Just completed bucket list of changing to the Magnacores and Champions on my '03 Disco II! Hooked the battery back up, and quickly lost my "happy place", replaced by flashing dash lights and engine not turning over at all. thinking the battery was dead (had done the plug and wire exchange over a long weekend), and the battery charger just blinked back at me and shut off, showing the battery in "abort" mode. Any ideas or fixes I can try? Went back to Doug's video on the plug changeout, and did not see anything related to this issue or 'to do following"

 

It does sound like a very dead battery. You should post this in the Disco 2 section of the forum. You’ll get a lot more views and hopefully replies there.