Improved battery calculations for devices without dedicated PMU

Display.h

@@ -266,14 +266,22 @@ void draw_battery_bars(int px, int py) {
     if (battery_ready) {
       if (battery_installed) {
         float battery_value = battery_percent;
+
+        // Disable charging state display for now, since
+        // boards without dedicated PMU are completely
+        // unreliable for determining actual charging state.
+        bool disable_charge_status = false;
+        if (battery_indeterminate && battery_state == BATTERY_STATE_CHARGING) {
+          disable_charge_status = true;
+        }
         
-        if (battery_state == BATTERY_STATE_CHARGING) {
+        if (battery_state == BATTERY_STATE_CHARGING && !disable_charge_status) {
           battery_value = charge_tick;
           charge_tick += 3;
           if (charge_tick > 100) charge_tick = 0;
         }
 
-        if (battery_indeterminate && battery_state == BATTERY_STATE_CHARGING) {
+        if (battery_indeterminate && battery_state == BATTERY_STATE_CHARGING && !disable_charge_status) {
           stat_area.fillRect(px-2, py-2, 18, 7, SSD1306_BLACK);
           stat_area.drawBitmap(px-2, py-2, bm_plug, 17, 7, SSD1306_WHITE, SSD1306_BLACK);
         } else {

Power.h

@@ -121,7 +121,7 @@ void measure_battery() {
           }
         } else {
           if (bat_voltage_dropping == true) {
-            if (bat_delay_diff > 0.008) {
+            if (bat_delay_diff > 0.01) {
               bat_voltage_dropping = false;
               bat_state_change_v = battery_voltage;
               // SerialBT.printf("STATE CHANGE to CHARGE at delta=%.3fv. State change v is now %.3fv.\n", bat_delay_diff, bat_state_change_v);