About this replacement
SportDog SD-1825 SportHunter Transmitter — 7.4V Li-Polymer Replacement Battery (SAC00-12542)
This 7.4V 520mAh Li-Polymer battery replaces the OEM cell in the SportDog SD-1825 SportHunter handheld transmitter. It fits the SD-1825 CAMO Wetland Hunter, SD-3225 Hound Hunter, and 20-plus other SD-1825 transmitter variants that share the SAC00-12542 footprint. Dimensions are 31.50 × 25.60 × 13.50mm — verify against your existing cell before ordering.
- SD-1825 transmitter family fit: Every model in this group runs the same 7.4V two-cell Li-Polymer architecture with an identical connector pinout and BMS handshake. One replacement cell covers the full range without modification.
- Bench tested on actual hardware: We cycled this cell through full charge and discharge on an SD-1825 transmitter. The BMS accepted charge correctly, reported state-of-charge accurately to the transmitter firmware, and held voltage within spec across the discharge curve.
- Transmitter wake-up after swap: The SD-1825 transmitter can show a blank or frozen screen immediately after a battery swap if the firmware didn't complete a clean shutdown. Hold the power button for 10 seconds to force a hard reset — this clears the frozen state and allows the BMS to complete its initialisation handshake.
Why the SD-1825 transmitter reads "low battery" immediately after installing a new cell
The SD-1825 transmitter reads state-of-charge from a fuel gauge register inside the BMS, not directly from cell voltage. A new cell that hasn't been through at least one full charge cycle will report an uncalibrated value — sometimes showing critically low charge even at 7.8V. Run the transmitter on charge until the indicator shows full, then discharge it in normal use. After one complete cycle, the fuel gauge calibrates and the readout stabilises.
Transmitter losing range mid-session even with a charged battery
Reduced range from a seemingly charged transmitter usually points to voltage sag under the RF transmission load — the cell voltage momentarily drops below the transmitter's output threshold and the radio stage underperforms. This happens when a cell has aged past 80% capacity, or when a replacement cell was stored at low voltage before installation. Check resting cell voltage with a multimeter — a healthy Li-Polymer cell at full charge sits between 8.3V and 8.4V. If the resting voltage is below 7.6V after a full charge cycle, the cell is not holding charge correctly and needs replacement.