About this replacement
360 S8 Plus / S8+ — 14.76V Li-ion Replacement Battery (INR21700M50LT-4S1P)
This is a 14.76V, 4000mAh (59.04Wh) lithium-ion battery pack for the 360 S8+ and S8 Plus cordless stick vacuum. It replaces OEM part INR21700M50LT-4S1P and fits the Botslab S8 Plus and QH100005 variants. When the original cell degrades and suction drops off early, this pack restores the motor to its rated voltage draw.
- S8 Plus / Botslab S8 Plus / QH100005 fitment: All four model designations — S8+, S8 Plus, Botslab S8 Plus, and QH100005 — use the same 14.76V four-cell series pack with this connector and BMS configuration. One replacement covers the full range.
- Bench tested on actual hardware: We ran this pack under sustained load matching the S8+ motor draw. The BMS held voltage within spec through repeated high-suction cycles and tripped correctly on simulated overcurrent without locking out the pack on recovery.
- Dock charging habit on the S8+: Do not leave the vacuum sitting on the charging dock between uses. The S8+ dock delivers a trickle charge continuously, and cells left under constant low-level charge develop capacity fade faster than cells charged only when depleted. Charge to full, then remove from the dock.
Cordless vacuum losing suction before the battery indicator reaches low
This happens when the motor pulls more current than the battery can sustain at rated voltage. A degraded or partially discharged cell pack sags under motor load — the vacuum loses suction, but the indicator still reads mid-charge because it measures resting voltage, not load voltage. A clogged filter makes this worse by forcing the motor to work harder, which increases current draw and deepens the voltage sag. If the filter is clean and suction still drops early, the cell pack is no longer holding its rated capacity under load.
Motor cuts out mid-clean then recovers after a short pause
This is a BMS overcurrent trip, not a motor fault. When airflow is restricted — by a blocked filter, full dustbin, or dense carpet — the motor draws sustained current above the pack's trip threshold. The BMS cuts power to protect the cells. After the pack cools and current drops to zero, the BMS resets and the vacuum starts again. Clean the filter and empty the bin first. If the cut-out continues on a clean filter, check that the replacement pack's BMS trip threshold matches the motor's rated draw — verify the pack is reading at or above 14.4V under load before ruling out a battery fault.