diff --git a/include/devices.h b/include/devices.h
index 3c7ad82..100c7a6 100644
--- a/include/devices.h
+++ b/include/devices.h
@@ -12,7 +12,7 @@ auto roomSensor = Builder<TemperatureSensor>::instance(TEMP_SENSOR)
         .withArea("Basement")
         .withParent(gatewayDevice))
     .withValueTemplate("{{ value_json.sensor.temperature }}")
-    .addPreconfigured(batterySensors<TemperatureSensor>(TEMP_SENSOR, 2.5, 4.5))
+    .addPreconfigured(batterySensors<TemperatureSensor>(TEMP_SENSOR, BATTERY_PERCENTAGE_TEMPLATE(2.5, 2)))
     .build();
 
 auto tankSensor = Builder<Sensor>::instance(new Sensor{ "Level", OIL_SENSOR })
@@ -34,7 +34,7 @@ auto tankSensor = Builder<Sensor>::instance(new Sensor{ "Level", OIL_SENSOR })
         .withValueTemplate("{{ value_json.sensor.value }}")
         .build()
     )
-    .addPreconfigured(batterySensors<Sensor>(OIL_SENSOR, 4.0, 6.4))
+    .addPreconfigured(batterySensors<Sensor>(OIL_SENSOR, BATTERY_PERCENTAGE_TEMPLATE(4, 2.4)))
     .build();
 
 auto presenceTracker = Builder<BinarySensor>::instance(PRESENCE_SENSOR)
@@ -44,7 +44,7 @@ auto presenceTracker = Builder<BinarySensor>::instance(PRESENCE_SENSOR)
         .withModel("AtTiny85")
         .withParent(gatewayDevice))
     .withValueTemplate("{{ value_json.sensor.state }}")
-    .addPreconfigured(batterySensors<BinarySensor>(PRESENCE_SENSOR, 2.7, 3.3))
+    .addPreconfigured(batterySensors<BinarySensor>(PRESENCE_SENSOR, BATTERY_PERCENTAGE_TEMPLATE(2.7, 0.6)))
     .withOffDelaySeconds(5*60)
     .withDeviceClass("presence")
     .build();
diff --git a/include/rc_devices.h b/include/rc_devices.h
index 32d5c90..c79ea06 100644
--- a/include/rc_devices.h
+++ b/include/rc_devices.h
@@ -1,6 +1,7 @@
 #pragma once
 
 #define MAIN_DEVICE_ID "rc-gateway"
+#define BATTERY_PERCENTAGE_TEMPLATE(min, diff) "{{ ((value_json.sensor.diagnostic.voltage|float-" #min ")|round(2)*100/" #diff ")|int }}"
 
 #include "esp.h"
 #include "ha.h"
@@ -72,22 +73,13 @@ struct EasyHomeSwitch : Switch {
     }
 };
 
-VoltageSensor* createVoltageSensor(const char* id) {
-    return new VoltageSensor{id, "Battery voltage", "{{ value_json.sensor.diagnostic.voltage }}"};
-}
-
-#define BATTERY_PERCENTAGE_TEMPLATE "{{ ((value_json.sensor.diagnostic.voltage|float-%.2f)|round(2)*100/%.2f)|int }}"
-BatterySensor* createBatterySensor(const char* id, float min, float max) {
-    auto len = snprintf(nullptr, 0, BATTERY_PERCENTAGE_TEMPLATE, min, max - min) + 1;
-    char* value_json = new char[len];
-    snprintf(value_json, len, BATTERY_PERCENTAGE_TEMPLATE, min, max - min);
-    return new BatterySensor{id, "Battery level", value_json};
-}
-
 template <class T>
-auto batterySensors(const char* id, float min, float max) {
-    return [id, min, max](Builder<T>& builder) -> Builder<T>& {
-        builder.addDiagnostic(createVoltageSensor(id)).addDiagnostic(createBatterySensor(id, min, max)).build();
+auto batterySensors(const char* id, const char* batterySensorTemplate) {
+    return [id, batterySensorTemplate](Builder<T>& builder) -> Builder<T>& {
+        builder
+            .addDiagnostic(new VoltageSensor{id, "Battery voltage", "{{ value_json.sensor.diagnostic.voltage }}"})
+            .addDiagnostic(new BatterySensor{id, "Battery level", batterySensorTemplate})
+            .build();
         return builder;
     };
 }