Charging spec. question

[Guest CIM1]

What precise conditions trigger the charging mode to be 'AC', 'USB' or 'discharging' on the blade - and does AC status indication mean blade is def. getting 700mA?

My assumption from reading other threads was:

AC = pins 2 & 3 shorted + volts across 1 & 4 (700mA draw)

USB = no short + volts across 1 & 4 (500mA draw)

discharging = no volts across 1 & 4

Confusion arises from buying a car USB charger which is quoted at 1A but does not appear to have a hard short between pins 2 & 3 on the charger socket - yet the phone says AC charging when it is plugged in using the blade's standard micro USB cable. Why would that be?

Only explanations I can see are either : my above assumptions are incorrect OR the short only appears when the car charger is powered up (and micro USB cable plugged in perhaps) OR I am failing to measure the short correctly.

Edited March 29, 2011 by CIM1