Robomow RK 1000 Replacement Battery 18.5V 6400mAh

Robomow RK 1000 / RK 2000 Series — 18.5V Li-ion Replacement Battery (753-11203)

This 18.5V 6400mAh Li-ion battery replaces the original pack in the Robomow RK 1000, RK 2000, and RK 2000 Pro robotic lawn mowers. It matches OEM part numbers 753-11203, 753-11204, 725-18426, 725-14826, and 725-14827. Capacity is 118.4Wh — same as the factory specification.

• RK 1000 and RK 2000 platform fit: These models share the same 18.5V battery bay, connector pinout, and BMS handshake protocol. One battery covers the full range listed — no adapter or wiring change needed.
• Bench tested on actual hardware: We cycled this pack through repeated blade-motor start loads on the RK platform. The BMS held steady through inrush current spikes on clean turf and flagged thermal cutoff correctly under sustained high-draw conditions — no false trips on flat ground.
• Seasonal storage tip: Before the first mow of the season, bring the battery indoors overnight if air temperature is below 10°C. Cold Li-ion cells carry higher internal resistance, and the blade motor's inrush current on startup can trip the BMS before the pack warms up.

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

The RK series blade motor draws significantly more current when cutting dense or wet grass. If the pack voltage sags below the BMS cutoff threshold during that inrush spike, the BMS shuts the pack down as a protection event — not a fault. This is more likely in the first five charge cycles before the cells have conditioned. Let the mower sit for five minutes, then restart — if the cutoff stops happening after a few cycles, the cells were still conditioning. If it persists beyond cycle five, check that the mowing zone boundary isn't set across a consistently wet patch.

Charger showing a fault light after the mower sat unused all winter

Li-ion cells self-discharge slowly over months. If the pack voltage drops below approximately 14V during long storage, the charger's acceptance circuit rejects it as a dead or damaged cell — this triggers the fault indicator. Place the battery in a warm room (above 15°C) for two hours, then reconnect it to the charger. Most chargers will then see the voltage recover slightly and begin a trickle-charge recovery cycle. If the charger still shows a fault after 30 minutes on reconnect, check terminal voltage with a multimeter — if it reads below 12V, the pack has deep-discharged past recovery.