diff --git a/libraries/SITL/SIM_BattMonitor_SMBus.cpp b/libraries/SITL/SIM_BattMonitor_SMBus.cpp
index 4d827335b2..3e31f57167 100644
--- a/libraries/SITL/SIM_BattMonitor_SMBus.cpp
+++ b/libraries/SITL/SIM_BattMonitor_SMBus.cpp
@@ -16,7 +16,7 @@ SITL::SIM_BattMonitor_SMBus::SIM_BattMonitor_SMBus() :
     add_register("Manufacture Name", SMBusBattDevReg::MANUFACTURE_NAME, O_RDONLY);
     add_register("Manufacture Data", SMBusBattDevReg::MANUFACTURE_DATA, O_RDONLY);
 
-     set_register(SMBusBattDevReg::TEMP, (int16_t)(15 + 273.15));
+    set_register(SMBusBattDevReg::TEMP, (int16_t)((15 + 273.15)*10));
      // see update for voltage
      // see update for current
      // TODO: remaining capacity
diff --git a/libraries/SITL/SIM_BattMonitor_SMBus.h b/libraries/SITL/SIM_BattMonitor_SMBus.h
index f4eb89ec28..22a5ae54c6 100644
--- a/libraries/SITL/SIM_BattMonitor_SMBus.h
+++ b/libraries/SITL/SIM_BattMonitor_SMBus.h
@@ -1,5 +1,7 @@
 #include "SIM_I2CDevice.h"
 
+#pragma once
+
 namespace SITL {
 
 class SMBusBattDevReg : public I2CRegEnum {
diff --git a/libraries/SITL/SIM_BattMonitor_SMBus_Generic.h b/libraries/SITL/SIM_BattMonitor_SMBus_Generic.h
index aecd12a885..e24ae5466d 100644
--- a/libraries/SITL/SIM_BattMonitor_SMBus_Generic.h
+++ b/libraries/SITL/SIM_BattMonitor_SMBus_Generic.h
@@ -1,5 +1,7 @@
 #include "SIM_BattMonitor_SMBus.h"
 
+#pragma once
+
 namespace SITL {
 
 class SMBusBattGenericDevReg : public SMBusBattDevReg {
diff --git a/libraries/SITL/SIM_BattMonitor_SMBus_Rotoye.cpp b/libraries/SITL/SIM_BattMonitor_SMBus_Rotoye.cpp
new file mode 100644
index 0000000000..c4e9d85d08
--- /dev/null
+++ b/libraries/SITL/SIM_BattMonitor_SMBus_Rotoye.cpp
@@ -0,0 +1,20 @@
+#include "SIM_BattMonitor_SMBus_Rotoye.h"
+
+SITL::Rotoye::Rotoye() :
+    SIM_BattMonitor_SMBus_Generic()
+{
+    add_register("External Temperature", SMBusBattRotoyeDevReg::TEMP_EXT, O_RDONLY);
+
+    set_register(SMBusBattRotoyeDevReg::SERIAL, (uint16_t)39);
+}
+
+void SITL::Rotoye::update(const class Aircraft &aircraft)
+{
+    SIM_BattMonitor_SMBus_Generic::update(aircraft);
+
+    const uint32_t now = AP_HAL::millis();
+    if (now - last_temperature_update_ms > 1000) {
+        last_temperature_update_ms = now;
+        set_register(SMBusBattRotoyeDevReg::TEMP_EXT, int16_t(be16toh(word[SMBusBattRotoyeDevReg::TEMP]) + 100));  // it's a little warmer inside.... (10 degrees here)
+    }
+}
diff --git a/libraries/SITL/SIM_BattMonitor_SMBus_Rotoye.h b/libraries/SITL/SIM_BattMonitor_SMBus_Rotoye.h
new file mode 100644
index 0000000000..853472b430
--- /dev/null
+++ b/libraries/SITL/SIM_BattMonitor_SMBus_Rotoye.h
@@ -0,0 +1,35 @@
+#include "SIM_BattMonitor_SMBus_Generic.h"
+
+#include <AP_Common/Bitmask.h>
+
+/*
+
+Testing:
+
+param set BATT_MONITOR 19
+reboot
+
+*/
+
+namespace SITL {
+
+class SMBusBattRotoyeDevReg : public SMBusBattGenericDevReg {
+public:
+    static const uint8_t TEMP_EXT = 0x07;
+};
+
+class Rotoye : public SIM_BattMonitor_SMBus_Generic
+{
+public:
+
+    Rotoye();
+
+    uint8_t cellcount() const override { return 3; }
+
+    void update(const class Aircraft &aircraft) override;
+
+private:
+    uint32_t last_temperature_update_ms;
+};
+
+} // namespace SITL
diff --git a/libraries/SITL/SIM_I2C.cpp b/libraries/SITL/SIM_I2C.cpp
index 5068ae521a..fe22ea396c 100644
--- a/libraries/SITL/SIM_I2C.cpp
+++ b/libraries/SITL/SIM_I2C.cpp
@@ -24,6 +24,7 @@
 #include "SIM_ToshibaLED.h"
 #include "SIM_MaxSonarI2CXL.h"
 #include "SIM_BattMonitor_SMBus_Maxell.h"
+#include "SIM_BattMonitor_SMBus_Rotoye.h"
 
 #include <signal.h>
 
@@ -45,6 +46,7 @@ static IgnoredI2CDevice ignored;
 static ToshibaLED toshibaled;
 static MaxSonarI2CXL maxsonari2cxl;
 static Maxell maxell;
+static Rotoye rotoye;
 
 struct i2c_device_at_address {
     uint8_t bus;
@@ -57,7 +59,7 @@ struct i2c_device_at_address {
     { 1, 0x40, ignored }, // KellerLD
     { 1, 0x70, maxsonari2cxl },
     { 1, 0x76, ignored }, // MS56XX
-    { 2, 0x0B, maxell },
+    { 2, 0x0B, rotoye },
 };
 
 void I2C::init()