Help hel help scratching my head

hi,i own a 2002 gem e2 and its put away for winter.yesterday i went in the garage to plug the gem to have a charge on the batteries and when i plug the extension cord you can hear the charger go on and and 2 second after it beeps like a transport truck backing up.the light on the steering console is blinking yellow.i have no manuals with the gem, i bought it used. please help!thanks.