XRobot M-788 Replacement Battery 14.4V 4000mAh Ni-MH

XRobot M-788 — 14.4V Ni-MH Replacement Battery

This is a 14.4V, 4000mAh Ni-MH replacement battery for the XRobot M-788 robotic vacuum cleaner. It slots into the M-788's battery bay and restores power to the drive motors and cleaning system. No OEM part number is published for this unit — fit is confirmed by voltage, form factor (179 × 51 × 52mm), and connector match.

• M-788 platform fit: The M-788 runs a 14.4V motor rail shared across its drive wheels and suction system. This cell matches that rail exactly — wrong voltage here causes the BMS to shut the unit down within seconds of startup.
• Bench tested on actual hardware: We ran this cell through full charge-discharge cycles on a 14.4V Ni-MH load tester. The BMS held cutoff at the correct low-voltage threshold and accepted charge without thermal event across repeated cycles.
• Dock charging habit on the M-788: Do not leave the M-788 sitting on its dock between uses indefinitely. Ni-MH cells in continuous trickle charge develop capacity fade faster than cells charged only when depleted. Charge to full, then remove from the dock.

Suction dropping before the battery indicator reaches low

The M-788's suction motor draws significantly more current when the filter is partially blocked. That extra draw causes voltage to sag across the Ni-MH cells before the indicator logic registers a low-battery state. The result is noticeably weaker suction while the indicator still shows charge remaining. Clean or replace the filter first — if suction recovers, the battery is not the cause.

Motor cuts out mid-clean and then recovers after a short pause

This is a BMS overcurrent trip, not a dead battery. When sustained suction restriction forces the motor to pull above the cell's rated current ceiling, the BMS disconnects the output to protect the cells — then resets once temperature and current drop. The cycle repeats if the restriction stays in place. Check the filter and brush roll for blockages before assuming the battery is faulty. After clearing any blockage, verify the resting pack voltage sits above 12.0V before returning the unit to service.