Sansa Clip - can't tell when to charge battery?

It’s all yellow, including battery, yet music was working for a short bit.  I plugged into computer to charge and it says “connected”  Not sure if it is charging and for how long does it charge?  What’s it supposed to say?  I thought the battery would be BLACK if it were empty.  I’m pretty savy but I don’t use it much and time just got away. Any updates I should have, please tell me. Thank you for helping me out.