diff --git a/include/rc_devices.h b/include/rc_devices.h
index f47fc04..d15f324 100644
--- a/include/rc_devices.h
+++ b/include/rc_devices.h
@@ -1,7 +1,9 @@
 #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 }}"
+#define BATTERY_PERCENTAGE_TEMPLATE(min, diff) "{% if value_json.sensor.diagnostic.voltage|is_number %}\
+ {{ ((value_json.sensor.diagnostic.voltage|float-" #min ")|round(2)*100/" #diff ")|int }}\
+ {% endif %}"
 
 #include "esp.h"
 #include "ha.h"