Brother PJ-520 Replacement Battery PA-BT-300 14.4V 360mAh

Brother PJ-520 / PJ-560 Series — 14.4V Ni-MH Replacement Battery (PA-BT-300)

This is a 14.4V, 360mAh Ni-MH replacement battery for the Brother PJ-520, PJ-522, PJ-523, PJ-560, and compatible models in the PJ portable printer range. It replaces OEM part numbers PA-BT-300, PA-BT-500, and LB4707001. The battery restores untethered operation for mobile receipt and label printing without an AC connection.

• PJ-500 and PJ-560 series compatibility: These models share the same 14.4V battery rail, connector pinout, and BMS handshake protocol. One cell fits across the range because Brother standardised the power architecture across both print-head generations.
• Bench tested on actual hardware: We ran this battery through charge cycles on a PJ-560 unit and monitored BMS cutoff thresholds. The protection circuit engaged correctly at undervoltage and capped charge termination at the expected delta-V peak — no overcharge drift detected.
• First-deployment print sequence: After installing, charge fully, then run five consecutive test prints before field use. The PJ series paper feed motor draws a brief current spike on each job — cycling through prints confirms the BMS has correctly profiled the new cell's current delivery curve before you rely on it in the field.

Why the PJ-520 refuses to print after sitting unused for months

Ni-MH cells self-discharge at roughly 1–2% per day at room temperature. A PJ-520 left on a shelf for several months can drop below 10V — well under the minimum motor drive voltage the BMS will allow. At that point the printer powers on but sends nothing to the paper feed or thermal head. Placing the discharged battery on charge for a full uninterrupted cycle before powering the printer is the only way to recover normal operation. If the charger light cycles rapidly and never settles, the cell voltage has dropped below the charger's recovery threshold — try a trickle-charge mode or replace the battery outright.

Faded or uneven print output on a charged battery

The PJ series thermal head requires a stable voltage feed to maintain consistent element temperature across the full print width. A degraded Ni-MH cell that reads 14V at rest can sag to 11–12V under the thermal head load, causing temperature variation mid-print and producing streaky or washed-out output. This is distinct from a paper or head-cleaning issue — if the fade appears immediately on a fresh sheet, measure terminal voltage under load rather than at rest. A healthy cell should hold above 13.2V during active printing.