About this replacement
Philips HP1304 / HP1310 Series — 1.2V Ni-MH Replacement Battery (ACN0021)
This is a 1.2V, 3000mAh Ni-MH cell that replaces the ACN0021 battery in Philips HP1304, HP1310, HP1318, and HP1319 electric shavers, plus six additional compatible models. It slots into the shaver housing and restores power to the cutting motor. Voltage and capacity match the original specification exactly.
- HP1304 / HP1310 series compatibility: These models share the same motor voltage rail, cell form factor (42.75 × 22.20 × 22.20mm), and ACN0021 part number. The cell connects directly to the existing BMS board without modification.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the HP1310 platform. The BMS accepted the cell cleanly, charge termination triggered at the correct voltage, and the motor drew current without a protection trip on start-up.
- Charging port moisture check: Philips HP-series shavers are often rinsed under tap water. Before connecting to the charger, dry the charging port completely — moisture bridging the contacts causes a BMS protection fault that the shaver reports as a dead battery rather than a charging error.
Capacity fade from daily partial charging on the HP1304
Ni-MH cells in shavers suffer from voltage depression when charged daily before the cell is meaningfully depleted. The BMS calibration drifts because it never sees a full discharge reference point. Over time the shaver's indicator reads full but the motor cuts out sooner than expected. Running the shaver to motor cutoff before charging — roughly every four to six cycles — resets the BMS reference and slows this drift.
Shaver motor speed dropping before the low-battery indicator lights
This happens when the cell's internal resistance has climbed enough that voltage sags under the motor's start-up load before the BMS formally reports a low-charge state. The indicator measures resting voltage, not voltage under load, so the two readings diverge as the cell ages. A fresh ACN0021 cell will restore stable motor speed because its internal resistance is within spec. After fitting the replacement, charge fully before first use to give the BMS a clean capacity baseline at 1.2V.