Sorry to post to a thread multiple years old, but this was the most comprehensive posting I found on the issue with Google so I thought it made sense to post my results here too.
My situation: I have a 2010 GTI Mk6 with the USA version of the RCD-510 radio. I have an iPod Classic 5th Generation (60GB) that I leave attached to the MDI port via the Apple connector at all times. My iPod is over 7 years and has poor battery life. When left in my car overnight, the iPod will be dead when I return. Looking at the iPod screen it will say "Very low battery" and after about 5 minutes of charging, it will then be recognized by the radio and function as normal. I looked into the SD card alternative, but I couldn't live with the limitations on total file size, # of folders, and the limited # of songs that can be played on "random". Also worth noting, I told my VW dealership about the issue and was told 1. there were no updates available for my radio and 2. it was a known issue and you must disconnect your iPod/iPhone/etc every time you leave the car.
Fix #1 (Failed): I first attempted to update the MDI software using the latest file on the (
VW website). Using a USB MDI cable and a thumb drive, the update successfully installed. Unfortunately, there was no noticeable difference in the functionality of the radio and my iPod continued to die almost every night.
Fix #2 (Failed): I read that some people have fixed their problems by buying a new MDI Apple cable, so I tried this. Unfortunately there was no change, and my iPod was still dead most days.
Fix #3 (Failed): I attempted to splice a USB MDI cable with a regular Apple USB cable. This did not work.
Fix #4 (Failed): Since I now had two MDI Apple cables, I decided to try installing a diode on the power wire to attempt stopping the car from drawing power from the iPod when the car was off. However, after testing the voltage levels on the power wire on the MDI Apple cable, I was able to determine that within ~45 seconds of the car being turned off, power to the iPod was stopped (at this point the iPod would no longer show it was being charged too). But the iPod could still play music (even with the car off and key out of the ignition) if you turned the radio back on. So the installation of the diode had no impact. The power would still turn off at the same time and then trickle down to 0V over a period of a couple seconds.
Fix #5 (Working! ): At this point, I figured the issue was either 1. the data wire connection is keeping the iPod awake despite the car being off or 2. the timing of when the car stops charging the ipod isn't syncing with data connection. I assumed #1 would require a programming solution, so I focused on potential issue #2. Using my old MDI Apple cable, I cut it open to expose the wires and cut the red (power) wire. I stripped the red wire on the side of the iPod connection and connected it to the red wire from a cut-open USB cable. I then plugged the USB cable into USB car charger. Because the GTI's cigarette lighter only has power when the car is on, the car will now automatically (and instantly) cut power to the iPod when the car turn's off. I've tested the solution for about a week now, and surprisingly it works! When turning on the car, the radio takes ~10 seconds to recognize the iPod (assuming because it's coming out of sleep), but it will then start playing from where it left off. Before the fix, if the iPod still had power, as soon as the car turned on, the iPod would instantly start playing (which is probably because it was already "awake".
Long term solution: Now that I know how to solve the problem, I can fairly easily wire up a "hidden" fix. This involves buying a 12v to 5v converter and tapping it into the cigarette lighter power source. The tutorial here (
link) gives a good description of how to access the cigarette wires. From there all I need to do is pull out the MDI insert in the center console and connect the red MDI wire with the output of the voltage converter. To remove the MDI insert, there are 2 slots on the passenger side that you push a flat screwdriver into which releases the tabs and then you can pull it out. I had to apply a decent amount of force to remove the insert and bent one of the clips, but luckily they're metal (not plastic) so I can bend it back into shape. After reassembling everything, the install should be completely hidden and I can plug my iPod into the MDI interface with my new MDI Apple cable (the one I didn't cut open) and all will work correctly.
Hope this helps you all!