yeah I would say if your battery is actually at 11.6 volts with no load it is probably only 10-20% charged. trust me I've worked with lead-acid batteries a lot. fully charged 12V battery will read 13V+. To double check it jump it but when you go to start it pull the + terminal all the way off your battery so it is running completely on the good battery. A dead battery will pull down a good battery. A lot of people assume that if you jump a dead battery it will instanly start, not really true.

Just make sure you never, never completely disconnect a running car from a battery, the alternator will send a big voltage spike through your system.