Perimeter R-21 Dog Collar Compatible Battery 6V 160mAh Silver Oxide

Perimeter R-21 / Ultra Fence Series — 6V Silver Oxide Replacement Battery (PTPRB-003)

This is a 6V, 160mAh silver oxide cell that replaces the PTPRB-003 battery in Perimeter underground fence collar receivers. It fits the R-21, Ultra Fence, PTPFS-003, and PTPCC-100 receivers, along with 11 additional models in the same collar family. At 21.67 x 12.00 x 12.00mm, it matches the original form factor exactly.

• R-21 and Ultra Fence collar compatibility: These models share the same 6V power rail, physical cell slot, and signal-detection circuit. A single cell swap covers the whole receiver family without adapter or modification.
• Bench tested on actual hardware: We cycled this cell through the R-21 receiver's boundary-detection circuit. Voltage held flat across the discharge curve — silver oxide chemistry does that. The receiver's signal threshold stayed triggered consistently from full charge down to cutoff.
• First outdoor check after installation: After fitting the new cell, walk the dog to the boundary wire before assuming the collar is live. The receiver needs the fence transmitter's 7–10kHz signal to confirm the circuit is closed — confirm the LED blinks at the boundary before returning to normal use.

Why the R-21 receiver stops correcting near the boundary after a battery swap

Silver oxide cells have a flat discharge curve, but a fresh cell straight out of packaging can sit slightly below the receiver's minimum detection voltage if stored for a long time. The R-21's signal-detection circuit needs a stable 5.8V or above to trigger the correction output. If the collar seems unresponsive near the wire, measure the new cell's open-circuit voltage before assuming a fault with the transmitter or wire loop. A fresh cell should read 6.2V at rest — below 5.8V, swap it.

Collar LED not flashing at the boundary line after cell replacement

This is almost always a seating problem, not a dead cell. The PTPRB-003 slot uses a friction contact — if the cell is tilted even slightly, the voltage doesn't reach the receiver board. Remove the cell, check the contacts for corrosion or debris, and reseat it with firm, even pressure until the cover clicks closed. Then walk directly over the buried wire and watch for the LED flash. If it still won't flash, confirm the transmitter console shows a closed loop — a break in the boundary wire will prevent any collar on the system from responding, regardless of battery condition.