Campervan Electrical Guide – Common DIY Questions Explained

So you are planning to build out your vehicle — or have already been living in your van conversion—and you want to add electrical.

Unless you are an electrical expert, you probably have a lot of questions. An auxiliary power system for your vehicle has many parts and needs a base level of electrical understanding to avoid potentially dangerous mistakes. Batteries, wire gauge, tools, and charging methods all require special consideration.

Don’t fret! We put together these 10 common questions and answers to help guide you through the process of installing an auxiliary power system. If you understand these concepts, you will be well on your way to kicking-off your campervan electrical project.

1.  Should I DIY or Buy a Packaged Product?

Before we get into the nitty-grity of campervan electrical systems, let’s consider this question—DIY or DIWhy?

Many vanlifers assume DIY is the best way to go, but this is not always the case. Whether or not to DIY depends on your individual power needs, how electrically savvy you are, and how much time you’re willing to put in. Sometimes it may not even be cost effective to DIY, so it’s important to understand your options.

First, we’ll consider the different “levels” of a vanlife electrical system and see your specific options.

Some of you only need to worry about charging your cell phone and knick knacks while on the road. These are truely a hardcore bunch—out there dangling their headlamp from their ceiling at night and living off ramen. Keep fighting the good fight—we salute you!

Power Options: Charge from your cigarette lighter.

To avoid living like a savage, the rest of us need some level of auxiliary power when vanlifing. How much power will be largely dependent on the accessories you’d like to have—electrical cooler, lights, and computer charging to name a few.

Power Options: Portable Power Unit (like Jackery), Pre-built System, DIY

A proper van conversion will require a full-blown auxiliary electrical system. This will bump you up to cushy life status—complete with roof fans, a water pump, kitchen appliances, and even climate control.

Power Options: DIY, Pre-built System

If you’re Level 2 or 3, the next question you need to ask is should I DIY or buy a packaged product. Many vanlifers choose to go the DIY route for a few reasons. First of all, packaged systems can be expensive and limited on customizability. For example, many products are limited on how much solar you can connect and battery expansion packs can be costly.

DIY, though, can be a serious undertaking if you’re not an electrical expert. The fact is, building an auxiliary power system in your vehicle is not common sense, and for many of you it will be the crux of your build.

Another option is a pre-built system, which combines DIY and plug & play. You can choose your own batteries, chargers, and inverter size to fit your specific needs. Get all the customizability of a DIY system, but without all the hassle that DIY comes with.

2. How much Battery Capacity Do I need?

Battery capacity is an important factor when choosing between DIY or packaged system. Package systems tend to get very expensive on the large end of capacity.

To calculate your battery capacity requirements, you will first need to estimate your daily power usage.

Next, take your daily estimated power usage and multiply by 1.5  to get your recommended battery capacity. We recommend that your battery capacity is 50% more than your power usage to ensure you don’t run out of power—running out of power can cause unfortunate food waste in your cooler and lightless nights.

...TO SIMPLIFY A BIT

If your power needs are small, you may want to consider packaged products like Jackery or Goal Zero. For anything larger than 500 Wh in capacity, it will likely make sense to go with DIY for cost saving reasons.

3. How Much Solar Wattage or Charging Do I Need?

Keep in mind that your power usage is limited by how much charging your system is capable of. It doesn’t matter how big your batteries are if you can’t charge them up! Power in must at least equal power out.

The amount of charging that you need will also help decide between packaged product or DIY. For example, the Jackery Solar Generator 1000 can only support 200W of solar. DIY, on the other hand, can support as much solar as your roof can handle—700W or more. 

On top of solar, you can also charge while driving. Many packaged products sell a charger that connects directly to your cigarette lighter. This allows for hassle free charging, but is limited because cigarette plugs only can charge so much—usually not more than 7A. DIY allows for a high amp alternator DC-DC charger. We highly recommend avoiding “battery isolator switches” in place of a proper DC-DC charger since they have no circuity to prevent overcharging of your auxiliary batteries. 

4.  I've Decided DIY Is for Me - Now What Do I Do?

Ok, so you’ve decided that DIY is for you. Maybe your required battery capacity or solar wattage exceeds package products limitations—or your wallet limitations—and building it yourself is half the reason you want to build out a van anyway. Get comfy, because the rest of this article is dedicated to arming you with all the knowledge you need to get started on your electrical system. So put on your learning cap and let’s get begin!

