A power outage in the height of Texas summer is just about the worst thing that can happen. During one that lasted several hours, I ended up driving across town and taking my elderly dog shopping, just to get her inside somewhere that had a/c. More recently, we've had some short power outages, lasting maybe an hour each. Still, that's enough time for my apartment to go from slightly-warmer-than-I'd-like to my-living-room-is-a-burning-hell. Looking for a back-up plan, I decided to see if battery operated fans were even a thing, and that's when I found this O2Cool fan. I was a little nervous about buying it, since a few reviewers said theirs didn't work or didn't last, but a few reviews from hurricane areas had me wanting to give it a try. So I ordered one and crossed my fingers.TL;DR: Awesome fan, works great!First off, I like the size and design. This isn't one of those tiny palm-sized USB fans; it's about a foot wide in total, with a 10" span inside for the actual fan blades. It's slightly taller than it is wide, but it's depth is pretty compact. The vented cover is sized just right for me to not accidentally slip a finger inside when I pick it up, though it does have a carrying handle if you want to play it really safe. It does come with an A/C adapter, which I guess is nice, but I don't really need. Then again, it may come in handy if one of my two regular fans goes out and I need a temporary replacement.It's kind of a battery hog in that it needs 6 D-batteries to run, but honestly, I think that's a good thing. Any less, and it'd be a much smaller, weaker fan that wouldn't last any time at all. I haven't had occasion to run it for hours and hours and hours, but according to other customers, it lasts 9+ hours on high and even longer on low. I think that will be plenty to get me through the next power outage. And about those low and high speeds... This thing has great air flow. I wouldn't want to set it up 10 feet away from me, but since it's not tied to a cord or outlet, that won't be a problem. On low speed, there's plenty of air flow, and on high speed, it's awesome. It's slightly less powerful than the 22" corded turbo fans I use on a daily basis.All in all, I'd say this is an awesome buy. I was impressed enough with the first one that I immediately ordered a second, and both work very well with both the A/C adapter and batteries. I'm stocked up on D batteries now, too, so it looks like I'm set to ride out the next power outage in comfort!Update 12/1/2108: I bought two of these fans to get me through a power outage, which hasn't happened yet. But a few weeks ago, my apartment's a/c went out in the middle of the night, and the two fans I brought into the bedroom just weren't enough. I ended up grabbing one of these battery operated fans, intending to use the included A/C cord, and set it up on my nightstand. But in my sleepy, overheated stupor, I turned it on and quickly fell asleep -- forgetting to plug it in. Six hours later, I woke up and called maintenance, and they had my a/c fixed fast. Then I went to unplug and put away this fan, only to realize I'd left it running on high for 6 hours on nothing but battery power! So yes, I can now say without a doubt that these little fans run great for at least several hours.Update: Here I am. Power outage. Texas. Summer. While my neighbors sit in their doorways trying to catch a weak breeze, my dog and I are comfortably lounging on the sofa, a fan trained on each of us, while she sleeps and I read my Kindle. This is EXACTLY the scenario I wanted to be prepared for, and these fans are everything I'd hoped for!

This is my third Treva 10 inch battery or wall plug powered fan. It puts out a lot of air for its size and is very cooling. I used it frequently last year when we had temporary power outages due to local construction. I highly recommend this fan as an emergency back-up or even for a regular cooling fan. I have a supply of D-cell batteries for various things around the hour. Surprisingly this fan runs for a couple of days with a new set of D-cells. It’s a life saver in August when the power is off and we are sweltering in the heat and humidity. Highly recommend.

The fan is very light and easy to take anywhere you go I sit on the job. I take it camping, but it also uses batteries and it also runs on low voltage. If you are looking for something portable to take around not too big not small. This might be for you. works great for me.

