Battery reporting keeps increasing not decreasing

[ahmedadelhosni]

Hello,

I have a normal door sensor based on My Slim node design. It has been running for around 3 months till now but the battery percentage is abnormal.

At the beginning I remember that the percentage begun as 72% so I thought maybe this is because my max voltage is defined as 3.3v not 3v. After some time, maybe 2 weeks it was 75%. It has been like this for like 2 months. Then I switched my gateway OFF for 3 weeks and switched it back ON now to see the battery voltage percentage and found it to be 80%

The batteries are two AAA 1.5v each.

Sketch:

/**
 * The MySensors Arduino library handles the wireless radio link and protocol
 * between your home built sensors/actuators and HA controller of choice.
 * The sensors forms a self healing radio network with optional repeaters. Each
 * repeater and gateway builds a routing tables in EEPROM which keeps track of the
 * network topology allowing messages to be routed to nodes.
 *
 * Created by Henrik Ekblad <henrik.ekblad@mysensors.org>
 * Copyright (C) 2013-2015 Sensnology AB
 * Full contributor list: https://github.com/mysensors/Arduino/graphs/contributors
 *
 * Documentation: http://www.mysensors.org
 * Support Forum: http://forum.mysensors.org
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 *
 *******************************
 *
 * REVISION HISTORY
 * Version 1.0 - Henrik Ekblad
 * 
 * DESCRIPTION
 * Motion Sensor example using HC-SR501 
 * http://www.mysensors.org/build/motion
 *
 */

#define MY_BAUD_RATE 9600 // For 1 MHz 

// Enable debug prints
#define MY_DEBUG
 
#ifdef MY_DEBUG
#define DEBUG
#endif

#ifdef DEBUG
#define DEBUG_SERIAL(x) Serial.begin(x)
#define DEBUG_PRINT(x) Serial.print(x)
#define DEBUG_PRINTLN(x) Serial.println(x)
#else
#define DEBUG_SERIAL(x)
#define DEBUG_PRINT(x) 
#define DEBUG_PRINTLN(x) 
#endif


// Enable and select radio type attached
#define MY_RADIO_NRF24
//#define MY_RADIO_RFM69


#if 0 
// Select soft/hardware signing method
#define MY_SIGNING_SOFT //!< Software signing
//#define MY_SIGNING_ATSHA204 //!< Hardware signing using ATSHA204A

// Enable node whitelisting
//#define MY_SIGNING_NODE_WHITELISTING {{.nodeId = GATEWAY_ADDRESS,.serial = {0x09,0x08,0x07,0x06,0x05,0x04,0x03,0x02,0x01}}}
// Enable this if you want destination node to sign all messages sent to this node.
#define MY_SIGNING_REQUEST_SIGNATURES


// SETTINGS FOR MY_SIGNING_SOFT
/// Set the soft_serial value to an arbitrary value for proper security (9 bytes)
#define MY_SIGNING_SOFT_SERIAL 0x11,0x02,0x03,0x04,0x05,0x06,0x07,0x08,0x09
/// Key to use for HMAC calculation in soft signing (32 bytes)
#define MY_SIGNING_SOFT_HMAC_KEY 0x10,0x20,0x30,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00

#define MY_SIGNING_SOFT_RANDOMSEED_PIN A7 //!< Unconnected analog pin for random seed

#endif

#include <SPI.h>
#include <MySensor.h>
unsigned long SLEEP_TIME = 120000; // Sleep time between reports (in milliseconds)
#define DIGITAL_INPUT_SENSOR 3   // The digital input you attached your motion sensor.  (Only 2 and 3 generates interrupt!)
#define INTERRUPT DIGITAL_INPUT_SENSOR-2 // Usually the interrupt = pin -2 (on uno/nano anyway)
#define CHILD_ID 0   // Id of the sensor child
#define CHILD_ID_BATTERY 1

//#define BATTERY_FULL 3000 // 3,000 millivolts for 2xAA (DOLA - changed to 5000 as it was tested on a laptop)
//#define BATTERY_ZERO 1900 // 1,900 millivolts (1.9V, limit for nrf24l01 without step-up. 2.8V limit for Atmega328 without BOD disabled))
#define VMIN 1900
#define VMAX 3300


long readVcc();

