How To Hook Up A Second Battery In My Truck? [7 Easy Steps]

A Second Battery can be a useful addition to your truck. In fact, most truck owners find it essential to hook up a second battery in a truck. The most significant benefit of a second battery is that it can run electronic gears and equipment even when the engine is off.

The primary battery, also known as the starter battery, helps to start the engine. When the engine is online, this battery works with the alternator and provides power across the truck. If the engine is off, it doesn’t provide power. But the second battery can provide power when the engine is off.

How to Hook up a Second Battery in a Truck? Many truck owners are concerned about it. Well, this article will discuss a step by step guide for installing a second battery in a Truck. Let’s check out the supplies you should require right below.

Supplies to Hook up a Second Battery in a Truck

Installing a second battery isn’t a difficult task if you have a proper understanding. First of all, you must know how a second battery supplies electrical power in your truck. After that, you have to determine the place where you want to set it up in the truck. Then, all you need are some supplies to install it.

To hook up a second battery in a truck, you should require the following supplies.

  • Battery
  • Battery Tray
  • Cables
  • Cables Crimping Tool
  • Isolator
  • Copper Lugs
  • Zip Ties

Installing a second battery costs around 400 dollars. You must purchase a good quality battery. You can get one at any automobile or auto-parts shop. Batteries are also available at online retail shops like Amazon. You also need a battery tray to mount the battery inside the engine compartment firmly. 

Then, you need positive and negative cables to connect the battery with the isolator and to ground the connection to establish power. Measure the length of the cables based on where you want to place the equipment. For removing the rubber part of the cables, you need to have a Cable Crimping Tool.

The most important part of this connection is the isolator. It gives the batteries two isolated identities, meaning that the starter battery and the second battery become disconnected from each other, and they work separately. The isolator also ensures that the two batteries get proper charging.

For connecting the cables tightly with the second battery, you must need some Copper Lugs.

Now, let’s jump to the Step by Step Guide of How to Hook up a Second Battery in a Truck right below.

How to Hook up a Second Battery in a Truck? – Step by Step Guide

Hopefully, you have collected all the necessary supplies you need for installing the second battery. Now you can complete the task in one sitting. Let’s check out the steps down below.

Step 1 – Choose a Location

First, you need to determine where you want to hook up the second battery. As you need to install an isolator with the second battery, the engine compartment should be a suitable place.

Most trucks already have space to hook up a second battery inside the engine compartment. Otherwise, you need to make some space by moving aside other parts. Many truck owners choose to keep the second battery inside the trunk. We recommend you to choose the engine compartment for installing it.

Step 2 – Mount the Battery Tray

In the engine compartment, you need to mount a battery tray onto which you can keep your second battery firmly. So, mount the battery tray by screwing it. Now place the battery firmly on it. You can run the cables through the holes of a battery tray.

Step 3 – Disconnect the Starter Battery

Now, disconnect the starter battery by disconnecting its negative and positive cables. First, remove the negative cable. Then, remove the positive one. You also have to disconnect the cable which connects the starter battery with the alternator.

Step 4 – Install the Isolator

Now, you have to place the isolator between the two batteries and wire them with the isolator. There are four terminals on an isolator. You have to connect the positive cable of the starter battery with one of the isolator’s terminals. Then, connect the alternator with another terminal of the isolator.

Step 5 – Wire the Second Battery

As things stand, the isolator is connected with the starter battery and alternator. Now, you have to connect the second battery with the isolator.

To do this, first, attach a positive cable with the positive terminal of the second battery. Use a cable crimping tool and copper lug to attach the cable tightly with the battery. Now, attach the other end of the cable with one of the isolator’s terminals. Now, the second battery is connected with the isolator.

Now, connect a negative cable with the negative terminal of the second battery. After that, ground the negative cable for establishing connection.

Step 6 – Reconnect the Starter Battery

Now you are almost done. The positive cable of the starter battery is already connected with the isolator (you did it in step 4). Now reconnect the negative cable of the starter battery to ground it for establishing connection. Here we are; now both the batteries are online and connected with the isolator.

Step 7 – Secure the Wiring

Use some zip ties to tie together some cables. This is to keep the cables firm and secure. Zip ties make sure your cables don’t become disconnected during bumpy rides.


A second battery can turn your truck into a home where you can run an inverter, charge your smartphone, laptop, or watch TV, and run Mini-Fridge or Hot-Plate. Hence, a second battery is more significant for the truck-owners who spend long hours in their trucks.

A second battery is easy to hook up. After reading this article, hopefully, now you know how to hook up a second battery in a truck. It can be a difficult task if you don’t know what you are doing. If you don’t have experience working with your truck before, we recommend you to take help while installing the second battery.

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