SYS_STATUS and rollover values for batteries (#1850)

message_definitions/v1.0/common.xml

@@ -5063,9 +5063,9 @@
       <field type="uint32_t" name="onboard_control_sensors_enabled" enum="MAV_SYS_STATUS_SENSOR" print_format="0x%04x">Bitmap showing which onboard controllers and sensors are enabled:  Value of 0: not enabled. Value of 1: enabled.</field>
       <field type="uint32_t" name="onboard_control_sensors_health" enum="MAV_SYS_STATUS_SENSOR" print_format="0x%04x">Bitmap showing which onboard controllers and sensors have an error (or are operational). Value of 0: error. Value of 1: healthy.</field>
       <field type="uint16_t" name="load" units="d%">Maximum usage in percent of the mainloop time. Values: [0-1000] - should always be below 1000</field>
-      <field type="uint16_t" name="voltage_battery" units="mV" invalid="UINT16_MAX">Battery voltage, UINT16_MAX: Voltage not sent by autopilot</field>
-      <field type="int16_t" name="current_battery" units="cA" invalid="-1">Battery current, -1: Current not sent by autopilot</field>
-      <field type="int8_t" name="battery_remaining" units="%" invalid="-1">Battery energy remaining, -1: Battery remaining energy not sent by autopilot</field>
+      <field type="uint16_t" name="voltage_battery" units="mV" invalid="UINT16_MAX">Battery voltage, UINT16_MAX: Voltage not sent by autopilot. Value is ambiguous on multi-battery systems. BATTERY_STATUS is a recommended alternative.</field>
+      <field type="int16_t" name="current_battery" units="cA" invalid="-1">Battery current, -1: Current not sent by autopilot. Value may overflow/rollover for very high currents (&gt; 327.67A). Value is ambiguous on multi-battery systems. BATTERY_STATUS is a recommended alternative.</field>
+      <field type="int8_t" name="battery_remaining" units="%" invalid="-1">Battery energy remaining, -1: Battery remaining energy not sent by autopilot. Value is ambiguous on multi-battery systems. BATTERY_STATUS is a recommended alternative.</field>
       <field type="uint16_t" name="drop_rate_comm" units="c%">Communication drop rate, (UART, I2C, SPI, CAN), dropped packets on all links (packets that were corrupted on reception on the MAV)</field>
       <field type="uint16_t" name="errors_comm">Communication errors (UART, I2C, SPI, CAN), dropped packets on all links (packets that were corrupted on reception on the MAV)</field>
       <field type="uint16_t" name="errors_count1">Autopilot-specific errors</field>
@@ -6397,12 +6397,12 @@
       <field type="uint8_t" name="id" instance="true">Battery ID</field>
       <field type="uint8_t" name="battery_function" enum="MAV_BATTERY_FUNCTION">Function of the battery</field>
       <field type="uint8_t" name="type" enum="MAV_BATTERY_TYPE">Type (chemistry) of the battery</field>
-      <field type="int16_t" name="temperature" units="cdegC">Temperature of the battery. INT16_MAX for unknown temperature.</field>
-      <field type="uint16_t[10]" name="voltages" units="mV">Battery voltage of cells 1 to 10 (see voltages_ext for cells 11-14). Cells in this field above the valid cell count for this battery should have the UINT16_MAX value. If individual cell voltages are unknown or not measured for this battery, then the overall battery voltage should be filled in cell 0, with all others set to UINT16_MAX. If the voltage of the battery is greater than (UINT16_MAX - 1), then cell 0 should be set to (UINT16_MAX - 1), and cell 1 to the remaining voltage. This can be extended to multiple cells if the total voltage is greater than 2 * (UINT16_MAX - 1).</field>
-      <field type="int16_t" name="current_battery" units="cA">Battery current, -1: autopilot does not measure the current</field>
-      <field type="int32_t" name="current_consumed" units="mAh">Consumed charge, -1: autopilot does not provide consumption estimate</field>
-      <field type="int32_t" name="energy_consumed" units="hJ">Consumed energy, -1: autopilot does not provide energy consumption estimate</field>
-      <field type="int8_t" name="battery_remaining" units="%">Remaining battery energy. Values: [0-100], -1: autopilot does not estimate the remaining battery.</field>
+      <field type="int16_t" name="temperature" units="cdegC" invalid="INT16_MAX">Temperature of the battery. INT16_MAX for unknown temperature.</field>
+      <field type="uint16_t[10]" name="voltages" units="mV" invalid="[UINT16_MAX]">Battery voltage of cells 1 to 10 (see voltages_ext for cells 11-14). Cells in this field above the valid cell count for this battery should have the UINT16_MAX value. If individual cell voltages are unknown or not measured for this battery, then the overall battery voltage should be filled in cell 0, with all others set to UINT16_MAX. If the voltage of the battery is greater than (UINT16_MAX - 1), then cell 0 should be set to (UINT16_MAX - 1), and cell 1 to the remaining voltage. This can be extended to multiple cells if the total voltage is greater than 2 * (UINT16_MAX - 1).</field>
+      <field type="int16_t" name="current_battery" units="cA" invalid="-1">Battery current, -1: autopilot does not measure the current. Value may overflow/rollover for very high currents (&gt; 327.67A)</field>
+      <field type="int32_t" name="current_consumed" units="mAh" invalid="-1">Consumed charge, -1: autopilot does not provide consumption estimate</field>
+      <field type="int32_t" name="energy_consumed" units="hJ" invalid="-1">Consumed energy, -1: autopilot does not provide energy consumption estimate</field>
+      <field type="int8_t" name="battery_remaining" units="%" invalid="-1">Remaining battery energy. Values: [0-100], -1: autopilot does not estimate the remaining battery.</field>
       <extensions/>
       <field type="int32_t" name="time_remaining" units="s">Remaining battery time, 0: autopilot does not provide remaining battery time estimate</field>
       <field type="uint8_t" name="charge_state" enum="MAV_BATTERY_CHARGE_STATE">State for extent of discharge, provided by autopilot for warning or external reactions</field>