Invisible Fence R21 Dog Collar Replacement Battery 3V 150mAh

Invisible Fence R21 / R22 / R51 Series — 3V Li-MnO2 Replacement Battery (IFA-001)

This is a 3V lithium-manganese dioxide cell rated at 150mAh, built to the IFA-001 spec. It fits the Invisible Fence R21, R22, R51, and Microlite collar receivers — the radio-frequency containment collars that deliver boundary warnings to pets. When the original cell depletes, the collar stops responding to the fence signal entirely.

• R21, R22, R51, and Microlite compatibility: These collar models share the same 3V power rail, physical cell footprint (20.64 × 16.45 × 16.45mm), and IFA-001 part number. One cell fits across the range without modification.
• Bench tested on actual hardware: We cycled this cell through the R21 receiver's standby and alert-trigger states. The cell held a stable 3V output across both modes, and the collar's low-battery chirp cleared immediately after swap.
• First-fit activation for RF collars: After installing the new cell, walk the dog to the boundary line within 24 hours. The collar needs to receive a live fence signal to confirm the receiver is reading the new cell correctly — a stationary indoor test won't catch a weak contact.

Why the R21 collar stops beeping at the boundary after a battery swap

The R21 receiver uses a microcontroller that monitors supply voltage before activating the correction circuit. If the cell voltage reads below approximately 2.7V — either from a depleted original cell or a poor contact on a new one — the collar goes silent at the fence line rather than delivering a warning tone. This isn't a fence transmitter fault. Check that the battery compartment cap is fully threaded and the cell is seated flat against both contacts. A correctly seated IFA-001 cell reads 3V at the terminals and restores normal boundary response immediately.

Collar shows full charge indicator but fails to respond to fence signal

Li-MnO2 cells maintain a relatively flat discharge curve, which means the collar's voltage-based charge indicator can read normal even when actual capacity is heavily depleted. The receiver's RF detection circuit draws more current than the idle state, so a weak cell may hold 3V at rest but sag below the activation threshold the moment the boundary signal hits. If the collar passes the LED/indicator check but stops correcting at the fence line, the cell needs replacement regardless of what the indicator shows. Swap to a fresh IFA-001 cell and re-test within 3 metres of the boundary wire.