diff --git a/Software/Software.ino b/Software/Software.ino
index 33a81c3c..fe9fcefd 100644
--- a/Software/Software.ino
+++ b/Software/Software.ino
@@ -244,7 +244,7 @@ void core_loop(void*) {
       led_exe();
       handle_contactors();  // Take care of startup precharge/contactor closing
 #ifdef PRECHARGE_CONTROL
-      handle_precharge_control();
+      handle_precharge_control(currentMillis);
 #endif  // PRECHARGE_CONTROL
 #ifdef FUNCTION_TIME_MEASUREMENT
       END_TIME_MEASUREMENT_MAX(time_10ms, datalayer.system.status.time_10ms_us);
diff --git a/Software/USER_SETTINGS.h b/Software/USER_SETTINGS.h
index a194dfab..bf870214 100644
--- a/Software/USER_SETTINGS.h
+++ b/Software/USER_SETTINGS.h
@@ -92,7 +92,8 @@
 //#define NISSANLEAF_CHARGER  //Enable this line to control a Nissan LEAF PDM connected to battery - for example, when generator charging
 
 /* Automatic Precharge settings (Optional) If you have a battery that expects an external voltage applied before opening contactors (within the battery), configure this section */
-//#define PRECHARGE_CONTROL      //Enable this line to control a modified HIA4V1 (see wiki) by PWM on the PRECHARGE_PIN.
+//#define PRECHARGE_CONTROL      //Enable this line to control a modified HIA4V1 via PWM on the HIA4V1_PIN (see Wiki and HAL for pin definition)
+//#define INVERTER_DISCONNECT_CONTACTOR_IS_NORMALLY_OPEN //Enable this line if you use a normally open contactor instead of normally closed
 
 /* Other options */
 //#define EQUIPMENT_STOP_BUTTON    // Enable this to allow an equipment stop button connected to the Battery-Emulator to disengage the battery
diff --git a/Software/src/communication/precharge_control/precharge_control.cpp b/Software/src/communication/precharge_control/precharge_control.cpp
index 761b75c1..6b792e04 100644
--- a/Software/src/communication/precharge_control/precharge_control.cpp
+++ b/Software/src/communication/precharge_control/precharge_control.cpp
@@ -2,20 +2,22 @@
 #include "../../datalayer/datalayer.h"
 #include "../../datalayer/datalayer_extended.h"
 #include "../../include.h"
-
-// Parameters
-
 #ifdef PRECHARGE_CONTROL
-
+// Parameters
 #define MAX_PRECHARGE_TIME_MS 15000  // Maximum time precharge may be enabled
-
 #define Precharge_default_PWM_Freq 11000
 #define Precharge_min_PWM_Freq 5000
 #define Precharge_max_PWM_Freq 34000
-#define PWM_Res 8
-#define PWM_OFF_DUTY 0
-
+#define Precharge_PWM_Res 8
+#define PWM_Freq 20000  // 20 kHz frequency, beyond audible range
 #define PWM_Precharge_Channel 0
+#ifndef INVERTER_DISCONNECT_CONTACTOR_IS_NORMALLY_OPEN
+#define ON 0   //Normally closed contactors use inverted logic
+#define OFF 1  //Normally closed contactors use inverted logic
+#else
+#define ON 1
+#define OFF 0
+#endif
 unsigned long prechargeStartTime = 0;
 static uint32_t freq = Precharge_default_PWM_Freq;
 uint16_t delta_freq = 1;
@@ -28,48 +30,33 @@ void init_precharge_control() {
 #ifdef DEBUG_LOG
   logging.printf("Precharge control initialised\n");
 #endif
-  pinMode(PRECHARGE_PIN, OUTPUT);
-  digitalWrite(PRECHARGE_PIN, LOW);
-  pinMode(POSITIVE_CONTACTOR_PIN, OUTPUT);
-  digitalWrite(POSITIVE_CONTACTOR_PIN, LOW);
+  pinMode(HIA4V1_PIN, OUTPUT);
+  digitalWrite(HIA4V1_PIN, LOW);
+  pinMode(INVERTER_DISCONNECT_CONTACTOR_PIN, OUTPUT);
+  digitalWrite(INVERTER_DISCONNECT_CONTACTOR_PIN, LOW);
 }
 
 // Main functions
-void handle_precharge_control() {
-  unsigned long currentTime = millis();
-#ifdef MEB_BATTERY
+void handle_precharge_control(unsigned long currentMillis) {
   int32_t target_voltage = datalayer.battery.status.voltage_dV;
   int32_t external_voltage = datalayer_extended.meb.BMS_voltage_intermediate_dV;
-#endif
 
