Dell Optimizer does not limit battery charging %

My Inspiron 15 laptop battery used to be limited to 50%. Since upgrading latest Bios (1.39.0), and latest Optimizer (6.3.2.0) charging is no longer limited and is permanently at 100% unless I unplug charger? What changed and how can I get the limiter back? All online help refers to a windows setting.I have Energy saver on, and do not see any reference to limiting charge %.

I note that I'm within a month of my basic hardware service contact expiring .... coincidence?

Please advise.