I worked as a summer camp counselor for 11 weeks in central Texas this last summer where there was no air conditioning in the cabin.  It worked really well even on low speed.  It had more air output than a 6 D-cell battery portable fan on high speed.  I had a small deep cycle battery that it ran off of (the battery was only rated for 23 amp hours).  I ran the fan on average 3-4 hours a day and I only had to recharge the battery every 2 weeks if I was really disciplined in turning off the fan when i wasn't using it.  If you are going to run it constantly over a weekend i would recommend a larger deep cycle battery in the 40 amp hour range.  It was no louder than a battery powered fan but there was so much more air output.  The kids in my cabin called the high setting "hurricane mode" because of the air output.  High speed was a bit loud (similar to a regular box fan), but if sound isn't an issue then it is the greatest 12v fan out there.