Deerma DEM-VC80 Replacement Battery 25.9V 2600mAh

Deerma DEM-VC80 Series — 25.9V Li-ion Replacement Battery (Q5S-26-01)

This is a 25.9V 2600mAh Li-ion battery built to fit the Deerma DEM-VC80 and DEM-VC80 Pro cordless stick vacuums. It matches OEM part number Q5S-26-01 and slots into the same battery bay as the original. Voltage and cell count are identical to factory spec.

• DEM-VC80 and VC80 Pro compatibility: Both models run the same 25.9V seven-cell series configuration and share the Q5S-26-01 connector and BMS handshake. One battery covers both variants without any modification.
• Bench tested on actual hardware: We cycled this battery through multiple charge and discharge passes on the DEM-VC80 platform. The BMS negotiated correctly with the charger, held cut-off at the expected low-voltage threshold, and the motor started cleanly on each pass without triggering an overcurrent trip.
• Dock charging on the VC80: Do not leave the vacuum sitting on the charging dock indefinitely. The VC80 dock does not drop to a true maintenance charge once full — continuous trickle current accelerates cell degradation. Charge to full, then remove the battery or vacuum from the dock.

Suction dropping before the battery indicator reaches low

The VC80 motor draws significantly more current when the filter is partially blocked. That increased draw causes voltage to sag across the cell pack before the indicator registers a low state. The result is noticeably weaker suction while the display still shows adequate charge. Clean or replace the filter first — if suction recovers immediately, the battery is not the cause. If the motor still struggles after a clean filter, the cell pack has lost capacity and the voltage sag happens earlier in every discharge cycle.

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

This is a BMS overcurrent trip, not a motor fault. When sustained suction restriction forces the motor to pull more than the BMS threshold — typically from a clogged filter or blocked nozzle — the protection circuit cuts power to prevent cell damage. The pack recovers once current demand drops and the BMS resets. Clear the filter and nozzle path before assuming the battery is faulty. If trips continue on an unobstructed vacuum, check that pack voltage under load stays above 22V — consistent sag below that point indicates a degraded cell in the series string.