UNDERSTANDING THE MAIN COMPONENTS

We’ll start with a quick overview of the main components of a campervan electrical system.

Batteries -

The heart of your electrical system. You can connect multiple batteries together to increase your total capacity.

Solar Panels -

Roof mounted solar panels are often the best way to keep enough charge in your batteries. You should consider flexible versions because they can be glued to your roof and do not require mounting frames.

Solar Charge Controller -

This component is wired in-between your batteries and solar panels and is absolutely necessary to regulate the charging of your batteries. The charge controller needs to be programmed to your specific battery type to ensure a proper charge profile. There are two types of charge controllers: MPPT and PWM. MPPT controllers are about 20% more efficient when compared to PWM, but are typically cost about 10 times more.

DC-DC Charger -

A DC-DC charger will connect your starter battery to your auxiliary batteries and charge while you drive. You should avoid "battery isolator switches" because they will overcharge your batteries on long drives.

Inverter -

An inverter allows you to use anything with a wall plug like a laptop charger, coffee maker, or blender. It transforms the 12V or 24V “Direct Current” in your batteries to 120V “Alternating Current”.

Fuse Box -

Everything within your electrical system needs to be fuse protected for safety reasons. To add fuse protection to lights or other accessories, you can wire everything to a fuse box.

Output Panel -

You’ll need an output panel to actually use the power in your batteries. Unlike an inverter, the output panel will wire directly to your fuse box and provide power at the same voltage as your auxiliary system—typically 12 or 24 volts.

Bus Bar -

These allow for easy “branch” connections and are a common addition to any auxiliary electrical system.

Connectors and Wiring -

You will need a slew of connector types and wire gauges to connect everything in your system together. We’ve dedicated a couple sections on this topic below.

5. What Batteries Should I Choose and How Many Do I Need?

Batteries come in multiple types, each with a unique set of pros and cons. The two main types used for campervans are “LiFePO4” and “AGM”. Deciding between these two is worth reading a whole article on its own—and lucky enough for you, we’ve written one! Check out AGM vs. LiFePO4 – Choosing the Best Type of Battery for Van Life for help with this question. One thing should be clear, though, you need to use identical batteries in your system. No connecting different types, sizes, or ages!

Regardless of what type you choose, you will have to understand battery capacity to decide on how many you will need for your setup. Battery capacity, or how much power a battery can store, is typically represented as Watt-hours (Wh). Watt-hours also represent how much power something uses. For example, a 100 Watt appliance used for 1 hour will use 100 Wh. 

You will also commonly see an Amp-Hour (Ah) rating on a battery. This is another way of representing battery capacity, though it is actually not a unit of capacity at all. To calculate capacity from amp-hours, simply multiply the Ah rating by the voltage of the battery. So, for a 12V 100Ah battery the total capacity is 12 x 100 = 1200 Wh. 

But it’s not quite that easy! — Watt-Hours ≠ Usable Watt-Hours

To make things a little more confusing, you can’t use 100% of your battery’s capacity without causing damage over time. This is referred to as it’s “usable capacity”. The usable capacity of a battery depends it's type. For example, you can discharge a much higher percentage of LiFePO4 batteries without causing damage.

AGM vs. LiFePO4 Usable Wh Comparison Chart

Now that we’ve explained all of this and you've selected the batteries you’d like to use, you're ready to calculate how many batteries you need. Next simply divide the Watt-hour value you got from our “Power Calculator” in Question 2 by the Usable Watt-hours of the battery. 

To simplify things a bit we typically recommend one 12V 100Ah LiFePO4 battery for a “Level 2” electrical system, and two to three 12V 100Ah LiFePO4 batteries for “Level 3”. The “Levels” I’m mentioning here are discussed at the beginning of this article.

6. Should I use a 12V or 24V system?

Batteries, solar panels, and most everything else can be wired for either 12 or 24 volts. 12V tends to be the most common for vehicle electrical systems because 12V accessories are slightly more common. The main reason to wire for 24V is if you have high power demands. In general, we recommend wiring for 24V if your total solar wattage is above 360W or your inverter is larger than 1000W. Any power demands over these values will force you to increase your wire gauge considerably, which can add up to a lot of $$$.

7. How do I determine the proper wire gauge?

Wire gauge, or the diameter of the conductor in the wire, is an important factor when designing your system. If your wire gauge is too small you will have excessive voltage drop and heat loss in your wire. This may cause things to not work properly and can even be a fire hazard.

Think opposite – The smaller the gauge number, the larger the wire.

