Thanks to Zolly, I solved the RC-N3 battery drain

[bbteach]

A YouTuber named Zolly solved the problem of DJI controllers ( I my case the RC-N3 ) battery getting drained to keep Android phones charged. See his video here:

Using his trick I built this USB C wire:


I haven't put shrink tube on yet because I am still testing.

It is made up of the following components:
1 watt 15 volt Zener diode ( 1N4744A DO-41 ), WMYCONGCONG Latching Push Button Switch ( WGCD 85 ), AGOZ 6inch Right Angle USB C cable ( ASIN: B0B8TJM38V ).



Steps:

1. Strip back the outer and inner covering of the USB cable
2. Cut the RED wire
3. Solder the diode across the switch legs ( stripe on the phone end of the cable )
4. Solder the switch legs on to each end of the RED wire

Test results in the next post:

 

[bbteach]

Testing results:

Test setup:

• Start with RC-N3, phone and Neo batteries fully charged
• Turn on phone, RC-N3 controller and Neo ( in that order )
• Verify phone IS BEING CHARGED by the RC-N3
• Verify the Neo is streaming video to the phone
• Set a 15 minute timer and leave everything alone for 15 minutes

At the end of 15 minutes turned off the Neo and the RC-N3. Checked the phone charge level. As expected it was 100%. Turn off the phone.
Put the RC-N3 on charge power ( power supply was ONLY charging the RC-N3 ). Start a stopwatch.
It took 18 minutes for the RC-N3 lights to go out ( indicated it was fully charged ).

• Press the switch button on the custom USB cable
• Verify all batteries fully charged
• Start all 3 components
• Verify the phone is NOT being charged by the RC-N3 controller
• Leave the Neo streaming video to the phone for 15 minutes
• Shut off the Neo and the RC-N3
• Check the phone charge level ( 97% )
• Shut off the phone

At the end of 15 minutes and with all units powered off. Connect the RC-N3 to the power supply and time how long until all lights turn off.

Results:

• With the RC-N3 charging to phone it took 18 minutes to recharge the RC-N3
• With the RC-N3 NOT charging to phone it took 8 minutes to recharge to RC-N3
• 44% reduction in battery recharge time on the RC-N3 when it is NOT charging the phone

Over a longer period, the reduction in RC-N3 battery use may be even more pronounced.

 

[bbteach]

I asked Grok ( Beta 3 ) to analyze what I did and offer comment. I am astonished at how brilliant Grok is.

By way of design, it suggested a standard diode or a 5.1 volt Zener diode would have worked fine.

It also suggests the DJI design was done because it is important to keep the phone active, as it provides communication with the Neo and video for FPV. That was smart of it to consider a potential safety issue. However, I told it DJI allows the phone charging to be disabled on iPhones. It did not pickup my point that DJI does not see this as a safety feature for iPhone users.