Zaco A4s 501929 Replacement Battery 14.8V 2600mAh

Zaco A4s / A6 / A8s / A9s — 14.8V Li-ion Replacement Battery (501929)

This is a 14.8V, 2600mAh lithium-ion battery for Zaco robot vacuum cleaners. It fits the A4s, A6, A8s, and A9s models using OEM part number 501929. Swap it in when the original cell no longer holds enough charge to complete a cleaning cycle.

• A4s / A6 / A8s / A9s platform fit: These models share the same battery bay dimensions, 14.8V four-cell architecture, and BMS connector pinout — which is why a single replacement cell covers the full range.
• Bench tested on actual hardware: We cycled this battery through charge and discharge on the A4s platform. The BMS responded correctly to motor-start current draw, and cell balancing ran without fault flags across multiple cycles.
• Dock charging habit on the A4s: Do not leave the vacuum sitting on the dock permanently between uses. Continuous trickle charging degrades lithium cell capacity faster than intermittent charge cycles. Charge to full, then remove from the dock until the next run.

Suction dropping before the battery indicator reaches low

The A4s motor controller draws harder when suction is restricted — a clogged filter forces the motor to compensate, pulling more current than the BMS expects at that state of charge. The BMS reads this as a near-empty cell and reduces output voltage to protect the pack. Clean the filter first. If suction recovers immediately after a filter clean, the battery was not the cause.

Motor cutting out mid-run and then recovering after a few seconds

This is a BMS overcurrent trip, not a dead battery. When the A4s hits a carpet transition or a blockage, current demand spikes sharply. If the pack is aged or the filter is partially restricted, that spike crosses the BMS overcurrent threshold and the circuit opens briefly. The BMS resets itself once current normalises — usually within a few seconds. If this happens on a new replacement battery, check for a blockage in the brush roll or inlet before assuming the cell is faulty. Confirm pack voltage reads at or above 14.4V at rest after a full charge.