How old is the battery? More than 5 years old it might be on its last legs. Is it the correct battery for the car? Should be 190mm tall, not the 175mm one for the hatchback. A lot of people fit the wrong one which causes connectivity problems.
http://www.peugeot206cc.co.uk/viewtopic.php?t=15776&f=1
http://www.peugeot206cc.co.uk/viewtopic.php?f=4&t=15783
ChicksFan, December 2014