Educator ET-400 Transmitter Replacement Battery 3.7V 700mAh

Educator ET-400 Series Transmitters — 3.7V Li-Polymer Replacement Battery (PL-752544)

This 3.7V, 700mAh Li-Polymer cell replaces the original battery in Educator ET-400, ET-402, K9-400, and K9-402 handheld transmitters. These are the remote control units used to communicate with Educator dog training collar receivers. The cell matches OEM part numbers PL-752544 and BN720LP and fits the 42.25 × 26.00 × 7.30mm battery cavity.

• ET-400 and K9-400 transmitter family: The ET-400, ET-402, K9-400, and K9-402 share the same transmitter housing, connector orientation, and BMS handshake protocol — one cell covers the full range without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on an ET-400 transmitter body. The BMS accepted the cell cleanly, reached full charge without fault flags, and held standby voltage at 3.7V under normal transmitter idle draw.
• First power-on after install: Charge the transmitter to 100% before pairing to the collar receiver. A partial charge state at first use can cause the transmitter to under-report battery level in the status display until a full charge cycle completes.

Why the ET-400 transmitter stops sending signals before the battery reads empty

Li-Polymer cells lose usable capacity as they age, but the transmitter's fuel gauge calibration doesn't update automatically. An old cell that once held 700mAh may now deliver under 400mAh while the display still reads 50%. The transmitter's low-voltage cutoff triggers before the gauge catches up, cutting output mid-session. Installing a new 700mAh cell and running one full charge-discharge cycle re-aligns the gauge reading with actual capacity.

Transmitter powers on but collar receiver shows no signal lock

After a battery swap, the transmitter firmware performs a brief internal reboot that can interrupt the paired connection to the collar receiver. The receiver doesn't automatically re-register — it waits for a fresh pairing handshake. Power both units off completely, then power the collar receiver on first, followed by the transmitter. The pairing LED on the ET-400 transmitter should confirm link within 10 seconds at standard operating range.