I have a few friends back in the states, all of which have gone through their respective field schooling. They work on all the European cars, BMW, Mercs, Audi etc. I was talking about this issue with them because i just put my car into winter storage. When i mentioned this "registration" deal, they about died laughing. according to the pros lol, the whole process is a sham. believe and do what you want.
The charging differences over the course of the batteries life, the low and high voltages issue is all controlled by that big ass black box adapter that is connected to your negative terminal. The Registration fee is no more than installing the battery and clearing the codes. see below
" "registering" a battery is a fancy way of saying they will erase any and all faulty codes due to a battery and synchronize all windows and sensors that have been reset due to battery... replacement. On a Benz, i perform a basic programming which is included in the battery replacement. It's nothing more than synchronizing nec. functions and sensors. This is done without scanning. If I diagnosing an issue and I see battery codes, I erase them. It is no harm to leave them in there. The 150 they are talking about is to replace the battery and erase fault codes. Code erasing is unnecessary. That little black box on your negative cable is a battery monitoring sensor that reports back to the battery control module to ensure proper charging. The sensor sees what's going on, a scanner doesn't tell it what to do. The batteries are glass mat construction and are expensive but last a long time and perform well. The sensor also monitors quiescent current draw when the car is sitting. If it has to it will shut the car completely down if the voltage is too low. But that's another topic. Maintain the battery is the most upmost importance for storage."
Thought this might be helpful