Get a 12VDC fan and run it off you 12VDC accessory port. If you only have one battery, you will need some way to monitor the voltage (should not let the voltage drop below 12.0VDC) and charge your battery everyday. At some locations in the mountains you can not use a generator so you may need to charge your battery using your TV to charge it.
Order a digital voltage display something like the one below on Amazon, they are inexpensive, it will let you know when you can no longer use you battery until it gets recharged. Do not use the USB chargers unless you have a fully charged battery.. but in the mountains you may not have cell service anyway.
Have fun!!!!!
Don