About this replacement
AL-KO Cordless String Trimmer — 18V Li-ion Replacement Battery
An 18V 2000mAh lithium-ion replacement battery for AL-KO cordless string trimmers and garden tools. Fits the Comfort GT 1825 and over 30 compatible AL-KO 18V models including the Comfort PS 181, Comfort HTA 1845, and Comfort PS 1815. Uses the same voltage rail and connector as the original B75, B100, B125, and related part numbers.
- AL-KO 18V platform compatibility: Models like the GT 1825 and PS 181 share the same 18V connector and BMS communication protocol, which is why one battery spans the full Comfort series lineup.
- Bench tested on actual hardware: We ran full charge/discharge cycles — the BMS held voltage steady under motor load and cut off cleanly at the low-voltage threshold without tripping a false fault.
- First charge after storage: If the battery has been sitting, run a full charge before first use. Li-ion cells that drop below the BMS sleep threshold may need two charge attempts to register on the charger.
Why 18V matters for a lightweight trimmer like the GT 1825
The GT 1825 weighs 2.1 kg with battery included, so cell weight is a real factor. At 2000mAh and 36Wh, this pack keeps mass down without dropping below the voltage level the motor needs to spin the 25 cm cutting line cleanly. The 18V platform also shares charger compatibility with Bosch Home and Garden tools, so one charger handles multiple tools in the shed.
Trimmer powers on but cuts out mid-use — what's happening
This usually means the BMS is tripping on an overcurrent spike, not a dead battery. On string trimmers, it happens when the line feeds too long and the motor lugs hard trying to spin excess line. Trim the cutting line back to the correct length, then reset the battery by removing it and reseating it firmly. If the tool still cuts out, check that the battery contacts are clean — debris on the terminal pads increases resistance and can trigger the same protection circuit.