Building A Battery Box: Powering Your Camper

Building a battery box for your camper van is a great way to keep your electrical components safe and organised. While it may not be essential, especially for modern sealed batteries, a battery box can provide peace of mind and customisation for your unique setup. In this article, we will discuss the benefits of building your own battery box, the materials and tools you will need, and the step-by-step process to create a secure and functional enclosure for your batteries. Whether you're an experienced DIY-er or a novice, creating a battery box for your camper can be a rewarding project that enhances your off-grid adventures.

Choosing the right battery type

Battery Technology and Performance:

• Flooded Lead-Acid Batteries (FLA): These are the oldest type of leisure batteries, using a combination of lead and sulphuric acid to generate electricity. They require regular maintenance due to acid evaporation and have a shorter lifespan compared to newer technologies. FLA batteries are more affordable upfront but may not be cost-effective in the long run due to their maintenance needs and shorter lifespan.
• Gel Cell Batteries: Gel cell batteries are similar to FLA batteries but use a gel instead of liquid electrolyte. They don't give off gases, have a longer shelf life, and can be installed sideways. However, they are more expensive upfront and have reduced performance if drained by more than 80%.
• Absorbed Glass Mat (AGM) Batteries: AGM batteries are commonly used in automotive and campervan applications. They are similar to FLA batteries but use electrolyte-soaked glass fibres, making them dry and sealed. AGM batteries are about 20% smaller and lighter than gel batteries and have a longer shelf life. However, they are more expensive upfront and may have reduced performance in cold climates.
• Lithium-ion Batteries: Lithium-ion batteries are at the forefront of battery technology. They are smaller, lighter, and more efficient than other types, delivering over 90% of their capacity. Lithium-ion batteries can be installed sideways and don't require frequent maintenance. However, they come with a higher upfront cost, and special considerations are needed for charging and discharging to protect the battery.

Budget and Cost Considerations:

When choosing a battery type, your budget will play a significant role. Here's how the different types compare in terms of cost:

• Flooded Lead-Acid Batteries: These are the most affordable upfront, making them a good choice if you're on a tight budget for your conversion.
• Gel Cell Batteries: Gel cell batteries have a higher initial cost than FLA and AGM batteries.
• AGM Batteries: AGM batteries also carry a higher upfront cost than traditional FLA batteries.
• Lithium-ion Batteries: Lithium-ion batteries have the highest upfront costs among the options. However, they tend to be more cost-effective in the long run due to their longer lifespans and higher efficiency.

Power Requirements and Battery Lifespan:

Consider your power requirements and how you plan to use your camper van. Different battery types have varying performance characteristics and lifespans:

• Flooded Lead-Acid Batteries: These batteries are less efficient, delivering around 50% of their amp hours. They have a shorter lifespan, typically lasting 4-8 years with regular maintenance.
• Gel Cell Batteries: Gel cell batteries are more efficient, providing around 80% of their stored energy. Their lifespan varies, with some lasting 2-4 years and others up to 15 years with moderate use.
• AGM Batteries: AGM batteries also offer better efficiency, delivering around 80% efficiency. They have a lifespan of 4-8 years with regular maintenance.
• Lithium-ion Batteries: Lithium-ion batteries are the most efficient, providing more than 90% of their stored energy. They have a long lifespan, estimated at 7-21 years, although they haven't been extensively tested in campervans for this duration.

In summary, if you're looking for a budget-friendly option and aren't concerned about long-term maintenance, flooded lead-acid batteries might be a suitable choice. On the other hand, if you want a balance between cost and performance, gel cell or AGM batteries could be a good option. For those seeking the most advanced technology, longest lifespan, and highest efficiency, lithium-ion batteries are the premium choice, although they come with a higher price tag.

Designing the box

The first step in designing a battery box is to determine the size and type of battery you will be using. This will dictate the dimensions and specifications of the box. In the example of a DIY van conversion, the author used two VMAX 155ah deep cycle batteries, which measured about 13-½” long, 6-¾” wide, and 11-½” tall. They decided to have the batteries sit side by side, so the inside of the battery box needed to be a 14” x 14” square. It's important to consider the orientation of the batteries and allow for sufficient clearance around the terminals.

The next step is to choose the material for the box. Plywood is a common choice for DIY battery boxes due to its durability and ease of workability. You'll need to measure and cut the plywood pieces according to your battery size and the desired dimensions of the box. Consider the thickness of the plywood to ensure it can support the weight of the batteries.

When designing the box, it's crucial to incorporate ventilation to prevent the buildup of hydrogen gas, which can be dangerous. Drill holes in the front, sides, and back of the box to allow for airflow. Place the ventilation holes towards the top of the box, as hydrogen gas is lighter than air and will rise. You can also add a vent or cover to direct the gas away from the camper.

To enhance the functionality of the box, consider adding features such as a lid, hinges, and a latch. This will allow easy access to the batteries and ensure they remain secure during transport. You may also want to include anchor points or straps to secure the batteries and prevent them from moving around.

Additionally, you can line the inside of the battery box with plastic to provide an extra layer of protection. This is especially useful if you're using a wooden box, as it will contain any battery acid spills and prevent corrosion.

Finally, think about the placement of the battery box in your camper. Consider the available space and how you want to access the batteries. You may need to make adjustments to the design based on the layout of your camper.

Constructing the box

The first step is to measure and cut out the plywood pieces according to the desired size and shape of your battery box. For angled pieces, you can use a carpenter's square to draw the measurements on the plywood before cutting.

