Bluno & iOS Bluetooth BLE Connection without Serial Command

Hello!
I am having a big issue with the BLE Connection between iPhone and the Bluno.
The connection and communication between both devices works very well when I upload the code from my Mac, but not anymore when I connect the Bluno to an external power source. I guess the problem is that in this case the Serial Command is not available anymore; thatswhy it can not send data anymore. The Bluetooth connection is still working after reconnection...
How to fix that ? I am working since days on it, but cannot find any solution
Thanks for your help!

ps. thats the arduino code i am trying to get to work - a very simple one, but just sending data when the bluno is connected to the computer, not anymore with external power source:

int i = 1000;
void setup() {
Serial.begin(9600);
}
void loop() {
i++;
Serial.println(i);
delay(1000);
}