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The Fi dog collar Series 3 (now sold as the Series 3+) is a GPS collar with a built-in cellular tracker on AT&T’s network, so a Fi membership is required. Fi rates the battery at up to 3 months, which assumes light activity near home; reviewers report about 1 to 2 months in regular use and about a day in Lost Dog Mode. Fi lists the tracker at 47 g, it works with iOS and Android, and it is not the best fit for very small dogs. Updated October 2026.
This review covers battery by use, weight, coverage, Android support, multiple dogs, membership terms, and who should pick something else. For the cheaper-to-run alternatives see GPS dog trackers with no subscription, and for runtime of every major tracker see Dog GPS Collar Battery Life: Real Numbers by Model.
📋 Table of Contents
- Fi Series 3+ GPS Dog Collar
- Fi Series 3 battery life: what to expect
- How heavy is the Fi Series 3? Is it too heavy for a small dog?
- Does Fi work with Android? Which carrier, and where?
- What membership comes with a new Fi Series 3?
- Does Fi have a geofence and a buzzer?
- Multiple dogs on one Fi account
- Fi Series 3+ vs Fi Mini vs Tractive vs Halo vs AirTag
- What the Fi app adds beyond tracking
- How to stretch the Fi battery
- Is the Fi Series 3 worth it?
- Pros, cons and common complaints
- Who the Fi Series 3 is not right for
- Frequently Asked Questions
- Sources we checked
- Related guides
Fi Series 3+ GPS Dog Collar
Fi Series 3+ GPS Dog Collar & Tracker, Membership Required, Gray L | GPS tracking collar for dogs with health & behavior monitoring, escape alerts, waterproof, LED, Apple Watch compatible
Included for 'Fi Series 3 GPS Dog Collar Review (2026): Battery & Plans' because the listing is waterproof, which is the attribute this article compares.
View on AmazonFi Series 3+ – AT&T cellular + GPS + Bluetooth/Wi-Fi – up to 3 months – 47 g tracker – membership required. Sold in small, medium and large collar sizes with a range of band colors.
Fi Series 3 battery life: what to expect
See also: 7 Best Refillable Frozen Dog Treat Toys for Long-Lasting Licks • Best Dog Door Mat for Muddy Paws: Sizing, Materials and Picks by Entryway
Fi’s own comparison chart lists the Series 3+ at up to 3 months. That is a best case for activity-tracking mode, where the collar mostly stays inside your home Wi-Fi zone and checks in lightly. Independent results are lower:
- Treeline Review (updated August 2026) measured about 10 weeks against the 3-month claim.
- Outdoor Life (updated February 2026) calls 1 to 2 months realistic and measured about 21 hours in Lost Dog Mode with good cell coverage.
Heavy live tracking, long walks outside the home zone and poor signal all pull the number down. The design is why the battery lasts at all: the collar uses a low-power link at home and speeds up location updates only when the dog leaves the safe zone. When the dog is out of the zone and in Lost Dog Mode, plan for roughly a day of runtime, so charge promptly after any escape.
How heavy is the Fi Series 3? Is it too heavy for a small dog?
Fi lists the Series 3+ tracker at 47 g (1.66 oz), and its lighter Fi Mini at 16 g (0.56 oz). A common rule of thumb is to keep a collar-mounted device to a small fraction of the dog’s body weight, and the collar is sized for medium and large breeds, so for dogs under about 10 pounds the module can look proportionally large. Fi’s lighter option for small dogs and cats is the Mini, which clips onto a collar and uses Verizon according to Fi’s support comparison.
Fi Mini
Fi Mini GPS Dog Tracker, Collar Attachment, Membership Required | Lightweight dog GPS locator, virtual fences, escape alerts, step & health tracking, pedometer, waterproof, fits most collars
Included for 'Fi Series 3 GPS Dog Collar Review (2026): Battery & Plans' because the listing is waterproof, which is the attribute this article compares.
View on AmazonFi Mini – collar attachment – 16 g – membership required. Battery ratings for the Mini differ between sources (Fi lists up to 2 months, Treeline Review lists up to 6 weeks), so check Fi’s current chart.
Does Fi work with Android? Which carrier, and where?
Fi supports both iOS and Android. The Series 3+ uses AT&T for GPS and cellular tracking, the Fi Mini uses Verizon and the Fi Ultra uses T-Mobile, per Fi’s support comparison. That means the answer to “is the Fi collar only AT&T?” is yes for the Series 3+: coverage follows AT&T’s US map, so rural gaps are possible. Fi sells and supports the collar for US networks, so check Fi support before relying on it in Canada or anywhere abroad. If you live in one country and your dog is somewhere else, a cellular tracker will only report where its carrier has coverage.
What membership comes with a new Fi Series 3?
Fi states that a membership is required for every Fi device. Retail listings differ: older listings said “6-Mo Membership Included” or “12-Mo Membership Included” in the title, while current listings say “Membership Required”, which means you add the plan during setup. Read the listing title before buying so you know whether any months are bundled, and check the plan terms in Fi’s app. Without an active membership the tracker cannot report location.
Does Fi have a geofence and a buzzer?
Fi has a safe-zone escape alert: you set a boundary in the app, usually your home address with a radius around the yard, and get a push notification when the collar leaves it. The collar then moves into faster updates. Fi does not list a tone, vibration or correction cue to keep the dog inside, so it alerts you rather than stopping the dog. If you want a collar that gives a cue at the boundary, see the Halo Collar review.
Multiple dogs on one Fi account
Each Fi tracker follows one dog, and Fi requires a membership for every device, so a second dog means a second collar and a second membership. You can share a collar with family members in the app so more than one person receives escape alerts. Confirm multi-dog plan terms in Fi’s app before you buy.
