Hi 351mustang, I'm sorry to hear about the problem you've been having and I'd like to help. Fully-charged, your RedTop should measure about 12.6-12.8 volts. If you can fully-charge it and totally disconnect it from your car for two to three days, then reconnect it, the battery should hold plenty of voltage to start your car. If it can hold voltage when disconnected for that timeframe, but loses voltage when connected, there is something in your car discharging it.
Your alternator is designed to maintain a battery that is nearly fully-charged, not recover deeply-discharged batteries. You may also not be giving the alternator a chance to do it's job, if you primarily start the car but don't drive it.
eCare Manager, OPTIMA Batteries, Inc.