 Replacing battery in 2001- 320 i
Thanks to both Darkhorse and Witeshark for their advice.
I fiddled around last night and got the radio/CD player and the clock working again without inputting any code. I took the battery off casually after reading the whole manual. There is no warning that I could have lost all the memory in the radio/CD player and the service reminder. But I have heard rumours about that though.
Just a friendly advice to owner who wants to replace the battery themselves, hook up a 12VDC power source (using 2x 6v lantern batteries or use a small amp charger before you disconnect the old battery so that the car electronic gadgets will not have a break of power supply. Otherwise you may lose memory in the gadgets like I did. A little extra work will save a lot of grieve. A 72- 41N Energizer (Walmart @ Cnd $89.95) fits nicely in 320-i.
Don't forget to cover the filler cap with duct tape and thick poly and hot glue the barbed nipple and connect the vent tube so that the hydrogen fume can escape and not filling the trunk.
That's my 2 bits. | 
