Yard Force SA800 Pro 28V 5000mAh Replacement Battery

Yard Force SA800 Pro / SA900 Series — 28V Li-ion Replacement Battery (862617)

This is a 28V 5000mAh (140Wh) lithium-ion replacement battery for Yard Force robotic lawn mowers. It fits the SA800 Pro, SA900, SA500 Eco, SA600H, and more than 22 additional SA-series models. Voltage and connector match the original pack — the mower's docking and charge cycle work as normal.

• SA-series platform fit: All listed models share the same 28V battery bay, dock connector, and BMS handshake protocol. Swapping between SA500, SA600H, SA800 Pro, and SA900 requires no adapter or firmware change — the battery communicates the same state-of-charge data to each base unit.
• Bench tested on actual hardware: We cycled this pack through repeated blade-motor inrush loads on a SA800 Pro test unit. The BMS held cutoff thresholds steady across full discharge cycles and accepted a charge from the OEM dock without fault codes.
• Seasonal storage tip: Before bringing the mower back into service after winter, bring the battery indoors overnight if temperatures are below 10°C. Cold Li-ion cells carry higher internal resistance, and the blade motor's inrush current on a cold pack can trip the BMS before the mower completes its first row.

BMS cutoff on thick-grass or wet-grass blade load

The SA800 Pro's blade motor draws a short inrush spike each time it re-engages after an obstacle pause. In dense or wet grass, those spikes come more frequently and at higher current than on a dry, light lawn. If the BMS reads that sustained spike pattern as an overcurrent event, it trips and the mower halts mid-zone. Letting the pack rest for five minutes resets the BMS thermal flag — the mower will resume normally after that cooldown.

Charger not accepting the pack after winter storage

Li-ion cells left in storage for several months will self-discharge past the BMS acceptance threshold — typically below 2.5V per cell. When a pack drops below that floor, the OEM dock refuses to begin a charge cycle and shows a fault light instead. To recover the pack, place it in a warm room (above 15°C) for two hours before attempting a charge. If the dock still shows a fault after warming, the cells have discharged too deeply for safe recovery and the pack needs replacing.