[Galaxy S I9000 Accessories] garbz:
There are a couple of threads here about different chargers. Some people claim different charging rates, some claim different resulting battery life, and some claims are outright outrageous from an engineering perspective.

So I did a test.

Short Answer: No unless using the computer

Charging from the wall is faster than charging from a computer. But the big NO comes in the form of people claiming improvements from chargers other than the official Samsung one.

Long answer:

So I proceeded to build a test rig and check various chargers in various conditions. The conditions tested were: Phone flat (10% charge), Phone nearly full (80% charge) and Phone Full. In all cases tests were done with the screen showing white, and all wireless on, and the screen showing black and in airplane mode to see what impact it had on different chargers.

The chargers which were tested:

700mA Samsung charger that came with the phone

Computer USB power

500mA generic wall USB charger with Chinese written all over it

800mA Car USB charger

1A iPhone wall USB charger

1A HTC wall USB charger (not sure which phone it comes with)

added a 30A bench supply just to be sure, only 80% test done.

Before I continue I should say that the screen off and screen on as well as airplane mode would have an impact on battery charging rate providing the charging current is constant. I.e. You draw 500mA from the wall when the screen is off and the screen is on, there's a difference which is only likely to be going into the battery.

The method was to build a little pass through device that gave me access to all the USB lines. I broke the 5V line and passed it through 2 multi-meters one measuring current through the line and the other measuring voltage.

Results:

Phone at 10%

0.7A Samsung -> 475mA

Computer -> 83-87mA (no voltage sag)

0.5A Generic -> 345-380mA (Note voltage sagging at 3.8V indicates that the device is underpowered)

0.8A Car -> 478mA

1A iPhone -> 470mA

1A HTC -> 476mA​

Phone at 80%

0.7A Samsung -> 472mA

Computer -> 84-90mA

0.5A Generic (test not repeated due to power concerns)

0.8A Car -> 471mA

1A iPhone -> 475mA

1A HTC -> 471mA

30A Bench -> 470mA​

Phone at fully charged

0.7A Samsung -> 12mA

Computer -> 11-14mA (noisy voltage line)

0.5A -> 12mA

0.8A Car -> 12mA

1A iPhone -> 12mA

1A HTC -> 12mA​

Variances with screen and cell networks:

No changes were observed on any charger between switching the screen off and displaying white as well as switching airplane mode off and on. Until that is the battery was fully charged.

The phone idles at 12mA on airplane mode with the screen off.

With the wireless and cell on the phone jumps between 10mA and 40mA every 2-10 seconds for about 3 seconds. It looks like it is polling the wireless.

With the screen on displaying white full brightness the phone jumps between 130mA and 170mA.

This is interesting as it would suggest that if the cell and wireless are on and the screen is set to maximum brightness you'll likely be draining your battery even through it's on charge if you're plugged into the computer.​

Discussion of results:

If your charger is underpowered expect problems. I wouldn't use a cheap Chinese USB -> wall adapter with the phone. But if your charger is capable of supplying at least 700mA then there is absolutely no difference going beyond that.

The computer only drawing less than 100mA is consistent with the windows driver interface saying that the phone has only requested 100mA from the USB slot. This is a driver issue as the USB2.0 spec should be able to provide 500mA from a USB port providing it is the only device on the hub drawing power.

The claim that you get more battery life out of a different charger is absurd. There were theories floating around about "topping up" batteries requiring a lot of power. Actually it's exactly the opposite. As batteries top up the power demands decrease a LOT. Above about 95% there was a noticeable slow decline in current draw. Eventually even before the battery full notice came on the phone was drawing less than 160mA from the wall, and about 10 seconds after saying battery is full it dropped down to the levels mentioned above.

There are a lot of things that can cause variances in battery life, but using a different charger is not one because

you are not using a different charger just providing power from a different source

. The charger is a small chip on the board of the SGS made by Maxim. If you provide the phone with 5V and >500mA it will happily draw the 500mA. The only exception being the computer power supply.