-  // Handle actual state machine. This first turns on Negative, then Precharge, then Positive, and finally turns OFF precharge
   switch (datalayer.system.status.precharge_status) {
     case AUTO_PRECHARGE_IDLE:
-
-#if 0
-      if (datalayer.battery.status.bms_status != FAULT && datalayer.battery.status.real_bms_status == BMS_STANDBY &&
-          /*datalayer.system.status.inverter_allows_contactor_closing &&*/
-          !datalayer.system.settings.equipment_stop_active) {
-        datalayer.system.status.precharge_status = AUTO_PRECHARGE_START;
-      }
-#else
       if (datalayer.system.settings.start_precharging) {
         datalayer.system.status.precharge_status = AUTO_PRECHARGE_START;
       }
-#endif
       break;
-
     case AUTO_PRECHARGE_START:
       freq = Precharge_default_PWM_Freq;
-      ledcAttachChannel(PRECHARGE_PIN, freq, PWM_Res, PWM_Precharge_Channel);
-      ledcWriteTone(PRECHARGE_PIN, freq);  // Set frequency and set dutycycle to 50%
-      prechargeStartTime = currentTime;
+      ledcAttachChannel(HIA4V1_PIN, freq, Precharge_PWM_Res, PWM_Precharge_Channel);
+      ledcWriteTone(HIA4V1_PIN, freq);  // Set frequency and set dutycycle to 50%
+      prechargeStartTime = currentMillis;
       datalayer.system.status.precharge_status = AUTO_PRECHARGE_PRECHARGING;
 #ifdef DEBUG_LOG
       logging.printf("Precharge: Starting sequence\n");
 #endif
-      digitalWrite(POSITIVE_CONTACTOR_PIN, HIGH);
-
+      digitalWrite(INVERTER_DISCONNECT_CONTACTOR_PIN, OFF);
       break;
 
     case AUTO_PRECHARGE_PRECHARGING:
@@ -97,24 +84,24 @@ void handle_precharge_control() {
         logging.printf("Precharge: Target: %d V  Extern: %d V  Frequency: %u\n", target_voltage / 10,
                        external_voltage / 10, freq);
 #endif
-        ledcWriteTone(PRECHARGE_PIN, freq);
+        ledcWriteTone(HIA4V1_PIN, freq);
       }
 
       if ((datalayer.battery.status.real_bms_status != BMS_STANDBY &&
            datalayer.battery.status.real_bms_status != BMS_ACTIVE) ||
           datalayer.battery.status.bms_status != ACTIVE || datalayer.system.settings.equipment_stop_active) {
-        pinMode(PRECHARGE_PIN, OUTPUT);
-        digitalWrite(PRECHARGE_PIN, LOW);
-        digitalWrite(POSITIVE_CONTACTOR_PIN, LOW);
+        pinMode(HIA4V1_PIN, OUTPUT);
+        digitalWrite(HIA4V1_PIN, LOW);
+        digitalWrite(INVERTER_DISCONNECT_CONTACTOR_PIN, ON);
         datalayer.system.status.precharge_status = AUTO_PRECHARGE_IDLE;
 #ifdef DEBUG_LOG
         logging.printf("Precharge: Disabling Precharge bms not standby/active or equipment stop\n");
 #endif
-      } else if (currentTime - prechargeStartTime >= MAX_PRECHARGE_TIME_MS ||
+      } else if (currentMillis - prechargeStartTime >= MAX_PRECHARGE_TIME_MS ||
                  datalayer.battery.status.real_bms_status == BMS_FAULT) {
-        pinMode(PRECHARGE_PIN, OUTPUT);
-        digitalWrite(PRECHARGE_PIN, LOW);
-        digitalWrite(POSITIVE_CONTACTOR_PIN, LOW);
+        pinMode(HIA4V1_PIN, OUTPUT);
+        digitalWrite(HIA4V1_PIN, LOW);
+        digitalWrite(INVERTER_DISCONNECT_CONTACTOR_PIN, ON);
         datalayer.system.status.precharge_status = AUTO_PRECHARGE_OFF;
 #ifdef DEBUG_LOG
         logging.printf("Precharge: Disabled (timeout reached / BMS fault) -> AUTO_PRECHARGE_OFF\n");
@@ -123,9 +110,9 @@ void handle_precharge_control() {
 
