 6+ houres.
When I recharge the battery before its empty I only get 4+ houres when its full.
I also read that the battery's lifetime is increased by only charging it that way.
My problem is the cradle that charges it everytime I sync.
Is there a way or tool to switch charging on/off for the cradel?
Thanks alot
Alex
The way I understand it, modern batteries do better when charged regularly in small increments. They do very badly with multiple deep discharges, which can actually damage them.
So I would actually disagree with you that what you are doing is a good idea.
If you still decide to do this, the simplest way is probably a manual activesync via bluetooth, using a dongle, as it actually charges via USB too.
Surur
Right the bluetooth thing would be a good idea.
And you might also be right that you should not charge it in such an extreme way...
I read this an a PC Magazin.
I don't know if its wrong or right. the only thing I know is that the battery lasts longer when I charge it thta way.
Thanks
Alex
The battery in the xda2 is designed for constant charging, I dont see how you would get more battery life because if you acheive your desired aim the xda2 will be discharging during sync and will give less battery time than if you let it top up the charge.
I read that Ion battaries have only a limited number of complete chargings bevor the are broken...
alex
Hello,
I have problem,
My MDA was shuting down about 40 / 50 % of power left !.
So i'm so stupid to get idea " help discharge battery manual to 0 % ".
I get light bulb, connect wires and wait about 15 minutes until light went down.
When light goes down, fast connect pda to charger (i don't want to destroy battery Li don't want to be discharged for long time).
But, it don't want to charge it... it's blinking red led about 30 minutes, and wont power on...
Grrrr
I'm so stupid to kill this battery ?
Do you have any idea ?
regards
seba22 said:
Hello,
I have problem,
My MDA was shuting down about 40 / 50 % of power left !.
So i'm so stupid to get idea " help discharge battery manual to 0 % ".
I get light bulb, connect wires and wait about 15 minutes until light went down.
When light goes down, fast connect pda to charger (i don't want to destroy battery Li don't want to be discharged for long time).
But, it don't want to charge it... it's blinking red led about 30 minutes, and wont power on...
Grrrr
I'm so stupid to kill this battery ?
Do you have any idea ?
regards
Click to expand...
Click to collapse
1.- Buy another battery
2.- READ here: http://wiki.xda-developers.com/index.php?pagename=UniversalSmallBattery and here: http://wiki.xda-developers.com/index.php?pagename=UniversalBatteryIssue
Good luck,
it appears that your battery can no longer hold enough power (ampacity) to sustain the needs of the unit, the reason why it shuts down although the power level shows that 40% or more was remaining. in short, it is no longer in its optimum state.
i made such conclusion as this was confirmed when you said that you drained it manually but your charger can no longer drive it back to normal charging state (just red led blinking). this happens when one of the cells of your battery, if not all, is in near open state and the current (A-amperes) can no longer normally pass through it due to large resistance (ohms), hence, not charging at all.
if you want to revive the battery, nonetheless, i would suggest to intermittently charge it manually using a more powerful charger, that is, the same voltage (V) but more power (VA-VoltAmpere) or ampere rating (take note, i strongly advise not to do the charging conventionally through the unit, it would certainly destroy the power circuit or the unit itself) until such time that it can be charged by the usual wall charger. Likewise, extra caution must be taken since prolonged charging using a more powerful charger may lead to battery explosion, thou i'm bit sure its not in such magnitude to kill . just joking..
seriously, even assuming you can drive it back, your battery will be most likely in the same state as it was before although there were rare occasions that boost-charging may revive the cells and will thereafter perform normally (fingers crossed), otherwise, sad to say you have to replace the battery with a new one to have a working uni once more hope this would help, regards..
Hi,
Thank you for reply.
What i do ?
I have problem with my computer, so i shut it down, and go in to bios.
I leave my PDA pluged in.
After 30 minutes, i started linux, and then i saw red led don't blinking !
I press power, and it's started ;>
I charged to 100 %, then discharge and charge again.
Now it's shuting down on 20 % !!
Previously it's going down about 50 %/ 60 %.
Now 20 %
I wan't to thow this battery to trash but now it's alive... i'm realy happy...
seba22 said:
Hi,
Thank you for reply.
What i do ?
I have problem with my computer, so i shut it down, and go in to bios.
I leave my PDA pluged in.
After 30 minutes, i started linux, and then i saw red led don't blinking !
I press power, and it's started ;>
I charged to 100 %, then discharge and charge again.
Now it's shuting down on 20 % !!
Previously it's going down about 50 %/ 60 %.
Now 20 %
I wan't to thow this battery to trash but now it's alive... i'm realy happy...
Click to expand...
