It'* a three year old Optima yellow top. To me it seems more like an alternator or loose connection problem, because the voltage will suddenly drop to a typical battery voltage, then jump back up.

Oops. You said Yellow.

There'* your answer. You're killing (or have killed) your alternator. A yellow top should never be run as a primary battery. Deep cycle batteries are bad news for automotive alternators. It should be run as a secondary battery behind an isolator that has current limiting capability.

As well..you still have a crack in the battery terminal and I bet the movement of WOT is assisting in a wiggling effect.

Hmm, the AC Delco 105 amp alternator lasted three and a half years with the battery before it went. This would be the second Napa Raylock rebuilt 140 amp to die in 4 months.

It did it again this morning, lasted for a couple minutes, voltage jumped up to 14.5 for about 30 seconds, then back down to 11.5 for several minutes, then back up to 14.8 (about a volt higher than normal ) and slowly went down over my 45 mile trip to work, but still never got within 2 tenths of where it normally is...

I don't quite get it.

You may have multiple problems here.....

But the yellowtop warning sticks. Trust me. I've had my share of deep-cycle batteries in RV'* and Boats. They don't mix well. At least not in a primary role. You need that yellow top in the trunk behind an isolator to limit the charge rate and prevent overloading the alternator. This applies to any automotive alternator.

Now if you had the alternator from a BOAT, that would be a different story. They're designed to handle the demands of deep-cycling batteries, but they're not designed to run as often or as long as automotive alts.

Go red-top. And those NAPA rebuilt alts have a good rep.

I wasn't familiar with Optima batteries so I checked out a few sites. Looks like the yellow top batteries are only warranted for 2 years (1 year replacement & another year prorated). Here'* the link http://www.dcbattery.com/optima_yellow.html

It seems like old batteries are hard on alternators. Anyone else put in a new alternator & then have to replace it and the battery within a month or two?

Ted, that'* common. Weak batteries stress alternators, and weak alternators stress batteries.

It'* a catch-22. We like to reccommend replacing them as pairs if the battery is 1-2 years old as a rule of thumb.