diff --git a/include/param_prj.h b/include/param_prj.h
index 15387b5..d35551a 100644
--- a/include/param_prj.h
+++ b/include/param_prj.h
@@ -47,7 +47,7 @@
    3. Display values
  */
 //Next param id (increase when adding new parameter!): 24
-//Next value Id: 2051
+//Next value Id: 2052
 /*              category     name         unit       min     max     default id */
 #define PARAM_LIST \
     PARAM_ENTRY(CAT_CHARGER, idclim,      "A",       0,      45,     45,     3   ) \
@@ -108,6 +108,7 @@
     VALUE_ENTRY(c3iac,       "A",     2034 ) \
     VALUE_ENTRY(c3udc,       "V",     2035 ) \
     VALUE_ENTRY(c3idc,       "A",     2036 ) \
+    VALUE_ENTRY(tmpobcmax,   "°C",    2051 ) \
     VALUE_ENTRY(test_time,   "s",     3000 ) \
     VALUE_ENTRY(test_timer_flag,   "X",     3001 ) \
     VALUE_ENTRY(test_timer_icvalue,   "X",     3002 ) \
@@ -128,7 +129,7 @@
 // SKUDAK customization suffix: bump on every Skudak-side change so the OpenInverter
 // web UI shows a distinct version (e.g. "4=1.20.R-S4") and we can visually confirm
 // the right firmware is flashed. Match the stm32-sine -S<N> convention.
-#define VERSTR STRINGIFY(4=VER-S4)
+#define VERSTR STRINGIFY(4=VER-S5)
 
 /***** enums ******/
 
diff --git a/src/chargercan.cpp b/src/chargercan.cpp
index c52f086..42c3ca2 100644
--- a/src/chargercan.cpp
+++ b/src/chargercan.cpp
@@ -108,16 +108,19 @@ void ChargerCAN::MapMessages(CanMap* can)
    can->AddRecv(Param::vcuchglim, 0x212, 0, 8, 1);
 
    /***** SKUDAK VCU telemetry (0x211) — SKUDAK-448 expanded charger telemetry *****/
-   // Byte 0:    state (0=Off, 1=WaitStart, 2=Enable, 3=Activate, 4=Run, 5=Stop)
-   // Bytes 1-2: udc (V, gain=1)
-   // Bytes 3-4: idc (0.1A, gain=10)
-   // Byte 5:    uaux (decivolts, gain=10) — 12V aux battery rail
-   // Byte 6:    soc (%, gain=1)
-   // Byte 7:    reserved
+   // Byte 0:    state     (0=Off, 1=WaitStart, 2=Enable, 3=Activate, 4=Run, 5=Stop)
+   // Bytes 1-2: udc       (V, gain=1)
+   // Bytes 3-4: idc       (0.1A, gain=10)
+   // Byte 5:    uaux      (decivolts, gain=10) — 12V aux battery rail
+   // Byte 6:    soc       (%, gain=1)
+   // Byte 7:    tmpobcmax (°C, gain=1, offset=-40)  — worst-case across all
+   //                       9 OBC probes; matches Tesla OBC's own CAN offset
+   //                       so receivers can decode with the same formula.
    // Consumed by stm32-hal-vcu Core/Src/main.c CHARGER_CAN_ID_OI_OBC_AUX handler.
-   can->AddSend(Param::state, 0x211,  0, 8,  1);
-   can->AddSend(Param::udc,   0x211,  8, 16, 1);
-   can->AddSend(Param::idc,   0x211, 24, 16, 10);
-   can->AddSend(Param::uaux,  0x211, 40, 8,  10);
-   can->AddSend(Param::soc,   0x211, 48, 8,  1);
+   can->AddSend(Param::state,     0x211,  0, 8,  1);
+   can->AddSend(Param::udc,       0x211,  8, 16, 1);
+   can->AddSend(Param::idc,       0x211, 24, 16, 10);
+   can->AddSend(Param::uaux,      0x211, 40, 8,  10);
+   can->AddSend(Param::soc,       0x211, 48, 8,  1);
+   can->AddSend(Param::tmpobcmax, 0x211, 56, 8,  1, 40);  // offset 40 → wire byte = temp + 40
 }
diff --git a/src/main.cpp b/src/main.cpp
index e0214b9..790efe8 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -77,6 +77,32 @@ static void Ms100Task(void)
 
    EvseRead();
 
+   // SKUDAK: derive a single "worst case" OBC temperature for downstream
+   // consumers (Polarity VCU broadcasts it on STATUS_SCREEN bytes 23/26).
+   // Aggregates the 9 per-module probes the Tesla OBC publishes on CAN
+   // 0x237/0x239/0x23B — max wins. Modules without a sensor read -40 °C
+   // (the DBC offset; raw byte 0); we ignore those so an absent module
+   // doesn't drag the worst-case down. If no probes are valid we leave
+   // tmpobcmax at -40 °C, which the VCU will display as "—".
+   {
+      const Param::PARAM_NUM probes[] = {
+         Param::c1tmp1, Param::c1tmp2, Param::c1tmpin,
+         Param::c2tmp1, Param::c2tmp2, Param::c2tmpin,
+         Param::c3tmp1, Param::c3tmp2, Param::c3tmpin,
+      };
+      int worst   = -40;
+      bool any_ok = false;
+      for (unsigned i = 0; i < sizeof(probes) / sizeof(probes[0]); i++) {
+         int t = Param::GetInt(probes[i]);
+         if (t <= -40) continue;  // No sensor / module not present
+         if (!any_ok || t > worst) {
+            worst  = t;
+            any_ok = true;
+         }
+      }
+      Param::SetInt(Param::tmpobcmax, any_ok ? worst : -40);
+   }
+
    canMap->SendAll();
 }