I’m glad you asked! Check out this awesome PDF I found yesterday that explains how you can figure out how long a battery will last running your electronics. Takes some basic math but it's not too hard to figure it out. You definitely want to use a Deep Cycle Marine Battery, you shouldn't need to recharge it as it's designed for boating and long use w/o requiring a recharge (car batteries are not).

https://www.batteryweb.com/pdf/inverter_battery_sizing_faq.pdf

I wish I could just tell you precisely but in the process of figuring that out, I came across this tent fan that uses a D-Battery Power pack with a DC adapter. It is so simple and exactly what I need. Check it out. I tested the fan and it moves air really well. It supposed to be able to run for 72 hours on low using 8 D-cell batteries. I can hook my inverter up to it and power the AC lights as well!

O2 Cool Portable Tent Fan with Emergency Device Charger and Auto Adapter

http://www.amazon.com/gp/aw/d/B0018EGJNE/ref=redir_mdp_mobile?ref_=cm_cr_pr_product_top

I am not very electronically or technically inclined but I will try to help out if you have anymore questions!