Congrats
@trini0t3y for your P85! I also owned 2014 P85 before (now an X).
I spent battery to under 3% many times and I have some suggestions.
- charge to 100% the night before when you plan to do a long distance trip. That would save your charging time significantly.
- try to time the charge at home to finish before you leave. You can leave home at 99% too. This will give you a warm battery so your car won't need battery heater at departure.
- if your trip leg is long start from speed limit plus 5mph and never go above 75. The consumption will be progressively worse if you speed up from there. Keep that speed up to the half point. Then you can speed up if the car has enough range.
- try to target 10% or more at arrival at superchargers.
- if you're under 20%, never mash the accelerator. The battery voltages drop harder if the battery is under high stress from acceleration. This means the battery groups (there are 96 battery groups in a pack) with least charge may give up, causing the car to shut down. Remember BMS tries to save the weakest group.
- if you think you're cutting it close, reduce your speed. This is the best technique to save your energy. Also drafting a semi would save as much as 10%. Enable range mode in your settings. In cold weather, if it's acceptable, reduce AC temp settings, and set to recirculation.
- climbing hills increase battery usage significantly. If you are running low, switch the map to satellite mode and see if there is elevation change to the next charger. If so expect higher consumption.
- be extra careful on night trip and very cold weather trip. Bring warm cloths for insurance.