Battery Charging information required please

I've been discharging and charging my battery regularly since I got my laptop, but I've recently read that this isn't such a good idea, and that it's better to discharge it occasionally but use mains power most of the time.

The information I've read also suggests it is detrimental to battery health for it to be constantly 100% charged. I understand that some manufacturers have settings where it is possible to set a maximum amount to the battery charge (say 75%) and then charge it up to 100% occasionally.

Does anyone know if Dell has a system like this?

Dell Inspiron 3521 i5