First of all - and I can't stress this enough -
charge the battery overnight, every night. A rental
ECV should be able to go all day at WDW if it is properly and fully charged overnight. And the place to charge it is inside your hotel room.
But also: don't leave an ECV unattended in a Resort Hallway (or patio) overnight to charge. You rented it, and you are responsible for it, and just like your luggage - it belongs in your room with you. (don't worry, you should have *plenty* of room at Yacht Club!

) If you find that you want more space, you can always visit the Front Desk (or call Housekeeping from your room phone) and ask to have the table & chairs removed for the duration of your stay. Remember that calls from your room to the "Front Desk" at WDW Resorts go to a centralized call center - so if you want to talk to someone at the Resort you are staying at, a quick trip to the Front Desk is your best bet.
Leaving your
ECV rental outside, unattended, (even on a patio) means that any of the following is possible:
- It can be stolen/moved (yes, even if you take the key); I have seen more things wind up in the bottom of hotel pools over the years than I care to remember, including personal mobility devices.
- It can be tampered with; this could mean you are responsible for not only the damage to the unit, but also will lose precious vacation time resolving an issue that could have been prevented if the unit was in your room to begin with.
- Someone could come along and unplug the device, so it doesn't charge overnight. You will spend the next day looking for outlets all day long (and they are not easy to find in the Parks!) instead of enjoying yourself!
- Someone could do any of the following: vomit on the unit, relieve themselves on the unit, allow their animal to relieve itself on the unit, pour food and/or beverages on the unit, etc...
It's just not worth it. None of us *want* to have to keep a mobility device in the confines of our hotel room, but you will have plenty of space at Yacht Club - there is a member here on the DISboards who famously got *4* mobility devices into a room at POP every night, and still had room for everyone to move around! (Plus, I'm not sure that every patio has electrical outlets...? I know that some of the patios we have had a other Deluxe Resorts have NOT had outdoor outlets)
Regarding rain: Some vendors will have a clear "shower cap" to put over the controls; others include a poncho. Obviously, we try to keep our scooters (and especially the exposed electronic controls) as dry as possible, but it's Florida, and you will most likely get caught in a shower at some point. Don't panic - use what the vendor supplies, and you can always wear a standard Parks poncho, put the back of the poncho OVER the seat back (so it hangs down behind the scooter) and put the FRONT of the poncho OVER the front of the scooter to cover the controls, and go on! Some vendors now have "weatherproof" or "rainproof" ECVs, however I would still carry a poncho just to cover the seat - you don't want to sit on a wet seat all day!
Be sure to let us know if you have any more questions about ECVs at WDW!