How Do You Set Up a Dual Battery System

How Do You Set Up a Dual Battery System

R
Renogy
Oct 15th 2024

Getting off the grid is an explosive experience that everyone should enjoy whenever they can. But even when we venture into the off-the-beaten, we still rely on our RVs or motorhomes to keep a semblance of home. That means, we still need to use the oven, watch TV, and charge our phones. Doing all this on the starter battery is a recipe for disaster. You need a dual battery setup, otherwise you risk draining the vehicle’s main battery.

Having a dual-battery system ensures we live our best lives while in the wild and still have the engine start when we want to go home. In this article, we shall look at what a dual battery system is and how to set it up.

What is a Dual Battery Setup?

In a dual battery setup, two batteries serve different purposes in the RV or motorhome. The primary battery focuses on igniting the engine as well as other small components like the radio and headlights. On the other hand, the second battery is the domestic battery. It caters to other household electronics like charging sockets, a TV, a fridge, and an oven, among others.

This setup is ideal for those who want to camp and still connect with the modern world. In most cases, these two batteries are paralleled. So that even when you accidentally drain the primary battery, the second one can step in to help you start the car.

How Does a Dual Battery System Work?

How does a dual battery system work

A dual battery setup is a great way to ensure you have a reliable power source regardless of where the adventure leads you. In this system, there are typically two connected batteries both serving different purposes. The primary battery is tasked with the ignition of the engine and other tasks like powering the headlights and the radio.

The second battery is tasked with powering other household electronics such as powering camp lights, a small fridge, or charging your laptop or phone. The second battery is connected to the vehicle’s main electrical system in a manner that doesn’t interfere with the primary battery’s ability to start the engine.

It is done using an isolator that ensures that when the engine isn’t running, only the secondary battery is used. The two batteries are also connected to the vehicle’s alternator. This means when the vehicle starts, both batteries will recharge. But the isolator will give priority to the primary battery.

The second battery will only start charging after the primary battery has received a sufficient supply of charge. In some advanced dual battery setups, the voltage-sensing system can determine the state of charge for both batteries. If the main battery is quickly being depleted, the system will disconnect the secondary battery from it.

Some dual battery systems also allow manual control over the two batteries. This way the users can disconnect the second battery from the primary one to prevent draining the latter. In some cases, you can also charge your secondary battery using solar panels, limiting its dependence on the primary one.

Pros and Cons of a Dual Battery Setup

Now that you know what a dual battery system is and how it works, let’s look at its pros and cons.

Pros

  • It's an efficient way to power household electronics.
  • You can ignite the vehicle engine with the second battery if the primary one is drained.
  • You can charge the secondary battery using solar panels.
  • Less worry about draining the primary battery when properly installed.

Cons

  • The upfront cost of buying an extra battery and setting up the system can be inconveniencing especially if you are on a tight budget.
  • There's added weight to the vehicle which in turn increases drag and consequently fuel consumption.
  • The dual battery system requires occasional maintenance which is an extra cost.

How Do I Know if I Need a Dual Battery System?

Determining whether you need a dual battery system depends on several factors related to your vehicle usage and electrical demands. If you frequently use power-hungry accessories like winches, fridges, or camping equipment when your vehicle isn't running, or if you often go on extended trips or off-road adventures, a dual battery setup might be beneficial.

This system becomes particularly valuable for 4x4s, RVs, or boats that require additional power for accessories.

Additionally, if you've experienced difficulty starting your vehicle due to a drained battery or if you live in or travel to areas with extreme temperatures affecting battery performance, a dual battery system could provide the reliability and power management you need.

By separating your starting battery from your accessory power, you can ensure your vehicle always starts while still having ample power for your electrical needs, making it an ideal solution for those who demand more from their vehicle's electrical system than a standard single battery can provide.

How Do You Hook Up Dual Battery Setup?

How to hook up a dual battery system

Now that we have sold you on the dual battery system, let’s look at how you can set it up in your van or RV. Here’s a simple step-by-step on how to hook up a dual battery setup.

1.Disconnect your Primary Battery

First things first, disconnect your primary battery from the vehicle. This is an important precaution. You can do so by simply disconnecting the negative terminal of the starter or primary battery.

2.Pick Out Your Second Battery

There are about 4 potential deep-cycle batteries you can use as your second battery in this system. You could use lead-acid, gel, AGM, or lithium for your secondary battery. Any can work but we recommend you use lithium or AGM. Read the batteries section below for a detailed explanation.

3.Pick an Installation Location

You will then need to decide where to set it up. Make sure to find a place that is dry and where the batteries won’t be affected by the elements. If you plan to go winter camping, find a spot that hovers between 41 and 113 degrees Fahrenheit.

