Hi,
Thanks everybody. As far as I know the polarity is positive on the inside and negative on the outside of the plug and so the inner pin of the jack (black part on the shield) is positive. I have used the same battery on my UNO and nothing happened this means my UNO worked perfectly.
Connecting the battery to the shield without NANO on the pins Vin and GND correctly marked I get a correct measuring positive voltage ...
Strange 