Wireless QI Phone Charger Powered by Raspberry Pi

By John74609

Updated 07 August 2024

I have a new phone and want the battery health to last as long as possible. Charging it to 100% overnight, every night, may reduce the battery capacity over time so I have been looking for a solution to help me to protect the battery.

Android does not offer a way to control the charging directly so I needed a solution external to the phone.

The Plan:

Build a solution to shut off the phone charger when it reaches a certain percentage by using a Raspberry Pi and a relay.

You can see the final board layout in a simple case on the second tab. Note that this is an original Raspberry Pi 1B, but the solution is likely to work with any Pi.

Bill of Materials:

Raspberry Pi (I used a 1B but any Pi should do, or even a Pico!)
5V Single Channel Relay Module 10A
5V 2A DC Power Adapter
USB Cable (to solder)
10 Watt USB Powered Qi Charging Pad (mine came from officeworks)

Additional Hardware:

An Android Phone (this guide uses an app called automate, I'm unsure of an iOS equivalent)
Soldering Iron

Details:

The solution works in two parts.

Firstly, I created a script that uses the Android Automate app ( a free app from llamalab).

The script performs the following steps:

Check if I am connected to my home WiFi
Check if the phone is currently being charged
If the battery level is over 85%, send an HTTP request to my Raspberry Pi

Secondly, I created a tiny web server running on a Raspberry Pi.

If this web server receives any request, it switches a relay to turn off the power to the phone charger. This is such a small script it would likely work on a Raspberry Pi Pico too!

#!/usr/bin/python
# Script to stop phone charging when an http request is received
# To stop the phone charging a relay is connected to a raspberry pi GPIO pin
# JKenyon 2024

# Libraries
import RPi.GPIO as GPIO
from time import sleep
import socket

# Define constants
SERVER_HOST = '0.0.0.0'
SERVER_PORT = 8001
RELAY_PIN = 24
SLEEP_TIME = 5*60*60 # 5 hours

# Define a simple web server that quits after it receives a connection
def waitForConnection():
  # https://www.codementor.io/@joaojonesventura/building-a-basic-http-server-from-scratch-in-python-1cedkg0842
  # Modified to exit when a connection is made

  # Create socket
  server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
  server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
  server_socket.bind((SERVER_HOST, SERVER_PORT))
  server_socket.listen(1)

  # Wait until we receive any connection (as we don’t parse anything this is pretty safe)
  client_connection, client_address = server_socket.accept()
  response = 'HTTP/1.0 200 OK\n\n'
  client_connection.sendall(response.encode())
  client_connection.close()

  # Close socket
  server_socket.close()

# Define a function to control the GPIO and switch off the charger
def switchOffChargerForTime(delay):
  GPIO.setmode(GPIO.BCM)
  GPIO.setup(RELAY_PIN, 0)
  sleep(delay)
  GPIO.setup(RELAY_PIN, 1)
  GPIO.cleanup()

while True:
  waitForConnection()
  switchOffChargerForTime(SLEEP_TIME)

The GPIO code is not necessarily the perfect way to control a relay. I chose to do it this way as the relay I have was not switching reliably at 3.3V. If you have a relay that is better behaved then you can change the power to the relay module to pin 1 (to supply 3.3V) and use GPIO.output(RELAY_PIN, GPIO.HIGH) and GPIO.output(RELAY_PIN, GPIO.LOW) to switch the relay.

The diagram in the second tab shows how everything is connected. I had originally planned to use the Raspberry Pi to supply the 5V to the charger, but this was a bit too much so I settled on using a separate power supply.