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USB charging cable for quick charging


ygoe
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The a6300 has a USB port for charging the battery inside. This uses 1.5 A with the chargers from Sony. Both the one that came with the camera (an AC adapter) and the one for my Xperia smartphone (a wall charger) work fine. But anything else can only make the camera charge with 0.5 A which takes at least three times as long. While some other chargers, including Anker's PowerIQ, can convince the smartphone that it should use 1.5 A, the camera isn't at all interested and remains at 0.5 A.

So my question is, how should a USB cable be designed to signal the a6300 camera that this is a Sony charger and it should use the full charging speed? The chargers do supply that current, the Anker one goes up to 2.4 A per port, but that doesn't help if the device won't use it.

From my experiments, I believe that I have setups with the USB data ports both open and short-circuited. Both isn't the solution. I guess there needs to be some kind of resistance of a certain value, or even a custom communication logic. I don't have equipment yet to measure the single lines of a USB plug.

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I could now measure the chargers and cables I used. The result is this: The Sony chargers have the data lines short-circuited. A Samsung QC 2.0 charger has 800 kΩ on the data lines and the Anker PowerIQ has no measurable connection while off. My assumptions about the cables I used were correct. One of them is short-circuited, the other is open.

A resistance isn't to be found when the Sony chargers are off. Even with the Sony charger turned on, a Sony camera (or phone) attached to the V+ and V- lines only, the D+ and D- lines are still short-circuited. Now I can only imagine that there's some communication protocol across other wires which probably cannot easily be injected by a cable or an adapter.

Has anybody ever managed to charge the a6300 faster than 0.5 A with a non-Sony charger?

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From my understanding of the exchange linked below, the "charger", as opposed to the "chargee", is perfectly dumb and supplies however much the chargee requires as current draw, within the charger's capabilities of course. If the chargee tries to draw more than the charger can supply, the charger's voltage drops. Which in turn the chargee senses so it reduces its demand on the charger. From my further understanding, there is no additional "handshake protocol" involved. Except that the charger (or cable) have their D+ and D- lines shortened, to indicate, what they are. You may come to different conclusions. See this.

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It is my understanding, too, that the chargee takes the current it wants. So it needs to be told how much current to take. This could be through shorted D+/D- wires, which is not the case with a6300. It could also be through voltage sensing, but the chargers I tried with all provide more than 1.5 A and the voltage shouldn't drop. (I can't measure that fast enough.)

After reading the plans on the linked page, I also measured resistance between V+/GND and D+/D- but again couldn't find any connection in the Sony chargers. The Anker one has 800 kΩ across D+/D- and 400 kΩ to each V+/GND wires, which doesn't seem like resistors but rather an inactive IC (which PowerIQ has – Anker chargers are not dumb but in some way active themselves).

I've just found another charger, some tiny untrusty China adapter. It's labelled to provide 5.3 V and 1 A. The a6300 actually takes 0.9 A out of it! In this adapter I measured resistors between 25 and 30 kΩ between D+/D- and V+/GND. Maybe this does actually make a difference. But like I said, I couldn't find such a pattern in the Sony charger so I cannot copy it for use with other chargers.

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