mazda rx7 loosing charge?

[buhrrito]

ok so my rx7, i turn it on and it reads 14v im assuming thats where it should be when its on. and then when i turn it off and it goes to 12 and then it suddenly goes to 10. could it be my battery or my alternator? or maybe something is pulling excessive enegry? it just started doing this.

 

[Garage411.com]

Could be trunk light staying on or something similar to that. Happend to me earlier. After I replaced the bulb the car never had charging issues anymore.