commander: Add missing parameter definition

src/modules/commander/commander_helper.cpp

@@ -291,7 +291,7 @@ float battery_remaining_estimate_voltage(float voltage, float discharged, float
 	static param_t bat_v_load_drop_h;
 	static float bat_v_empty = 3.4f;
 	static float bat_v_full = 4.2f;
-	static float bat_v_load_drop = 0.1f;
+	static float bat_v_load_drop = 0.06f;
 	static int bat_n_cells = 3;
 	static float bat_capacity = -1.0f;
 	static bool initialized = false;

src/modules/commander/commander_params.c

@@ -67,6 +67,16 @@ PARAM_DEFINE_FLOAT(BAT_V_EMPTY, 3.4f);
  */
 PARAM_DEFINE_FLOAT(BAT_V_CHARGED, 4.2f);
 
+/**
+ * Voltage drop per cell on 100% load
+ *
+ * This implicitely defines the internal resistance
+ * to maximum current ratio and assumes linearity.
+ *
+ * @group Battery Calibration
+ */
+PARAM_DEFINE_FLOAT(BAT_V_LOAD_DROP, 0.06f);
+
 /**
  * Number of cells.
  *