Another John was thinking very hard :
I noticed these emerge 3-4years (??) ago, trumpeted as a miracle cure,
but they were very expensive then, and I was sceptical of the power, the
battery life, and the tool life. Probably time to look at them again.

I have no experience of them, but suspect they are only good for light
duties. I also suspect the weight of the battery might make using them
harder work than it need be, often at awkward angles. I don't find my
Bosch mains trimmer too much of a problem to use and I have quite a lot
of hedge to cut.