Don't Use REDTOP Batteries in Overlanding Vehicles

We've said this a lot of different ways, but each time we hear a story like the one we're about to share, it compels us to once again remind people about using the correct OPTIMA batteries in their applications. OPTIMA REDTOP batteries are powerful batteries for SLI (Starting/Lighting/Ignition) applications, but they are not designed or warrantied for deep-cycle use, including vehicles equipped with winches and refrigerators. These are common accessories in vehicles used for overlanding, like OPTIMA Brand Ambassador, Woody Swearingen's Toyota. Woody knows better than to use REDTOPs in these applications, but since others do not, we'll do our best to explain.

The story starts with an imported Toyota Land Cruiser, equipped with at least a winch and a refrigerator, whose owner decided to purchase a pair of REDTOP batteries. As we mentioned many times before, if your vehicle has accessories that can deep-cycle batteries, we strongly recommend purchasing YELLOWTOP batteries that are designed and warrantied for deep-cycle use, including winching and vehicles equipped with a refrigerator.

Ok, what's done is done. REDTOP batteries could work just fine, if they are only used for engine starting in that application. Having dedicated starting and isolated house batteries for overlanding rigs is really a good idea, because if one battery (or bank) has an issue in the middle of nowhere, you always have a backup. If you put all your electrical eggs in one basket and rely on the same batteries to power your accessories and start your engine, you could find yourself stranded in the middle of nowhere, even if the batteries are still fine, but just deeply-discharged from use.

Fully-charged, REDTOP batteries will measure about 12.6-12.8 volts and YELLOWTOP batteries will measure about 13.0-13.2 volts. Whenever any lead-acid battery is discharged below 12.4 volts and is left sitting in that state, sulfation will begin forming in the battery, which diminishes lifespan and capacity. Vehicles that are simple from an electrical standpoint can typically sit for several months at a time with minimal voltage drop. However, more electrically complex vehicles should always be stored with some type of quality battery maintenance device as a best practice. Those without electrical access should fully-charge and completely disconnect their batteries when the vehicle is put into storage and fully-recharge them with a battery charger (not the vehicle's alternator), when they are brought out of storage.

Given the typically complex and electrically-demanding makeup of overlanding vehicles, this makes proper voltage maintenance a key component for any overlanding rig, just as someone would make an annual point of greasing the u-joints, ball-joints and the leaf spring bushings. Unfortunately, the owner in this example allowed their batteries to become completely discharged over the winter. No word on how long they sat in that state or if they were properly-recharged or just jump-started. (As an additional reminder, alternators are not designed to charge "dead" batteries)

The fact that these two batteries were discharged over the winter indicates there could be a significant parasitic draw in the vehicle. A typical parasitic draw is about 25 milliamps and anything over 100 milliamps should be addressed. It could've been that the refrigerator or glove box light was accidentally left on or it could just be the way the vehicle is wired to operate. Either way, if the draw cannot be reduced, a maintenance charger that meets or exceeds the draw should be used (we've seen RV batteries get discharged even WITH a maintenance charger connected).

Another thing to keep in mind when modifying vehicles for overlanding, is that the OE manufacturers typically design their electrical systems to function properly, as the vehicles were equipped from the factory. When winches, refrigerators, auxiliary lights and other electrical accessories are added in the aftermarket, these OE systems may not be up to the task.

Unfortunately, many consumers significantly modify their vehicles from an electrical standpoint, without giving a second thought to the batteries. A few will upgrade their batteries when they add in a winch, refrigerator or other accessories, but not give any thought to the factory alternator that is now facing demands that could far exceed the original design. A few will also upgrade the alternator, but not take into account that an electrical system is only as robust as the wiring that connects it all together, including the run of wire going to the refrigerator in the back of the vehicle.

A select few will cover all their bases, in large part, because many people rely on advice from a variety of sources, anywhere from highly-trained professionals in a best-case scenario to random people on the Internet, to provide them with guidance on properly-building out their systems. The quality of that advice can vary significantly and when we see someone who chose the wrong type of batteries, did not run an isolated house battery and deeply-discharged their battery over the winter, it begins to paint a familiar and unfortunate picture.

The stranded overlander was able to contact someone, who came out to their location with two replacement batteries and they initially noted the voltage was fine and the charging system seemed to be operating fine, within a range of about 27.6V to 28.5V. We recommend typical alternator output, as measured directly at the battery terminals to be about 27.4V to 29.4V (13.7-14.7V for 12-volt applications), so a measurement of 27.6 is definitely on the lower end of what we'd like to see.

Given what we already knew about this application, it came as no surprise, that the owner later reported one of their batteries was getting more of a charge than the other and that further testing would be done to determine the cause. There were no updates after that, but we hope they sorted out their issues and we hope sharing their story will help you avoid similar issues.