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I have a variety of fast charge plugs and cables as well as an Anker power bank and a Nitecore NB10000. They support up to 3A @ 5V, 2A @ 9V and 1.5A @ 12V (i.e. 15W-18W). I believe the S10e is limited to 15W charging speed (1.67A @ 9V).

No matter what I use (even using the official Samsung plug and cable) on my S10e, the charge speed seems completely variable. I'm testing with both 3C Battery Monitor and an in-line USB power meter.

The fastest speeds I see at 5V are about 3W-5W with all power sources. Every now and then by plugging and re-plugging I can get it to switch to 9V and then it will charge at 9W. How is the charging voltage negotiated by the phone?

Another issue is every now and then the phone thinks it has moisture in the charging port (using exactly the same bone dry connector as the last 30 mins) and will be stuck like this every time I plug it in for 5 minutes. How is the moisture determined and how do I reduce the false positives?

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    The reason is simple: Samsung still uses the outdated proprietary charging methods "Qualcomm Quick Charge 2.0" respectively Samsung "Adaptiv Fast Charge" instead of using the standardized USB-PD (Power Delivery) which is included in "Qualcomm Quick Charge 4.0".
    – Robert
    Nov 19, 2020 at 14:33
  • I wasn't aware that many phones had started using USB-PD. And what are the metrics for it choosing what voltage to charge at?
    – Turkeyphant
    Nov 19, 2020 at 21:14
  • USB-PD uses a special communication channel between charger, cable and device to negotiate the capabilities and calculate the possible charge modes.
    – Robert
    Nov 19, 2020 at 22:28
  • I meant how do QC chargers negotiate this?
    – Turkeyphant
    Nov 20, 2020 at 11:35
  • As I said the method is proprietary. Not sure if it is fully documented. As far as I know they measure the resistor between certain USB connectors in the cable. And based on the result assume if the other side supports QC and which version.
    – Robert
    Nov 20, 2020 at 11:38

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This is Samsung's fault but also potentially the fault of the charging bricks.

Samsung implements outdated and disallowed proprietary charging methods "Qualcomm Quick Charge 2.0" respectively Samsung "Adaptive Fast Charge" instead of using the standardized USB-PD (Power Delivery) which is included in "Qualcomm Quick Charge 4.0".

These methods are slower and less reliable than USB-PD.

The issue is that some chargers also attempt to support disallowed proprietary charging protocols instead of supporting USB-PD as they should be according to the USB-C spec. For example Anker's PowerIQ3 technology cycles between PD, QC 3.0/2.0, Samsung, and Apple modes in an attempt to fool older phones to work with it. This doesn't actually work.

This means that when a charger is connected to a Samsung phone, it initially negotiates USB-PD first and charges at full speeds according to the spec. However the phone will then decide to check the D+ and D- lines for a proprietary charging method, and that causes the charger to drop out of USB-PD mode.

This is why you are getting slow speeds.

When the power brick and the phone implement multiple proprietary charging modes in addition to USB-PD everything goes wrong. Proprietary methods were disallowed in the USB-C spec for this very reason. If the phone simply stuck with the spec and implemented USB Type-C current, USB PD, and USB BC 1.2, you'd get consistent and correct behaviour all of the time and not have to wait hours for your phone to charge.

USB-PD should always win but the way the complicated proprietary charging mode switching Anker have built into these chargers you end up losing out. If the phone simply did not implement these disallowed proprietary charging methods and only used followed the proper spec you wouldn't have these issues.

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