classic case of inventing that which already exists.
Granted you COULD make a battery backpack to power your Lawnmower,
but we got one of these.
Neuton Battery Lawn Mowers -
Its good, light, easy to start, and gets about 45 minutes on a battery so we have one fresh and two kind of slipping.
They go like camcorder batteries.
But it is really really quiet, and light enough for a child to handle.
It could be wider though.
Oh look, these guys make battery backpacks ! Solar Backpacks, Inverters.
All the stuff you need. ( really not enough juice)
http://solar-catalog.com/pwr_port.ht...werpack%201000