Site: make battery discharge limit availability explicit (#32728)

core/loadpoint.go

@@ -1605,9 +1605,9 @@ func (lp *Loadpoint) boostPower(batteryPower float64) float64 {
 		}
 	}
 
-	if maxDischargePower := lp.site.GetBatteryMaxDischargePower(); maxDischargePower > 0 {
+	if maxDischargePower := lp.site.GetBatteryMaxDischargePower(); maxDischargePower != nil {
 		// limit delta to what the battery can still provide
-		delta = min(delta, max(0, maxDischargePower-batteryPower))
+		delta = min(delta, max(0, *maxDischargePower-batteryPower))
 	}
 
 	res := max(0, batteryPower) + delta + lp.site.GetResidualPower()

core/loadpoint_boost_test.go

@@ -11,7 +11,7 @@ import (
 
 type mockSite struct {
 	site.API
-	maxDischargePower float64
+	maxDischargePower *float64
 	residualPower     float64
 	optimized         int
 }
@@ -20,7 +20,7 @@ func (m *mockSite) Optimize() {
 	m.optimized++
 }
 
-func (m *mockSite) GetBatteryMaxDischargePower() float64 {
+func (m *mockSite) GetBatteryMaxDischargePower() *float64 {
 	return m.maxDischargePower
 }
 
@@ -40,15 +40,22 @@ func TestBoostPower(t *testing.T) {
 	s := &mockSite{}
 	lp.site = s
 
-	// No max discharge power limit
-	s.maxDischargePower = 0
+	// No max discharge power limit (nil)
+	s.maxDischargePower = nil
 	// EffectiveMaxPower will be 230 * 16 * 3 = 11040
 	res := lp.boostPower(0)
 	assert.Equal(t, 11040.0, res)
 	assert.Equal(t, boostContinue, lp.batteryBoost)
 
+	// Discharge power limit is 0W (battery empty)
+	s.maxDischargePower = new(float64)
+	lp.batteryBoost = boostStart
+	res = lp.boostPower(0)
+	assert.Equal(t, 0.0, res)
+
 	// With max discharge power limit
-	s.maxDischargePower = 5000
+	limit5000 := 5000.0
+	s.maxDischargePower = &limit5000
 	lp.batteryBoost = boostStart
 	res = lp.boostPower(0)
 	assert.Equal(t, 5000.0, res)
@@ -89,7 +96,8 @@ func TestBoostPower(t *testing.T) {
 	// limit is 50W (less than the standard 790W delta)
 	// without raw negative power, delta would be restricted to 50W
 	// with raw negative power (-2000W), headroom is 2050W, so delta is allowed to be 790W
-	s.maxDischargePower = 50
+	limit50 := 50.0
+	s.maxDischargePower = &limit50
 	s.residualPower = 0 // base delta = 100 + 690 = 790
 	lp.batteryBoost = boostContinue
 	res = lp.boostPower(-2000)

core/site.go

@@ -111,7 +111,7 @@ type Site struct {
 	excessDCPower            float64                     // PV excess DC charge power (hybrid only)
 	auxPower                 float64                     // Aux power
 	battery                  types.BatteryState          // Battery cached and published state
-	batteryMaxDischargePower float64                     // Max discharge power of all battery meters
+	batteryMaxDischargePower *float64                    // Max discharge power of all battery meters
 	batteryMode              api.BatteryMode             // Battery mode (runtime only, not persisted)
 	batteryModeExternal      api.BatteryMode             // Battery mode (external, runtime only, not persisted)
 	batteryModeExternalTimer time.Time                   // Battery mode timer for external control
@@ -765,7 +765,11 @@ func (site *Site) updateBatteryMeters() {
 
 	// written from the meter goroutine, read via GetBatteryMaxDischargePower
 	site.Lock()
-	site.batteryMaxDischargePower = max(0, maxDischargePower)
+	if maxDischargePower >= 0 {
+		site.batteryMaxDischargePower = &maxDischargePower
+	} else {
+		site.batteryMaxDischargePower = nil
+	}
 	site.Unlock()
 
 	// retain the last known soc when every battery read failed this cycle, so a

core/site/api.go

@@ -47,7 +47,7 @@ type API interface {
 	//
 
 	GetBatterySoc() float64
-	GetBatteryMaxDischargePower() float64
+	GetBatteryMaxDischargePower() *float64
 	GetPrioritySoc() float64
 	SetPrioritySoc(float64) error
 	GetBufferSoc() float64

core/site_api.go

@@ -164,10 +164,13 @@ func (site *Site) GetBatterySoc() float64 {
 }
 
 // GetBatteryMaxDischargePower returns the current battery max discharge power
-func (site *Site) GetBatteryMaxDischargePower() float64 {
+func (site *Site) GetBatteryMaxDischargePower() *float64 {
 	site.RLock()
 	defer site.RUnlock()
-	return site.batteryMaxDischargePower
+	if site.batteryMaxDischargePower == nil {
+		return nil
+	}
+	return new(*site.batteryMaxDischargePower)
 }
 
 // Loadpoints returns the loadpoints as api interfaces.

core/site_battery_limit_test.go

@@ -49,7 +49,7 @@ func TestBatteryMaxDischargePowerAggregation(t *testing.T) {
 	}
 
 	site.updateBatteryMeters()
-	assert.Equal(t, 0.0, site.GetBatteryMaxDischargePower())
+	assert.Nil(t, site.GetBatteryMaxDischargePower())
 
 	// both batteries with limit
 	m3 := &mockBatteryPowerLimiter{Meter: &mockMeter{}, discharge: 3000}
@@ -59,7 +59,9 @@ func TestBatteryMaxDischargePowerAggregation(t *testing.T) {
 	}
 
 	site.updateBatteryMeters()
-	assert.Equal(t, 5000.0, site.GetBatteryMaxDischargePower())
+	if res := site.GetBatteryMaxDischargePower(); assert.NotNil(t, res) {
+		assert.Equal(t, 5000.0, *res)
+	}
 }
 
 type mockBatterySocLimiter struct {
@@ -100,7 +102,9 @@ func TestBatteryMaxDischargePowerWithMinSoc(t *testing.T) {
 
 	site.updateBatteryMeters()
 	// Only m2 should contribute
-	assert.Equal(t, 3000.0, site.GetBatteryMaxDischargePower())
+	if res := site.GetBatteryMaxDischargePower(); assert.NotNil(t, res) {
+		assert.Equal(t, 3000.0, *res)
+	}
 
 	// Both empty
 	m3 := &mockLimiter{mockBatterySocLimiter: mockBatterySocLimiter{Meter: &mockMeter{}, soc: 15, min: 20}, discharge: 3000}
@@ -110,5 +114,7 @@ func TestBatteryMaxDischargePowerWithMinSoc(t *testing.T) {
 	}
 
 	site.updateBatteryMeters()
-	assert.Equal(t, 0.0, site.GetBatteryMaxDischargePower())
+	if res := site.GetBatteryMaxDischargePower(); assert.NotNil(t, res) {
+		assert.Equal(t, 0.0, *res)
+	}
 }