85 911 electrical problem
 

Turned key - nothing - no lights, radio, starter, nothing. Assumed battery dead and hooked up charger. Lights came on but car would not start and charger indicated that batter was fully charged. Checked battery cells and all ok. Disconnected charger and interior lights etc. would go on for a while and then nothingness once again. Any ideas would be appreciated.

I've read that once a battery goes completely discharged, it's ruined and won't accept enough of a charge to start the car. Apparently yours is receiving enough to power the lights for a little while but that's it. Try charging it for a few hours, and if it still won't engage the starter, my guess is you need a new one. Good luck and keep us posted.