PROGRESS A21P 18V Cordless Vacuum Replacement Battery 1500mAh

PROGRESS A21P / A21PL — 18V Li-ion Replacement Battery

This is an 18V 1500mAh Li-ion replacement battery for the PROGRESS A21P and A21PL cordless stick vacuums. It slots into the same battery housing as the original and runs the same 18V motor rail. Capacity is 1500mAh (27Wh), matching the factory specification.

• A21P and A21PL fitment: Both models share the same 18V battery platform, connector pinout, and BMS handshake protocol — one battery fits either unit without modification.
• Bench tested on actual hardware: We ran the battery through full charge and discharge cycles on the A21P platform. The BMS held the 18V rail steady under normal suction load and tripped correctly when the motor was stalled — no false cutoffs during standard cleaning passes.
• Dock charging habit on the A21P: Do not leave the vacuum on the charging dock continuously. The A21P charger does not switch to a true maintenance mode — prolonged dock time pushes trickle current into fully charged cells and accelerates capacity fade. Charge to full, then remove from the dock.

Suction dropping before the battery indicator reaches low on the A21P

The A21P motor draws more current when airflow is restricted — a partially blocked filter forces the motor to work harder, pulling the cell voltage down faster than normal. The battery indicator reads state-of-charge, not voltage under load, so it can still show two bars while the motor is already voltage-sagging. The result is noticeably weaker suction well before the low-battery warning appears. Clean or replace the filter first — if suction recovers immediately, the battery is not the cause.

Motor cuts out mid-clean and then restarts after a few seconds

This is a BMS overcurrent trip, not a dead battery. When suction is sustained against a blockage — a sock caught in the head, a clogged filter, or a full dustbin — the motor current spikes past the BMS threshold and the circuit opens to protect the cells. The BMS resets automatically once current drops, which is why the vacuum restarts after a short pause. Clear the blockage, empty the bin, and check the filter before resuming — if the trip repeats on an unobstructed floor, test cell voltage under load; it should hold above 15V during normal operation.