Cannot code battery

I just did this myself and had the same problem with my 2015 A5. First, make sure you have the hood open and the door as well (stupid I know.) When you input the new ASCII code, it must be a total of 26 characters (spaces included). So if your part number (1st set of numbers) is only 10 digits, you'll need to put 2 spaces after before the 3 letter vendor code. Then one space after vendor code and a 10 digit serial for a total of 26. It will not accept any other format. Example: I replaced mine with an H8 AGM 95ah DieHard battery which didn't come with a BEM code, but I found a generic number online to input for it. The 1st set tells it the type of battery (supposedly, honestly don't think it knows on our older non UDS BEMs) and the vendor code and serial # are completely irrelevant. So I entered 000915105CE (1 space) JCB (Johnson Control Battery) (1 space) 260924DIEH (date of installation plus DieHard) and voila. Code accepted. Try adding 2 spaces after your 1st set. And honestly all it does is tell the ecu you have a new battery and not to overcompensate for the dying old one anymore with the alternator. Hope this helps.

Also, after you get the code to accept, remove obd, turn the car off, lock the doors, wait about 2 to 3 minutes and start the car. Then turn the wheel all the way left and all the way right (or just drive it). This should clear all the annoying alarms. Then do a full scan and clear all the codes and you should be good to go. You can go through channels 4-22 or so to look at all the battery stats. Your battery aging should read 100% now to indicate a fresh battery.