Limit Battery discharge to base load below 70% SoC.

TODO: Configurable threshold.

This assumes the Battery will always fully discharge overnight and is
intended to reduce the discharge speed so the average SoC is closer to
50% for longer battery life.

src/PowerLimiter.cpp

@@ -901,7 +901,12 @@ int32_t PowerLimiterClass::getSolarPower()
 
 int32_t PowerLimiterClass::getBatteryDischargeLimit()
 {
-    auto currentLimit = Battery.getDischargeCurrentLimit();
+    auto const& config = Configuration.get();
+    float currentLimit = Battery.getDischargeCurrentLimit();
+    float batterySoC = Battery.getStats()->getSoC();
+    float inverterEfficiencyFactor = getInverterEfficiency(_inverter);
+    float baseLoadAC = config.PowerLimiter.BaseLoadLimit;
+    float baseLoadDC = baseLoadAC / inverterEfficiencyFactor;
 
     if (currentLimit == FLT_MAX) {
         // the returned value is arbitrary, as long as it's
@@ -912,11 +917,17 @@ int32_t PowerLimiterClass::getBatteryDischargeLimit()
     // This uses inverter voltage since there is a voltage drop between
     // battery and inverter, so since we are regulating the inverter
     // power we should use its voltage.
-    auto const& config = Configuration.get();
     auto channel = static_cast<ChannelNum_t>(config.PowerLimiter.InverterChannelId);
     float inverterVoltage = _inverter->Statistics()->getChannelFieldValue(TYPE_DC, channel, FLD_UDC);
+    float dcPowerLimit = inverterVoltage * currentLimit;
+
+    if (batterySoC < 70 && dcPowerLimit > baseLoadDC) {
+      MessageOutput.printf("[DPL::getBatteryDischargeLimit] Limit reduced by SoC to: %f\r\n",
+                baseLoadDC);
+      dcPowerLimit = baseLoadDC;
+    }
 
-    return static_cast<int32_t>(inverterVoltage * currentLimit);
+    return static_cast<int32_t>(dcPowerLimit);
 }
 
 float PowerLimiterClass::getLoadCorrectedVoltage()