My battery will not hold a charge

My battery will not hold a charge. I've changed the alternator, twice, as the first time it tested bad. Now the alternator and battery both test good and the car won't go more than 5 miles without the battery light coming on and the car dying down. After it won't start and I hear the "click click click" so, my starter is working. Someone said fusible link, but I can't find where that would be or how to change it? Any suggestions or photos would be helpful thank you