Strange electronics problems after battery change

[X5Sport]

A request to all of you electronics wizzards - I know we have a few.

Although this is not strictly an E53 problem as it's occurring on a 2005 E46 convertible, there are similarities with the electronics systems that might mean you folks can help. The car is fitted with the full MkIV nav system, OBM and TV function plus a CD changer and MD player in the head unit.

Here's the situation. Battery changed on the car as the old one was not holding its charge. Upon reconnection the following entertainment system hardware no longer worked:
Nav Audio
Power function on left side of head unit (orange LED is out), and all of the buttons on that side.
No Radio or associated functions.
No CD changer - cannot eject disc cartridge either.
No MD - not selectable as the LHS buttons don't work on the head
TV Audio.


The Nav and TV receivers both work (the TV receiver was as deaf as a post and only saw a fraction of what it should - but is now fine) but there is no audio - presumably because the amp is off and won't switch on.

I have done the following:
Checked fuses 7 & 41 - I think these match the E53 as well - both are fine and there is 12V on the two circuits. No other fuses are listed for the CD changer or radio. I also pulled the fuses for the OBM system and checked them.

Interestingly the main 30A fuse for the roof motor was blown - though how a battery change caused that I can't work out.

I have also disconnected the new battery again, touched the two leads together to kill any stray voltages and then reconnected. It made no difference, but was probably worth a try.

I believe frome reading info on this an other sites that all the devices must 'reconnect' via the iBus. I have no way of checking that this is happening. Has anyone else ever come across this, or knows where to look?

The indy dealer has had the car back. They took all day working through the electrical system and got the audio, radio, Tv Rx now at proper reception on both analog and digital going, but the CD changer is still down. The dealer won't say what they did or found, but I think they're just as frustrated having pored over the wiring diagram. Where does the CD changer get its power from? Suggestions? Clues? What really happened and if it happens again what do we do?

I need to change the battery on my E53 soon too as it's 5 years old and a bit dodgy in cold weather and I don't want to have the same issues with mine, hence wondering what to do to avoid the same thing on mine?