innobay Personal Fan USB/Rechargeable Battery Operated with LED Light, Quiet (4-inch, Black)

I bought this fan primarily for running on the treadmill and I was not expecting it to be that effective...but hey, it would be better than no fan at all, right?In short, WHOA.This fan totally BLOWS - it feels like it moves more air than my Vornado Flippi V8 desktop fan...probably because the airflow is much more concentrated. On just one 18650 battery that came supplied with it, the fan ran for the 60 minutes that I'd spent running and still had decent charge left over afterwards (at about 3.79V, compared to ~4.15V when fully charged for standard 18650 Lithium ions). Better still, the fan even runs off of USB power alone, so if you have a large capacity battery-pack you don't even need an 18650 battery inside it: you could just plug it in and run it for a LONG time! It will also charge the battery while running on high off USB, if you'd like.I then took it to the San Diego Safari Park, and even though I was wearing a vest and a long-sleeved shirt, by afternoon when it was about 75F my buddies were starting to drench, but I had all my gear on with the fan running and I didn't even break a sweat! Towards the end of the day my friends were starting to fight over this simple $20 gadget, which they ALL wish they had. Furthermore, this thing is small and light...so light that if you leave it on high sitting on the table, it could almost blow itself over. It won't sitting by itself, but if you nudge it just slightly on a table when on high, it'll blow itself over...that's how strong it is. That being said, carrying it around when hiking or just strolling through some amusement parks won't be an issue at all.For $20 bucks I'd highly recommend it! Also, there are cheaper alternative versions of this brand selling with a lower capacity battery. I'd say do yourself a favor and get this version which comes with a high-quality Samsung 18650 rated at about 2200-2400 mAh. It'll last many more recharge cycles, not to mention a couple of more minutes when you really need it. I have a bunch of Panasonic 18650s rated at 3400 mAh for my flashlights, and with one of those in it I've never complained about battery life. On a technical note, the fan will accept both flat-top and button-top 18650 batteries (there are two types), due to its spring on the negative terminal. Again, the fan totally "blows!"

This is an initial review. The fan moves a lot of air. I just received it so I have no opinion on its longevity yet. Some reviewers have stated that they can't find replacement batteries. I believe that is because they are trying to use protected 18650 batteries which are longer than the fan's battery compartment. You have to use unprotected 18650 batteries. I have verified that some Panasonic NCR18650B batteries that I happen to have on hand fit in the battery compartment and power the fan just fine. The fan comes with a Samsung ICR18650-26J battery. I can't find that J version but I found plenty of other versions of ICR18650-26 batteries on Amazon. However, I don't intend to buy any ICR18650 batteries in the future because my NCR18650B batteries work fine. The ICR18650 batteries are older technology and the most dangerous per my online reading. Online blogs also said the ICR18650 battery could be temperamental which could explain some reviewers problems keeping their battery charged. I plan on buying NCR18650BF batteries as more spares for this fan in the future which is even newer technology than the NCR18650B battery. It too will probably fit in the fan compartment because it is supposed to be the same length as the NCR18650B battery. One last note, these rechargeable 18650 batteries are shipped almost depleted so you have to charge them for hours to get them fully charged. My intelligent lithium battery charger confirmed that the battery that came with the fan was almost depleted right out of the box.

In the instructions it says to line the positive and negative ends of the battery up correctly. Not seeing any positive or negative markings on the battery I removed the pink covering only to find no positive or negative markings underneath. Apparently this protective pink covering should not have been removed and you just have to figure out on your own somehow what the positive and negative sides of the battery are. Now I have a defective battery. Better instructions would be nice.UPDATEGot a replacement fan. It turns off within minutes of being turned on. Tired of getting junk on Amazon.

If like me you suffer in the heat, you will love this fan. It is SO effective. Very light weight, free standing and will fit in to larger handbags. 5 1/2 h x 4 1/4 w x 1 1/2 d (inches)