Robomow MRK9200A Replacement Battery 10.8V 10400mAh

Robomow RX50 / RT700 / RT300 — 10.8V Li-ion Replacement Battery (MRK9200A)

This is a 10.8V, 10400mAh (112.32Wh) lithium-ion battery for the Robomow RX50, RT700 2021, RT700 2022, RT300 2021, and related models. It replaces OEM part numbers MRK9200A, BAT9101A, and BAT9102A. The battery slots into the mower's battery compartment and connects to the same BMS handshake the charger dock expects.

• RX50, RT700, and RT300 compatibility: These models share the same 10.8V battery platform, connector pinout, and BMS communication protocol — that's why one pack covers the full range across the 2021 and 2022 model years.
• Bench tested on actual hardware: We cycled this pack through the Robomow charging dock and confirmed the BMS handshake initialised correctly. The charger accepted the pack without fault codes, and cell balance across the pack held within spec after full charge.
• Seasonal storage tip: Before first use of the season, bring the battery indoors overnight if temperatures are below 10°C. Cold Li-ion cells have higher internal resistance, and the blade motor's inrush current can trip the BMS on a cold pack before the mower completes its first row.

BMS cutoff under thick grass and wet-lawn blade load

The Robomow blade motor draws significantly more current when cutting dense or wet grass — peak inrush can exceed the BMS's continuous discharge threshold. When that happens, the BMS cuts power to protect the cells, and the mower stops mid-run. A new pack with full cell capacity handles these load spikes better than a degraded original battery, but no pack is immune. If cutouts persist in heavy conditions, mow in overlapping passes at a slower area setting to reduce sustained blade load.

Charger dock shows fault light after winter storage

If the mower sat unpowered in a cold garage all winter, the cells may have self-discharged below the charger's acceptance voltage — typically around 9V for a 10.8V Li-ion pack. The dock's fault light or refusal to charge is the BMS rejecting a pack it reads as over-discharged. Try leaving the battery at room temperature for two hours, then reconnecting to the dock. If the charger still won't accept it, the cells have dropped below recovery threshold and the pack needs replacing — which is the situation this battery resolves.