Xiaomi Mi 1C Cordless Vacuum Replacement Battery 25.2V 2500mAh

Xiaomi 1C / Dreame V8 V9 Series — 25.2V Li-ion Replacement Battery (WN4)

This is a 25.2V 2500mAh Li-ion battery pack for the Xiaomi Mi Vacuum Cleaner 1C and Dreame V8, V9, and V9B cordless stick vacuums. It slots into the same bay as the original WN4 pack and communicates with the same BMS circuitry. Use the capacity figure from this listing — 2500mAh — not figures quoted elsewhere.

• 1C and Dreame V-series compatibility: These models share the same 25.2V battery bay, WN4 connector pinout, and BMS handshake protocol. Swapping between them does not require any firmware change or adapter.
• Bench tested on actual hardware: We ran this pack through full charge and discharge cycles on the 1C platform. The BMS held steady under motor-start inrush and did not trip on sustained high-speed suction mode.
• Dock charging habit on stick vacuums: Do not leave this vacuum on the charging dock permanently. Continuous trickle charging accelerates capacity fade on Li-ion packs faster than normal cycle ageing. Charge to full, then remove it from the dock.

Suction dropping before the battery indicator reaches low

The 1C motor draws significantly more current when the filter is partially blocked — sometimes two to three times normal draw. The BMS reads this as a voltage sag and throttles output to protect the cells, even when the indicator still shows adequate charge. The vacuum appears to lose suction, but the battery is not the root cause. Clean or replace the filter first, then retest before assuming the battery is at fault.

Motor cutting out mid-clean and then recovering after a few seconds

This is a BMS overcurrent trip, not a dead battery. When sustained suction resistance — from a clogged filter or blockage — pushes draw above the BMS threshold, the pack cuts power and waits for current to drop before reconnecting. The cut-out and recovery cycle will keep repeating until the restriction is cleared. Check the filter, brush roll, and inlet for blockages, then confirm the pack reads at least 24V on a multimeter before assuming it needs replacing.