When installing an auxiliary battery, you have a few different options. If your truck has an auxiliary battery bay, you don’t have to worry about positioning it. For those who aren’t so lucky, you’ll need to decide where to install the second battery in the first place. In your case, with the battery already in place, you can either connect it to your electrical system or leave it disconnected and simply plug a 12-volt outlet directly into it. Either method will work, and it’s really up to you how much work you want to do and what you’re looking for in a finished product.

First of all, we want to start with a quick word of caution about actually connecting your new deep cycle battery to your electrical system. There are two important things to consider: deep cycle batteries are not designed to operate on a “shallow cycle” like starter batteries, and your electronics will not differentiate between the deep cycle and starter batteries if both are connected.

With that in mind, you may want to connect both batteries with disconnect switches. It’s fine to connect both batteries at once as long as they’re connected in parallel, but with two disconnect switches you have more control. The reason they need to be connected in parallel is because of the way voltage and current work in parallel versus series circuits. If you connect the batteries in series, you’ll end up with a total of 24 volts DC, and the electrical system is designed to operate at 12-14 volts or thereabouts, so it’s easy to see how that could cause a problem. With the batteries connected in parallel, the voltages of the batteries don’t add up.

If you use disconnect switches, you can disconnect your starting battery when you are camping and the electrical system will only use the deep cycle battery. You can then activate the deep cycle disconnect switch when you start the vehicle and drive normally, since the deep cycle battery is not designed for that kind of shallow cycle operation. If you choose to go this route, you can simply use a 12 volt outlet extender to get power where you need it at your campsite.