Electrolytes is a topic I struggle with as well. I don't know if you've taken a look at it yet, but my pharm instructor strongly recommended a book to help understand it better. It's "Fluids and Electrolytes Made Incredibly Easy". I found an older, slightly used edition on Amazon for about $10...fyi. I just got it in the mail a week ago and haven't had a chance to look at it yet, but that will be some "light reading" for me to do this summer. LOL. Maybe go to B&N and flip through it. That's my (2 cents). :)
Hope that helps.