I hope this thread isn't getting off topic, but since the DeLorean's electrical system does not charge well at idle while the radiator fans are running, it is important to select a battery that can stand up to this abuse. I seriously considered buying a deep cycle Optima for my DeLorean, but what made me get the red top instead was a matter of higher cold crank amps and the fact that I don't let the car sit for extended periods without use. If I were doing it again, I just might get the yellow top since the Optima has an incredibly high CCA capacity for a deep cycle. This is a relatively new thing as batteries go -- combining spiral glass mat technology with deep cycle chemistry . In the past I was accustomed to the fact that deep cycle batteries just could not produce the CCA needed to reliably start a car. So when I was shopping for my last Optima, I passed up the yellow top while telling myself that the manufacture's claims seemed unrealistically high. Another factor that I considered is that the DeLorean's CCA needs tax the upper limits of what the yellow top can produce. I'm not sure whether or not this could cause it to fail prematurely. The tip that Jason quoted from the web site applies to all lead acid (typical car) batteries in general -- not just the Optima brand. Deep cycle batteries have a different chemistry that allows them to be fully discharged for prolonged periods of time without significant damage. This is very unlike typical car batteries (including the Optima red top) which have the longest life when stored in a fully charged condition. A good way to think of this is to compare it to storing milk. Storing a lead acid battery while discharged is equivalent to storing milk in the hot sun. It will spoil quickly that way. And to any degree that a lead acid battery is cyclically discharged is just like repeatedly taking milk from the refrigerator and allowing it to get warm. This all contributes to how soon the rest of the milk will eventually spoil or how soon the battery will not have enough CCA capacity left to start the car. This is why some people are so particular about keeping trickle chargers on their batteries. It can make an enormous difference in the life of batteries in cars that are seldom driven. And with the DeLorean in particular, consider driving home with the a/c on, radiator fans running & head lights on. Even with a high performance alternator, there may not be enough current output with typical city driving to keep the car running and keep the battery fully charged at the same time. If you regularly subject your battery to this kind of abuse, don't expect it to last very many years. Using deep cycle batteries in cars is not at all customary, and I certainly don't know everything about batteries. Can anyone say if taxing the upper limits of a deep cycle battery (as in automotive use) will cause it to prematurely fail? If not, then my opinion is that the Optima yellow top would be the best choice for the DeLorean. Yet the red top Optima is still a great choice because it recharges more quickly & with less effort than old fashioned wet cell batteries as well as better tolerates being stored partially discharged and cannot leak acid on the carpet or explode. I really should apply for a job with Optima! :-) Walt Tampa, FL > Well after much research, and help from the list (big thanks to > Marty) I purchased a Optima Yellow-Top battery. > Jason > #16665