The "charger" is actually a battery management IC inside the smart phone. Assuming your phone uses a Li-Poly battery, the battery will be rated at a nominal voltage of 3.7v and a fully-charged voltage of 4.2v or thereabouts.
The battery capacity of a LI-Poly battery in a smartphone is rated in mAh, and a typically value might be 1300 mAh. The charge rate is often denoted as C and signifies a charge rate equal to the capacity of a battery in one hour. For a 1300 mAh battery, C = 1300 mA.
The charging current is typically set externally to the charger chip using a couple of resistors. Values of 0.5C (650 mA in this case), 0.8C and 1C are common. A rate of 2C (2600 mA or 2.6A) would be classified as a fast charge.
Sometimes the resistor network can be adjusted by the microcontroller inside the phone, so it can set the charging current to either 100 mA or 500 mA when connected to a regular USB port, or to a higher value (e.g. 1C) when connected to an AC adapter, colloquially known as "wall-warts".
These AC adapters are not chargers, but simply AC to DC converters. The current available for charging will be limited by the output of the converter (i.e. if it supply 1A, the charger chip cannot charge the battery more than 1A), but if you replace a lower current wal-wart with a higher one, then the battery might be charged faster, however the charging current will still be limited by the charger chip -- whichever is lower, the AC adapter capacity or the charger chip setting.
Client device should enumerate host to determine current which is
possible for host to provide. However can safely assume at least 100
(150) mA even without it. If client found out that it is connected to
charging port (CP), it can safely drain up to 1.5 A of current. In
case of standard downstream port (SDP), client have to ask for
high-power mode using USB protocol communication (which host might or
might not allow), before draining more current.
This premise is completely wrong, in all aspects.
To start, "client devices" do not "enumerate host", the host enumerates the plugged devices.
"USB client" is not asking for "high-power mode" using USB protocol. All detection of port power capabilities are done completely outside the USB protocol, it is an independent process and is/was devised as such.
"USB clients" are not asking for anything. The host provides a "charging signature" that advertises its capability, and the "client" just takes everything it can or what it needs.
A "USB client" however might have different needs that are not necessary at the top of port power capability. The device might have its battery fully charged, and won't draw any more charge from the port or draw only a little. Or it can have a normally-discharged battery, and then it will draw the maximum, which depends on particular battery, and might not be equal to the charging port capability. Or the device can have a nearly dead or very weak battery, so it will take only a small "pre-charge" current.
More, normal mobile device do have a circuitry that monitors the voltage level on VBUS, and reduce their charging consumption down, so the VBUS level is maintained at least at 4 - 4.5 V level. The voltage drop can be due to the calbe being too thin, or the current draw exceeds nominal rating for the charging port. All chargers are supposed to be not just a source of fixed voltage - they should have a "soft" cut-off load curve, so the device can reduce its consumption and maintain healthy VBUS level. This feature differentiates chargers from constant-voltage power supplies.
Considering the information given above, you should re-evaluate all conclusions from your experiments.
Best Answer
There's a factor of \$\small \sqrt 3\$ for three phase