diff --git a/README.md b/README.md
index dbfb46d..f703e19 100644
--- a/README.md
+++ b/README.md
@@ -40,6 +40,9 @@ stop 06:00
 password 12
 ~~~
 
+WARNING: If the internal backup battery gets empty and the device looses power, the configuration and date get lost (since there are stored in SRAM).
+In this case, replace the battery and reconfigure the device.
+
 connections
 ===========