Van Electrical System with Secondary Alternator for Near Limitless Power

This example electrical system is a monster and gives you virtually unlimited electrical power in your camper van. If want the best off-grid capability, this is probably the best system for you.

This sample electrical system was developed with the support and input from engineers at both Lithionics and Wakespeed so you can have confidence in what we're presenting here!

We hope you find the post valuable and, of course, we appreciate when our readers purchase their materials from our store. You can save a bundle by purchasing many of the primary electrical components with our discounted bundle. In short, the more that your purchase the higher the savings. We also sell many of the various components individually with competitive pricing.

We also offer installations of the secondary alternator at our shop in Sarasota, FL. Please email us for more information and pricing.

This is a pretty long and detailed post so we've provided some navigation below.

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We have designed various camper van power systems. Each of them has a blog post and a detailed PDF wiring diagram. We also sell discounted product bundles for each system design in our store and you can even hire us to install them into your van at our facility in Sarasota, Florida.

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Overwhelmed? You’re not alone! Electrical systems can be extremely confusing. That’s why we've gone into so much detail in this post. I’ve worked with many DIY van builders who, understandably, can’t wrap their head around their electrical system. However, most of the time, once they purchase all the components and start to lay it out it starts to come together for them. So, I recommend you do the same. Get all the materials, decide where you’re going to install your system and measure that area. Then tape out a section of a table or counter top and start putting the various components together into that space. This will help you get an idea of where each device should be located and everything will likely start to make more sense. Then you can use either tape or string to start “virtually” hooking things up. Some people use various colors of electrical tape to represent various wire gauges. Going through this exercise will help you plan your install and understand how everything works together!

If you want to learn more about how electricity works and take a deep dive, I recommend a free PDF book published by Victron called Wiring Unlimited.

Contact us for more information or to get something scheduled!

Why Use a Secondary Alternator?

In the last year or so, we’re seeing many more van builders including 400 to 600 amp hours (or more) of battery storage capacity in their rigs. Prior to that, a “large’ system was maybe 300 amp hours. These higher capacity systems are absolutely fantastic for powering your loads for long periods of time while boondocking off grid. Massive battery banks even open up the possibility of using an energy efficient 12-volt air conditioner overnight (check out our comparison of these).

However, there are three main problems with these large battery banks. First it’s bloody expensive. But, if you want top-quality batteries with intelligent, built-in BMS systems, you’ll just have to bite that bullet. Secondly, it takes up a lot of space. Using fewer, higher density/higher capacity batteries, as we recommend in this post makes this much less problematic. Finally, with that much battery capacity – especially if you’re using a lot of it regularly – it becomes nearly impossible to adequately recharge with solar or DC-DC chargers. As your battery bank grows in size, so does your need for charging. We think adding a powerful secondary alternator is the best solution to this problem.

And here’s the thing about a camper van…. you’re going to drive it – that’s sort of the point, right? So, if you can power everything in your van from the engine while driving (or the fuel tank you already have), you are going to have an incredibly capable off-grid rig. Imagine this: fast and reliable battery charging from a secondary alternator, water heating from your engine coolant lines with a Isotemp water heater and perhaps a Webasoto gasoline or diesel heater sipping tiny bits of fuel from your van’s tank. In fact, in many ways, this system makes having solar panels superfluous which can free up roof space on your van for vent fans, air conditioners and rooftop decks!

But, What About Solar?

Solar panel charging is a great “bonus” charging source when conditions are “just right” but it’s not reliable like driving since conditions are often not optimal. Obviously, solar charging is only possible during the day and they have to be in the sun and, of course, you also have weather and seasons to contend with. We’ve seen some van builds that have their entire roof covered with solar panels so that they can generate enough power to run a residential-style “split” AC system which is a very complex installation by comparison to a rooftop unit and frankly, may not work correctly after bouncing down the road for thousands of miles. Think about this… they have to be parked in the hot sun during the day in order for this to work at all which is defeating to the goal because it will cause the the air conditioner run more which means that there is less energy available to charge the batteries which will be needed to run the air conditioner through the entire night.

