My local indy just did an "A" service on the ML320, when I went to pick it up he made a point to tell me I should use a battery tender on it since we only drive it around 3k a year. He explained that sudden battery death could cause the various computers to power down and not be able to power up again. One customer had to spend around 5k to replace the various control modules on a late model E320.

If I could put a class III hitch on a W126, the ML320 would be long gone.