Anticipating a problem
 

Hi to everyone. I'm a new member, hoping that you Nissan experts can give me some advice.
I have an Almera Tino 1800 cc, eight years old but I've had it for six. Very good car, always reliable, but I think the battery is about due for replacement. My problem is, when the battery is disconnected it will cut out the radio, which can't then be reactivated without a code, which is not noted in the documentation I got from the S/H dealer when I bought the car. Is there any way to avoid cutting out the radio when changing the battery ? Or for finding out the code sequence before doing so ? The alternative, I understand, is a trip to the dealer for an expensive recoding procedure.