fix(battery): preserve energy below minimum state of charge (#1483)

src/akkudoktoreos/devices/genetic/battery.py

@@ -366,6 +366,9 @@ class Battery:
 
         # Raw extractable energy above minimum SoC
         raw_available_wh = max(self.soc_wh - self.min_soc_wh, 0.0)
+        if raw_available_wh == 0.0:
+            # A measured SoC below the reserve must not be raised by discharging.
+            return 0.0, 0.0
 
         # Maximum raw discharge due to power limit, scaled to the slot duration.
         # max_charge_power_w is a power [W]; energy movable in one slot is

src/akkudoktoreos/devices/genetic/inverter.py

@@ -304,6 +304,9 @@ class Inverter:
         discharged_raw_wh = battery._discharged_raw_wh_per_slot
         discharging_efficiency = battery.discharging_efficiency
         raw_available_wh = max(soc_wh - min_soc_wh, 0.0)
+        if raw_available_wh == 0.0:
+            # Match Battery.discharge_energy(): preserve a SoC below the reserve.
+            return 0.0, 0.0
         max_raw_wh = max(
             battery.max_charge_power_w * battery.slot_duration_h - discharged_raw_wh[hour], 0.0
         )

src/akkudoktoreos/devices/genetic0/genetic0battery.py

@@ -227,6 +227,9 @@ class Genetic0Battery:
 
         # Raw extractable energy above minimum SoC
         raw_available_wh = max(self.soc_wh - self.min_soc_wh, 0.0)
+        if raw_available_wh == 0.0:
+            # A measured SoC below the reserve must not be raised by discharging.
+            return 0.0, 0.0
 
         # Maximum raw discharge due to power limit
         max_raw_wh = self.max_charge_power_w  # TODO rename to max_discharge_power_w