About this replacement
Garmin T 5 mini / TT 15 mini — 3.7V Li-ion Replacement Battery (361-00035-09)
This 3.7V, 1200mAh Li-ion battery replaces the original cell in the Garmin T 5 mini and TT 15 mini GPS dog tracking collars. It fits the standard collar housing with no modification. Voltage and capacity match OEM spec (361-00035-09 / 010-11828-40).
- T 5 mini and TT 15 mini collar fit: Both collar models share the same battery bay dimensions, connector pinout, and BMS handshake protocol — that is why one cell covers the full lineup. The TT 15 mini adds training stimulation hardware but draws from the same 3.7V rail.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on a TT 15 mini unit. The BMS accepted the cell without fault codes, balanced within normal parameters, and the collar powered GPS acquisition on the first attempt after install.
- First-fix GPS acquisition after swap: After fitting a new battery, take the dog outside immediately and leave the collar powered on in open sky. GPS trackers perform a cold start after any power interruption — the almanac data is lost and the unit must redownload satellite positions from scratch, which takes longer than a warm start.
Why the T 5 mini drains faster in rural or wooded hunting areas
In areas with weak GPS satellite visibility or poor cellular signal, the collar's radio and GPS module both increase transmit power and polling frequency to maintain a fix. This draws significantly more current from the 3.7V cell than normal open-field use. Dense tree canopy forces the GPS chipset into extended acquisition cycles, which compounds the drain. If battery life drops noticeably on hunt days versus backyard use, that is the cause — not a faulty cell.
Collar shows charged but won't sync location to the Garmin app after a battery swap
After a full power interruption, the collar drops its active Bluetooth and cellular session with the paired handset. The Garmin app does not always reconnect automatically — it waits for the collar to re-register on the network. Power cycle the collar once fully, then force-close and reopen the Garmin app on your phone. If the collar still shows offline, navigate to the device settings in the app and tap "Reconnect Device" to trigger a fresh pairing handshake.