12-Volt Secondary Alternator Example Power System – Nations, Wakespeed & Victron

This post details how to install a powerful, super off-grid capable camper van power system that uses a Nations secondary alternator paired with a Wakespeed WS500 regulator, Victron Energy Smart lithium batteries, and a bunch of other Victron Energy equipment! 

This is part of a series of posts and we highly encourage you to check out the others!

  1. This post is an introduction to a 12-volt secondary alternator electrical system and why you might want to consider one for your van, RV, or other mobile application as well as a FREE example wiring diagram (see below) using Victron batteries and other gear that corresponds to our discounted product bundle which makes it easy to get you everything you need at an awesome price!
  2. A video tour of this system installed into a Sprinter van that shows how it works.
  3. A technical deep dive video about the Wakespeed WS500 alternator regulator used in these systems.
  4. Another blog post about a 48-volt secondary alternator power system that also includes a FREE example wiring diagram and product bundle.

Since this post was first written in September of 2021 we’ve helped many customers install these systems and we have them in our own personal vans, which are truly incredible!

This is a super long post where we’ve attempted to take all the knowledge we’ve gathered about a secondary alternator system for a van or RV and organize it into one place!

Example Wiring Diagram

We worked extensively with Victron Energy and Wakespeed to design a system that will work reliably and safely! However, electrical systems are complicated and we recommend that you either have your system installed by a professional or, if you do it yourself, have it inspected by a professional when it’s completed. Please use the information provided at your own risk.

FREE Camper Van Power System Resources & Wiring Diagrams

If you're confused about your DIY camper van electrical or solar system, you've come to the right place. We have tons of resources including blog posts, videos and detailed example wiring diagrams (see below),If you're really stuck, we also offer consulting and design services. Our "choosing a system" page offers some additional advice and includes an example load calculation that you can use.

Below are some of our example power systems for camper vans/RVs. The Victron-based systems all have a corresponding blog post, free detailed PDF example wiring diagram, and a corresponding discounted product bundle. Ultimately, you'll probably customize your system to your particular needs and perhaps combine ideas from one or more of the example systems.

Please consider purchasing your power system equipment from our store. Our bundles offer great pricing (yeah, better than Amazon), free shipping and you'll have access to expert support and you'll be supporting our ability to create more content!

Finally, there are a few things that we don't sell in our store (yet!) that you might need so we keep a list of these products in this Google Sheet of recommended camper van products.

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 CAN bus-enabled BMS systems like our Victron Energy Smart Lithium battery example, 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 an 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 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 camper van electrical system wiring diagrams.

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 vehicle and engine RPMs).

To put this into practical terms, without considering any solar charging, recharging a 600 amp hour battery bank at 30 amps while driving would take nearly an entire day (20 hours). If you used two Orion DC-DC chargers (which is fairly common), you’d still need to drive for about 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 when 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 WS500 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! 

3. High Quality, CAN Bus Enabled Lithium Batteries

In a system this powerful, it’s essential that the batteries are up for the job! They must be reliable, robust and one of the brands/types that is officially supported by Wakespeed to work correctly and safely.

You can visit the “technical” tab on the Wakespeed product page to see which battery brands are qualified for safe and effective use. Each of the qualified battery types has a corresponding configuration file available. In order to be considered for qualification, the manufacturer must provide batteries to Wakespeed for testing and engage in “engineer-to-engineer” level conversations with the Wakespeed team. These measures are to ensure that installers can have the highest level of confidence in the functionality and safety of their systems.

We also highly recommend batteries that have CAN data connection to their BMS. CAN stands for “controller area network“. It is a highly reliable standard that uses messages to allow many “devices” inside a system to communicate with each other. CAN is used extensively in the automotive industry and has various implementations in the mobile world including RV-C for RVs and NMEA 2000 in the marine world. If you have lithium batteries that have a CAN connection that the Wakespeed can read (or a “language” that it can “translate”), the Wakespeed will use the data available digitally on the CAN bus such as voltage, current, and temperature to very accurately control charging. It can also monitor other messages from the batteries such as disconnect warnings to prevent situations like load dumps.

At Vanlife Outfitters, the CAN-enabled batteries we use in secondary alternator camper van electrical systems are Victron Energy Smart batteries (paired with a Lynx Smart BMS and Cerbo GX).

Links to example wiring diagrams can be found at the top of this post!