Next, you'll want to drill pocket holes in the plywood pieces. Pocket holes are essential for joining the sides of the box together securely. Drill pocket holes on three sides of the angled side pieces, avoiding the top side. For the bottom piece, drill pocket holes on the sides facing the front and back of the box.

Now it's time to screw the box together. Using 1-inch pocket hole screws, fasten the pieces of plywood together, ensuring everything is lined up and in place. A right-angle clamp can be helpful to hold the pieces in position while screwing.

If you want to allow for airflow within the box, create a spacer using 1x3 furring strips. Cut the strips to size and join them together using pocket holes and 1-1/4 inch pocket hole screws. Place the spacer inside the battery box and secure it permanently using cabinet screws driven from the outside.

Before moving on, it's a good idea to dry-fit your batteries to ensure they fit snugly inside the box.

The next step is to drill holes for ventilation and wiring. Drill several holes in the front, sides, and back of the box using a spade drill bit or a hole saw. These holes will allow for airflow and the escape of any gases released by the batteries. Drill additional holes for wiring, ensuring they are placed conveniently for your setup.

Install anchor points for ratchet straps inside the box to secure the batteries in place. Use a piece of plywood as a spacer, along with wood glue and self-tapping screws to attach the D-ring anchor points to the front and back of the box.

If desired, you can line the inside of the box with plastic sheeting for added protection against potential acid leaks. Use spray adhesive to glue the plastic layers in place and secure the top with tape. Alternatively, you can use epoxy and fiberglass for a cleaner finish.

Finally, install the lid, hinges, and latch. Screw and glue a nailer strip to the flat section at the top of the box, then position the lid and attach the piano hinge and safety hasp latch.

Installing the battery

Now that you've got all your parts together, it's time to plug in all the pieces.

Step 1: Attach the charge controller and 12V outlets to the outside of the battery box. We just used small screws, but you can also drill small holes into the box to use nuts and bolts.

Step 2: Wire the battery to the charge controller. Cut off about 12-15” from the 12V plug cable and use this. Attach the leads to the battery (red=positive; I drilled a hole in the battery box to thread the leads through. In the photo, we drilled the hole near the top, but would suggest drilling it near the bottom where the controller is).

Then, strip the free ends and insert them into the battery terminals on the charge controller.

Wire the 12V outlets to the battery in the same way. Again, we drilled a hole and left the fuse on the outside of the box.

Finally, attach the 12V plug to the charge controller by stripping the free ends and inserting them into the “solar” leads on the controller. (Note that charge controllers are designed to accept varied electrical current and output a “controlled” current to charge batteries. The controller we’re using is designed to accept up to 18 amps of current, so it works with most vehicles’ cigarette lighter. If your vehicle puts out more than 18 amps from its cigarette lighter plugs, you may need a different controller).

And just like that, you've got portable electricity to power you through your next outdoor adventure.

Other tips for installing the battery:

• Make sure your vent is towards the top of the box – hydrogen is lighter than air, so it will float to the top of the enclosure.
• You don’t need a fan, and the ability to swap out the air constantly in the box; just make sure when you build it that you cut a couple of holes in the side to let any breeze through the box and for the air to swap out.
• We also lined the inside of the battery box with plastic to help contain battery acid in the (extremely unlikely) event of a spill. This step is completely optional, and if you have LiFePO4 batteries it’s completely unnecessary.
• We layered the inside of the battery box with plastic – just in case something goes catastrophically wrong and we have an acid leak (again, very unlikely with AGM batteries). Battery acid will eat right through wood, but plastic will contain it.

Safety considerations

When building a battery box for your camper, there are several safety considerations to keep in mind to protect yourself and your vehicle. Here are some detailed guidelines to ensure a safe and effective battery box installation:

• Ventilation: Ensure proper ventilation in your battery box to prevent the buildup of explosive gases. Battery boxes should be vented to allow hydrogen gas to escape. Design the ventilation system to direct gases away from the vehicle and its occupants.
• Battery Type: Different battery types have varying safety considerations. Flooded lead-acid batteries require regular maintenance and are more prone to leaking and venting corrosive gases. Absorbed Glass Mat (AGM) batteries are sealed and maintenance-free, making them safer and less likely to leak. Lithium-ion batteries are the most efficient but also require careful handling and ventilation to prevent overheating.
• Secure Installation: Ensure that your battery box is securely mounted to prevent it from sliding, falling, or tipping over during transit. Use bolts or industrial-strength Velcro to attach the box near the power source.
• Battery Protection: The battery box should provide full protection for your battery. Use heavy-duty materials that are resistant to water, corrosion, and acid leaks. The box should also have a secure lid to prevent accidental contact with battery terminals.
• Easy Access: Design the battery box with easy access in mind. You will need to regularly check and charge your battery, so ensure the box has a convenient opening mechanism and provides sufficient space to work with the battery.
• Safety Gear: Invest in safety gear such as gloves, eye protection, and a respirator when working with batteries. These will protect you from harmful chemicals and potential sparks that could ignite explosive gases.
• Fuse and Surge Protection: Install fuses and surge protectors to safeguard your vehicle's electrical system from overloads, short circuits, and power surges. These safety devices will help prevent electrical fires and damage to your appliances.
• Battery Maintenance: Regularly maintain your battery and battery box to ensure optimal performance and longevity. Check the battery's electrolyte and water levels, and keep the connections tight and free from corrosion. Store your RV batteries properly during winter to prevent freezing and discharge.

Frequently asked questions