RK2020 – Fast charge mod by Bozzy

!!!Attention!!! This mod is not needed on new revision units. The new revision units do not have a reset button located near the speaker cut out on the bottom of the unit.

PART 1: Installing 2 A charging module

What it does:

• Fast charges your RK2020 up to 2 A charging current.
• Provides a hardware battery indicator whilst charging (4 LEDs on module indicate 25%, 50%, 75%, and 100%)
• Provide an alternative charging method in case the onboard charging circuit fails or is damaged.

1. You need three wires to successfully complete this mod.
2. Solder VIN on your 2 A charging module to any one of the orange points marked on the diagram. You only need to solder to one of these, so choose the one that is easiest for you.
3. Solder GND/BAT- on the module to BT- on your board, and solder BAT+ on your module to BT+ on the board.

Potential problems:
• Damaged FB2/lifted pad. If FB2 is damaged, solder the wire on the FB2 marked pad in the diagram. The device should still charge through the module.
• If the FB2 pad is lifted, you can solder to any of the two orange marked pads on the USB C port shown in the diagram above. The battery should still be charged by the module.

PART 2: Using reset button as hardware battery monitor

What it does:

• Allows the 4 built in LEDs on the charging module to be used on demand at the click of a button to indicate battery level
• More accurate (although not precise) method of measuring battery charge compared to current software solutions

1. You need to have already installed the charging module from part 1 for this mod to work.
2. Locate your reset switch, and de-solder the two legs marked in green. You will need to also either bend the legs up off the board or lift the pads by heating/scraping with a knife.
3. You can use a multi-meter to measure resistance between either of the two legs and ground. Place one probe onto a shielding (USB shielding, SD card shielding) or a ground point (BAT – or GND on module). If the legs are soldered you will get about 1 kΩ of resistance. When the legs are un-soldered you should have a broken circuit, (infinite resistance) and multi-meter will not give a reading. (If reading is 0 then you have a short to ground).

4. Finally solder the yellow wire as shown in the diagram above. Test by pressing the reset switch. A single press should activate the LEDs on the module to show battery level.

Potential problems:

• Reset button doesn’t indicate battery level whilst screen is on. You can put the device to sleep mode and then press the reset button to show battery level.
• If your LEDs turn on spontaneously without the press of either reset switch or the switch on the module, then you have not correctly de-soldered the two legs on the reset switch.
• The reset switch nor the switch on the module work anymore. This is again caused by a short to ground. Check you de-soldering and try again. Measure resistance between the legs marked in green and ground.

Alternative reset button mod:

You will need to de-solder and completely remove the original reset switch. Position your module such that when the button is pressed, it activates the key switch on the module.

Special Thanks:

Alwaysbefun – Check out his Youtube video on completing this mod and the original idea. https://www.youtube.com/watch?v=jLCZh3cRG4Q
Bozzy – Creating the guide, diagrams and reset switch mod.
Steven Rios – Coming up with the idea of positioning the module to use as a HW battery monitor.
Christian Haitian – Hosting the guides and maintaining the RK2020 wiki. https://github.com/christianhaitian/rk2020/wiki