Panasonic HHF-1PSC MJ70 Replacement Battery 1.2V 1200mAh

Panasonic MJ70 / MJ80 Series — 1.2V Ni-MH Replacement Battery (HHF-1PSC)

This is a 1.2V, 1200mAh Ni-MH replacement battery for the Panasonic MJ70, MJ80, MJ88, SJMR100, and over 40 additional compatible models. It matches the original HHF-1PSC cell format, voltage, and connector. Swap it in when the original cell no longer holds a charge or the player fails to power on at all.

• MJ and SJMR series fit: These models share a single-cell 1.2V Ni-MH bay with the same footprint — 66.78 × 16.70 × 5.96mm — and identical terminal orientation. No adapter or modification needed across the listed models.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on MJ-series hardware. The BMS accepted the cell cleanly, trickle-charged correctly from a depleted state, and terminated charge without error flags.
• First charge after installation: Media players in this series enter a low-voltage protection state if the cell sits discharged for weeks or months. Connect the charger immediately after installing and leave it connected for at least 30 minutes before attempting to power on — the player needs a slow trickle before it accepts normal charge current.

Battery percentage jumping after a cell swap on the MJ series

Panasonic's MJ and SJMR players use a voltage-threshold method to estimate charge level — there is no fuel gauge IC tracking actual coulombs. After a cell swap, the player reads an unfamiliar voltage curve and maps it incorrectly. The percentage indicator will jump or display inaccurately for the first one or two full charge cycles. Run two complete charge-to-discharge cycles and the indicator will recalibrate to the new cell's curve.

Playback cutting out before the battery indicator shows empty

The audio amplifier in these portable players draws a short current spike at the start of each track — higher than the steady playback draw. Late in the discharge curve, a degraded or cold cell sags below the minimum operating voltage during that spike, triggering a shutdown even though the indicator still shows charge remaining. This is a voltage sag issue, not a capacity issue. If playback cuts out consistently, check that the cell terminals are seated firmly and that the player is not cold — Ni-MH cells lose voltage headroom quickly below 10°C. Warm the device to room temperature and recharge to confirm the fault.