iPhone not showing correct battery %?

Lately I've noticed my iPhone 4 battery has been dropping faster than normal. Within an hour to 1.5 hours of being off the charger my phone is down in the mid to low 80's range.

Just today my phone has been unplugged since about 11 AM, and I haven't done anything on it besides play some music and check a few emails and it was down to about 84%

However, after I respring my springboard, my battery % goes back up about 8%? Is this normal? I just respringed when my phone was at 86% and after the respring my battery read 92%

 

it's died on me a couple times when I was at work and forgot my charger, so I have done a full recharge on the battery about 2-3 times over the past few months