About this replacement
SportDog FieldTrainer 425 / SD-425 Series — 3.7V Li-Polymer Replacement Battery (SAC54-13734)
This 3.7V, 190mAh lithium-polymer battery replaces the OEM cell in the SportDog FieldTrainer 425, FieldTrainer 425S, SD-425, and SD-425S training collars. It powers the collar's remote training receiver and communication circuit. Dimensions are 25.90 x 20.48 x 5.20mm — verify your cell matches before installing.
- FieldTrainer 425 and 425S platform: The SD-425 and SD-425S share the same receiver housing, connector, and BMS handshake requirements. Both collars draw from the same 3.7V cell with identical footprint — one battery covers the full family.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the SD-425 receiver board. The BMS accepted charge without fault flags and held stable voltage through the full training-signal output cycle.
- First GPS acquisition after swap: After installing the new battery, take the dog outside immediately. The collar performs a cold GPS start after any power interruption — allow 5 to 10 minutes outdoors for the first location fix. Subsequent warm starts are faster.
Why the FieldTrainer 425 collar drains faster in rural or open fields
In low-signal areas, the collar's receiver circuit works harder to maintain communication with the handheld transmitter. If the transmitter and collar are at or near the 500-yard range limit, the collar draws more current sustaining that link. A 190mAh cell has limited headroom under this kind of continuous load. Keep the transmitter within closer range during the first few sessions to confirm baseline battery behaviour with the new cell.
Collar shows charging but returns to 0% immediately after unplugging
This usually means the original cell has failed open — it accepts surface charge but holds no capacity. The symptom appears on the charger LED as a normal green ready light, then the collar dies within seconds of unplugging. The fix is a cell replacement, not a charger replacement. After fitting the new battery, charge until the indicator shows full, then verify the collar powers on and holds voltage above 3.6V at rest.