The New Apple Watch's Slightly Larger Battery
iFixit Apple Watch Series 6 Teardown Finds Larger Battery and Bigger Taptic Engine in Thinner Casing
Apple is using a 1.17Wh battery in the 44mm Apple Watch Series 6, which is just a slight increase (3.5 percent) over the battery used in the prior-generation Apple Watch Series 5.
I'm in the middle of my battery testing compared to the Series 5, explaining my double-watch wearing at the top of this post, and this marginal increase aligns pretty well with my early results (accounting for 1 year of battery health degradation).
I'll have my full results in the upcoming review, but early signs point to a marginally improved battery.