About this replacement
Flymo Grass Trimmer — 18V Li-ion Replacement Battery
This 18V 3000mAh (54Wh) Li-ion battery fits the Flymo UltraTrim 260, EasiCut 450, UltraReach 420, EasiTrim 250, and 15 additional models. Flymo's 18V cordless trimmer line shares a common battery platform across its consumer range. Capacity sits at 3000mAh — a step up from the 2500mAh packs that shipped with some earlier units.
- Cross-model compatibility — UltraTrim, EasiCut, UltraReach, EasiTrim: These models run the same 18V rail and use the same slide-in connector and BMS communication protocol, so one battery pack services the full range.
- Bench tested on actual hardware: We ran full charge/discharge cycles — the BMS held voltage steady under cutting load and tripped the low-voltage cutoff cleanly before cell damage could occur.
- First charge after storage: If the pack has been sitting, run a full charge before first use — Li-ion cells that ship partially discharged need one complete cycle to calibrate the fuel gauge on the trimmer's indicator.
Why capacity matters on a line trimmer
Grass trimmers draw current in bursts — harder when cutting thick growth, lighter on open lawn. A 3000mAh cell handles those peaks better than a worn original pack that can no longer hold its rated capacity. The BMS on this unit also limits discharge rate, which protects the motor windings from voltage sag during heavy cuts.
Trimmer powers on but cuts out immediately — here's why
This usually means the BMS is tripping on overcurrent within seconds of startup. The most common cause is a partially blocked cutting head creating excessive motor load at start. Clear any debris from the spool, check that the line length isn't over-extended, then reinsert the battery. If the problem continues, the issue is with the motor or head assembly — not the battery.