Sony Xperia Marshmallow update beta includes 'soft charging' allowing the battery to live longer
Studies have found that you can increase the number of years that a battery can hold its charge, by not letting it fully recover to 100% each time you plug in. Of course, the caveat is that you will never get to experience the full life of your battery on a day-by-day basis. You might have to charge your phone more often than usual over the course of a week, a month, or even longer.
The first time you charge your phone following the update, you will receive a message that 'Charging optimization' is enabled. You can disable this by going to Settings > About phone > Status > Charging optimization.
In addition to the Charging optimization feature, the update includes the latest version of the Xperia Home launcher, which now includes support for landscape orientation, bug fixes and a number of improvements. Xperia Z2, Xperia Z3 and Xperia Z3 Compact owners who are members of the beta program will receive the update shortly.
source: XperiaBlog via AndroidandMe