Dual-battery systems are a great addition to any overlanding rig. They provide the extra power for your portable refrigerator, speakers, computers, lights, and everything else you take along. They also provide some comforting redundancy when you’re out there off-grid. They have their drawbacks, though.
First, they are not a good DIY project for most of us, as the tight engine compartments of modern vehicles usually require some custom brackets and wiring, not to mention some real mechanical expertise for installation. A dual-battery system may also void the warranty, and any high-quality system will be expensive, which is fair, considering the engineering required to bring it to market.
In place of a dedicated dual-battery system, I’d suggest a high-quality portable battery. You’ll get several benefits in one of these units. Because they’re portable, you can use them in any rig, move them around camp, and so on. Let’s look at some features of a popular and solid unit, the Dometic PLB40.
There’s a bit of terminology and technology to understand here, but not much. One of the most important factors is just how good lithium-ion phosphate batteries have gotten. Dometic says this one will power a powered cooler for up to 40 hours, and the whole unit comes in at under 18 lbs. It’s pretty small, at about 8”x8”x10”, and the spec sheet says the operating temperature range is 32–113° F. The rest of the features are top notch as well, but this battery can power your gear for a weekend or more and not consume much space in your rig.
Because it’s portable, it’s flexible, and the PLB40 has some slick features that make daily use convenient. First, you can charge it from any AC outlet. You can also charge it with DC power from your rig, or connect solar panels of 8–25V to the DC port. Couldn’t be simpler.
When you need to charge devices from the unit, you have two standard USB ports, a standard DC port, and a threaded 2-pin port. The 2-pin port looks like a household AC outlet, but it’s DC. Many portable coolers have the 2-pin plug built in to the DC plug, so you just unscrew the DC part and expose the threaded 2-pin plug. It’s really slick and holds securely. If you want to charge a computer, for example, get a 150W inverter and plug it into the DC port.
The LED display tells you a few things, including charge status and info on any problems like a blown fuse. For a bit more flexibility, the integrated DC to DC charger lets you charge the PLB40 from your rig’s 12V while also powering the fridge.
Tempted by cheapo version for half the price? As with a cheap powered fridge, that’s too much downside risk for me. If one of those units fails when I’m far out there having fun, all my food could spoil and I’d have to cut the trip short. I like to have a reliable unit that I’ll use for years.
One non-obvious tip: if you leave the Dometic unit, or anything else, plugged into a power port in your vehicle while the vehicle is turned off, make sure the port turns off too. Don’t risk draining your starting battery for auxiliary uses.
Dometic PLB40 Portable Lithium Battery, 40 Ah
The Dometic PLB40 Ah Lithium Iron Phosphate battery delivers high levels of mobile power – up to 40 hours of Dometic CFX 40W cooling on a single charge. Designed for powering powered coolers and other 12 V appliances while being off-grid. Thanks to its lightweight and compact design you can enjoy true independence and travel off-grid for longer.