Click to collapse
that calls for celebration.. cheers :
Actually we should never ever discharge lithium battery unless you have voltage meters and know what you are doing, if A (that is one with ONE Cell) lithium battery's voltage gets lower than 3.6V it already started to damage the chemical make up of the battery and cases the battery's size to reduce greatly
And fast charging actually reduces the battery life, because the fast charging generate heat, and the heat will create gas inside the sealed battery and causes the battery to expend, and it changes the pressure of the chemical make up inside the battery and will greatly reduces the current and size of the battery... that is why sometimes you can see the lithium battery actually expend when you View it from the side....
I had maybe over 100 lithium battery from all the phones, and the electronic powered helicopter I have.... so I would say I know it pretty well
SOG said:
Actually we should never ever discharge lithium battery unless you have voltage meters and know what you are doing, if A (that is one with ONE Cell) lithium battery's voltage gets lower than 3.6V it already started to damage the chemical make up of the battery and cases the battery's size to reduce greatly
And fast charging actually reduces the battery life, because the fast charging generate heat, and the heat will create gas inside the sealed battery and causes the battery to expend, and it changes the pressure of the chemical make up inside the battery and will greatly reduces the current and size of the battery... that is why sometimes you can see the lithium battery actually expend when you View it from the side....
I had maybe over 100 lithium battery from all the phones, and the electronic powered helicopter I have.... so I would say I know it pretty well
Click to expand...
Click to collapse
well said, cheers mate
Hi, do you have any workaround how to set my Legend to not charge the battery while it is connected to PC's USB port?
When I want only to transfer some files to SD card and plug the device into USB, it starts to charge. It is very important for me because it continuously damages battery if this happens several times only for some minutes. In Windows mobile there is a great option to not charge when device is connected to USB. I hope there is an option to do this also on android.
pe3ksve3k2 said:
Hi, do you have any workaround how to set my Legend to not charge the battery while it is connected to PC's USB port?
When I want only to transfer some files to SD card and plug the device into USB, it starts to charge. It is very important for me because it continuously damages battery if this happens several times only for some minutes. In Windows mobile there is a great option to not charge when device is connected to USB. I hope there is an option to do this also on android.
Click to expand...
Click to collapse
I'm pretty sure the batteries today doesn't take any harm of this type of charing. Correct me if i'm wrong
arxx said:
I'm pretty sure the batteries today doesn't take any harm of this type of charing. Correct me if i'm wrong
Click to expand...
Click to collapse
Hmm, on the hand way I am pretty sure that it harms the battery ... 1minute chargings are not good for battery...
I am also certain it DOSEN't damage the batteries...
However.. There are several reasons to disable charging when connection to a PC.
For instance, using a USB hub without additional powers, the drain the phone will put on the hub, will make the rest of the stuff connected to it stop working.
Or simply just to preserve the batteries when using a laptop. The batteries on laptop is bad enough as it is, so no need to put more drain on them...
Interessting reading:
www!batteryuniversity!com/partone-12!htm
*replace ! with .
Lithium-based batteries (like those used in basically every single mobile phone now) love to be topped up constantly. In fact, they suffer permanent damage to the lifetime of the battery if they are ever empty. Don't worry about charging them for a few seconds are a few hours, as long as you don't let them go flat.
Lithium batteries will only work best for a few years from the day they are manufactured (not their sale date, by the way). You'll notice if you have an old mobile phone or iPod that they'll start to run low faster and faster the older they get. This is just a consequence of the chemicals they are made of. It's also why some people refuse to buy Lithium-powered devices that don't make it easy to replace the battery (like iPods, for example).
Also, Lithium batteries don't hold their full capacity right away. They have to be charged for 300% of their capacity for them to be running at peak, although you do not need to do this all at once. This is why some devices come with advice that you discharge them completely a few times right at the beginning. I never do this, because as I advised earlier you do not want to let them go flat. Instead, I charge it up to 100%, use the device down to 50%, charge back to 100%, over and over, since each of those charging sessions contributes to the total 300% necessary.
Nickel-Cadmium batteries were the old sort of rechargeable batteries used in other sorts of devices (toys, remote controls, etc). The best care advice for them is to leave them in the charger until they are needed, and use them until they are completely flat before charging again.
Hi all, there is a way to turn off the charging function when using USB ,
1-install FdcSoft TaskMgr from here
dotfred.net/TM/FdcSoft_TaskMgrv3.3_WM6.5.cab
2-go to Devices--->$device\BAT1(BAT1 and stop this service
3-thats All
To Use charge restart this service
hey thx for the tips! but after stop the service my o2 keep saying batt low...
Is there any reason why we would want to turn off this service?
I heard that it keeps your battery in good shape
peepe1302 said:
I heard that it keeps your battery in good shape
Click to expand...
Click to collapse
I'm not so sure about that... I've always charged both my O2 and the O1 before through usb and the battery has always been fine.
