A battery showing flat after ages is better news that it showing full after minutes.
What charger are you using? If it's a massive battery and a little trickle charger then it probably still isn't charged.
The 36 hours was on an Optimate. I have tried 4 different chargers ( from small units to a 100A jump start charger) and the optimate is still showing test mode and it refuses to take a charge of any of them. Think it is dead!