I have a Chevy Tracker with a totally discharged battery due to being garaged for six months. I borrowed a Schumacher 12/8/2 SpeedCharge, but when I plugged it in the outlet the red 'check' light came on and 18.8 kept flashing on and off all night. Nothing else seems to respond - no matter what I press. How do I set this thing to re-charge my battery? Any help would be much appreciated. I am a not-so-dumb greying blonde! Thanks in advance