i just bought a new battery and instead of my computer automatically going into sleep mode when my battery runs low it runs all the way out until my mac shuts down. is there any way to make to computer sleep when my battery runs below a certain percent? i tried making some changes in system prefs but didn't have any luck. also is it bad for the battery to leave it plugged in after it is fully charged? whats a normal battery life supposed to be? mine doesn't last much longer than an hour thanks!