You can't change how much the battery stores without getting a new battery. Unless you are saying that the battery is not charging. Then you need to start trying to find out where. New power brick, then new battery, then need to have someone test the power jack on the laptop.
Lenovo should have different power options such as power saver, balanced, or high performance. This only affects the battery life when your laptop is not connected to the wall. Plus, all chargers have a set voltage to charge the battery. You don't want to change it.