I bought this fan as a replacement for the one I broke (accidently knocked it off the cabinet; it was working great until then). The fan itself is great! It's quiet and powerful, even on its lowest setting. And I love the flexibility of using a power adapter or batteries. So, absolutely 5 stars for the fan. However, I'm giving the overall purchase experience 4 stars because the first fan Amazon shipped in a bag and guess what -- it broke! The fan also appeared to have been used as the box was torn & the power supply was not wrapped up. The replacement fan arrived in a box this time but was missing the power cord. Fortunately, I was able to use the old power cord to get a functioning fan without having to replace it a 3rd time. Treva needs to reconsider their packaging and Amazon needs to reconsider their packing. Other than that, my new fan is FANtastic and I hope to not drop this one!

The fan works just as described. Like that it runs on batteries which I need during blackouts and it provides a nice breeze.

This fan is everything. It's light and easy to pick up and move around, it's nice and narrow so it fits on a window sill, and it's so quiet that my cat (who is afraid of fans) walked up to it to investigate and wasn't scared as it blew his fur back as though he was in a wind tunnel. The sheer amount of air this thing moves is insane and yet it's also stable enough on high speed that it doesn't even wobble or tip back (unlike my faithful lasko box fans that need to be propped against a nearby wall so they dont push themselves backwards even on the lowest speed). Finally, the fan of my dreams is a reality.

Ran for 9 HOURS on batteries !!! I got two of these units for an outdoor event. I brought a bunch of D batteries assuming this thing was just going to blow through them ( no fan could run for 8 hours, right ?! ). I initially did what the directions said and ran both fans on low, but within 30 minutes of turning them on, my wife set them on High. We were under a popup tent for an event, on a concrete street in 95 degrees Florida heat. After a few hours, we just forgot they were running on batteries, and random people were popping in our tent to steal some air from our fan ( ha ha ). Then at the end of the event, I realized we never switched the batteries, and these freaking fans had run non-stop for NINE HOURS. Both of them, without flaw.Needless to say, these are going with us from now on. I am super impressed, even more so by what happened the next day. So we got these units home and I took the batteries out of them and ended up putting one next to my bed to run at night since they had a nice breeze. I had this fan plugged in.Around 10 AM the power went out because of a storm, but this fan kept on running for 5 minutes. I was confused since the batteries were out, and I had no idea how the fan could still be running. Turns out the fan is so efficient that it was literally running off the stored charge in the capacitor in the power brick that the unit uses for power.I honestly can't get over how impressive that is. NO BATTERIES. NO POWER. And the thing still ran for 5 minutes just off the stored charge in the power brick that was plugged into the outlet... even though everything else in my house was dead !!!

I use them in my motorhome to mainly just for air circulation to help with the AC’s in this South Florida heat. They do the job great, they are quiet, and the last one ran nonstop for two or more years before it quit.

Si lo que quieres es un ventilador que ocupe poco espacio, que sea practico y portatil definitivamente este ventilador es para ti.Si lo que buscas es algo con potencia te sugiero buscar mas opciones, ya que este ventilador cuenta unicamente con 2 velocidades, siendo la velocidad alta no muy util para espacios grandes.En general un buen producto por su tamaño y portabilidad.

Brilliant battery fan, so powerful and well constructed. Bought for here in Australia for when we have blackouts which are a common occurrence in summer. Used it twice when power cut out and it was a 43”C day, worth the wait in having it shipped from America, subsequently bought another for myself and one each for relatives. Makes so much sense having this as a backup cooling system. Fantastic brand, sturdy and affordable. Totally recommend.

Works a treat xx good fan for if you have to leave dogs in the car for couple of minutes ....With windows ajar as well , but keeps air circulating . Will be great for use in caravan awning as well

works great - been a few weeks now and it goes 24 - 7 circulating heat from woodstove in kitchen to rest of house and it moves enough air to keep house warm and it nice and quiet too - have not tried it on batteries yet - but thought it be handy to keep air moving even when hydro goes off, was a good price , very fast shipping - I happy

veru good