         // Add event
       } else if (datalayer.system.status.battery_allows_contactor_closing) {
-        pinMode(PRECHARGE_PIN, OUTPUT);
-        digitalWrite(PRECHARGE_PIN, LOW);
-        digitalWrite(POSITIVE_CONTACTOR_PIN, LOW);
+        pinMode(HIA4V1_PIN, OUTPUT);
+        digitalWrite(HIA4V1_PIN, LOW);
+        digitalWrite(INVERTER_DISCONNECT_CONTACTOR_PIN, ON);
         datalayer.system.status.precharge_status = AUTO_PRECHARGE_COMPLETED;
 #ifdef DEBUG_LOG
         logging.printf("Precharge: Disabled (contacts closed) -> COMPLETED\n");
@@ -147,8 +134,8 @@ void handle_precharge_control() {
           !datalayer.system.status.inverter_allows_contactor_closing ||
           datalayer.system.settings.equipment_stop_active || datalayer.battery.status.bms_status != FAULT) {
         datalayer.system.status.precharge_status = AUTO_PRECHARGE_IDLE;
-        pinMode(PRECHARGE_PIN, OUTPUT);
-        digitalWrite(PRECHARGE_PIN, LOW);
+        pinMode(HIA4V1_PIN, OUTPUT);
+        digitalWrite(HIA4V1_PIN, LOW);
 #ifdef DEBUG_LOG
         logging.printf("Precharge: equipment stop activated -> IDLE\n");
 #endif
@@ -159,4 +146,4 @@ void handle_precharge_control() {
       break;
   }
 }
-#endif  // AUTO_PRECHARGE_CONTROL
+#endif  // PRECHARGE_CONTROL
diff --git a/Software/src/communication/precharge_control/precharge_control.h b/Software/src/communication/precharge_control/precharge_control.h
index c29e1992..74883503 100644
--- a/Software/src/communication/precharge_control/precharge_control.h
+++ b/Software/src/communication/precharge_control/precharge_control.h
@@ -17,19 +17,10 @@ void init_precharge_control();
 /**
  * @brief Handle contactors
  *
- * @param[in] void
+ * @param[in] unsigned long currentMillis
  *
  * @return void
  */
-void handle_precharge_control();
-
-/**
- * @brief Handle contactors of battery 2
- *
- * @param[in] void
- *
- * @return void
- */
-void handle_contactors_battery2();
+void handle_precharge_control(unsigned long currentMillis);
 
 #endif  // _PRECHARGE_CONTROL_H_
diff --git a/Software/src/devboard/hal/hw_3LB.h b/Software/src/devboard/hal/hw_3LB.h
index ded31420..e5d01c01 100644
--- a/Software/src/devboard/hal/hw_3LB.h
+++ b/Software/src/devboard/hal/hw_3LB.h
@@ -61,6 +61,10 @@
 // SMA CAN contactor pins
 #define INVERTER_CONTACTOR_ENABLE_PIN 36
 
+// Automatic precharging
+#define HIA4V1_PIN 25
+#define INVERTER_DISCONNECT_CONTACTOR_PIN 32
+
 // SD card
 //#define SD_MISO_PIN 2
 //#define SD_MOSI_PIN 15
diff --git a/Software/src/devboard/hal/hw_devkit.h b/Software/src/devboard/hal/hw_devkit.h
index c16621b5..a9dd49c6 100644
--- a/Software/src/devboard/hal/hw_devkit.h
+++ b/Software/src/devboard/hal/hw_devkit.h
@@ -62,6 +62,10 @@ The pin layout below supports the following:
 // Equipment stop pin
 #define EQUIPMENT_STOP_PIN GPIO_NUM_12
 
+// Automatic precharging
+#define HIA4V1_PIN GPIO_NUM_17
+#define INVERTER_DISCONNECT_CONTACTOR_PIN GPIO_NUM_5
+
 // BMW_I3_BATTERY wake up pin
 #ifdef BMW_I3_BATTERY
 #define WUP_PIN1 GPIO_NUM_25  // Wake up pin for battery 1
diff --git a/Software/src/devboard/hal/hw_lilygo.h b/Software/src/devboard/hal/hw_lilygo.h
index 887f925f..8dbf4f74 100644
--- a/Software/src/devboard/hal/hw_lilygo.h
+++ b/Software/src/devboard/hal/hw_lilygo.h
@@ -53,6 +53,10 @@
 #define PRECHARGE_PIN 25
 #define BMS_POWER 18  // Note, this pin collides with CAN add-ons and Chademo
 
+// Automatic precharging
+#define HIA4V1_PIN 25
+#define INVERTER_DISCONNECT_CONTACTOR_PIN 32
+
 // SMA CAN contactor pins
 #define INVERTER_CONTACTOR_ENABLE_PIN 5
 
diff --git a/Software/src/devboard/hal/hw_stark.h b/Software/src/devboard/hal/hw_stark.h
index 152e189f..74f2ce2f 100644
--- a/Software/src/devboard/hal/hw_stark.h
+++ b/Software/src/devboard/hal/hw_stark.h
@@ -51,6 +51,10 @@ GPIOs on extra header
 #define PRECHARGE_PIN 25
 #define BMS_POWER 23
 
+// Automatic precharging
+#define HIA4V1_PIN 19  //Available as extra GPIO via pin header
+#define INVERTER_DISCONNECT_CONTACTOR_PIN 25
+
 // SMA CAN contactor pins
 #define INVERTER_CONTACTOR_ENABLE_PIN 2