I purchased this fan for the specific purpose of having some kind of cooling device available during a power outage. As such, I wanted to know exactly how much cooling time I would get from one battery. I’m using a 60-volt, 6.0 Ah “flex-volt” battery; however, my 20 volt, 4.0 Ah battery also (obviously) works.
https://www.amazon.com/DEWALT-DCE511B-Corded-Cordless-Jobsite/dp/B075RFBTS3

