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How long it takes to charge SGS2?

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#1
mastakila

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Hi,

I am about to get SGS2 to replace my SanFran and have some questions that hopefully someone can answer...

How long it takes to fully charge SGS2?
Is there noticeable time difference between charging from PC->USB and AC->USB?

My last question is really directed to users who had SanFran before and can compare battery life of both mobiles.

Thanks!

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#2
dfghggfgfd

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The supplied charger is rated 700mA only, which isn´t that much more than the 500mA from USB (900mA with USB 3.0, although I´m not sure if the phone uses that). I´m using my old Nokia power-adapter, which can give 1,2A and is much faster than USB or the supplied charger.

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#3
maedox

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From empty it's ~ 6 hours via USB, 3-4 hours on AC. Way too long if you ask me, but you can just charge it more often.

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#4
maedox

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The supplied charger is rated 700mA only, which isn´t that much more than the 500mA from USB (900mA with USB 3.0, although I´m not sure if the phone uses that). I´m using my old Nokia power-adapter, which can give 1,2A and is much faster than USB or the supplied charger.


You can feed a lot of amps but it will still just draw what it needs, which I suspect is around 1 A. I might be wrong though. Bottom line: higher ampère doesn't necessarily charge it faster. It is of course faster than on the wimpy 0.7 A in the box... Why the h*** would they not give us 1 A as everyone else?!

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#5
spvdk

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Info has apparently been found in the software that shows, that charging is crippled to 650mAh. This is also consistant with my testing that shows, that no matter how powerful a charger you use, it still takes 3,5 hours (!) to fully charge a completely flat battery. Considering that high battery consumption is a big problem on this device, limiting the charge level this bad is not a great move by Samsung.

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#6
maedox

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Info has apparently been found in the software that shows, that charging is crippled to 650mAh. This is also consistant with my testing that shows, that no matter how powerful a charger you use, it still takes 3,5 hours (!) to fully charge a completely flat battery. Considering that high battery consumption is a big problem on this device, limiting the charge level this bad is not a great move by Samsung.


I bet they have a good reason for doing it. Considering the wicked good job they have done otherwise, I will let it slide. Just charge more often. :)

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#7
spvdk

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I think an external charger and an extra battery should be on everybodys wishlist. Makes the battery issues less important and frustrating.

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#8
Genieuk

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Have already ordered an external battery pack.

This should keep me topped up when on a long journey, or on the way back home after work.

http://www.amazon.co...XMCII/ref=nosim

Posted Image

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#9
mastakila

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for me short battery life and long charging time is reason not to buy this phone.

i would expect from a "mobile" device to be operational (with medium usage) for at least 48 hours without charging and if battery dies to be able to recharge it in 2-3h. In case of SGS2 it looks like battery lasts for a day (~18h) and then I have to charge it overnight.
its kinda annoying that mobile device needs to be connected to the charger so often and for so long.

personally I would prefer thicker and heavier phone with battery that's adequate to device power requirements (2500-3000mha)

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#10
c0m47053

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My understanding is that the slow charge is to extend the life of the battery and prevent premature (even catastrophic) failure of the battery. I picked up three cheap Hong Kong replacement batteries from the bay for £6, that return at least similar battery performance to the OEM. I would love a ROM dev to remove the restrictions on charging ampage.

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#11
dfghggfgfd

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My understanding is that the slow charge is to extend the life of the battery and prevent premature (even catastrophic) failure of the battery.


If you only charge your phone, the power supply isn´t a real problem, finally 700mA@5V is enough to charge the battery in about 2h, well at least in theory.

There are only 2 problems:

The main problem might be, that you want to use your phone for something while it is charging. And the device can consume most of the power for the actual usage, so not much is left to charge the battery.


A minor problem are the charging-characteristics of Li-Ion-cells. It is not possible to fully charge a Li-Ion-battery under 3h.

Charging is divided in 2 stages.
In the first stage charging should be done at about 0,5-1C. C in this case means the rated Capacity of the battery, so a 1,6Ah-cell should be charged with 0,8-1,6A
This stage lasts until cell-voltage is about 4,2V

With 700mA@5V the power-supply can only give about 0,8A @ 4,2V which is just the lower limit of the recommended charging-current. In reality it is a bit higher most of the time, as the voltage only tops at 4,2V. Cell-Voltage shouldn´t be under 3V, which is probably the limit where the phone switches off to prevent over-discharging. So during the first charging-stage from a completely flat battery voltage will rise from 3 to 4,2V and at 3V the power-supply can at least give about 1,3A.

This first stage lasts from one (when charging with 1C) to two (when charging with 0,5C) hours.
As the voltage rises quite linear, we can assume an average voltage of about 3,6V which means an average current of about 1,1A or 0,68C, so with the supplied power-adapter stage 1 (from a complete flat battery) must be at least 1,5h. But only if you are not using the phone at all.

This will charge the battery to about 75-85%

After this the charging-device switches into stage 2, also called the saturation-stage. In this stage the voltage remains constant at the set limit (usually about 4,2V) and the charging-current constantly drops. The saturation-stage lasts at least another 2h to get the missing 15% of charge into the battery.



The conclusion is:

Charging will get slower the higher the charging-level already is. In stage 1 because the voltage rises and the power-supply can not provide enough current, and if we are already in stage 2 because the battery can´t be charged any faster without risking damage.

And using the phone during charging will significantly increase the charging-time significant.

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