In addition to the compatibility, quality, and CAN bus, Victron batteries pack a lot of storage into a small space compared to most of the internal BMS batteries on the market which is, of course, a huge advantage in a camper van or RV!

Installing Nations Alternator

Installing the alternator onto your vehicle can be one of the most difficult parts of this system if you’re not mechanically inclined and pretty familiar with working cars. We offer mechanical and electrical installation of these systems (alternator only or alternator with the wiring/etc.) from our workshop in Sarasota, FL.

That said, if you’re up for the job, one of the things we love about the Nations alternator kits is how complete they are. The kits are unique to each vehicle and engine and come with everything you need to mount the additional alternator – from adapter brackets to belts. Typically you’ll receive two boxes from Nations: one with the alternator itself and the second with the other parts. The kits include very good/detailed instructions so we won’t dive too deep into the vehicle-specific installation process. In our experience, the Promaster kits are the most complicated and the Sprinter kits are the easiest and quickest. The Transit installation sits in the middle of this spectrum.

One thing that does trip folks up during the installation is that there is only one “marked” terminal for wiring the charging current output to your system. It’s labeled “B+” and is for the positive charging cable. The negative charging cable can connect to one of the large mounting bolt locations. Below is a photo of these wires connected to the Nations alternator on a Promaster van. We show 4/0 AWG wire used for these runs. If the length of this wire run is less than 15′ you can use the smaller, 2/0 AWG wire instead.

In our experience, the Nations 280 amp alternator will output anywhere between 120 and 150 amps at idle and considerably more – 200 to 250 amps when driving. The range you’ll see depends on your vehicle and the engine RPMs. Even the lowest output from the Nations alternator is very substantial compared to most other charging sources that are typically used in a camper van or RV such as solar or shore power. There are dozens of factors that determine how much power you’ll get from a solar panel array (time of day, time of year, how dirty or clean they are, temperature, etc.), but a simple rule of thumb for averaging this range is to predict 5 amps of charging current to a 12 volt battery for every 100 watts of solar. So, even on a perfect sunny day, a roof smashed full of solar panels doesn’t close to the alternator’s output. Shore power is typically one of the most powerful and reliable charging sources. In this example system, the Victron MultiPlus 12/3000/120 inverter/charger can charge up to 120 amps. With these comparisons, you can see that charging at 200 amps or more is really amazing!

Victron Smart Lithium Batteries

The Victron Smart lithium batteries used in this example system are available in various capacities. We recommend either the 200 amp hour or 330 amp hour versions. Whichever size you pick, you should stick with the same capacity in your battery bank, and, importantly,  you’ll need at least 2x batteries (ideally 3x or more) in the system.

All lithium batteries have a recommended maximum (continuous) charging current as well as a maximum (continuous) discharge current rating. Below is this information for the Victron Smart lithium batteries used in this example system. Looking at the 200 amp hour version of the battery (circled in red), you can see that the recommended charge current (highlighted in green) is 100 amps which is far less than the alternator is capable of charging. By adding two batteries, you aggregate this capability for a maximum recommended charge current of up to 200 amps. This is cutting it close since the alternator can charge beyond 200 amps – particularly if you have other charging happening at the same time – perhaps something like solar panels. While not ideal, it would work since the Wakespeed is aware of the charging current that’s being generated AND the capabilities/limitations of the batteries so it will respect the limitations and state of the battery. More on this is below in the Wakespeed configuration section of the post. If you use the 330 amp hour version of the Victron Smart lithium batteries, the recommended maximum charging current goes up to 150 amps per battery giving you plenty of extra headroom.

On the discharge (load) side of the equation, in most systems, the inverter/charger is the biggest draw since it can power energy-hungry things like microwaves, induction cooktops, 120VAC air conditioners, etc. In the example system, we’re using the popular Victron Energy MultiPlus 12/3000/120 inverter/charger. Taking another look at the specs for the 200 amp hour version of the Victron Smart lithium batteries, you can see the recommended discharge is 200 amps (highlighted in yellow). Meanwhile, the MultiPlus inverter/charger can run loads greater than 3000 watts for long periods of time which is 230-250 amps depending on the load and the battery voltage at the time. So, once again, having 2x or more batteries in parallel gives you the performance you need.

