Hi.. I bought a new imac on 13th June. No problems till now. Al good. Today morning, when i switched it on, I saw that the back fan is moving with more speed and sound . Earlier, I never heard the fan sound. Also, on startup the brightness is set to max , while my settings was very low brightness.. Howcome, its starting with max brightness now, when I dont have changed anything ? And what about the fan sound and speed ? And yes, does the iMac has a battery also ? For what ? Its always plugged to AC current, then what is the battery doing ? I never knew that. Just downloaded istat pro and it shows HD 35 degree and Battery 55%. Wht is it ?