About this replacement
Allflex RS320 / PW320 — 9.6V Ni-MH Replacement Battery (51FE0421)
This is a 9.6V, 700mAh Ni-MH replacement battery for the Allflex RS320 and PW320 handheld livestock identification scanners. It replaces OEM part number 51FE0421. The RS320 and PW320 share the same voltage rail, connector, and BMS handshake, so one pack covers both readers.
- RS320 and PW320 compatibility: Both models run the same 9.6V power architecture and use an identical dock connector and BMS communication protocol. The same cell configuration satisfies both devices without any modification.
- Bench tested on actual hardware: We cycled this pack through repeated scan-trigger bursts on the RS320 and monitored BMS response at varying charge states. The protection circuit held voltage within spec across simulated multi-hour tagging sessions without false cutoffs.
- First-install charge on the RS320: Before taking the scanner out to the yards, seat the new pack in the cradle and run a full charge cycle. Ni-MH cells at partial charge are most vulnerable to inrush current from the scan trigger — a full cell prevents BMS trips on the first tag read of the shift.
Why the RS320 cradle shows a charging error on a new pack
Allflex cradles use contact resistance as part of their charge-initiation check. A new pack straight from packaging often has oxidation or residue on the gold-plated terminals. If the cradle reads contact resistance above its threshold, it flags a fault and suspends charging. Wipe the pack's terminal strip with a dry cloth before seating it. Once contacts are clean, reinsert the pack firmly — the cradle LED should shift from error to charging within a few seconds.
Scanner not reading ear tags after battery swap
The RS320's RFID reader module requires a stable voltage above approximately 8.5V to power the antenna and decode tag responses. If the replacement pack is shipped at a low state of charge, the cell voltage under load can sag below that threshold — the scanner powers on but the reader circuit never fully initialises. The fix is straightforward: charge the pack fully before first use, then retest. A fully charged 9.6V Ni-MH pack holds enough headroom to sustain the antenna inrush on the first scan trigger.