Roborock A20 Replacement Battery 21.6V 4000mAh Li-ion

Roborock A20 / A20 Pro / A20 Flexi Pro — 21.6V Li-ion Replacement Battery (BRR-07-6S1P-4000LF)

This is a 21.6V, 4000mAh (86.4Wh) lithium-ion battery for the Roborock A20, A20 Pro, and A20 Flexi Pro robotic vacuums. It replaces OEM part numbers BRR-07-6S1P-4000LF and BRR-07-6S1P-4000LS. Fit this when the original cell no longer holds a full charge or the vacuum shuts down mid-cycle.

• A20 series platform compatibility: The A20, A20 Pro, and A20 Flexi Pro share the same 6S1P cell configuration, 21.6V nominal rail, and BMS handshake protocol. All three accept this pack without firmware or connector modification.
• Bench tested on actual hardware: We ran this pack through full charge and discharge cycles on the A20 platform. The BMS responded correctly to the charger handshake, cell balancing activated across all six cells, and overcurrent cutoff triggered at the expected threshold under simulated motor load.
• Dock charging habit on the A20: Do not leave the A20 on the charging dock continuously between uses. Robotic vacuums on permanent dock contact trickle-charge the cells and accelerate capacity fade. Charge to full, then remove the vacuum from the dock until the next scheduled clean.

Suction dropping before the battery indicator reaches low

The A20's BMS monitors cell voltage under load, not at rest. When the filter is partially blocked, the motor draws more current than the rated load profile. The BMS reads a sharper voltage sag on the cell group and reduces motor power early to protect the pack — before the indicator registers low. The vacuum appears to lose suction while the battery still shows capacity remaining. Clean the filter and check the brush roll for hair wrap before assuming the cell is at fault.

Motor cutting out and recovering during a cleaning cycle

This is an overcurrent trip, not a dead battery. The A20's BMS will interrupt motor power if sustained current draw exceeds its cutoff threshold — typically triggered when suction is restricted under heavy carpet or a blocked intake. The pack resets after a few seconds once current demand drops. If cut-outs are frequent, remove the filter and check for blockage at the brush roll housing; a clear airpath brings sustained draw back within the BMS window. If the cut-out persists on a clear filter, measure resting cell voltage — a healthy pack sits above 21.0V after a full charge.