Complete electrical failure

[GL5]

Hi,

I need some help. My B6 (55 plate, Sport, 197'000 miles) is experiencing complete failure of the battery, it completely drains, unable to unlock remotely, even to the point where the clock stopped. This has happened numerous times now, its not the battery as replacing it has made no difference. It’s been with the auto electrician who cannot find anything at fault as it will not drain for him, but it will do with my motor mechanic. I am hesitant to use the car as there seems to be not set pattern on when the battery fails/drains. Does anyone have any info on this or advice?

Many thanks

Robert