Purchased for a trip to hot and humid Orlando.This review is BEFORE the trip - in a 74F, 20% humidity roomInitial comments:The device looks and feels very rugged. It had better, for a $280 unit.Even so, I think a fall from your neck onto concrete could do enough damage to make it stop working.Pairing with the app was super easy on iOS.Controls through app are very good.People complain about the battery life - and I agree. It is bad. BUT there is a pretty simple way to get a SIX HOUR cooling session with max cooling. Read on...I talk about the tests I ran later. If you don't want to read that, here is the summary:- To preserve the life of your Coolify batteries, try to keep the charge between 20% and 80%. Lithium batteries don't like to go outside that range.- Coolify can run at maximum fan and cool for about 75 minutes using its built-in batteries. After that (when the battery gets low), Coolify stops cooling and just lets the fans blow air. That is a pretty bad cooling span.- BUT THERE IS GOOD NEWS: If you have a 20W charger, Coolify charges at about the same rate as it consumes energy at max speed. This means that if you have a 20W charging pack connected while using Coolify, you can use it pretty much until the charger battery is depleted, and then about 60 minutes after that when the Coolify battery kicks in.- So if you have, say, a 20000mA 20W charging device connected, you can run Coolify at 100% for approximately SIX HOURS until the charger is depleted, and then maybe another hour on the Coolify battery. And COLD will work during that entire time. The Coolify comes with a long enough USB-C cable so that you can keep the charger in your backpack or pocket.- I recommend the Anker Zolo 20000mA battery pack. It is small, lightweight, and only costs $30. Anker brand has not let me down. They also have a 10000mA version for $20 that is even smaller and lighter. These Anker chargers also DO NOT get hot. Other brands do.- A 10000mA charger can sit in your pocket pretty comfortably. If you can handle the discomfort of something around your neck for many hours, you can certainly tolerate a small charger in a pocket.- A 20000mA charger is better suited for a backpack or fanny pack.With that summary aside, here is something interesting:I thought the Coolify was a straight Peltier cooler (i.e. not an efficient device at all), but the specs call out R-410A REFRIGERANT. Personally, I am not buying the claim that this tiny device has refrigerant inside of it, along with a compressor and evaporator. Without those, you don't truly have an A/C. Nor do I think having a refrigerant under pressure in the vicinity of your neck is safe. So I am calling B.S. If this is somehow a real micro A/C unit, then they have truly invented something cool (pun intended).Now for the battery tests:Test #1: Run cool mode with max fan continuously and report battery % every 30 minutes.NOT connected to a charger - just running as anyone would expect to use it.Results:0 min, 100% / 30 min, 68% / 60 min, 40% / 90 min, 12%I stopped the test after 90 min, as running Lithium to 0% is not healthy for the battery.The plates were definitely NOT cold at the end of the test compared to the start.So I think there comes a point where Coolify goes into a "low battery" mode and turns off cooling, leaving the fans running.Test #2: Charge Coolify, reporting charge level every 30 minutes. Also report how much my charging device depletes along the way. Coolify claims it supports 20W charging, so I am using a brand new Anker Zolo, 20000mA charger ($30). I am using the charger's built-in USB-C cable, rated for 20W. Fantastic price for an Anker 20000mA charger!Results:Coolify: 0 min, 10% / 30 min, 44% / 60 min, 72% / 90 min, 91%Anker: 0 min, 100% / 30 min, 89% / 60 min, 81% / 90 min, 72%Battery in the Coolify is 6000mA, and my Anker battery is 20000mA, so it makes sense that Anker is around 70% after charging the Coolify.Based on first two tests, the charge curve of the Coolify is very similar to the discharge curve.After 90 minutes at full speed, Coolify went from 100% to about 12%After 90 minutes of 20W charging, Coolify went from about 10% to about 91%So theoretically, if the charger was connected to the Coolify while Coolify was operating at full speed, the Coolify battery would not drain much at all; main drain would be on the charging device battery. So test #3 sets out to see if this is true.Test #3: Run cool mode with max fan again, BUT keep Anker 20000mA charger connected.Again, to get maximum use, needs to be connected to a 20W charger, or the charger cannot keep up.Results:Coolify: 0 min, 94% / 30 min, 94% / 60 min, 94% / 90 min, 94% / 120 min, 94%Anker: 0 min, 69% / 30 min, 62% / 60 min, 55% / 90 min, 49% / 120 min, 43%Most importantly, the Coolify plates stayed COLD during this test.I didn't run the test longer, but you can see that eventually the Anker battery would deplete and the Coolify battery would take over.Doing the math, a 20000mA 20W charger would run about 6 hours and a 10000mA 20W charger would run about 3 hours.So, this is a $270 cooler that only cools for an hour with its miserable battery. But adding a $30 external battery to it makes the cooling last SIX HOURS. That suddenly makes it a pretty good deal.Could a cheaper cooler do this? Probably in terms of the battery. But this one has more cooling surfaces, more fans, and stronger fans. So based on that, I think this is a great buy if you are gong on a trip to a very hot area.The one thing I am REALLY concerned about is the rain and sweat. How will it affect the cooler over time?If I remember, I will follow up.