RCT: fix batteryhold grid-charging and BatteryNormal nil pointer panic (#31294)

meter/rct.go

@@ -24,7 +24,37 @@ type RCT struct {
 	conn          *rct.Connection // connection with the RCT device
 	usage         string          // grid, pv, battery
 	externalPower bool            // whether to query external power
-	rSocStrategy  *uint8          // remembers overwritten soc strategy value
+
+	mu           sync.Mutex
+	rSocStrategy *uint8 // remembers overwritten soc strategy value
+}
+
+// takeRSocStrategy atomically returns and clears the saved soc strategy, or nil
+// if none is saved (e.g. BatteryNormal applied twice in a row, #31471).
+func (m *RCT) takeRSocStrategy() *uint8 {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	s := m.rSocStrategy
+	m.rSocStrategy = nil
+	return s
+}
+
+// setRSocStrategyIfAbsent saves strategy unless a value is already saved.
+func (m *RCT) setRSocStrategyIfAbsent(strategy uint8) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	if m.rSocStrategy == nil {
+		m.rSocStrategy = &strategy
+	}
+}
+
+// hasRSocStrategy reports whether a soc strategy is currently saved
+func (m *RCT) hasRSocStrategy() bool {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	return m.rSocStrategy != nil
 }
 
 var (
@@ -161,12 +191,12 @@ func NewRCT(ctx context.Context, uri, usage string, batterySocLimits batterySocL
 				}
 
 				// read soc strategy to reset afterwards
-				if m.rSocStrategy == nil {
+				if !m.hasRSocStrategy() {
 					strategy, err := m.queryUint8(rct.PowerMngSocStrategy)
 					if err != nil {
 						return err
 					}
-					m.rSocStrategy = &strategy
+					m.setRSocStrategyIfAbsent(strategy)
 				}
 			}
 
@@ -174,11 +204,11 @@ func NewRCT(ctx context.Context, uri, usage string, batterySocLimits batterySocL
 
 			switch mode {
 			case api.BatteryNormal:
-				eg.Go(func() error {
-					err := m.conn.Write(rct.PowerMngSocStrategy, []byte{*m.rSocStrategy})
-					m.rSocStrategy = nil
-					return err
-				})
+				if strategy := m.takeRSocStrategy(); strategy != nil {
+					eg.Go(func() error {
+						return m.conn.Write(rct.PowerMngSocStrategy, []byte{*strategy})
+					})
+				}
 
 				eg.Go(func() error {
 					return m.conn.Write(rct.BatterySoCTargetMin, floatVal(batterySocLimits.MinSoc/100))
@@ -202,7 +232,13 @@ func NewRCT(ctx context.Context, uri, usage string, batterySocLimits batterySocL
 				})
 
 				eg.Go(func() error {
-					return m.conn.Write(rct.BatterySoCTargetMin, floatVal(batterySocLimits.MaxSoc/100))
+					// hold at current SoC (not MaxSoc): otherwise the gap between current
+					// and target SoC lets the inverter charge from the grid (#31280)
+					soc, err := m.queryFloat(rct.BatterySoC)
+					if err != nil {
+						return err
+					}
+					return m.conn.Write(rct.BatterySoCTargetMin, floatVal(soc))
 				})
 
 			case api.BatteryCharge:

meter/rct_test.go

@@ -0,0 +1,38 @@
+package meter
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// TestRCTTakeRSocStrategy verifies that a repeated BatteryNormal application
+// (no intervening non-normal mode) is a no-op instead of a nil dereference (#31471).
+func TestRCTTakeRSocStrategy(t *testing.T) {
+	m := &RCT{}
+
+	// nothing saved yet
+	assert.Nil(t, m.takeRSocStrategy())
+
+	m.setRSocStrategyIfAbsent(4)
+	strategy := m.takeRSocStrategy()
+	require.NotNil(t, strategy)
+	assert.Equal(t, uint8(4), *strategy)
+
+	// second take without an intervening set must not repeat the value or panic
+	assert.Nil(t, m.takeRSocStrategy())
+}
+
+// TestRCTSetRSocStrategyIfAbsent verifies the saved value is never overwritten
+// while still present, matching the original guard's intent.
+func TestRCTSetRSocStrategyIfAbsent(t *testing.T) {
+	m := &RCT{}
+
+	m.setRSocStrategyIfAbsent(4)
+	m.setRSocStrategyIfAbsent(7)
+
+	strategy := m.takeRSocStrategy()
+	require.NotNil(t, strategy)
+	assert.Equal(t, uint8(4), *strategy)
+}