Optima red top. Wouldn't start car after being on Battery Tender. Jump starts and runs fine. Bought a new charger/maintainer for AGM batteries that supposedly desulfates. After a couple of days with this charger it would start the car, but still seemed weak. Battery fully charged last night. Voltage was down to 11.96 by this morning NOT hooked up to anything overnight. Is the battery toast, or is it probably a sulfation issue given the fact that I saw some improvement after using the new charger? If it's the latter, what are the chances of reviving it with a prolonged desulfation?

Thanks,
Aaron

Battery should stay above 12 volts overnight, unassisted, otherwise it is probably dead.

That was my thought initially after reviewing other threads on the topic, but after seeing some improvement in it's characteristics, thought maybe sulfation may just be the problem. Hate to fork out the cash for a new battery. Of course I don't want to have to wait three weeks with this one on a charger to drive. Just got my car back on the road after a few years in hibernation.

I wouldn't let the cost of a new battery keep me off the road.

That's a perfect example of "penny wise and pound foolish"

Have you tried option #2 for charging your battery as detailed on the optima website?