add lower limit to prevent triggering on power loss (#20720)

Co-authored-by: Comma Device <device@comma.ai>

selfdrive/thermald/power_monitoring.py

@@ -16,7 +16,8 @@ CAR_VOLTAGE_LOW_PASS_K = 0.091 # LPF gain for 5s tau (dt/tau / (dt/tau + 1))
 CAR_BATTERY_CAPACITY_uWh = 30e6
 CAR_CHARGING_RATE_W = 45
 
-VBATT_PAUSE_CHARGING = 11.0
+VBATT_PAUSE_CHARGING = 11.0           # Lower limit on the LPF car battery voltage
+VBATT_INSTANT_PAUSE_CHARGING = 7.0    # Lower limit on the instant car battery voltage measurements to avoid triggering on instant power loss
 MAX_TIME_OFFROAD_S = 30*3600
 
 class PowerMonitoring:
@@ -27,6 +28,7 @@ class PowerMonitoring:
     self.power_used_uWh = 0                     # Integrated power usage in uWh since going into offroad
     self.next_pulsed_measurement_time = None
     self.car_voltage_mV = 12e3                  # Low-passed version of pandaState voltage
+    self.car_voltage_instant_mV = 12e3          # Last value of pandaState voltage
     self.integration_lock = threading.Lock()
 
     car_battery_capacity_uWh = self.params.get("CarBatteryCapacity")
@@ -51,6 +53,7 @@ class PowerMonitoring:
         return
 
       # Low-pass battery voltage
+      self.car_voltage_instant_mV = pandaState.pandaState.voltage
       self.car_voltage_mV = ((pandaState.pandaState.voltage * CAR_VOLTAGE_LOW_PASS_K) + (self.car_voltage_mV * (1 -  CAR_VOLTAGE_LOW_PASS_K)))
 
       # Cap the car battery power and save it in a param every 10-ish seconds
@@ -161,7 +164,7 @@ class PowerMonitoring:
     now = sec_since_boot()
     disable_charging = False
     disable_charging |= (now - offroad_timestamp) > MAX_TIME_OFFROAD_S
-    disable_charging |= (self.car_voltage_mV < (VBATT_PAUSE_CHARGING * 1e3))
+    disable_charging |= (self.car_voltage_mV < (VBATT_PAUSE_CHARGING * 1e3)) and (self.car_voltage_instant_mV > (VBATT_INSTANT_PAUSE_CHARGING * 1e3))
     disable_charging |= (self.car_battery_capacity_uWh <= 0)
     disable_charging &= (not pandaState.pandaState.ignitionLine and not pandaState.pandaState.ignitionCan)
     disable_charging &= (not self.params.get_bool("DisablePowerDown"))