Has anyone use an external battery and checked what the charging status indicate, does it says USB or AC. If it says AC what brand is your external battery charger. I have been using a Mophie Powerstation and it indicates USB while charging and it takes a very very long time.
For HTC devices and most, (but not all USB) charged devices:
AC means it is charging from a source that can not support a data connection.
USB, means the HTC
thinks the source can support a data connection and it may be attached to a shared USB port, so it restricts its energy draw.
There is a wiring difference in some charger ports and some "charge only" cables that tells the handset whether a data connection data is possible or not.
The reason it makes this distinction is that the normal USB port on a computer is only rated at .5 amps, or even if there might be more than half an amp available, the port might be shared, and pulling more than half an amp might canalization power from other devices causing them not to be able to function. Therefore, the USB specifications state that the phone must not draw more than half an amp if it "Thinks" its connected to anything that might be a computer.
The wall charger is rated at 1 amp. But it's port is wired to indicate this.
The phone detects this by measuring the resistance of the data pins tx/rx on the usb cable. If those are shorted together, the handset assumes that it is connected to a charge-only device, and it will draw up to 2 amps if the charger can support it.
This shorting of the two data pins can be established in one or two places.
1) in the USB cable.
2) in the charger
The HTC charger shorts the data pins, telling the phone its ok to go ahead and draw as much as it can get. (which the charger limits to 1 amp).
I have an
Anker battery pack.
It has two outlets, one rated at at .6 amps, the other rated at 2.0 amps.
Using a standard USB cable:
- The .6 amp port shows on the phone as being AC, meaning the data lines were shorted together.
- The 2 amp port shows as USB. (Probably to protect dumb devices such as mice or cheesy mp3 players etc, which might not know what to do with that much amperage).
However, using the USB cable that came with the Anker, both ports show up as AC, which means that the Anker USB cable has the data pins shorted, and can never be used for data.
Sure enough, using that Anker cable, the HTC thinks my laptop is the same as the wall charger, and it probably tries to draw more than half an amp, but the laptop is not bothered by this, but won't deliver more than half an amp.
Charging the HTC using the Anker 2 amp port with the Anker supplied usb cable allows the HTC to charge quite fast, faster than the wall charger. (I once timed it, but I forget the details). It was enough faster that I actually prefer charging from the battery pack than from the wall charger.
See also
USB pinout and wiring @ pinouts.ru (the part about USB power usage).
I hope that answers your question. Very pleased with my Anker, by the way. It will charge two phones at once, OR it will charge my HOX 4 time.
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