The Brains: A Lynx Smart BMS with the Cerbo GX

The Victron Smart lithium batteries require an external Battery Management System (BMS). Externalizing the BMS has quite a few advantages that we detail in this other blog post. One major advantage of this particular system is that it enables the Wakespeed regulator to communicate with the BMS (and therefore the batteries) digitally via a CAN bus which makes the system more robust and reliable. It also opens up the possibility for some pretty cool monitoring. More on that later!

The external BMS also means that the batteries themselves pack more power into a smaller space compared to batteries with an internal BMS as illustrated in the image below.

The BMS we’re using in this system is the Victron Energy Lynx Smart BMS. By the way, any Victron Energy component that has the word “Smart” in its name means that it can be configured, monitored, and controlled via Bluetooth with their free VictronConnect app. In addition, this system uses a Victron Energy Cerbo GX.

You can think of the Cerbo GX as a tiny computer with an operating system that is specifically designed for mobile power systems like your van or RV (VenusOS). You connect up all your electrical system components to the Cerbo GX using its wide range of “inputs” and the Cerbo GX allows you to monitor and control them through a simple touchscreen interface. Typically this is facilitated through either the 5″ Touch 50 display or the 7″ Touch 70 display but you can also be done via Bluetooth or even remotely through the Victron Remote Monitoring service called VRM. You can also connect things like water tank sensors, temperature sensors, and more.

If you take a close look at our example wiring diagram, you’ll see that the 3x batteries have a short cable coming out of them with circular (M8) connectors. You connect each battery together (daisy chained) with these cables and then that chain of batteries is connected to the Lynx Smart BMS with a longer set of these same M8 cables.

Then, the Lynx Smart BMS is connected to the Cerbo GX using VE.Can. CAN stands for “controller area network“. It is a highly reliable standard that uses messages to allow many “devices” inside a system to communicate with each other. CAN is used extensively in the automotive industry and has various implementations in the mobile world including RV-C for RVs and NMEA 2000 in the marine world. Victron’s version is called VE.Can and uses RJ45 (ethernet style) connectors.

With all this wired up, the batteries can communicate with the Lynx Smart BMS which can, in turn, communicate with the rest of the power system through the Cerbo GX.

OK, back to the BMS. Its job is to listen to the batteries to make sure that they are never damaged. Specifically that they don’t get overcharged (over voltage), too discharged (under voltage), too hot, or too cold.

The Lynx Smart BMS is part of the Lynx system from Victron. Many people use the Lynx Distributor in their power systems because it’s a very clever combination of two high-capacity bus bars (DC positive and DC negative) with circuit protection with (Mega fuses) on each of the DC positive terminals that are packaged up in a compact case with a cover. The Lynx Smart BMS bolts right onto one or more Lynx devices.

In our example system, we use 1x  Lynx Power In and 1x Lynx Distributor as illustrated below. The Lynx Power In is on the left side and is used to connect each of the batteries to put them in parallel. The wires from the batteries to this Lynx Power In should be the same lengths and the positive cable run is protected by a 250 amp terminal/MRBF fuse. Note that you can use a Lynx Distributor for this left-side/battery connection point but the fusing inside the Lynx Distributor would be slightly redundant. In the middle is our Lynx Smart BMS. Inside the Lynx BMS are two important things. One is a current shunt on the DC negative side. This allows the BMS to also serve as a “battery monitor” which is similar in function to the popular BMV-712. The second is an integrated, 500 amp “contactor” which is the equivalent of those large, typically red, main disconnect switches you see in so many power systems. Finally on the right side is the Lynx Distributor that is wired up to all the loads and charging sources.


Now that you can visualize how all these components fit together, let’s discuss how they work together. Think of the batteries as the boss. They are one of the most expensive parts of your power system, so it’s important to protect them from distress (over voltage, under voltage, too hot, too cold). The Cerbo GX is the brain. It’s connected to the BMS and most everything else in the system (inverter/charger, solar charge controller, etc.). And, of course, the BMS is the manager (remember, it stands for Battery Management System). The BMS is always listening to the batteries and is responsible for responding if they are distressed. Meanwhile, the Cerbo GX can communicate errors or issues to you and other system components which should respond to the boss.

Disconnecting Loads & Chargers to Protect the Batteries

Let’s consider how the Lynx Smart BMS can manage some key functions:

  1. Disconnect loads from discharging when necessary which is typically when they are overly discharged (low voltage) or too hot or too cold.
  2. Stop any charging when necessary – typically when the batteries are overcharged (high voltage) or too hot or too cold.

