The Natural Philosopher wrote:

And can your cordless keep that up for two or three hours to section a
full sized tree?

I only nip down and do a couple of hours worth at a time to get rid of
the tree, the section of trunk was [guestimating] a few hundred kilos,
so levering it about to avoid the saw touching the ground takes a lot of
time, the saw's not running for long periods, but I'd expect it to need
maybe a set of batteries per hour if it was.