I dread all those extension cords when using the hedge trimmer and other stuff. I found that if I connect the E-bike battery of a friend to it the hedge trimmer runs somewhat slower but reliably. It had 53V DC.
Those machines contain brush-type universal motors, probably with a compensation winding but not sure. Is is safe to run these with 40-60V DC over long periods of time or is there some sort of motor pathology that could hit?
If ok I could build a stack of 12-15 Li-Ion 18650 cells which, at 1.5A to 2A, should afford me about 45min of runtime. Or maybe build three sets of 4S or 5S batteries I could use for other stuff and then connect those in series when bushes need to be trimmed 2-3 times per year. With reverse-polarity protection diodes, of course, so I won't fry their individual BMS'es.