Efco Sirius 1200 Replacement Battery 25.2V 2300mAh

Efco Sirius 1200 — 25.2V Li-ion Replacement Battery

This is a 25.2V, 2300mAh (57.96Wh) Li-ion replacement battery for the Efco Sirius 1200 cordless lawn mower. It slots into the same battery bay as the original pack and runs on the same voltage rail. Use it as a direct swap when your original battery no longer holds a working charge.

• Sirius 1200 compatibility: The Sirius 1200 blade motor runs on a 25.2V nominal Li-ion rail. This pack matches that voltage and uses a BMS tuned to handle the blade motor's inrush current spike at startup — the same load profile the OEM pack manages.
• Bench tested on actual hardware: We ran this pack through startup load cycles on the Sirius 1200 platform. The BMS held through repeated blade engagement, including simulated heavy-load conditions, without triggering a false cutoff.
• Seasonal storage tip: If the mower has been in an unheated garage from autumn through spring, bring the battery indoors overnight before first use. Below 10°C, Li-ion cells carry higher internal resistance, and the blade motor's inrush current can trip the BMS on a cold pack before the cells have warmed up.

Charger showing fault after the mower sat all winter

Li-ion cells self-discharge slowly in storage. If the Sirius 1200 battery sat unused from late autumn to spring, cell voltage can drop below the charger's acceptance threshold — typically around 2.5V per cell. When that happens, the charger sees a pack it cannot safely charge at full current and throws a fault light instead of starting. Some chargers include a recovery or trickle-charge mode; check the Efco charger manual for that option. If no recovery mode exists, the pack has dropped too low to recover and needs replacing.

Mower cuts out mid-row then restarts after a short pause

This is thermal protection activating, not a fault with the battery itself. Sustained cutting through thick or wet grass forces the blade motor to draw continuous high current, heating the cells until the BMS shuts output to protect them. The pack typically recovers once cell temperature drops — usually after a five-minute rest with the mower stopped. If this happens repeatedly on a single charge cycle, reduce the cutting pass width so each row takes less blade load. Avoid cutting wet grass where possible, as moisture resistance roughly doubles the motor's sustained current draw.