We also recommend you place the second battery in a battery box if you are installing it inside the vehicle. This will protect it against scraps, bumps, and falling items from shorting out the terminals. To prevent voltage loss, ensure the wires connecting the two batteries aren’t too long.

If you have no choice but to install your second battery in the back, please opt for a cable that is thick enough to combat voltage loss. The thickness is ultimately determined by the amperage of the DC charger. Read the manual of the charger to determine the cable you can use for the setup.

4.Fit Lugs and lay Cables

Next, you will lug all cables connecting the system. To do so, use a pair of needle nose pliers to strip 15mm of the wires and then apply the lugs. Make sure to slide the heat shrink over the lugs to seal them.

5.Install Circuit Breakers

Circuit breakers are very integral when it comes to electrical connections. Having one will give you peace of mind that the vehicle won’t go up in flames. So, yes install one close to each battery (about 15cm). In case things go wrong, your circuit breaker will overload and cut power to protect the entire system.

6.Connect the Isolator

The battery isolator is a crucial part of the system. It ensures charge goes to both batteries when the engine starts. Typically, it prioritizes the primary battery by picking current from the alternator. Once full, it sends the remaining current to the secondary battery. To connect your isolator, you’ll connect the positive terminal of your primary battery to the positive terminal of the isolator.

Next, you’ll connect the primary battery’s negative terminal to the secondary battery’s negative terminal. And finally, connect the secondary battery’s negative terminal to the isolator’s negative terminal.

7.Mount Your DC Charger

To charge the second battery, you need a DC-DC charger (alternator Charger). When mounting your DC charger, find a spot where it will get enough ventilation because it heats up when the batteries are charging. You also want a place much closer to your second battery to minimize voltage loss. Find a flat surface where it won’t be knocked over, then drill and fasten the setup with bolts.

8.Test the System

After successfully installing the DC charger, you will connect the negative cable back to the primary battery. To test the system, use a multimeter to ensure every connection is working as it should.

Types of Batteries Used for Secondary Batteries

When setting up your dual battery system, the chemistry of your secondary battery plays an integral towards the experience. There are about four possible types to use in this setup. Let’s look at each one of them and help you through the selection of your secondary battery.

Lead-acid Batteries

Most cars use lead-acid make for their starter (primary) batteries. It’s possible to use a lead-acid as a secondary battery, but these aren’t good for prolonged use. They also can only be installed under the hood because they need proper ventilation to prevent the build-up of hydrogen gas.

AGM Batteries

Another option is AGM. These are quite common for the dual battery setup because they are versatile and can charge without emitting hazardous gases. They provide reliable power without necessarily needing too much maintenance. They also have low internal resistance, making them ideal for power tools like winches.

Gel Batteries

The other option is gel batteries. However, these are significantly heavier and have shorter shelf-life. They also require a low charging voltage than lead-acid and AGM, meaning that you need a separate complex setup to incorporate them into the system.

Lithium-ion Batteries

The last option and our best recommendation is the lithium-ion battery. Lithium batteries are half the weight and offer double the power of all the above. They also offer a reliable and consistent power supply over long periods without depleting beyond safe limits.

Charging and Maintaining Your Dual Battery System

Like all technology, the dual battery system isn’t immune to wear and tear. So, take these steps to ensure, you get the best value for money possible. First, ensure to regularly inspect your setup before setting off for the trip and after you arrive at the destination. Check for loose or damaged wiring and inspect the batteries for corrosion.

Also, if you are using lead-acid batteries, ensure to check on the fluid levels. Add distilled water if the fluid levels are low. Keep both batteries clean and free from debris that could damage them. Morever, make sure your alternator is working fine.

Lastly, if the two batteries in your system are of different chemistry, make sure to balance out the charge between them. Most DC chargers support this feature. If you follow these simple steps, you will certainly get the best of your dual battery system.

Conclusion

Venturing to remote destinations doesn’t have to be a complete blackout or disconnect from the world. With the dual battery setup, you can enjoy both worlds without necessarily putting a strain on your primary battery. Hopefully, our detailed guide has clarified why it’s important and how to use it.

Frequently Asked Questions About Dual Battery System

1. Can the secondary battery drain the primary battery?

Yes, especially if the isolator isn’t installed properly. The isolator is supposed to send charge from the alternator to the second battery when the engine is switched on. When the vehicle is off, the isolator should cut the second battery from draining the primary one.

2. Will dual batteries hurt the alternator?

It is possible. Most alternators are meant to charge only one battery and adding a second battery could cause it to overheat and ultimately damage it. That’s why you need a DC-DC charger (alternator charger) to help control the second battery charge state.

3. What can I run off a dual battery?

A dual battery system setup can power a range of domestic appliances. These include a mini-fridge, a cooker, camping lights, a kettle, and other power-hungry applications like a winch.

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