Garmin TT25 GPS Dog Collar Replacement Battery 3.7V 1200mAh

Garmin TT25 / Alpha 100 — 3.7V Li-ion Replacement Battery (361-00035-16)

This is a 3.7V, 1200mAh Li-ion battery for Garmin TT25 GPS dog tracking collars and the Alpha 100 handheld unit. It replaces OEM part number 361-00035-16. The TT25 fits inside a collar worn by hunting or working dogs and transmits real-time GPS location to the Alpha 100 handler unit.

• TT25, A04223, and Alpha 100 compatibility: These devices share the same 3.7V cell footprint and connector pinout. The BMS in each unit uses the same charge termination voltage, so the same cell services both the collar and the paired handheld without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the TT25 platform. The BMS accepted the cell without fault codes, balanced correctly to 4.2V at full charge, and held the low-voltage cutoff at the expected threshold before shutdown.
• First GPS acquisition after battery swap: After installing this battery and powering the TT25 on, take the dog outdoors immediately. GPS trackers perform a cold start after any power interruption — the collar needs 5 to 10 minutes of open-sky exposure to download almanac data and get its first fix. Subsequent power cycles will acquire faster.

Battery draining faster in rural and low-signal areas

The TT25 collar runs GPS and cellular transmission simultaneously. In areas with weak cellular signal, the collar's radio module increases transmit power to maintain contact with the network, pulling significantly more current from the cell. GPS signal degradation under heavy tree canopy adds to this — the receiver stays active longer searching for satellite lock. Expect noticeably shorter charge cycles during hunts in dense forest or remote rural terrain compared to open-field use.

Collar not syncing to the Alpha 100 after a battery swap

After a full power interruption, the TT25 drops its active pairing session with the Alpha 100. The collar does not automatically re-register — the Alpha 100 needs to re-acquire it. On the Alpha 100, navigate to Dog List, select the TT25 collar, and trigger a fresh contact. If the collar still does not appear, confirm it has completed its GPS cold start first, as the collar's communication module is lower priority than GPS acquisition during boot.