In this example system we don’t have any solar panels but they could certainly be added in the same manner as we have them on our other example electrical system.

This system takes advantage of three innovative products, all working together and all sold in our store!

We offer most of these components sold in a discounted bundle. If you purchase them in the bundle you'll save about $700 off our already discounted prices!

This blog post has a companion Google Sheet material list that includes the primary components that included in our discounted bundle all the way down to the to wire lugs and heat shrink you can purchase from a little outfit called

1. The Nations 280 Amp Secondary Alternator Kit

Our kit from Nations Alternator includes the powerful alternator itself which outputs an average of 200 amps and can surge up to 280 at high RPMs! When you compare that to a pair of 30 amp DC-DC chargers that are commonly used in a more “traditional” camper van electrical system, it’s nearly 3.5 times more charging capability. In our testing we see anywhere between 120-150 amps of charging current at idle and around 200 amps or higher when driving (depending on engine RPMs).

To put this into practical terms, without considering any solar charging, recharging a 640 amp hour battery bank at 30 amps while driving would take nearly an entire day (21 hours). If you used two Orion DC-DC chargers (which is fairly common), you’d still need to drive for over 10 hours to recharge. With this system you can charge at an average of 200 amps which would take just over 3 hours of driving which is much more in line with real world vanlife. You might spend two or three days at a campsite, off grid, drawing down your battery and then drive to your next destination. With this system, just a few hours of driving will restore your battery bank.

The Nations alternator kit comes with everything you need for the installation including a vehicle-specific mounting bracket, hardware, belts, etc. The installation is not difficult for anyone who has some experience working on cars. It’s also possible to hire your local mechanic to install the secondary alternator – something any qualified mechanic can help you with easily.

One important feature of the Nations alternator that wasn’t immediately obvious to us but was explained by our friends at Wakespeed is that it uses something called “avalanche diodes”. Why is that important? Imagine your secondary alternator system is up and running, charging away as you drive and something goes wrong such as the fuse connecting the alternator output to your 12 volt DC bus blowing or someone accidentally disconnecting the battery(s) from the system using the disconnect switch. That situation is referred to as an “uncontrolled disconnect”. When that happens the Wakespeed regulator (more on that below) can detect this and respond quickly with the alternator to dissipate the remaining electricity that now has no place to flow to (often referred to as a “load dump“). However, there is a brief period of time where voltage spikes significantly. If the alternator didn’t use avalanche diodes, this voltage spike would be up to 130 volts (!) going into a 12 volt system, which is as bad as it sounds. However, with the avalanche diodes, the voltage is moderated to about 30 volts and, get this, apparently 12 volt systems are designed to handle voltage spikes up to 45 volts. Those diodes just saved your van!

Nations Alternator Charging Capabilities Table

2. Wakespeed WS500 Regulator

The Wakespeed regulator is the brains of the operation and interfaces with the alternator and batteries to charge the batteries with the correct voltage, current and temperature parameters. You can think of the regulator as the device that turns the alternator into an intelligent battery charger rather than just producing current. And, like all battery chargers, it must be configured/programmed to charge the specific batteries you’re using. The Wakespeed regulator is the most advanced regulator of its kind and is regarded by many in the marine/boat world as the very best and most reliable option.  It constantly monitors 5 parameters of charging and is highly configurable.

Want to learn more about the Wakespeed WS500? We have another post that is a technical deep dive on the Wakespeed including a 1.5 hour video with the founders! 

Another great feature of the Wakespeed WS500 is it’s ability to intelligently manage the charging current from the alternator so that it doesn’t exceed the maximum charging current of the battery. For example, if you only had one of the Lithionics batteries, the Wakespeed would be aware of this (via the CAN bus) and automatically limit the 200 amp output of the Nations alternator to the maximum recommended charge current for that battery which is 150 amps. Meanwhile any “remaining” current (50 amps in this case) can flow into your DC power system to power loads (air conditioners, refrigerators, inverter, etc.) while also maxing out the charging of the battery!

