I did this for a neighbor a few years ago but I can't find the pictures. He had an electric like this, 8 amp, 120 volts.
I added a piece of plywood to the base of the handle and placed a small 12 volt battery and a 800 watt inverter. I charged it with a small solar panel in the shed. The inverter was cheap, but it had a "soft start" feature. The lawnmower also worked as a small portable power station. I used it for cutting the grass, then I would plug the weed eater into it and then the hedge trimmer. Worked great.