diff --git a/include/power.h b/include/power.h
index a1033041..12e8c032 100644
--- a/include/power.h
+++ b/include/power.h
@@ -12,10 +12,10 @@
 #define NO_OF_SAMPLES 64  // we do some multisampling to get better values
 
 #ifndef BAT_MAX_VOLTAGE
-#define BAT_MAX_VOLTAGE 4300 // millivolts
+#define BAT_MAX_VOLTAGE 4200 // millivolts
 #endif
 #ifndef BAT_MIN_VOLTAGE
-#define BAT_MIN_VOLTAGE 3200 // millivolts
+#define BAT_MIN_VOLTAGE 2800 // millivolts
 #endif
 
 uint16_t read_voltage(void);
diff --git a/platformio.ini b/platformio.ini
index 306ec661..93fad964 100644
--- a/platformio.ini
+++ b/platformio.ini
@@ -45,7 +45,7 @@ description = Paxcounter is a device for metering passenger flows in realtime. I
 
 [common]
 ; for release_version use max. 10 chars total, use any decimal format like "a.b.c"
-release_version = 1.9.984
+release_version = 1.9.99
 ; DEBUG LEVEL: For production run set to 0, otherwise device will leak RAM while running!
 ; 0=None, 1=Error, 2=Warn, 3=Info, 4=Debug, 5=Verbose
 debug_level = 3
@@ -57,12 +57,12 @@ platform_espressif32 = espressif32@1.12.0
 monitor_speed = 115200
 upload_speed = 115200
 lib_deps_lora =
-    MCCI LoRaWAN LMIC library@>=3.1.0 ; MCCI LMIC by Terrill Moore
+    MCCI LoRaWAN LMIC library@3.1.0 ; MCCI LMIC by Terrill Moore
 lib_deps_display =
-    ss_oled@4.1.2 ; simple and small OLED lib by Larry Bank
-    BitBang_I2C@2.0.2
-    QRCode@>=0.0.1
-    TFT_eSPI@>=2.2.0
+    ss_oled@4.1.2 ; fast and small OLED lib by Larry Bank
+    BitBang_I2C@2.0.3
+    QRCode@0.0.1
+    TFT_eSPI@2.2.0
 lib_deps_matrix_display =
     Ultrathin_LED_Matrix@>=1.0.0
 lib_deps_rgbled =
@@ -110,7 +110,7 @@ framework = arduino
 board = esp32dev
 board_build.partitions = min_spiffs.csv
 upload_speed = ${common.upload_speed}
-;upload_port = COM5
+;upload_port = COM8
 platform = ${common.platform_espressif32}
 lib_deps = ${common.lib_deps_all}
 build_flags = ${common.build_flags_all}
diff --git a/src/paxcounter.conf b/src/paxcounter.conf
index 4c89cf72..c98cc7b9 100644
--- a/src/paxcounter.conf
+++ b/src/paxcounter.conf
@@ -69,7 +69,7 @@
 #define USE_OTA                         1       // set to 0 to disable OTA update
 #define WIFI_MAX_TRY                    5       // maximum number of wifi connect attempts for OTA update [default = 20]
 #define OTA_MAX_TRY                     5       // maximum number of attempts for OTA download and write to flash [default = 3]
-#define OTA_MIN_BATT                    3600    // minimum battery level for OTA [millivolt]
+#define OTA_MIN_BATT                    50      // minimum battery level for OTA [percent]
 #define RESPONSE_TIMEOUT_MS             60000   // firmware binary server connection timeout [milliseconds]
 
 // settings for syncing time of node with a time source (network / gps / rtc / timeserver)
diff --git a/src/power.cpp b/src/power.cpp
index 4ab413a1..4d1920c5 100644
--- a/src/power.cpp
+++ b/src/power.cpp
@@ -224,18 +224,20 @@ uint8_t read_battlevel() {
   const uint16_t batt_voltage_range = BAT_MAX_VOLTAGE - BAT_MIN_VOLTAGE;
   const uint8_t batt_level_range = MCMD_DEVS_BATT_MAX - MCMD_DEVS_BATT_MIN + 1;
   const int batt_voltage = read_voltage() - BAT_MIN_VOLTAGE;
-  const uint8_t batt_percent = (batt_voltage > 0)
-                                   ? (float)batt_voltage / (float)batt_voltage_range * 100.0
-                                   : MCMD_DEVS_BATT_NOINFO;
+  const uint8_t batt_percent =
+      (batt_voltage > 0)
+          ? (float)batt_voltage / (float)batt_voltage_range * 100.0
+          : MCMD_DEVS_BATT_NOINFO;
   uint8_t lmic_batt_level;
 
-  ESP_LOGD(TAG, "batt_voltage = %d mV / batt_level = %u%%", batt_voltage,
-           batt_percent);
+  ESP_LOGD(TAG, "batt_voltage = %dmV / batt_level = %u%%",
+           batt_voltage + BAT_MIN_VOLTAGE, batt_percent);
 
   if (batt_percent != MCMD_DEVS_BATT_NOINFO)
 #ifdef HAS_PMU
     lmic_batt_level = pmu.isVBUSPlug() ? MCMD_DEVS_EXT_POWER
-                                       : (float)batt_percent / (float)batt_level_range * 100.0;
+                                       : (float)batt_percent /
+                                             (float)batt_level_range * 100.0;
 #else
     lmic_batt_level = (float)batt_percent / (float)batt_level_range * 100.0;
 #endif // HAS_PMU