3. Lithionics Batteries

There are a number of reasons we are recommending Lithionics batteries for this system.

First off, they are quite likely the very best lithium battery you can buy on the market today. If you want to know why, check out this video from the Fit RV who compare Lithionics to a “B” battery.

Secondly, using Lithionics batteries makes this system much easier to install and configure. The engineers at Lithionics have worked with the engineers at Wakespeed to work out all the technical stuff needed to make this system work reliably with the fewest wires and programming headaches. In our research, we came across many posts like this where folks were using batteries such as Battleborn and running into all manner of trouble. It’s not that it doesn’t work in the end, it’s just that it can be considerably more complicated.

Thirdly, the Lithionics batteries have very high quality built-in battery management systems (BMS) and integrated Bluetooth capability. So, if you download the Lithionics mobile app you can monitor a wide range of battery information (state of charge, voltage, etc.) right from the app with incredible accuracy. In addition these smart batteries can communicate with the Wakespeed regulator through the CAN data bus. This enables the regulator to very precisely charge the batteries and send “warnings” to the alternator in situations where the BMS in the battery needs to cut off charging which prevents very nasty situations like “load dumps” from destroying not only your electrical system but all the components connected to it. Very few other lithium battery options have this data bus.

Going back to how the engineering teams at Lithionics and Wakespeed work together to make these systems work flawlessly, here is a specific example. As we were working with these companies to develop this example system, testing was wrapping up on the latest Wakespeed firmware (version 2.4.3) which added the ability for the Wakespeed regulator to “know” how many Lithionics batteries were connected and which particular models they are. With this information the regulator can even more precisely provide the exact charging profile for the batteries and maximize the output of the Nations alternator. These continual improvements are a huge benefit of an integrated system like this.

Finally, remember the space concern? Check out the image below that clearly illustrates how much space you save using two high capacity/high density batteries instead of 6+ smaller capacity batteries.

Another cool feature of the Lithionics batteries is that they have a built-in heating system so that you can charge and discharge them in extreme cold temperatures.

Important Installation/Use Notes

When installing these batteries into your electrical system, Lithionics recommends 4' (or longer) size 2/0 cabling from the battery terminals to your disconnect switch. Then you may use a minimum of 8' of 4/0 cabling for the rest of the pathway to a MultiPlus inverter/charger (from the battery switch, through the main fuse, to the Lynx Distributor (bus bar) and from the Lynx to the MultiPlus DC power in). Our example wiring diagrams call this out.

We then recommend using the manual disconnect switch as follows:

When going from "use mode" to "storage mode" first turn off the batteries from the system using your disconnect switch and then turn off the batteries themselves with the power switch on the batteries.

When going from "storage mode" to "use mode" you should first ensure that your battery disconnect switch is off, then you can turn on the batteries with the power switch on the batteries. Once you observe a solid LED light on the battery switch you can then turn on the battery disconnect switch.

This configuration and procedures will protect the battery from damage by the inverter.

If you are using Lithionics batteries with a Victron MultiPlus or MultiPlus II 12/3000/120, you should be aware these units draw the most current during "pre-charge", and require special consideration. You should ensure that you're using the latest firmware on the batteries (2.07 or higher). In addition, as of January 2022, Lithionics has updated their battery hardware to add an "internal pre-charge circuit".

If you're using two or more batteries in your system (as our examples show), it's important to differentiate the batteries on the CAN bus. By default, each battery will have the same "battery id" and "CANSA" which are 1 and 70 respectively. Think of these as their sort of address on that network. You can leave one battery as is, with the default settings but you need to change these addresses on the second (or third, etc.) batteries. This is very simple and this video shows how to do it.

If you want a deeper dive into why Lithionics batteries are awesome, you can check out this other post with it’s accompanying video and Lithionics Battery factory tour.

