I have a Ryobi 40 volt 16" chain saw with 4ah batteries. I cut up a 16" diameter tree on 2 batteries... 2' pieces for the fire pit. Soft wood tree(boxelder) though. Haven't tested it on oak! Boxelder is great in the fire pit after drying 2 years. Faster burn, not a lot of coals to deal with end of the night...
Also have a 40 volt Ryobi string trimmer. Can do my entire 1 acre yard on one battery.
Need to get the Ryobi 40 volt compressor.
Have the 20 volt shop vac from them, sweet piece of kit for cleaning the car! And the circular saw, drill, detail sander/trim cutter, grinder... standardized on one tool brand instead of 3 different brands and batteries! The little 1/4 inch impact just built 2 raised garden beds driving in 3" lag screws, battery lasted 2 days... I do need to order the 1/2 inch impact from them yet...