Your Tesla will be charged at the start of your trip and will have plenty of range to get to the mid trip supercharging location listed on your Rental Itinerary or communicated to you by your Tesloop Concierge.
A J1772 adapter may also be available in your vehicle in case an emergency charge is needed and the vehicle is not close enough to make it to a Tesla Supercharger. This will allow you to charge at most public chargers, though not all chargers are free.
Charging the battery to 100% is not recommended. The vehicle charge limit will be set to 80-90% by default.
Letting the battery fall under 20% is not recommended.
Your Tesloop Concierge will be able to monitor your vehicle's battery remotely and may reach out to you.