2002 Peugeot 406 car electrical

peugeot 406 hdi 2.0 estate 2002, iv been trying to pin point the problem. I have for about a month and a half now, to no avail, ill start from when the problem first started. I was driving as you do and the wipers came on, i thought i must have knocked the wiper stalk, got home and parked up, a couple of hours later went to the car to go down to shops, switched ignition on and the key immobiliser came up on the dash and car wouldnt start so i switched the ignition off and on and it cleared its self, cutting a long story short it got progressively worse. when i switch the ignition on now, the engine immobiliser comes up on the screen above the radio, the wipers start up, the lights come on, nothing working properly. i read on the internet somewhere to disconect the battery for a time, i done this and the car started up and everything was working as it should be, but not for long, the whole
process started all over again. i have tried code after code. i even tried a new bsi, ecu, and the key that went with it all, i also fitted anew transponder, to no avail. it seems to decode its self when i reconnect the battery. Is there something wrong with the battery