Technaxx TX-75 Replacement Battery 3.7V 7800mAh Li-ion

Technaxx TX-75 / Sender TX-75 — 3.7V Li-ion Replacement Battery (4652)

This is a 3.7V, 7800mAh Li-ion replacement battery for the Technaxx TX-75 and Sender TX-75 wireless home security cameras (also fits model 4648). It matches the OEM part number 4652 and slots into the same battery bay as the original cell. Voltage and capacity are identical to factory spec.

• TX-75, Sender TX-75, and 4648 compatibility: All three models run on the same 3.7V single-cell Li-ion rail with the same physical footprint and connector orientation. The BMS in each unit reads cell voltage against the same threshold table, so the same replacement cell works across the entire lineup without any firmware adjustment.
• Bench tested on actual hardware: We cycled this cell through the TX-75 BMS under simulated motion-event loads — including combined IR LED and processor spikes. The BMS did not trip on cold-start draw, and protection circuitry on the cell responded correctly to over-discharge cutoff tests at the expected low-voltage threshold.
• First-install power cycle: After fitting the new cell, power cycle the camera once through the Technaxx app. The firmware must re-register the cell before motion recording events log correctly to cloud storage — skipping this step can cause silent recording gaps even when the camera appears online.

Why the TX-75 app shows 0% or a frozen percentage after a battery swap

The TX-75 uses a voltage-threshold indicator — not a fuel-gauge IC — to estimate charge level. When a new cell is installed, the camera reads an open-circuit voltage that may not map cleanly to its threshold table until the cell has been through one complete charge cycle. The percentage display can stick at 0%, jump erratically, or show a stale value from the previous cell. Run the battery down to the low-voltage cutoff through normal use, then charge it fully in one uninterrupted session — the indicator recalibrates against the known 3.7V nominal and reports correctly from that point.

Motion trigger dropout after battery replacement on the TX-75

Each motion event pulls current from both the IR LED array and the image processor simultaneously — this combined spike is the highest instantaneous load the TX-75 places on the cell. If the replacement cell's BMS has a conservative peak-current threshold, it can cut out for a fraction of a second, causing the camera to miss the trigger entirely or log an incomplete clip. The TX-75 does not retry a failed motion event — the frame is simply dropped. Verify the cell seats fully in the bay contacts and that no corrosion on the terminals is adding resistance that pushes the spike over the BMS limit.