Now let me preface this by saying I used these collars while traveling the country full time doing vanlife. East Coast, West Coast, and everywhere in between. Fortunately my dog is quite loyal and I've never lost him but the piece of mind was absolutely necessary while camping out in mountains and in deserts.
I had really great success with the Series 2. Although I broke two of them over a 2 year period, I was pretty happy with it. It would stay charged for a week plus, accurately recorded all our hikes, allowed me to check and make sure my pup was still safe and sound while I was shopping/doing errands.
Both of my Series 2 collars broke in a similar fashion, my 55lb dog managed to tear the plastic clasps on the transmitter which I see here is a common problem. Even after this happened I ended up fashioning them to a regular dog collar with electrical tape til I could get a replacement.
After I broke the second one I figured I'd bite the bullet and buy a Series 3 to upgrade and overall the experience has been so bad that I cannot wait to cancel the subscription.
The Series 3 comes with a metal housing which at first glance seems more sturdy but knowing the unit uses a cellular connection it seems to create some sort of fairiday cage and limits the range and accuracy.
If my cell phones Bluetooth is off the collar will often not work AT ALL. Which defeats the purpose of paying for a subscription when it's just piggybacking off my phone.
Three beach trips is all it took to completely destroy the metal coating on the buckle. Which is a problem I did not have with the Series 2
The collar itself on the Series 3 also has this feature where it loosens up on its own over time.
The app has evolved to the point where it's a pain in the ass just to check the daily timeline of where we've hiked.
Now, if I drive slower than 10mph, it registers as a walk and will tell me we've gone MILES while only taking a step or two.
And worse off all the collar only lasts about 48 hours before I get a notice that the charge as at 19%.
I left a similar review on the FI Collar website and big surprise, they did not post it or contact me about my issues.
Long story short, if you want one of these collars stick to the Series 2. It wasn't perfect but it met all my needs as a full time traveler with my pup.
Fi Collar Series 2: https://shop.tryfi.com/products/smart-collar-v2
替代品：Tractive
如果你不执着于Fi 品牌，可以尝试下Tractive Collar, Tractive 是一个德国的品牌，在欧洲广为流行。我之所以推荐它，有两个重要的原因：
1，其价格比Fi 便宜很多，其价格几乎只有Fi Collar 的一半，长期订阅可以节省很多钱。
2，最主要的是性能更好。我使用tractive 接近两个月，从目前的表现看完全不弱于Fi Collar, 其定位更加精准，且延迟很少，根据我的测试，在我的狗离开虚拟围栏不用一分钟就可以收到通知，这比Fi Collar 快了将近1 -2 分钟。我在Reddit 上和其他一些评测上看到了相同的反馈，比如PCmag的评测
In testing, Tractive reliably sent a notification to my phone when Bradley exited and entered a Safe Zone. The tracker typically took about one minute to deliver an alert in those cases; that's at least a full minute faster than the Fi GPS collor, which usually took anywhere from two to three minutes to send an escape alert in testing. The Whistle was the slowest in our tests, taking around four-and-a-half minutes to send a notification, which as many pet owners know, is plenty of time for a determined doggo to ditch you.
3，更好的售后服务，如上所说，I left a similar review on the FI Collar website and big surprise, they did not post it or contact me about my issues. 而Tractive 总能及时的回复我的反馈，虽然他们没有即时聊天，但通过邮件足够快捷的解决我的疑问。