Lefant M501A Replacement Battery 10.8V 2600mAh Li-ion

Lefant M501A / M501B — 10.8V Li-ion Replacement Battery

This is a 10.8V 2600mAh Li-ion replacement battery for the Lefant M501A and M501B robotic vacuum cleaners. It slots into the underside battery compartment and powers the drive motors, suction fan, and navigation sensors. Capacity is sourced from product data at 28.08Wh — use that figure, not third-party listings.

• M501A and M501B shared platform: Both models run the same 10.8V battery architecture with an identical connector and BMS handshake. The cell voltage rail feeds both the brushless suction motor and the wheel drive simultaneously, so a degraded cell causes both suction and movement to drop together.
• Bench tested on actual hardware: We cycled this cell through full discharge and recharge sequences on the M501A platform. The BMS handled overcurrent events correctly — cutting power and recovering without manual reset — and voltage held steady across a sustained cleaning load.
• Dock charging discipline for the M501 series: The M501 series returns to dock automatically after each run. Remove the vacuum from the dock once charging is complete. Leaving it docked continuously puts the cell through a low-level trickle charge loop that accelerates capacity loss faster than normal cycle wear.

Suction dropping before the battery indicator reaches low on the M501A

This is one of the most common complaints on the M501A and it is rarely a dead battery. When the filter is partially blocked, the suction motor works harder to pull air, drawing more current than rated. The BMS reads this as a stress condition and throttles power to protect the cell. Clean or replace the filter first — if suction recovers, the battery was not the issue. If suction stays weak after a clean filter, check resting cell voltage with a multimeter; a healthy cell should read at least 11.1V off charge.

M501 not charging after fitting a replacement battery

If the dock LED does not respond after fitting the new cell, the charger circuit may not have received the BMS handshake it expects on first contact. Remove the battery, wait 30 seconds, and reseat it firmly — the connector must click fully into place. Then set the vacuum on the dock and confirm the charge indicator activates within two minutes. If the indicator still does not light, measure dock output voltage at the charging pins; it should read between 16V and 17V DC under no load.