// Initialize motion message
MyMessage msg(CHILD_ID, V_TRIPPED);

unsigned int ADCValue;
double Voltage;
double Vcc;
long oldvoltage = 0;

void setup()  
{  
  pinMode(DIGITAL_INPUT_SENSOR, INPUT);      // sets the motion sensor digital pin as input
}

void presentation()  {
  // Send the sketch version information to the gateway and Controller
  sendSketchInfo("Door Sensor", "1.0");

  // Register all sensors to gw (they will be created as child devices)
  present(CHILD_ID, S_MOTION);

}

void loop()     
{     
  wait(25);       // Short delay to allow switch to properly settle
  
  // Read digital motion value
  boolean tripped = digitalRead(DIGITAL_INPUT_SENSOR) == HIGH; 
        
//  Serial.println(tripped);
//  send(msg.set(tripped?"OPEN":"CLOSED"));  // Send tripped value to gw (OPENHAB)
  send(msg.set(tripped?"1":"0"));  // Send tripped value to gw (Domoticz)
  
 /*
  Vcc = readVcc()/1000.0;
  ADCValue = analogRead(0);
  Voltage = (ADCValue / 1023.0) * Vcc;
*/
long voltage = readVcc();
//Serial.println(voltage);
  if (oldvoltage != voltage) { // Only send battery information if voltage has changed, to conserve battery.

    long batteryVolt = readVcc();
    DEBUG_PRINT("Battery voltage: "); DEBUG_PRINT(batteryVolt); DEBUG_PRINTLN(" mV");
    uint8_t batteryPcnt = constrain(map(batteryVolt,VMIN,VMAX,0,100),0,255);   
    DEBUG_PRINT("Battery percent: "); DEBUG_PRINT(batteryPcnt); DEBUG_PRINTLN(" %");
    sendBatteryLevel(batteryPcnt);
    
    
 //   sendBatteryLevel(round((voltage - BATTERY_ZERO) * 100.0 / (BATTERY_FULL - BATTERY_ZERO)));
    oldvoltage = voltage;
    
  }
//  Serial.print(Vcc);
//  Serial.print ( " " );
//  Serial.println(Voltage);
  
  // Sleep until interrupt comes in on motion sensor. Send update every two minute. 
  sleep(INTERRUPT,CHANGE);
}

long readVcc() {
  // From http://provideyourown.com/2012/secret-arduino-voltmeter-measure-battery-voltage/
  // Read 1.1V reference against AVcc
  // set the reference to Vcc and the measurement to the internal 1.1V reference
#if defined(__AVR_ATmega32U4__) || defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__)
  ADMUX = _BV(REFS0) | _BV(MUX4) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1);
#elif defined (__AVR_ATtiny24__) || defined(__AVR_ATtiny44__) || defined(__AVR_ATtiny84__)
  ADMUX = _BV(MUX5) | _BV(MUX0);
#elif defined (__AVR_ATtiny25__) || defined(__AVR_ATtiny45__) || defined(__AVR_ATtiny85__)
  ADMUX = _BV(MUX3) | _BV(MUX2);
#else
  ADMUX = _BV(REFS0) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1);
#endif

  delay(2); // Wait for Vref to settle
  ADCSRA |= _BV(ADSC); // Start conversion
  while (bit_is_set(ADCSRA, ADSC)); // measuring

  uint8_t low  = ADCL; // must read ADCL first - it then locks ADCH
  uint8_t high = ADCH; // unlocks both

  long result = (high << 8) | low;

  result = 1125300L / result; // Calculate Vcc (in mV); 1125300 = 1.1*1023*1000
  return result; // Vcc in millivolts
}

Code has lots of unused variables and commented lines and the signing is not compiled in the project. a bit messy and needs to be cleaned up.
Thanks.

[TheoL]

I think I remembered some graph on this forum. A battery will report a higher percentage when it's starting lose it's power. So the readings seem to be normal.

[AWI]

@ahmedadelhosni There is a (positive) voltage - temperature relation with Alkaline cells. So for Egypt it could be an explanation..

With lithium cells I also found that voltage tends to decrease during a "stress" period and returns slowly to a higher voltage.

[ahmedadelhosni]

Impressive and annoying

So is there any workaround to solve this ? looks like it is a normal behavior and reproducible.

[AWI]

@ahmedadelhosni There is nothing to solve ... My Electric car runs 40 km on a load in winter (-2 C) and 80km in summer (22 C). Your sensor could run a few years if well built and using low self discharge batteries.

A graph of one of my sensors...you can see the temperature effect (although small).

[hek]

Perpetuum mobile

[AWI]

@hek with the climate temperature rising each year... yes