In Apple’s second macOS Catalina 10.15.5 beta the company added a new “Battery Health Management feature” for Macs (that can be disabled), which is designed to prolong the battery life and battery health of modern Mac notebooks (aka those with Thunderbolt 3 ports) by reducing the rate of chemical aging.
Battery Health Management is an intelligent feature that analyzes the battery status of a Mac notebook and its charging pattern, and based on this information, it may preserve battery health by not charging a MacBook to full capacity.
Charging a MacBook to 100 percent and then letting it sit plugged in without draining the battery through use can lead to reduced battery life, which is what Apple is aiming to avoid. Macs that are often used plugged in and with the battery full may have the Battery Management feature kick in to stop charging short of a full charge.
Battery Health Management is entirely opt-in and can be disabled for those who do not want to use the feature.
MacDailyNews Take: If you mostly use your MacBook Pro or Air plugged in, you’ll most likely want to keep Battery Health Management enabled.
Simple directions for disabling the feature and more in the full article here.