diff --git a/MethodicConfigurator/ArduCopter_configuration_steps.json b/MethodicConfigurator/ArduCopter_configuration_steps.json
index 0817e26..6184250 100644
--- a/MethodicConfigurator/ArduCopter_configuration_steps.json
+++ b/MethodicConfigurator/ArduCopter_configuration_steps.json
@@ -102,6 +102,7 @@
         },
         "derived_parameters": {
             "BATT_ARM_VOLT": { "New Value": "(vehicle_components['Battery']['Specifications']['Number of cells']-1)*0.1+(vehicle_components['Battery']['Specifications']['Volt per cell crit']+0.3)*vehicle_components['Battery']['Specifications']['Number of cells']", "Change Reason": "Don’t allow arming below this voltage" },
+            "BATT_CAPACITY": { "New Value": "(vehicle_components['Battery']['Specifications']['Capacity mAh'])", "Change Reason": "Total battery capacity specified in the component editor" },
             "BATT_CRT_VOLT": { "New Value": "(vehicle_components['Battery']['Specifications']['Volt per cell crit'])*vehicle_components['Battery']['Specifications']['Number of cells']", "Change Reason": "(Critical voltage + 0.0) x no. of cells" },
             "BATT_LOW_VOLT": { "New Value": "(vehicle_components['Battery']['Specifications']['Volt per cell low'])*vehicle_components['Battery']['Specifications']['Number of cells']", "Change Reason": "(Low voltage + 0.0) x no. of cells" },
             "MOT_BATT_VOLT_MAX": { "New Value": "(vehicle_components['Battery']['Specifications']['Volt per cell max']+0.0)*vehicle_components['Battery']['Specifications']['Number of cells']", "Change Reason": "(Max voltage + 0.0) x no. of cells" },
diff --git a/MethodicConfigurator/ArduPlane_configuration_steps.json b/MethodicConfigurator/ArduPlane_configuration_steps.json
index 0817e26..6184250 100644
--- a/MethodicConfigurator/ArduPlane_configuration_steps.json
+++ b/MethodicConfigurator/ArduPlane_configuration_steps.json
@@ -102,6 +102,7 @@
         },
         "derived_parameters": {
             "BATT_ARM_VOLT": { "New Value": "(vehicle_components['Battery']['Specifications']['Number of cells']-1)*0.1+(vehicle_components['Battery']['Specifications']['Volt per cell crit']+0.3)*vehicle_components['Battery']['Specifications']['Number of cells']", "Change Reason": "Don’t allow arming below this voltage" },
+            "BATT_CAPACITY": { "New Value": "(vehicle_components['Battery']['Specifications']['Capacity mAh'])", "Change Reason": "Total battery capacity specified in the component editor" },
             "BATT_CRT_VOLT": { "New Value": "(vehicle_components['Battery']['Specifications']['Volt per cell crit'])*vehicle_components['Battery']['Specifications']['Number of cells']", "Change Reason": "(Critical voltage + 0.0) x no. of cells" },
             "BATT_LOW_VOLT": { "New Value": "(vehicle_components['Battery']['Specifications']['Volt per cell low'])*vehicle_components['Battery']['Specifications']['Number of cells']", "Change Reason": "(Low voltage + 0.0) x no. of cells" },
             "MOT_BATT_VOLT_MAX": { "New Value": "(vehicle_components['Battery']['Specifications']['Volt per cell max']+0.0)*vehicle_components['Battery']['Specifications']['Number of cells']", "Change Reason": "(Max voltage + 0.0) x no. of cells" },