diff --git a/src/RainGauge.cpp b/src/RainGauge.cpp
index 43e3b514..b7ad831d 100644
--- a/src/RainGauge.cpp
+++ b/src/RainGauge.cpp
@@ -37,6 +37,7 @@
 // History:
 //
 // 20220830 Created
+// 20230716 Implemented sensor startup handling
 //
 // ToDo: 
 // -
@@ -71,6 +72,10 @@ typedef struct {
     uint8_t   head;
     uint8_t   tail;
 
+    /* Sensor startup handling */
+    bool      startupPrev; // previous state of startup
+    float     rainStartup; // rain gauge before startup 
+
     /* Rainfall of current day (can start anytime, but will reset on begin of new day) */
     uint8_t   tsDayBegin; // day of week
     float     rainDayBegin; // rain gauge @ begin of day
@@ -94,6 +99,8 @@ RTC_DATA_ATTR nvData_t nvData = {
    .rainBuf = {0}, 
    .head = 0,
    .tail = 0,
+   .startupPrev = false,
+   .rainStartup = 0,
    .tsDayBegin = 0xFF,
    .rainDayBegin = 0,
    .tsWeekBegin = 0xFF,
@@ -172,6 +179,8 @@ RainGauge::printCircularBuffer(void)
 void
 RainGauge::reset(void)
 {
+    nvData.startupPrev    = false;
+    nvData.rainStartup    = 0;
     nvData.tsDayBegin     = 0xFF;
     nvData.rainDayBegin   = 0;
     nvData.tsWeekBegin    = 0xFF;
@@ -222,19 +231,27 @@ RainGauge::timeStamp(tm t)
 }
 
 void
-RainGauge::update(tm t, float rain, float raingaugeMax)
+RainGauge::update(tm t, float rain, bool startup, float raingaugeMax)
 {
     uint8_t  head_tmp; // circular buffer; temporary head index
 
     // Seconds since Midnight
     uint32_t ts = timeStamp(t);
-    
+
     if (rain < nvData.rainPrev) {
-        nvData.rainOvf++;
+       // Startup change 0->1 detected
+       if (!nvData.startupPrev && startup) {
+           // Save last rain value before startup
+           nvData.rainStartup = nvData.rainPrev;
+       } else {
+           nvData.rainOvf++;
+       }
     }
+   
+    nvData.startupPrev = startup;
     nvData.rainPrev = rain;
     
-    rainCurr = (nvData.rainOvf * raingaugeMax) + rain;
+    rainCurr = (nvData.rainOvf * raingaugeMax) + nvData.rainStartup + rain;
 
     // Check if no saved data is available yet
     if (nvData.wdayPrev == 0xFF) {
diff --git a/src/RainGauge.h b/src/RainGauge.h
index 5318779d..f92bf532 100644
--- a/src/RainGauge.h
+++ b/src/RainGauge.h
@@ -38,6 +38,7 @@
 //
 // 20220830 Created
 // 20230330 Added changes for Adafruit Feather 32u4 LoRa Radio
+// 20230716 Implemented sensor startup handling
 //
 // ToDo: 
 // -
@@ -111,9 +112,11 @@ class RainGauge {
      * 
      * \param rain         rain gauge raw value
      * 
+     * \param startup      sensor startup flag
+     * 
      * \param rainGaugeMax overflow value; when reached, the rain gauge is reset to zero
      */  
-    void  update(tm timeinfo, float rain, float raingaugeMax = RAINGAUGE_MAX_VALUE);
+    void  update(tm timeinfo, float rain, bool startup = false, float raingaugeMax = RAINGAUGE_MAX_VALUE);
     
     
     /**
diff --git a/test/makefiles/Makefile_Tests.mk b/test/makefiles/Makefile_Tests.mk
index d537e1ae..89b62761 100644
--- a/test/makefiles/Makefile_Tests.mk
+++ b/test/makefiles/Makefile_Tests.mk
@@ -4,7 +4,8 @@ SRC_FILES = \
   $(PROJECT_SRC_DIR)/RainGauge.cpp \
 
 TEST_SRC_FILES = \
-  $(UNITTEST_SRC_DIR)/TestRainGaugeReal.c #\ 
+  $(UNITTEST_SRC_DIR)/TestRainGauge.c
+  #$(UNITTEST_SRC_DIR)/TestRainGaugeReal.c #\ 
   #$(UNITTEST_SRC_DIR)/TestRainGauge.c
   
 include $(CPPUTEST_MAKFILE_INFRA)
diff --git a/test/src/TestRainGauge.cpp b/test/src/TestRainGauge.cpp
index 5beb5c1e..269070a4 100644
--- a/test/src/TestRainGauge.cpp
+++ b/test/src/TestRainGauge.cpp
@@ -183,6 +183,14 @@ TEST_GROUP(TestRainGaugeMonthlyOv) {
   }
 };
 
+TEST_GROUP(TestRainGaugeStartup) {
+  void setup() {
+      rainGauge.reset();
+  }
+
+  void teardown() {
+  }
+};
 
 /*
  * Test rainfall during past hour (no rain gauge overflow)
@@ -1075,3 +1083,38 @@ TEST(TestRainGaugeMonthlyOv, Test_RainMonthlyOv) {
   
 }
 
+
+/*
+ * Test that rain gauge values are preserved after sensor startup,
+ * i.e. sensor reset or battery change
+ */
+TEST(TestRainGaugeStartup, TestRainStartup) {
+  tm        tm;
+  time_t    ts;
+  float     rainSensor;
+    
+  printf("< RainStartup >\n");
+   
+  setTime("2023-07-16 8:00:00", tm, ts);
+  DOUBLES_EQUAL(0, rainGauge.pastHour(), TOLERANCE);
+  DOUBLES_EQUAL(0, rainGauge.currentDay(), TOLERANCE);
+  DOUBLES_EQUAL(0, rainGauge.currentWeek(), TOLERANCE);
+
+  setTime("2023-07-16 8:05:00", tm, ts);
+  rainGauge.update(tm, rainSensor = 10.0);
+  DOUBLES_EQUAL(0, rainGauge.pastHour(), TOLERANCE);
+  DOUBLES_EQUAL(0, rainGauge.currentDay(), TOLERANCE);
+  DOUBLES_EQUAL(0, rainGauge.currentWeek(), TOLERANCE);
+
+  setTime("2023-07-16 8:10:00", tm, ts);
+  rainGauge.update(tm, rainSensor = 15.0);
+  DOUBLES_EQUAL(5, rainGauge.pastHour(), TOLERANCE);
+  DOUBLES_EQUAL(5, rainGauge.currentDay(), TOLERANCE);
+  DOUBLES_EQUAL(5, rainGauge.currentWeek(), TOLERANCE);
+
+  setTime("2023-07-16 8:15:00", tm, ts);
+  rainGauge.update(tm, rainSensor = 0, true);
+  DOUBLES_EQUAL(5, rainGauge.pastHour(), TOLERANCE);
+  DOUBLES_EQUAL(5, rainGauge.currentDay(), TOLERANCE);
+  DOUBLES_EQUAL(5, rainGauge.currentWeek(), TOLERANCE);
+}