Site: retain last battery soc when all reads fail (#31211)

core/site.go

@@ -668,21 +668,27 @@ func (site *Site) updateBatteryMeters() {
 		mm[i].Controllable = new(controllable)
 	}
 
-	var batterySocAcc float64
-	var totalCapacity float64
-
-	if lo.SomeBy(mm, func(m types.Measurement) bool { return m.Capacity == nil || *m.Capacity <= 0 }) {
-		// any capacity is missing
-		batterySocAcc = sumOfSocs(mm)
-		totalCapacity = float64(len(site.batteryMeters))
+	// retain the last known soc when every battery read failed this cycle, so a
+	// transient meter error does not report the pack as empty (0%)
+	if lo.EveryBy(mm, func(m types.Measurement) bool { return m.Soc == nil }) {
+		site.log.WARN.Printf("battery soc: read failed, keeping last %.0f%%", site.battery.Soc)
 	} else {
-		// all capacities available - weigh soc by capacity
-		batterySocAcc = weightedSumOfSocs(mm)
-		totalCapacity = lo.SumBy(mm, func(m types.Measurement) float64 { return *m.Capacity })
-	}
+		var batterySocAcc float64
+		var totalCapacity float64
 
-	site.battery.Soc = math.Min(100, batterySocAcc/totalCapacity)
-	site.battery.Capacity = totalCapacity
+		if lo.SomeBy(mm, func(m types.Measurement) bool { return m.Capacity == nil || *m.Capacity <= 0 }) {
+			// any capacity is missing
+			batterySocAcc = sumOfSocs(mm)
+			totalCapacity = float64(len(site.batteryMeters))
+		} else {
+			// all capacities available - weigh soc by capacity
+			batterySocAcc = weightedSumOfSocs(mm)
+			totalCapacity = lo.SumBy(mm, func(m types.Measurement) float64 { return *m.Capacity })
+		}
+
+		site.battery.Soc = math.Min(100, batterySocAcc/totalCapacity)
+		site.battery.Capacity = totalCapacity
+	}
 
 	site.battery.Power = lo.SumBy(mm, func(m types.Measurement) float64 {
 		return m.Power

core/site_battery_test.go

@@ -1,6 +1,7 @@
 package core
 
 import (
+	"errors"
 	"testing"
 	"time"
 
@@ -11,6 +12,36 @@ import (
 	"go.uber.org/mock/gomock"
 )
 
+// TestBatterySocRetainOnReadError guards that a failed soc read keeps the last
+// known soc instead of reporting the pack as empty (discussion #26560).
+func TestBatterySocRetainOnReadError(t *testing.T) {
+	ctrl := gomock.NewController(t)
+
+	meter := api.NewMockMeter(ctrl)
+	meter.EXPECT().CurrentPower().Return(0.0, nil).AnyTimes()
+
+	battery := api.NewMockBattery(ctrl)
+	battery.EXPECT().Soc().Return(0.0, errors.New("read failed")).AnyTimes()
+
+	var bat api.Meter = &struct {
+		api.Meter
+		api.Battery
+	}{
+		Meter:   meter,
+		Battery: battery,
+	}
+
+	site := &Site{
+		log:           util.NewLogger("foo"),
+		batteryMeters: []config.Device[api.Meter]{config.NewStaticDevice(config.Named{}, bat)},
+	}
+	site.battery.Soc = 84
+
+	site.updateBatteryMeters()
+
+	assert.Equal(t, 84.0, site.battery.Soc, "soc retained when the read fails")
+}
+
 func TestApplyBatteryMode(t *testing.T) {
 	for _, tc := range []struct {
 		internal, expected api.BatteryMode