Why Android smartphone is not charging from a weak charge?

Question

Android

Once upon a time there was a case of a friend's Galaxy S2 simply did not charge from old chargers on a half-lamp.
Now I don’t have Galaxy at hand, I’m experimenting with Motorola Photon Q. The same effect, everything works from charging at 1-2 amperes, it doesn’t work from 500mA. At the same time, the phone can be charged, for example, from USB 2.0, and there the current cannot be more than 500 mA.
Charges are checked - there is a current, the voltage is appropriate. I checked including the resistance in charging and measuring the voltage. For example, charging for an iPad at 2.1A when the resistance is turned on at 2 ohms gives more than 4 volts. 500mA of charging naturally give out volts, or sometimes they turn off altogether, then I just take more resistance.
Actually, what's the matter here? Is it something to do with the firmware, maybe it limits charging? Maybe it's somehow controlled by the hardware? Maybe newfangled chargers not only work on power, but also betray something on the data bus?
Update:
In general, we close Data + and Data- (those in the middle) and in most cases everything will work. For iPhones and other fastidious animals
, the link is rones.su/techno/zaryadka-mobilynika-po-usb.html

Answer 1

In general, we close Data + and Data- (those in the middle) and in most cases everything will work. For iPhones and other fastidious animals
, the link is rones.su/techno/zaryadka-mobilynika-po-usb.html

Answer 2

According to rumors, iron manufacturers are slightly expanding the usb 2.0 specification and there you can really load higher.
type in google - usb charging downstream port