Wire gauge is represented by a number from 0000 to 40. The smaller the number, the bigger wire gauge. 00 is bigger than 0 and 2 is bigger than 8, and so on. In general, most DIY systems will stay in the range of 2 to 16. Anything larger or smaller is not typically needed.

To determine the proper wire gauge, you will need to know the maximum possible amps that can travel through the specific section of wire in question. To calculate amps, simply divide the wattage of the accessory that you’re connecting by the system voltage.

Here's a few example calculations…

• A 1000W inverter connected to a 12V battery can potentially draw 83.3A (1000W / 12V = 83.3A). That’s a lot of juice! 
• 10W LED lights on the other hand will only draw up to 0.8A when connected to a 12V battery (10W / 12V = 0.8A).
• 400W of solar panels wired for 24V can generate 16.7A in full sun (400W / 24V = 16.7A).
• All wires connected to a 30A solar charge controller need to be sized for… you guessed it… 30 amps. This includes wires to/from your solar panels, to/from your battery, and to/from your fuse box.

Once you know either amperage or wattage through your wires, you can follow the charts below to ensure proper wire gauge for each individual section of wire in your system. 

Notice how increasing the system voltage decreases the required wire gauge. This is because doubling the voltage decreases the amps by half. 

Also notice that longer wires will require thicker gauges. This is because a large voltage drop will occur in a long wire. A larger gauge is required to offset that voltage drop.

8.  Ok so I understand wire gauge, but what types of wire do I need to use?

On top of wire gauge, you also need to consider wire type. The two main types of wire you will use in your van conversion are AWG and PV.

AWG stands for American Wire Gauge and is what you should be using for any section of wire that is completely inside your van. If a wire is not certified “AWG” then you can not be certain on how it will perform—so best to stay away from that and stick to AWG. Be sure to check the comments, though! Many suppliers falsely advertise their wires as AWG.

PV Cable is specifically designed for use with solar panels. It’s insulation is more rugged than other types of cable and it should be used for any cable that is permanently installed outdoors. It’s UV and weather resistant and can handle a large temperature range.

9. What are the different wire connections?

When you’re building an electrical system, one thing is for certain—your wire connecting knowledge needs to be up to par. A typical system will have dozens upon dozens of connections and each will need a specific type depending on the situation. Here’s a few common ones that you are sure to run into…

Butt-Connection: A butt connection will be used to connect two pieces of wire together. To do this, you’ll need a butt connector and a crimping tool. The connectors will be rated for a certain wire gauge range, so be sure to buy the right size.

Ring-Connection: A ring connection will be used to connect a wire to your fuse box or bus bar. You will also use a larger version called a “lug” to connect large wire gauges directly to your battery terminals. As with a butt-connector, your ring connector needs to be sized for your wire gauge and you'll need a wire crimper to put them on.

Ferrule-Connection: A ferrule connection is a little more obscure but should be used to connect wires to your solar charger. A ferrule will greatly improve your connection by reducing contact resistance and decreasing oxidation of the wire. A special ferrule crimper is needed for this connector.

10. What tools will I need?

Wiring an electrical system will require an assortment of tools. Here’s a list of electrical specific tools you’ll need to complete the job.

Wire Striper ($8-$30): To use the connectors mentioned above, you will first need to strip the end of the wire. The version pictured here will make all the striping you do worlds easier when compared to cheaper versions.

Crimper ($20-$100): One of these will be required for the dozens of butt and ring connectors you’ll be using. It's important to do a quick pull test on every crimp to make sure the connection is solid. Just give a firm tug on the wire and make sure it doesn't budge at all in the connector. If it does, cut it off and start over.

Digital Clamp Meter ($25-$45): A voltmeter is essential for checking your work and troubleshooting. A clamp on version is super handy for quickly checking amperage in a wire. Just make sure it's rated for DC current.

Cable Cutter ($15-$30): These allow you to cut large gauge wires, which you'll be using for your battery cables and inverter wires.

Ferrule Crimper ($18-$25): You’ll only use this for crimping ferrule connectors for  your solar charger. Hopefully a buddy will have one for loan.

Lug Crimper ($25-$35): Also only used a few times… You’ll need one of these to connect lugs to your large gauge wires.

Conclusion

If you stayed with us this long, congratulations! You probably have the grit it takes to DIY your own campervan electrical system. Or you may have realized that a packaged product may be the route for you. Either way, we hope to have passed on some tidbits that will help you get started!