Just followed the tip up top and it worked perfectly. This is a new TB48 battery from my dealer, never been opened.
Here's what I did:
Opened top of battery. Gently pry front and back areas where there are "clips". Used wooden skewers to loosen the plug (it's obvious). Just pull straight out, not up. Let it sit, disconnected for 1.5 hours, plugged it back in and boom - bright lights. Hooked it up to the charger. Charged in full. Put into the bird. Pushed battery button to start up, said needed to update battery. Got bin file, started only Inspire 1. Battery upgraded flawlessly. Warning came on saying battery was not fully charged and to charge it (77%). Charged it up (only took about 20 minutes), put back in inspire, powered everything up this time and 100% all around.
I am still going to take it easy and cycle the battery a few times before I call it a complete fix.