Secondary Alternator Example Electrical Diagram for Camper Van

Now that we’ve covered the primary components that are unique to this system and make it work so well, let’s dive into the wiring diagrams themselves. We have 3x configurations available (2x, 3x and 4x batteries) – each with slight differences – mostly in how the data bus for the batteries is wired up. In the 3x and 4x configurations we also use a second Victron Energy Lynx Distributor to connect the batteries in parallel to the system. The parts list sheet details these differences as well.

Below is a low resolution image of the 2x battery configuration. However, we highly recommend downloading the PDF versions using the buttons below.

If you’d like to see photos of these various components in “real life” you can check them out in this album – the captions describe what is shown in each photo.

Video Tour

Fancy Monitoring with Victron Cerbo GX and GX Touch 50

Since this is such an amazingly capable electrical system, we decided to go all-in and “upgrade” from the “standard” Victron Energy BMV-712 battery monitor to a Cerbo GX with a GX Touch 50 screen. Honestly, this is pretty cool!

The Cerbo GX is the device that all the signals connect to for monitoring and the GX Touch 50 is a small, full-color, touch screen that you would typically locate with the rest of your monitors/switches/control panel and it allows you to control, monitor and interact with all the various devices from it’s slick (and responsive) touch-screen interface. The Cerbo GX has a super wide range of compatible inputs. In this example, the MultiPlus inverter/charger is connected to the Cerbo GX using the VE.Bus, the SmartShunt is connected via VE.Direct and, if you had a Victron SmartSolar MPPT charge controller it could also connect to the Cerbo GX with a VE.Direct connection. In addition, we show a “room temperature sensor” so you can monitor the room temperature. However, the same temp sensor could be used in other ways such as monitoring the refrigerator temperature and you could even get two of these sensors (about $25 each) and do both. There are even ways of using the Cerbo GX to monitor your tanks such as your fresh water or grey water tanks but that’s getting beyond the scope of this post and will be the topic of a future one!

Often vans with a Victron MultiPlus inverter/charger will use the remote control panel in order to easily turn it on/off or into charging-only mode. The remote panel also includes a handy dial used to adjust the maximum input current the MultiPlus will pull from the shore power connection. This is a great feature that allows you to literally “dial in” your current draw based on the capacity of outlet you’re plugged into – typically either a 15amp or 30amp circuit. But, if you use this “fancy monitoring” approach with the Cerbo GX and GX Touch screen, it will override the setting on the MultiPlus essentially ignoring the dial on the remote panel. And, since you can also control the state of the MultiPlus from the touch screen, you don’t need the remote panel in this scenario.

Not Fancy Enough? Connect It To The Interwebs!
Want to get even fancier? Now that you have a “GX device” (The Cerbo GX), if your van has an internet connection (as most of us do), you can create an account on the Victron Remote Management (VRM) website and have your Cerbo GX send regular data updates from all the devices you’re monitoring on your GX Touch 50 screen to this online portal. This is a “free for life” monitoring solution that is really amazing for monitoring and troubleshooting and you can also set alarms for various things such as battery state of charge or other settings. For now the full set of data (advanced data) is kept for 6 months but the basic data is kept for at least 5 years. The advanced data is primarily for troubleshooting and if you want to keep your own archive, you can download your data into .csv or Excel files. VRM even allows you to control the components remotely and update firmware on them if that is enabled on the GX device.

Track Your Van with GPS
If you add a USB GPS receiver to your Cerbo GX you can also monitor it’s GPS location and use the “geo fencing” feature to notify you if your van moves somewhere you think it shouldn’t which is a really great security feature. This video shows how this works.

About Main Disconnect/Battery Switch

The 2x battery example system uses the Blue Sea 9001e battery selector switch that has connections for two batteries. So, in this dual battery setup, you can choose between using/charging one single battery at a time or both in parallel. This is shown in the image below. Typically you’d probably want to use the “1 + 2” position that connects both batteries together but having the option to isolate for troubleshooting, repairs or even limiting how much energy you’re using while having a “backup” battery are all useful.

The photo below illustrates the various switch positions.

