Posted: Sep 10, 2019
What is Different About a Marine Battery?
What makes marine batteries different than regular car batteries? One key difference is that many marine batteries offer threaded battery terminals, that allow you to make eyelet connections to your battery. Most car batteries use a standard SAE-sized terminal, which isn't always found in marine applications. Many marine batteries also may have a different label or appearance (sometimes blue, like the OPTIMA BLUETOP), but sometimes there is no difference internally between a marine battery and it's automotive counterpart.
Some marine batteries only offer the alternate or additional terminals and often a shorter warranty, but are otherwise identical internally. Why the shorter warranty? Mainly because a lot of folks who use batteries in boats (and RVs) don't do a good job of maintaining proper voltage in their batteries and anytime a battery is discharged below 12.4 volts and is left sitting in that state, it begins to sulfate. That makes regular use of a quality battery maintenance device a great idea for anyone who has a boat or RV that doesn't see regular use (and even some that are used regularly).
Just because some marine batteries are basically the same as their automotive counterparts doesn't mean all of them are. Some marine batteries are designed for deep-cycle use, including OPTIMA BLUETOP batteries with light-gray cases (D34M, D27M and D31M). The OPTIMA BLUETOP with a dark gray case (34M) is basically the marine version of our Group 34 REDTOP starting battery. The 34M is fully-charged at about 12.6-12.8 volts, while those BLUETOPs with the light gray cases are fully-charged at about 13.0-13.2 volts and other marine batteries designed for deep-cycle use may be the same way.
If you're going to use your marine battery for a deep-cycle application, like a trolling motor or live well, it's a good idea to make sure you choose a marine battery designed & warrantied for deep-cycle use. If you just need it to start an engine and don't have any significant electrical accessories, then a starting battery will work just fine, like the 34M BLUETOP. You can see the full lineup of OPTIMA BLUETOP marine batteries here.