Maybe someone can help, I’m struggling to get this right. I want to use Adafruit’s MAX17048 LiPo battery gauge:
I tried to take inspiration from this thread:
Ok so I tried modifying a-marcel’s code and got it to at least produce some output but the numbers seem wildly wrong:
[18:28:14][D][sensor:127]: 'Voltage': Sending state 3616.25000 with 0 decimals of accuracy
[18:28:14][D][sensor:127]: 'Percentage': Sending state 3.10937 with 0 decimals of accuracy
I confess that I really don’t understand what this is doing or why we need all these bit shift operators.
void update() override {
float voltage = 1.25f * (float)(read16(MAX17043_VCELL) >> 4);
voltage_sensor->publish_state(voltage);
uint16_t percentage_tmp = read16(MAX17043_SOC);
float percentage = (float)((percentage_tmp >> 8) + 0.003906f * (percentage_tmp & 0x00ff));
percentage_sensor->publish_state(percentage);
}
Why all the complicated formulas? Does the sensor not produce a simple voltage number and percentage so the data has to be massaged like this?
Ok…so I think I have this solved but maybe someone else can check my work. I copied these formulas from the source code of the Adafruit driver:
So now my code looks like this:
void update() override {
//float voltage = 1.25f * (float)(read16(MAX17048_VCELL) >> 4);
float voltage = (float)(read16(MAX17048_VCELL)) * 78.125 / 1000000;
voltage_sensor->publish_state(voltage);
uint16_t percentage_tmp = read16(MAX17048_SOC);
//float percentage = (float)((percentage_tmp >> 8) + 0.003906f * (percentage_tmp & 0x00ff));
float percentage = (float)(percentage_tmp) / 256;
percentage_sensor->publish_state(percentage);
}
Now it produces outputs that look like a voltage and percentage:
[06:24:58][D][sensor:127]: 'Voltage': Sending state 3.56000 with 0 decimals of accuracy
[06:24:58][D][sensor:127]: 'Percentage': Sending state 93.23047 with 0 decimals of accuracy
Does it look right to you? Am I missing anything?
The values are a bit odd, a fully charged battery started at 103% and 4.2V. Methinks my formulas aren’t quite optimized correctly.
but at least I can watch the values change as the battery discharges.
This is working great, if anyone else needs a solution for monitoring battery life. Here’s the full code in case anyone else needs it.
MAX17048_component.h - put this file in your esphome folder:
#include "esphome.h"
#define MAX17048_ADDRESS 0x36
#define MAX17048_VCELL 0x02 // voltage
#define MAX17048_SOC 0x04 // percentage
#define MAX17048_MODE 0x06
#define MAX17048_VERSION 0x08
#define MAX17048_CONFIG 0x0c
#define MAX17048_COMMAND 0xfe
class MAX17048Sensor : public PollingComponent, public Sensor {
public:
Sensor *voltage_sensor = new Sensor();
Sensor *percentage_sensor = new Sensor();
MAX17048Sensor() : PollingComponent(10000) {}
void setup() override {
// Initialize the device here. Usually Wire.begin() will be called in here,
// though that call is unnecessary if you have an 'i2c:' entry in your config
ESP_LOGD("custom", "Starting up MAX17048 sensor");
Wire.begin();
}
uint16_t read16(uint8_t reg) {
uint16_t temp;
Wire.begin();
Wire.beginTransmission(MAX17048_ADDRESS);
Wire.write(reg);
Wire.endTransmission();
Wire.requestFrom(MAX17048_ADDRESS, 2);
temp = (uint16_t)Wire.read() << 8;
temp |= (uint16_t)Wire.read();
Wire.endTransmission();
return temp;
}
void update() override {
float voltage = (float)(read16(MAX17048_VCELL)) * 78.125 / 1000000;
voltage_sensor->publish_state(voltage);
uint16_t percentage_tmp = read16(MAX17048_SOC);
float percentage = (float)(percentage_tmp) / 256;
percentage_sensor->publish_state(percentage);
}
};
Put this in your ‘includes’:
esphome:
includes:
- MAX17048_component.h
and this in your sensor section:
- platform: custom
lambda: |-
auto max17048_sensor = new MAX17048Sensor();
App.register_component(max17048_sensor);
return {max17048_sensor->voltage_sensor, max17048_sensor->percentage_sensor};
sensors:
- name: "Voltage"
unit_of_measurement: V
accuracy_decimals: 2
- name: "Percentage"
unit_of_measurement: '%'