improve battery tracking

lib/Battery/battery.cpp

@@ -33,6 +33,12 @@ double Battery::getBatteryVoltage() {
     return (int)(res*100+0.5)/100.0;
 }
 
+bool Battery::isBatteryLow(uint8_t percent) {
+    if (this->getBatteryPercent() <= percent && this->batteryVoltage > this->absurdLowVoltage)
+        return true;
+    return false;
+}
+
 double Battery::readInputVoltage() {
     // Reference voltage is 3v3 so maximum reading is 3v3 = 4095 in range 0 to 4095
     double reading = analogRead(this->pin);

lib/Battery/battery.h

@@ -73,13 +73,28 @@ class Battery {
          */
         uint8_t getBatteryPercent()   {return this->batteryPercent;}
 
+        /**
+         * @brief Checks if the battery is low.
+         * 
+         * The function will also return false if the battery voltage is
+         * absurd low. This is for the case that the uController is powered
+         * by usb and no battery is connected.
+         * 
+         * @param percent the limit the battery have to
+         * @return true if the battery is low
+         * @return false if the battery is high
+         */
+        bool isBatteryLow(uint8_t percent);
+
     private:
         double readInputVoltage();
         void calculateBatteryVoltage();
         void calculateBatteryPercent();
 
+        uint8_t absurdLowVoltage = 5;
         uint8_t pin;
         uint8_t batteryPercent;
+        uint8_t batteryLowPercent = 10;
         uint16_t delay = 20000;
         uint32_t r1;
         uint32_t r2;