Efco Sirius 1200 Compatible Battery 25.2V 3400mAh Li-ion

Efco Sirius 1200 — 25.2V Li-ion Replacement Battery

This 25.2V 3400mAh lithium-ion battery is a direct replacement for the Efco Sirius 1200 cordless lawn mower. It slots into the Sirius 1200's battery bay and powers the cutting deck and blade motor. Capacity is 85.68Wh — matching the original specification.

• Sirius 1200 blade motor compatibility: The Sirius 1200 blade motor draws a sharp inrush current on startup. This pack's BMS is rated to handle that spike without nuisance tripping under normal grass conditions. The 25.2V nominal voltage matches the motor controller's expected input rail.
• Bench tested on actual hardware: We cycled this pack through repeated load sequences simulating blade start, run, and stop. The BMS held across all cycles, and cell balance remained within spec at full discharge.
• Seasonal storage tip: Before the first cut of the season, bring this battery indoors overnight if temperatures are below 10°C. Cold Li-ion cells carry higher internal resistance, and the blade motor's inrush current can trip the BMS on a cold pack before the mower even reaches the lawn.

BMS cutoff on thick grass or wet-grass blade load

The Sirius 1200 blade motor pulls significantly more current through dense or wet grass than on a dry, short lawn. If the instantaneous draw exceeds the BMS threshold — typically caused by bogged blades or a low blade-speed condition — the pack will cut power as a protection measure. This is the BMS doing its job, not a battery fault. Let the pack rest for two minutes, then restart on a lighter section of lawn to reset the BMS state.

Charger not accepting the pack after winter garage storage

If the Sirius 1200 battery sat in a cold garage over winter without a maintenance charge, cell voltage may have dropped below the charger's acceptance threshold — typically around 20V for a 25.2V pack. The charger sees this as a fault and refuses to engage. Some chargers have a recovery or "wake" mode — insert the pack, wait 30 seconds, then remove and reinsert. If the charger still shows a fault, check cell voltage with a multimeter; any reading above 18V means recovery is likely possible with a compatible balance charger set to Li-ion recovery mode.