Add pv_current formula metric for MPPT PV current

The /Pv/x/I topics are deprecated in Venus OS. Add a derived formula
metric that calculates PV current as I = P / V for:
- Solarcharger total PV current (Yield/Power / Pv/V)
- Solarcharger per-tracker current (Pv/{tracker}/P / Pv/{tracker}/V)
- Multi RS Solar per-MPPT current (Pv/{n}/P / Pv/{n}/V)

Author: Copilot

custom_components/victron_mqtt/_vendor/victron_mqtt/_victron_formulas.py

@@ -4,7 +4,15 @@
 
 from typing import TYPE_CHECKING
 
-from ._victron_enums import ChargeSchedule, ESSModeHub4, ESSState, ESSUserMode, GenericOnOff, PreferRenewableEnergyEnum
+from ._victron_enums import (
+    ChargeSchedule,
+    ESSModeHub4,
+    ESSState,
+    ESSUserMode,
+    GenericOnOff,
+    PreferRenewableEnergyEnum,
+)
+from .constants import MetricType
 from .data_classes import GpsLocation
 from .formula_common import left_riemann_sum_internal
 from .writable_metric import WritableMetric
@@ -259,3 +267,29 @@ def prefer_renewable_energy_set(
         metric.set(PreferRenewableEnergyEnum.FULL_CHARGE_ACTIVE)
 
     return enabled, None
+
+
+def pv_current(
+    depends_on: dict[str, Metric], _transient_state: FormulaTransientState | None
+) -> tuple[float, None] | None:
+    """Calculate PV current from power and voltage (I = P / V).
+
+    Since /Pv/x/I topics are deprecated in Venus OS, this formula derives
+    PV current by dividing PV power by PV voltage.
+    """
+    power_metric = None
+    voltage_metric = None
+    for metric in depends_on.values():
+        if metric.metric_type == MetricType.POWER:
+            power_metric = metric
+        elif metric.metric_type == MetricType.VOLTAGE:
+            voltage_metric = metric
+
+    if power_metric is None or voltage_metric is None:
+        return None
+    if power_metric.value is None or voltage_metric.value is None:
+        return None
+    if voltage_metric.value == 0:
+        return None
+
+    return power_metric.value / voltage_metric.value, None

custom_components/victron_mqtt/_vendor/victron_mqtt/_victron_topics.py

@@ -1777,6 +1777,15 @@
         name="MPPT {mpptnumber} PV voltage",
         metric_type=MetricType.VOLTAGE,
     ),
+    TopicDescriptor(
+        topic="$$func/multi/pv_current",
+        message_type=MetricKind.SENSOR,
+        short_id="multi_mppt_{mpptnumber}_current",
+        name="MPPT {mpptnumber} current",
+        metric_type=MetricType.CURRENT,
+        precision=2,
+        depends_on=["multi_mppt_{mpptnumber}_power", "multi_mppt_{mpptnumber}_voltage"],
+    ),
     TopicDescriptor(
         topic="N/{installation_id}/multi/{device_id}/Relay/0/State",
         message_type=MetricKind.SWITCH,
@@ -2551,6 +2560,15 @@
         name="PV tracker {tracker:solarcharger_tracker_{tracker}_name} voltage",
         metric_type=MetricType.VOLTAGE,
     ),
+    TopicDescriptor(
+        topic="$$func/solarcharger/pv_current",
+        message_type=MetricKind.SENSOR,
+        short_id="solarcharger_tracker_{tracker}_current",
+        name="PV tracker {tracker:solarcharger_tracker_{tracker}_name} current",
+        metric_type=MetricType.CURRENT,
+        precision=2,
+        depends_on=["solarcharger_tracker_{tracker}_power", "solarcharger_tracker_{tracker}_voltage"],
+    ),
     TopicDescriptor(
         topic="N/{installation_id}/solarcharger/{device_id}/Relay/0/State",
         message_type=MetricKind.SWITCH,
@@ -2583,6 +2601,15 @@
         name="PV yield power",
         metric_type=MetricType.POWER,
     ),
+    TopicDescriptor(
+        topic="$$func/solarcharger/pv_current",
+        message_type=MetricKind.SENSOR,
+        short_id="solarcharger_pv_current",
+        name="PV current",
+        metric_type=MetricType.CURRENT,
+        precision=2,
+        depends_on=["solarcharger_yield_power", "solarcharger_voltage"],
+    ),
     TopicDescriptor(
         topic="N/{installation_id}/solarcharger/{device_id}/Yield/User",
         message_type=MetricKind.SENSOR,