thank you both for your answer. I see, I could use 6*AA in the Vin, but then, what would happen at end of battery life ? I will be below the voltage, so will the arduino suffer from that ?
Nothing will "suffer" or be harmed when the voltage goes too low, it just stops working.// Per.
Isn't it possible for the bootloader to be corrupted if the voltage is too low?
Only if you turn off the BOD-fuse (Brown out detect)
would something like that be regulated and a 'trusted' source of 5v ? http://www.amazon.fr/dp/B001HG1ZFK
What about boost regulator ? why do you mention it ?
I'm ok with cheap stuff on ebay