Fi Series 3+ vs Fi Mini vs Tractive vs Halo vs AirTag
| Tracker | Network | Rated battery | Plan | Cues at boundary |
|---|---|---|---|---|
| Fi Series 3+ | AT&T cellular + GPS | Up to 3 months (low activity) | Required | Alert only |
| Fi Mini | Verizon cellular + GPS | About 6 weeks to 2 months, sources differ | Required | Alert only |
| Tractive DOG 6 | Cellular + GPS | Up to 14 days (6 without Power Saving Zones) | Required | Alert only |
| Tractive DOG 6 XL | Cellular + GPS | Up to 42 days (20 without Power Saving Zones) | Required | Alert only |
| Halo Collar 5 | GPS fence + cellular | Up to 48 hours | See Halo’s terms | Yes |
| Apple AirTag (collar mount) | Bluetooth and UWB, crowd-sourced | Months, no live GPS | None | None |
Whistle trackers are no longer an option: Tractive acquired the brand and Whistle devices stopped working on August 31, 2025.
Tractive DOG 6
Tractive Smart Dog GPS Tracker | Live Pet Tracker with Virtual Fence | Vital Signs Monitoring of Heart & Respiratory Rate | Bark Monitoring | Dog Collar Attachment (Black)
Included for 'Fi Series 3 GPS Dog Collar Review (2026): Battery & Plans' as a representative home product in this roundup; selection reflects the product set returned for this topic.
View on AmazonTractive DOG 6 – cellular + GPS – up to 14 days with Power Saving Zones – membership required. A shorter-battery alternative if you prefer a clip-on tracker. See the Tractive review and GPS tracker vs Fi Series 3.
What the Fi app adds beyond tracking
Fi positions the collar as a daily-use device, not only an emergency tool. The app shows activity, rest and sleep trends and lets you set a daily goal. That is useful as a baseline for how active your dog normally is, though it is not a medical device. If you notice a sudden, lasting change in your dog’s energy, appetite or behavior, talk to your veterinarian rather than relying on an app graph.
How to stretch the Fi battery
- Set the safe zone around your home and keep the collar on your home Wi-Fi so it can stay in low-power mode.
- Avoid leaving live tracking on after a walk. Use it for the walk or the escape, then let the collar go back to normal.
- Recharge soon after any Lost Dog Mode episode, since that mode drains the battery in about a day.
- Keep the Fi app and collar firmware updated.
- Expect fewer days in cold weather, when rechargeable cells lose some capacity.
Is the Fi Series 3 worth it?
It fits owners of medium and large dogs who want live tracking, escape alerts and a collar that lasts weeks between charges, and who accept a required membership. It is a weaker fit for tiny dogs, for owners who want a boundary cue, and for anyone outside AT&T coverage. If battery life is your top concern, compare it with the Tractive XL models in our ranked battery picks before you decide.
Pros, cons and common complaints
- Pros: long battery for a cellular collar, integrated tracker with no clip to lose, escape alerts, activity and sleep data in the app, works with iOS and Android.
- Cons: membership required, AT&T-only coverage on the Series 3+, not suited to very small dogs, no correction cue at the boundary.
- Common complaints: battery lasts weeks rather than the full 3 months in regular use, Lost Dog Mode drains the battery in about a day, and the tracker needs cell signal to report.
Who the Fi Series 3 is not right for
The tracker is built into the Fi collar band, so you cannot move it to a different collar. Dogs that need a specific collar type, such as a wide band for a sighthound or a training collar, may not be a match. Owners who want to avoid a monthly plan should look at radio or no-plan options. Owners of tiny dogs should look at the Fi Mini or a lighter tracker. For escape artists that need a correction cue, a GPS fence collar is the closer fit.
Frequently Asked Questions
How long does the Fi Series 3 battery last?
Fi rates it at up to 3 months at low activity. Treeline measured about 10 weeks and Outdoor Life reports 1 to 2 months in regular use, and roughly a day in Lost Dog Mode.
How much does the Fi Series 3 weigh?
Fi lists the Series 3+ tracker at 47 g (1.66 oz). The Fi Mini is lighter at 16 g.
Does the Fi Series 3 work with Android?
Yes. Fi supports both iOS and Android through its app.
Is the Fi collar AT&T only?
The Series 3+ uses AT&T. Coverage follows AT&T’s US map, with possible gaps in remote areas. The Fi Mini uses Verizon.
Can the Fi Series 3 track multiple dogs?
One tracker follows one dog, and each Fi device needs its own membership. Several people can be added to the same collar to receive alerts.
Is the Fi Series 3 good for small dogs?
Not for very small ones. For dogs under about 10 pounds, look at the 16 g Fi Mini or another lightweight tracker.
Does the Fi Series 3 include a membership on a new purchase?
Fi requires a membership for every device. Older listings bundled 6 or 12 months; current listings say “Membership Required”, so check the listing title.
Does Fi have a geofence?
Yes. You set a safe zone in the app and get a push alert when the collar leaves it. There is no tone or vibration cue.
What happens to tracking if my phone battery dies?
Alerts go to every person added to the collar’s account, so add a second user as a backup. Charge your phone before you rely on live tracking.
Sources we checked
- Fi product comparison and “Fi difference” pages (battery, weight, membership, Android)
- Fi support comparison of Series 3+, Mini and Ultra (carriers)
- Treeline Review, GPS dog collar battery life measured vs claimed, updated August 10, 2026
- Outdoor Life, best GPS dog collars, updated February 13, 2026
- Tractive battery page
Related guides
- Which Fi tracker to buy
- Dog GPS collar battery life by model
- Longest-lasting GPS dog collar picks
- AirTag vs GPS collar
- Halo Collar review
- Pet tech hub
