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I have a 5v battery connected to a mobile device on the VBUS and GND which is charging at 590mA. I would like to increase this to 900mA with BC1.2

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The Data+ and Data- are currently shorted otherwise there is no charge, my questions are: Does BC1.2 increase the charge by sending power through the Data+ line ? Is is possible to modify the cabling in the photo to reach a charge of 900mA ?

beaumondo
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    Charging current is determined by your device, since you already "informed" the device (by connecting D+/D- together) that it is a port with 1.5A capability. So, the device just can't take more current for internal reasons. You can't increase it by changing the port signature. – Ale..chenski Dec 04 '20 at 00:34

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To use BC1.2 the D+ and D- just have to be shorted and left floating, as you have done. These lines are not used to transmit any power. They simply inform the device that the Charging Port is capable to deliver up to 1.5A.

If the device, which is supposed to be charged, does not react to this signal, then it is not capable to charge with the BC1.2 spec.

Actually, check out this question here: What is the ideal way to handle data pins D+ and D- on a USB power adapter to be compatible with fast charging on devices?
The answers there explain all the intricate detail with the different ways the different manufactures might implement fast charging. As you can see, it really depends opon the device you use.

jusaca
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  • Thanks for clarifying about not transmitting any power. The device is capable of BC1.2, the manufacturer confirmed, and it works with a higher current using a USB car adapter cigarette plug, but it still only charges at 590mA. In some diagrams i have seen a 200ohms resistor, could that help ? – beaumondo Nov 27 '20 at 13:30
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    If the device would really be designed with the BC1.2 spec it should definitly work the way you build it. That it does not suggests that it is using some other standard, like the 2.7V mode or the 1.2V, which are explained further in the link I posted. – jusaca Nov 27 '20 at 13:46
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    Quick ways to find out: Either use two pairs of voltage dividers and check the behaviour of the device with both D+ and D- on 2.7V (or 1.2V respectively) or measure the voltage on the data lines of your USB adapter that seems to be able to charge with that higher current. – jusaca Nov 27 '20 at 13:49
  • You were right, the D+ line was connected to the GND, which it shouldnt have been. On shorting the D+ and D- the device now charges at 900mA – beaumondo Dec 01 '20 at 19:38