Vax Air Cordless Switch AC21 20V Replacement Battery 2000mAh

Vax Air Cordless Switch AC21 / H85 — 20V Li-ion Replacement Battery

This 20V 2000mAh (40Wh) lithium-ion battery fits the Vax Air Cordless Switch AC21 and Air Cordless Switch H85 stick vacuums. It slots into the same battery bay as the original and connects to the same discharge contacts. Voltage and capacity match the factory specification exactly.

• AC21 and H85 shared platform: Both models run from the same 20V battery bay with identical contact layout and BMS communication protocol. One battery works across either unit without modification.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the AC21 platform. The BMS handshake completed correctly, protection circuits tripped at the expected undervoltage threshold, and the charger accepted the pack without fault codes.
• Dock charging habit on the AC21: Remove the battery from the charging dock once the indicator shows full. The AC21 dock does not cut trickle current completely — leaving the pack on charge continuously accelerates capacity fade faster than normal cycling alone.

Suction dropping before the battery indicator reaches low

The AC21 motor draws significantly more current when airflow is restricted — a partially blocked filter can push draw well above rated levels. The BMS responds by reducing available current before the LED indicator registers low, which reads as a suction drop rather than a battery warning. This is a protection response, not cell failure. Clean or replace the filter and the motor returns to full draw immediately.

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

This is a BMS overcurrent trip, not a failing cell. Sustained restricted airflow — from a clogged filter or blocked nozzle — forces the motor to pull above the pack's continuous current limit. The BMS opens the discharge circuit to protect the cells, then resets once temperature and current drop. Check the filter and clear any blockage at the nozzle before concluding the battery is at fault. If the pack voltage reads above 18V after recovery, the cells are intact.