Actually, I even noticed that charging through usb takes longer but once it's charged it also lasts longer (this happened on the O1, haven't made the same comparison on the O2 yet)
Dunno if plugging / unplugging the usb cable too frequently can have some sort of ill effect on the battery life, but it's not like we're plugging it every 10 minutes is it?
Never had a battery problem with a "normal" usb usage and usb charging enabled so far...
Yes but not anymore
peepe1302 said:
I heard that it keeps your battery in good shape
Click to expand...
Click to collapse
It's always good to drink all the juice so the battery don't develop a offline or fake "memory".
Also the multi cell assembly insde the battery praticly don't allow batery memory anymore.
Thx for the reference
Regarding battery life
Hi,
Actually, for a battery it depletes it's life every second. There is no way of preventing this But we can extend the service life. For example the most basic rules:
1-Do not charge your battery unless it is almost empty
2-Avoid deep discharging (this is not possible with a PDA coz it has an early shut down routine)
3-Do not overcharge the battery (also this not possible, coz there is a voltage limiter by hardware)
4-Do not leave your battery in a high temperature environment (for example in a car during summer, we are using chemical-reaction batteries)
the rest is do not puncture, do not short circuit boola boola boola
ok, finally while using your PDA with a USB charging interface, it should stop charging when the battery is full (Even my mother's old nokia doing this)
Plus, how much it costs for a new battery? only few bucks.. ehh.. (not for an original one ofcourse)
PDA batteries, in most cases, are 3.7volts (charging voltage is 5volts by USB) and 1200 to 1500mAh (for the ones who doesnt know what is "mAh": it is the capacity of the battery and it means if you pull for example for a 1300mAh battery, 1300 "mili ampers per hour" it will deplete. Some of my friends they are using 3.7V 2000mAh batteries while their PDAs supplied with 1230mAh batteries, thus, standby time goes up to a week. They are not using their originals ofcourse. I dont understand why manufacturers are not supplying PDAs with these kind of batteries by standart. Even a chinese made battery can be so efficient. (I am using a chinese one, my original battery is 1300mAh, i could find 1500mAh same battery)
I spoke to my friends, they are not charging their 2000mAh batteries via USB/charger while battery is in the phone. Because there is an internal electrical resistance of every battery. May be PDA's battery charging circuit get damaged! Because of this if you plan to use a high capacity battery, charge it seperately by using another charging equipment.
Finally when you want to sell out your PDA install the original battery (which you have never used before hehe ) and get a higher price
This might be some really big idiotic question, but what if the service is down and the battery drains and the phone shuts itself off, will it turn on by connecting the charger to the phone?
I ask this because with the service off even the real phone charger wont work (at least while it is on)!
houssam10001 said:
Hi all, there is a way to turn off the charging function when using USB ,
1-install FdcSoft TaskMgr from here
dotfred.net/TM/FdcSoft_TaskMgrv3.3_WM6.5.cab
2-go to Devices--->$device\BAT1(BAT1 and stop this service
3-thats All
To Use charge restart this service
Click to expand...
Click to collapse
I just did what you said, and now the device\BAT1(BAT1 completely disappear! How am i supose to turn it on again now?
And no, i obviously didn't delect it, i just stoped the service and it vanished from the damn list!
im very interested in this but how can you restart the charging service?
For example if i leave all night charging, does it damage the battery? Some batteries after fullycharged, they wont charge anymore. What about u8800?
And what happens if i charge while phone is open and not fully empty? Does it damage?
My charge lasts 16 hours, why is it? I dont use wifi, games, etc. Please help
All ROMs should stop the charging process when reached 100% (the icon changes, on the stock ROM the flash disappears of the icon), therefore I believe that the battery cannot be damaged by leaving the phone plugged in the whole night.
I'm sure that it doesn't matter when you recharge the phone, if it's 10% or 50% it makes no difference to the charging process or the battery. It use to matter on the Li-Nch batteries, but those are long gone...
The fact that the battery only lasts 16 hours, it's an unrelated problem, that I've been struggling with for months now...It's one of the system/hardware components that hangs and doesn't allow the phone to go to sleep...therefore, the battery lasts up to 24h.
Look at this thread, so many users are affected by this...probably most of them and only the recent kernels (.void/Miui) have measures against this problem.http://forum.xda-developers.com/showthread.php?t=1043760
I did not make any rom differences or overclock. Still stops the charging?
Sometimes i charge from pc via usb, can it damage?
It goes 16 hours without wifi or blueetooth or 3g. I dont use too much but goes for 16 hours.
http://forum.xda-developers.com/showthread.php?t=1043760
Here, it is about sleeping mode. My phone goes black screen after 15 seconds idle. What is sleeping mode?
