Really like the idea of reducing the global warming footprint by using battery's to

replace gas engines..where possible..

Haha!  Apply a little physics. It takes a certain amount of energy to do a given job. Whether that is mowing a lawn, taking a family for a holiday 200 km from home, or shifting a thousand ton of freight.

The energy has to come from somewhere!

At the moment if you think wind and solar can do the job - in my opinion you need a large dose of reality.  They cannot.

So basically  - for base load [to charge your electric lawn mower] you have to burn something. 

You can 'save' the planet by using renewables - but in the meantime China goes its merry way building more coal fired power, that undoes all the 'savings' that even the USA makes.

I say this as an Aussy, one of 0.3% of the world's population, who have been conned into shutting down coal fired power in the quest of 'saving the planet'.  But what would I know - I just farmed God's earth for over 50 years!