Running a Cordless Electric Lawn Mower on an eBike Battery?

As many of you know, some time ago I experimentally bought a cordless electric mower. However the largest capacity battery it would accept held only 200 watt hours of energy. This was enough to get through just under half my lawn, including the strips of grass between the sidewalk and the street.

I wound up returning it because I felt for what I paid ($350) it ought to have been able to do the job on a single charge. There exist high end lithium cordless mowers like the Ego 56v that would do the entire lawn on one charge but…