Aquajack 211 Pool Cleaner Replacement Battery 11.1V 2600mAh

Aquajack 211 Pool Cleaner — 11.1V Li-ion Replacement Battery (PSD 18650)

This 11.1V Li-ion battery replaces the original pack in the Aquajack 211 robotic pool cleaner. It fits the 211 model directly and carries a 2600mAh (28.86Wh) capacity. The three-cell 18650 configuration matches the voltage rail the 211's drive motor and control board expect.

• Aquajack 211 fitment: The 211 runs its brush motor and navigation logic from a single 11.1V three-series Li-ion pack. The PSD 18650 cell format and BMS output match the voltage and connector spec the unit draws from — no adapter or modification needed.
• Bench tested on actual hardware: We ran this pack through full charge and discharge cycles on the bench. The onboard BMS engaged correctly at low-cell cutoff and handled the inrush current when the brush motor started from rest without tripping.
• Pool cleaner charge discipline: Remove the Aquajack 211 from its charging cradle once the pack reaches full charge. Leaving a Li-ion robotic cleaner on continuous cradle charge accelerates capacity fade — the trickle current at full state-of-charge degrades cell chemistry faster than normal cycling.

Suction dropping on the 211 before the battery indicator shows low

A partially blocked filter forces the brush and suction motor to draw harder than rated current. This causes voltage to sag at the pack terminals even when cell charge is still adequate. The 211's control board reads that sag as reduced available power and scales back motor speed — which the user sees as suction loss, not a battery fault. Clear the filter basket and check the debris bag before concluding the battery is at fault.

Motor cutting out mid-cycle and then recovering after a pause

This is a BMS overcurrent trip, not a motor failure. When the 211's intake is restricted — by debris buildup or a clogged filter — sustained high current draw triggers the battery's protection circuit, which cuts output to prevent cell damage. After a short pause, the BMS resets and the unit powers back on. Fix the restriction first: clear the filter and inlet, then resume the cycle. If trips continue with a clean filter, check that pack voltage at rest reads above 10.5V.