here is something you can do:

1. go to Control Panel > Power options . Then for the one that is selected click " Change Plan Settings ". then click on "Change Advanced Power Settings" scroll down to the battery section. there are some options in there you can change etc.

2. You can also download a sidebar gadget that will show you the current battery level (quite large) and it will give alerts when the battery gets low. and you can change the alert levels.