It’s VERY important that this switch is NEVER turned off while the vehicle is running and the secondary, Nations alternator is outputting current! If you do, you’ll create the kind of “load dump” scenario we described earlier in this post. However, there are times that you want to put your van in storage or you need to work on the electrical system and use this battery disconnect switch. This is the reason we included a simple toggle switch that is wired inline with brown ignition wire. This effectively disables the secondary alternator charging. So, just remember to switch that toggle switch off before switching the main battery selector off. You might even consider putting a note or a label on the battery switch to remind you!

For the 3x and 4x battery configurations, a secondary Victron Lynx Distributor with it’s integrated fusing becomes a more elegant (in our view) option to connect each battery up to the system in parallel. The Lithionics batteries have an integrated power switch that can be turned off – much like an appliance. When you do, the Wakespeed regulator will adjust accordingly “knowing” that one (or more) of the batteries is no longer connected via the CAN bus.

Configuring the Wakespeed Regulator

Once physically installed and wired up, the Wakespeed WS500 regulator must be configured for your particular batteries. During this time you can also update your Wakespeed unit to the latest firmware.

If you’re not purchasing the Wakespeed Regulator from us that comes pre-configured, you’ll need to configure it for the particular batteries you’ll be using. It’s worth mentioning again that Wakespeed strongly recommends you use one of the battery systems that is listed on their technical page. On that page, in the “WS500 Configuration Files” section of the table, you’ll see links to both a PDF wiring diagram and .zip file with the configuration files for each battery system they have tested and support. The .zip files also include the configuration utility itself.

Once you have downloaded those files you’ll need a Windows computer connected to the USB port on the Wakespeed WS500 (you’ll need to remove the cover to access the port). From there you’ll simply double click the “update.bat” file inside the .zip file you downloaded and follow the prompts on the screen. There is further detail in Wakespeed’s Configuration Utility Guide (PDF) but it’s a pretty straightforward process. Most installers will only need to read through the first 7 pages in the guide. The remaining pages of the guide are for customizations and configurations for battery systems/situations where Wakespeed has not provided the battery-system-specific .zip file of configuration data.

You can also configure the Wakespeed WS500 with an Android device. Simply search for “wakespeed” in the app store and install. Android devices can connect to the USB port on the Wakespeed (front panel must be removed) using an OTG cable like this one. Once you have the app and are connected to the Wakespeed you can select your alternator and battery combination from the menu and the app will handle the rest!

Here’s a good video that also outlines the process.

Why This Is Awesome Example #1
Running a Mabru 12-volt Rooftop Air Conditioner Overnight

Let’s run a scenario where you run a Mabru 12,000 BTU air conditioner in your camper van overnight for 8 hours. Let’s assume it’s cycling on and off about half of the time such that the compressor is only operating for 4 hours during that 8 hour block of time. I’m choosing the Mabru unit in this example because of it’s extreme energy efficiency. If you take a look at our comparison spreadsheet, you’ll see that the Mabru uses about the same amount of power as the Dometic 2000 RTX while producing nearly twice the cooling capacity! The reason is that Alain Mabru has leveraged his decades of marine cooling experience to engineer an innovative “inverter” system for the compressor. This design provides substantial improvements in energy efficiency, quieter operation and longer longevity than traditional compressors.

Scenario #1, it’s freaking hot. So, you’re operating the unit on “high” with the medium fan speed. That’s going to draw about 51.2 amps. Running for those four hours (50% duty cycle overnight) would consume around 205 amp hours from your battery bank. This means that you have something like 115 remaining amp hours of capacity for other loads throughout your day and you could fully restore the energy consumed by the air conditioner by driving (or idling) for just one hour!

Scenario #2, it’s hot but not freaking hot. In this case you’re operating the unit in the “eco” mode drawing 25.2 amps for the same 4 hours (50% duty cycle overnight). In this scenario you would consume only around 100 amp hours from your battery bank which means that you have something like 215 remaining amp hours of capacity for other loads throughout your day and you could fully restore the energy consumed by the air conditioner by driving (or idling) for only a half hour!

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