About this replacement
Seauto Shark / STA40 — 21.9V Li-ion Replacement Battery (SAT-4P6S)
This is a 21.9V, 10400mAh Li-ion replacement battery for the Seauto Shark and STA40 cordless robotic pool vacuum cleaners. It slots into the same battery bay as the original SAT-4P6S pack and restores power to both the drive motor and navigation systems. Capacity listed above matches the product data — 227.76Wh total.
- Shark and STA40 compatibility: Both the Shark and STA40 run the same 21.9V battery rail with the SAT-4P6S connector and BMS handshake. Swapping in this pack triggers the same charge-state handshake as the factory unit — no re-pairing or firmware changes needed.
- Bench tested on actual hardware: We cycled this battery through full motor-start load on the Shark platform. The BMS held stable voltage delivery across debris-suction peaks without dropping into protective cutoff under normal operating conditions.
- Post-session terminal care: Rinse the battery housing with fresh water after each pool session before connecting to the charger. Chlorine and salt residue on the battery terminals builds contact resistance that reads to the BMS as a low-charge fault — not a dead cell.
Seauto Shark stopping mid-cycle on peak debris suction
The Shark's BMS monitors instantaneous current draw from the drive and suction motors. When the cleaner hits a heavy debris patch or climbs a wall transition, motor current spikes sharply above steady-state draw. If the battery is below roughly 70% charge when the cycle starts, that spike can push current past the BMS threshold and trigger a protective cutoff — the unit stops and the indicator flashes. Starting each cycle with a fully charged pack keeps the voltage margin wide enough to absorb those peaks without cutoff.
Cleaner powers on but motor runs noticeably slower than before
Reduced motor speed is the first sign of voltage sag — the battery can't sustain the 21.9V rail under load and the motor controller reduces drive output to compensate. This happens most often when the pack is partially charged or when terminal corrosion is adding resistance to the circuit. Check the terminals first: clean metal contacts with a dry cloth before charging. If the sluggishness clears after a full charge cycle, the pack was low — not faulty.