I have a MBP 13" mid 2012. I upgraded the HD, put an SSD Samnsung 840 EVO 500Gb. It should use much less power than te HD. With the HD, I had 6-7 hours battery life, running Mavericks. As soon as I put the SSD, upgraded to Yosemite. Now, with SSD and Yosemite, I get a little more than 4 hours battery life. Can Yosemite drain battery this fast, even using SSD?