Verified this with Tech Support this weekend, I ended up at a Supercharger with about 3% battery in my 75D Model X. Plugged in and the screen showed 0 Kw, no miles charged, and a 90 minute charge time. The energy showed brief runs to 6Kw and back down to 0. Per tech support this is expected behavior, at low battery levels the Supercharger must trickle charge for 30-60 minutes before "opening up". For me it was about 45 minutes showing 0 miles charged, then suddenly it kicked in and ran at full rate. It did come in almost exactly as stated on screen at 90 minutes. I've found that the in car planner will happily put you to 2-4% at the next Supercharger when planning trips, so it's worth giving yourself the extra time at the previous charger so as not to find yourself with a 60-90 minute charge time instead of 20ish.