There is no 2-way communication with a USB charger. That only happens on a PC. I can assure you, if you were to disassemble this charger, there would only be connections on 2 of the 4 pins (2 being power and 2 being TX/RX) on the USB port.
Any device that supplies power will have a maximum amperage rating and any device that draws power will have a power requirement.
Generally speaking, you need your power supply (ie, charger) to simply supply enough power. If your power supply can supply more power, fine. It makes no difference to the device. It's not the power supply determining how much current to "give" the device, but rather the device that determines how much power it needs to draw, up to the maximum the power supply can give.
Consider your home power circuits. They are typically 15 ampers. That doesn't mean when you plug in your TV, 15 amps are delivered to it and the TV explodes. The TV simply draws the amount of current it needs. The more current a circuit provides, the more quantity and power-hungry of devices you can supply with that circuit.
What happens when you try to turn on the microwave, dishwasher, and a blender all at once? The circuit breaker trips. That's exactly what will happen in any power supply. Generally, they will just shut off, but cheaper devices like this have a fuse:
Wrong. The method of communication is *very* simplistic, but it does occur. The charger has the D+ and D- lines either tied together or connected through a voltage divider to the VCC and GND lines. When the device sees the expected voltage on D+ and D-, or D+ and D- shorted together (it varies between apple, android, palm, etc), then the device will charge at its maximum rate. This is part of the USB spec, any charge pulled over 100ma must be negotiated with the host. In the case of chargers, the negotiation process is very simplistic. Do some research before you go making claims that have absolutely no basis in reality.[wikipedia.org]
The charger has the D+ and D- lines either tied together or connected through a voltage divider to the VCC and GND lines.When the device sees the expected voltage on D+ and D-, or D+ and D- shorted together (it varies between apple, android, palm, etc), then the device will charge at its maximum rate.
When I was researching charge-only USB cables, I saw the same D+, D- terminology. I thought these lines were for data transmission only, so why would they be in a charger?
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