Plane: integrate BattMonitor exhausted method

BatteryMonitor object made static
Removed unused macros for battery voltage and current monitoring

ArduPlane/ArduPlane.pde

@@ -466,7 +466,7 @@ static int32_t altitude_error_cm;
 ////////////////////////////////////////////////////////////////////////////////
 // Battery Sensors
 ////////////////////////////////////////////////////////////////////////////////
-AP_BattMonitor battery;
+static AP_BattMonitor battery;
 
 ////////////////////////////////////////////////////////////////////////////////
 // Airspeed Sensors

ArduPlane/defines.h

@@ -199,10 +199,6 @@ enum log_messages {
 #define ALTITUDE_HISTORY_LENGTH 8       //Number of (time,altitude) points to
                                         // regress a climb rate from
 
-
-#define BATTERY_VOLTAGE(x) (x->voltage_average()*g.volt_div_ratio)
-#define CURRENT_AMPS(x) (x->voltage_average()-g.curr_amp_offset)*g.curr_amp_per_volt
-
 #define AN4                     4
 #define AN5                     5
 

ArduPlane/sensors.pde

@@ -50,16 +50,7 @@ static void read_battery(void)
 
     battery.read();
 
-    if (!usb_connected &&
-        battery.voltage() != 0 && 
-        g.fs_batt_voltage > 0 && 
-        battery.voltage() < g.fs_batt_voltage) {
-        low_battery_event();
-    }
-    if (!usb_connected &&
-        battery.monitoring() == AP_BATT_MONITOR_VOLTAGE_AND_CURRENT &&
-        g.fs_batt_mah > 0 && 
-        battery.pack_capacity() - battery.current_total_mah() < g.fs_batt_mah) {
+    if (!usb_connected && battery.exhausted(g.fs_batt_voltage, g.fs_batt_mah)) {
         low_battery_event();
     }
 }