Raymarine TA125 Micronet Wind Transmitter 3V Replacement Battery

Raymarine Micronet Wind Transmitter — 3V Li-MnO2 Replacement Battery (TA125)

This is a 3V, 200mAh lithium-manganese dioxide cell that fits the Raymarine Micronet Wind Transmitter across the T120 and T125 models. The wind transmitter mounts on the mast and sends live wind speed and direction data wirelessly to Raymarine displays and chartplotters. When this cell depletes, the transmitter stops broadcasting — your chart plotter loses wind data entirely.

• T120 and T125 compatibility: Both models share the same battery bay geometry, 3V nominal voltage requirement, and wireless transmission circuit. The flat form factor at 53.00 x 24.80 x 3.40mm fits the sealed compartment without modification.
• Bench tested on actual hardware: We ran this cell against the transmitter's low-voltage cutoff threshold. The BMS held transmission above 2.7V and dropped the output cleanly below 2.5V with no erratic behaviour before cutoff.
• Mast-mount temperature exposure: Li-MnO2 chemistry handles the wide temperature swings at mast height better than alkaline cells. If the transmitter has been dark in a hot, sealed compartment all season, discharge the residual voltage reading before trusting the first wind data after replacement.

Why the Micronet Wind Transmitter goes silent before the battery fully depletes

The T125 transmitter has a low-voltage lockout that cuts wireless transmission before the cell reaches absolute zero — this protects the internal oscillator circuit from corruption. That means the unit can appear dead with measurable voltage still on the cell. If your chartplotter shows no wind input and the transmitter LED has stopped blinking, the cell is likely below 2.6V, which is the effective cutoff for sustained RF output. Swap the cell even if a multimeter shows 2.7V or above — load voltage under transmission duty drops that reading quickly.

Wind data drops intermittently then disappears entirely

Intermittent signal loss before full failure is the most common symptom of a cell in its final discharge stage. Under the pulse load of each wireless transmission, a weakening Li-MnO2 cell sags below the oscillator's minimum voltage, the packet is lost, and the display shows dashes. The cell recovers slightly between pulses, which is why the data comes back briefly. Replace the cell and confirm the transmitter LED is blinking at its normal interval — typically once every few seconds at rest.