NARWAL J3 Replacement Battery 14.4V 4900mAh BP4S2PPM5B

NARWAL J3 / J4 — 14.4V Li-ion Replacement Battery (BP4S2PPM5B)

This is a 14.4V, 4900mAh (70.56Wh) lithium-ion battery for the NARWAL J3 and J4 robotic vacuum cleaners. It replaces OEM part numbers BP4S2PPM5B and BP4S2PPM5D. The battery powers the motorized brush roll and suction motor — the two highest-draw components in the machine.

• J3 and J4 compatibility: Both models run the same 14.4V architecture and use the same connector and BMS handshake protocol. The cell configuration and protection circuit are identical across the two platforms, so one battery covers both units.
• Bench tested on actual hardware: We ran this battery through full charge and discharge cycles on the J3. The BMS held voltage within the expected window under sustained motor load, and the protection circuit tripped correctly when we simulated a blocked suction path — then reset cleanly once load was removed.
• Dock charging habit on the J3 and J4: Do not leave the vacuum sitting on the charging dock permanently. Continuous trickle charging accelerates capacity fade on lithium-ion cells at this voltage. Charge to full, then remove from the dock until the next use cycle.

Suction dropping before the battery indicator reaches low

This happens when the motor draws more current than the cell can sustain at its present state of charge. A partially blocked filter raises motor demand — the cell voltage sags early, and suction weakens even though the indicator shows capacity remaining. The BMS reads pack voltage, not motor efficiency, so the indicator lags behind real performance. Clean the filter and check the brush roll for hair wrap before assuming the battery is the cause.

Motor cuts out mid-clean then recovers after a few seconds

This is a BMS overcurrent trip, not a dead battery. When the suction path is restricted — blocked filter, tangled brush, or a debris jam — the motor pulls current above the BMS threshold and the circuit opens to protect the cells. The pack resets automatically once current drops. Clear the blockage, check the filter for compacted debris, and restart the vacuum. If the trip keeps occurring with a clean filter, measure pack voltage resting at 15.8V–16.2V to confirm the cells are holding charge correctly.