Cursed Chico said:
I did not make any rom differences or overclock. Still stops the charging?
Sometimes i charge from pc via usb, can it damage?
It goes 16 hours without wifi or blueetooth or 3g. I dont use too much but goes for 16 hours.
http://forum.xda-developers.com/showthread.php?t=1043760
Here, it is about sleeping mode. My phone goes black screen after 15 seconds idle. What is sleeping mode?
Click to expand...
Click to collapse
Charging from USB is somewhat preferable to wall charger, due to it charging slower, therefore generating less heat. Although, a wall charger won't do any harm. When the screen is off and the phone is not doing anything, the CPU is suppose to go into a deep sleep state, yet with this phone it does not.
wall charging should be preferable in my experience
Ok, let me clarify a few things here.
The battery recharging process is simple, when the battery reaches 2.2V, then the current inside is not enough to sustain the hardware and it's considered empty. Any standard phone charger, will pump current until the voltage is 4.3 and then the so called "negative delta v" signal is being sent and the charger stops pumping.
USB is a BUS designed to carry data, but to be able to carry data it needs to provide a power supply to the connected device. Therefore, any USB should be able to deliver 5V and 500mA to any device connected.
As this phone's battery, according to the wall charger specification, takes up to 1Amp, the simple math tells us that the wall charger will charge the battery twice as fast. Since I've been dealing with batteries, I can tell you that in this case USB charger is a much better choice to recharge this battery, as it delivers only 500mA. The less current going through the electrodes, the lower the chance of damaging the battery due to high temperature.
For more info:
http://www.mpoweruk.com/chargers.htm
http://en.wikipedia.org/wiki/Battery_charger
http://en.wikipedia.org/wiki/Lithium-ion_battery
According to Wikipedia:
"Most modern cell phones, laptops, and most electric vehicles use Lithium-ion batteries. These batteries last longest if the battery is frequently charged; fully discharging them will degrade their capacity relatively quickly.[23] When storing however, lithium batteries degrade more while fully charged than if they are only 40% charged. Degradation also occurs faster at higher temperatures. Degradation in lithium-ion batteries is caused by an increased internal battery resistance due to cell oxidation. This decreases the efficiency of the battery, resulting in less net current available to be drawn from the battery."
These batteries last longest if the battery is frequently charged; fully discharging them will degrade their capacity relatively quickly.
So we must usually charge from usb and must stop before reaching %100 charge, maybe %98?
But when connect to pc, there is an icon shown, before disconnecting we need to click "disconnect secure" icon on system tray, if i dont do, it damages the system of phone?
Cursed Chico said:
But when connect to pc, there is an icon shown, before disconnecting we need to click "disconnect secure" icon on system tray, if i dont do, it damages the system of phone?
Click to expand...
Click to collapse
There is a very small chance on XP, dunno about vista, no harm on win7.
So we should usually charge from usb and must stop before reaching %100 charge, maybe %98?
It is more safe since there is half of the current that passes compered to Charging with the AC adapter. But it theoretically takes almost double time.
Cursed Chico said:
So we should usually charge from usb and must stop before reaching %100 charge, maybe %98?
Click to expand...
Click to collapse
Yes, that's correct. But, I wouldn't worry about stopping before 100%. I know for sure that the stock ROMs are stopping the charging process when reached 100%.
Cursed Chico said:
But when connect to pc, there is an icon shown, before disconnecting we need to click "disconnect secure" icon on system tray, if i dont do, it damages the system of phone?
Click to expand...
Click to collapse
No.You're not going to damage anything by disconnecting the cable directly. That "safe disconnect" is only for data transfer, nothing to do with charging.
Because of the exploding nature of li-ion cells when misused, the battery itself has a protection circuit to prevent overcharge and discharge. So whatever how much the rom wants to charge, the battery will protect itself...
Exactly; the ROM does not have any influence on the charging process - that is why your phone can charge the battery even though it is turned off. The whole process is completely independent from the software your phone is running.
In 2011 it is very hard to damage a battery, it will most likely die from old age. There is just one thing that is not the best thing to do: Trying to switch on the phone when the battery is empty already. If the voltage of the battery drops below a certain point, the battery might be damaged and thus have less capacity afterwards.
To be on the safe side I always turn off the phone a few minutes before the battery is completely empty.
I agree that there is a separate circuit that does the charging, so no matter if the phone is on or off, battery would still charge. But, I believe that the Rom can interfere with the charging process, that's why on some Roms you get the flashing buttons when phone is fully charged or sometimes you can't unlock the phone from the first attempt, when battery is full.
In reality, i believe that charging process has 2 control points, the default (when phone is switched on) and the "failsafe" one that charges the phone when voltage has dropped below a certain value (which has to be is different in terms of current values, as there is no power consumption).