I am using EGO 56V Battery 33cm Line Trimmer. Cost around RM800, but very quiet and reliable. The battery is 56V, can use up to 1 hour of continuous use. If you find the line not sharp enough, change it to the star-shaped type, it will transform to as sharp as the traditional steel blade trimmer type.

You can also buy the mower, where the battery is interchangeable between their equipment. Only thing is it's expensive.