UONI S1 Replacement Battery 14.4V 5200mAh Li-ion

UONI S1 / V980 Series — 14.4V Li-ion Replacement Battery

This is a 14.4V 5200mAh (74.88Wh) lithium-ion battery for the UONI S1, V980 Max, V980 Plus, and V980 Pro cordless stick vacuums. It slots into the battery housing of these models and connects to the same BMS handshake circuit as the original cell pack. Capacity is taken from product data — 5200mAh is the rated cell capacity for this pack.

• S1 and V980 platform compatibility: These models share a 14.4V battery rail and the same physical connector housing, which is why a single replacement cell pack covers the full lineup. The BMS protection board in each vacuum expects the same voltage thresholds on charge and discharge, so one cell configuration works across all four variants.
• Bench tested on actual hardware: We ran this pack through full charge cycles and monitored the BMS cutoff behaviour under load. The protection board triggered cleanly at both the high-voltage charge limit and the low-voltage discharge floor, and the charge cycle balanced across the cell strings without flagging a fault.
• Dock charging habit on the V980 series: Do not leave the vacuum sitting on the charging dock continuously. These cordless vacuums develop capacity fade faster when held at full charge under trickle current. Charge the pack to full, then remove it from the dock.

Suction dropping before the battery indicator reaches low

The UONI S1 and V980 motors draw significantly more current when the filter is partially blocked or the bin is full. This elevated draw causes the cell voltage to sag under load, and the BMS interprets the sag as a near-depleted pack — even when the indicator still shows charge remaining. The motor then throttles back or cuts briefly to protect the cells. Clean the filter and empty the bin first; if the problem persists, the original battery's cells have likely lost enough capacity that voltage sag under any moderate load triggers the cutoff early.

Motor cuts out mid-clean and then recovers after a few seconds

This is a BMS overcurrent trip, not a power failure. When suction is restricted — by a blockage, a clogged filter, or sustained use on thick carpet — the motor pulls harder to maintain airflow, and current spikes past the protection board's threshold. The BMS trips the output, the motor stops, and after a few seconds the BMS resets and allows restart. The fix is to locate the restriction: remove the floor head and check the inlet, then pull and wash the filter. If the motor continues to trip after clearing the airway, check that the battery voltage reads above 12.8V on a multimeter at the connector — sustained trips below that threshold mean the cells are depleted and replacement is needed.