Init. battery voltage from ADC reading, instead of fixed value (#3761)

src/Power.cpp

@@ -223,7 +223,17 @@ class AnalogBatteryLevel : public HasBatteryLevel
             raw = raw / BATTERY_SENSE_SAMPLES;
             scaled = operativeAdcMultiplier * ((1000 * AREF_VOLTAGE) / pow(2, BATTERY_SENSE_RESOLUTION_BITS)) * raw;
 #endif
-            last_read_value += (scaled - last_read_value) * 0.5; // Virtual LPF
+
+            if (!initial_read_done) {
+                // Flush the smoothing filter with an ADC reading, if the reading is plausibly correct
+                if (scaled > last_read_value)
+                    last_read_value = scaled;
+                initial_read_done = true;
+            } else {
+                // Already initialized - filter this reading
+                last_read_value += (scaled - last_read_value) * 0.5; // Virtual LPF
+            }
+
             // LOG_DEBUG("battery gpio %d raw val=%u scaled=%u filtered=%u\n", BATTERY_PIN, raw, (uint32_t)(scaled), (uint32_t)
             // (last_read_value));
         }
@@ -357,6 +367,8 @@ class AnalogBatteryLevel : public HasBatteryLevel
     const float noBatVolt = (OCV[NUM_OCV_POINTS - 1] - 500) * NUM_CELLS;
     // Start value from minimum voltage for the filter to not start from 0
     // that could trigger some events.
+    // This value is over-written by the first ADC reading, it the voltage seems reasonable.
+    bool initial_read_done = false;
     float last_read_value = (OCV[NUM_OCV_POINTS - 1] * NUM_CELLS);
     uint32_t last_read_time_ms = 0;