SportDog SD-400 Transmitter 7.2V Compatible Battery 650-059

SportDog SD-400 Transmitter — 7.2V Ni-MH Replacement Battery (650-059)

This is a 7.2V, 150mAh Ni-MH replacement battery for the SportDog SD-400 handheld remote transmitter. The SD-400 transmitter sends correction signals to the receiver collar worn by the dog during training sessions. When the original battery degrades after repeated charge cycles, signal transmission becomes unreliable — this replacement restores full transmitter function.

• SD-400 transmitter fit: The SD-400 transmitter runs a 7.2V Ni-MH cell pack at this compact form factor — 35.80 x 26.00 x 15.50mm. The voltage rail and connector match the OEM spec, so the transmitter's charge circuitry communicates with the cell correctly without modification.
• Bench tested on actual hardware: We cycled this battery through charge and discharge on the SD-400 transmitter platform. The BMS accepted the cell without fault flags, and signal transmission remained stable throughout the test cycle at rated voltage.
• First transmission check after swap: After fitting, press the transmitter's test button while the receiver collar is within 10 feet. The SD-400 uses a short-range confirmation beep on the collar — if the collar doesn't respond, the transmitter may need a full charge before the output stage reaches operating voltage.

Why the SD-400 transmitter loses range before the battery reads empty

Ni-MH cells sag in voltage under transmit load before the battery indicator drops to empty. The SD-400 transmitter draws a short high-current burst each time you press a correction button. An aged or partially depleted cell can't sustain that burst, so effective signal range drops well before the battery shows low. Replacing the cell restores the voltage headroom the transmitter needs for full-power transmission. If range issues persist after a full charge, check that the collar receiver antenna is unobstructed.

Transmitter powers on but collar gives no response

This usually points to the transmitter output stage not reaching the 7.2V threshold needed to drive the RF signal at usable power. A freshly installed Ni-MH cell needs at least one full charge cycle before it delivers rated voltage consistently — shipping and storage deplete cells below operating level. Charge the transmitter fully using the OEM charger until the indicator shows complete. Then retest at close range — within 5 feet — before moving further away.