[T-Mobile Samsung Galaxy S II SGH-T989] MisterEdF:
My multimeter measurement tests are with OEM Samsung cables as well as 90cent Monoprice cables and the 500mah OEM Samsung charger and a 2.1mah OEM Apple IPAD charger and a 2.5 AMP Scosche car charger. The car charger test plugged into a 150 AMP 12VDC highly regulated power supply formerly used to power a Ham Radio computer based repeater system that belonged to local towns OEM before we upgraded to a 200AMP unit.

The test cable that goes between the MicroUSB cable and the various chargers when using the multimeter is a 6 INCH Male->Female USB cable with the +5V line broken out and split for attachment of the multimeter and all other lines kept intact.

Testing was also down with the Battery Monitor Widget Pro app which eliminated the jumper cable & multimeter which was consistent as well with each test and remained consistent even when BOTH were used.

While the app didn't agree with the multimeter current reading of ~430mah it did show ~530mah with every charger and every cable (and does supposedly measure INTERNAL charging rate data from the chipset which could explain the 20% variation).

No matter which means (internal app monitoring with only the SAMSUNG cable or external multimeter monitoring with the breakout cable tossed into the mix or both together) the measurements were IDENTICAL for each power supply & cable tested. Either 430mah with the meter or 530mah with the battery app no matter which supply or cable was used.

I believe the testing is valid as my results were consistent across all cables & chargers as well as the internal app the reads directly from the phones chipset with my meter removed despite the varying rated outputs of the different chargers.

Other than that, a DEV on the ATT GS2 I777 forum found the data sheet for the chip in the phone which handles the charging duties which, on the I777 (and the Infuse) limits the charge rate to, IIRC around 500-600mah. He was able to jack it up a bit in the kernels he has written for the 1777 and the Infuse but stated he didn't want to go beyond +100mah or so because it would cause issue with the phone.

Edit: I see you modified your post after I replied. :) Just to add, if the chipset limits the charging to 600mah what you say would make sense. If the charger is poorly rated the use of your NAV app, if it exceeds the 600mah charge rate of the chipset will surely discharge the battery rather than keep it charged however if the charger was properly rated and kept charging at the 600mah max rating of the chipset despite the battery drain from the app it would keep it charged instead of discharging. You are 100% correct there. My tests were based on relatively good quality chargers.

Now where I differ is with some others here who say they can charge their battery in 1 hr or 2 hrs from ZERO to FULL. Since the max charge rate is (for arguments sake) 600mah (and I beleive it to be much less) and the battery is 1850mah, do the math: 1850/600 is xx hrs. Can't change that. However if the battery meter on the phone which can be notoriously inaccurate depending on the ROM and/or Kernel says 10% when in reality it might be 40 or 50% it would SEEM to charge much faster because it wasn't really discharged.