New Batteries for the Rumble Bee

Running good batteries is an important part of making any vehicle reliable for backcountry driving and backcountry skiing trailhead access. In the case of our trucks, I keep it simple and eventually stuff in the biggest aftermarket gel cell or dry cell battery I can fit. Optima is a good brand for this mod, as is Odyssey.

In the case of Rumble Bee, our rock crawler Willys Jeep, we needed more than just a swap since the battery was located too close to the scorching hot exhaust manifold in the engine compartment, and overheated during our last Moab trip (short story, the battery vented and sprayed acid all over our engine compartment). Thus, a relocation was in order as well as a new battery. But where to relocate the battery in our tiny Willys? Fortunately, the Jeep has a commodious storage area “toolbox” under the passenger seat — a perfect place for locating batteries. Odyssey sells a model that’s just the right thickness to do this, and I completed the project last weekend. Two model PC680MJ batteries fit perfectly, wired in parallel with connections routed through steel conduit up to the engine compartment.

Batteries installed in Jeep under-seat compartment. Wrench for scale.

Most dual battery setups are rigged with battery isolator systems that charge both batteries but separate them during use and while the vehicle isn’t running. The Odysseys are such high quality several people recommended I simply wire them in parallel so they behave as one battery. We’ll see how that goes (I’d still use an isolator if I put a dual battery system in any of our daily drivers.)

Using two of these smaller Odyssey batteries still gives us 34 amp hours of power for about 30 lbs weight, meaning we’ve got the same or slightly better battery capacity as before, only with relocated high-quality units that have an 8 to 12 year design life and can be drained down to zero charge without damage. On top of that we’ve got room to mount another PC680 in the same area, something we might need since we use a winch. Only problem with the project is what to do with the spare parts I used to carry in the under-seat compartment. Because of the last few year’s improvements The Bee is a lot more reliable than it used to be, so I’ll leave some of the junk behind. I guess we’ll squirrel the rest away in cracks and crannies.