Yellow top!! I have one in the GN, and it only let me down once, and that is because I had not started the car for a 2 months in the freezing tundra of South Dakota where below zero temperatures are common in the winter. After a good charge it has given me no problems and I now try to start my car on a regular basis. So Optima'* are good just don't let them sit!

And the yellow top may be why you went through 3 alternators. Yellows are deep-cycle. Automotive alternators aren't intended to charge them. Red is for automotive use.

Not quite right. Yellow'* are for automotive use also, you just have to use them correctly/have a use for them.

To be fair, the first was replaced within days of the battery, it was already gone. The second was 4.5 years later. The third was to replace that dud that lasted only a few weeks.

Somebody help me out here on deep-cycle batteries killing alternators. I've owned two old police cars that came with Delco deep-cycle marines batteries and never replaced an alternator, although they were, admittedly, the size of a bushel basket.

My convertible (9.5:1 455) has a 100 amp alternator I had a local guy modify to one wire.

Given the fact that modern voltage regs are just an off/off switch, I fail to see how the battery could affect the charging system.

Your thoughts, gentlemen?

In a police car it makes sense to have a deep cycle. They sit for long periods of time with lots of equipment turned on. It would be bad for them to try to take off and have a no-start situation.

At the same time, I cant elaborate on the deep cycle killing alts. I am curious though.