Discharge Control
In this system, there are what we refer to as “smart” loads that are connected directly to the Cerbo GX which can relay messages from the BMS on behalf of the batteries and control those connected loads digitally. For example, the Victron MultiPlus inverter/charger can stop powering loads when told to by the system. Very smart.

Then there are the “dumb loads”. We refer to them as “dumb” because they can’t communicate directly with the Cerbo GX the way the “smart” loads can. In this example system, that would be everything that is wired up to the AD/DC load center on the DC side – things like lights, refrigerator, vent fans, and 12 volt outlets. Another example might be a 12 volt air conditioner that is wired up to a terminal on the “loads and chargers” Lynx Distributor (right side). But, take a look at the illustration of the Lynx system above. These “dumb” loads are electrically “downstream” from the main disconnect switch (contactor) that is built into the Lynx Smart BMS.

This opens up two ways to handle load disconnects of “dumb” loads. The simplest approach is to let the BMS turn off (open) its integrated contactor/switch which will electrically disconnect (turn off) everything connected on that right side Lynx Distributor (including charging sources). This is what we show in our example diagram. Obviously, you don’t want this to happen while you’re out there camping in your van so you’ll want to pay attention to any warnings on your touch screen and monitor your battery state of charge.

The other way is to make use of the ATD (allow to discharge) relay available on the Lynx Smart BMS to create a sort of “staggered” shutdown where specific, chosen loads, such as your 12 volt load center are disconnected before the entire system shuts down. This might be particularly important in a marine environment where you would want to shut down something like your refrigerator before everything on the boat, including your navigation equipment!

The Lynx Smart BMS has a bunch of terminals on the bottom that Victron calls the “multi connector” (see photo below). Our example wiring diagram illustrates how we will connect to many of these. If you wanted to have the type of staggered shutdown we describe above, this is where you could also wire up a Smart BatteryProtect device to the so-called ATD (allow to discharge) relay that can be configured to disconnect the loads that is supplies power to (such as a 12 volt load center/fuse box or a 12 volt air conditioner, etc.) BEFORE the entire system shuts down as a result of the main contactor/switch in the Lynx Smart BMS opening/shutting off. You can see an example of using a Smart BatteryProtect in this other wiring diagram.


Charging Control
OK, now let’s turn our attention to disabling charging side of the equation in situations when the batteries tell the BMS they don’t want to be charged. Here again, the so-called “smart” chargers that are communicating directly with the Cerbo GX/BMS  can receive and respond to the triggers digitally. So, just like the discharge example above,  the MultiPlus inverter/charger can be controlled in this way to stop charging. The same is true for a Victron Smart MPPT solar charge controller that has a VE.Direct connection to the Cerbo GX – which is the majority of them.

The last charging source in our example system is the dedicated, secondary alternator that is being regulated by the Wakespeed WS500. Similar to the ATC (allow to discharge) relay on the Lynx Smart BMS  that’s described above, the Lynx Smart BMS also has an ATC relay (allow to charge) relay. In this system, we will be wiring up the “feature in” (white wire) from the Wakespeed “van harness” such that it receives this ATC (charge disconnect) signal to stop charging when the batteries trigger this state. This is illustrated in the example wiring diagram and detailed more in the Wakespeed wiring harness and configuration section of this post.

Wakespeed WS500 Regulator

Now that the batteries and BMS are all sorted out, let’s talk about the Wakespeed WS500 regulator and how it’s used in our example system. We’ll keep this fairly basic, but if you want to take a much deeper dive, you can check out our video with the Wakespeed creators.

The Wakespeed regulator turns a fairly basic, but very powerful Nations alternator, into an intelligent, reliable, and smart charging source for your batteries. As we mentioned before, you’ve spent a ton of money on the batteries, so it’s essential that the charging equipment is compatible and will respect the charging profile of the batteries and that’s exactly what the Wakespeed does! Later in this post, we’ll discuss how to configure the Wakespeed to charge the Victron Smart lithium batteries used in this system.

CAN Wiring and Wakespeed “Van Harness”

The Wakespeed regulator should be located near the rest of your primary electrical system components such as the batteries, inverter/charger, etc. In a camper van, this is quite often near a rear wheel well in the back of the van.

In our example system, we’re using the “white box” version of the Wakespeed regulator that incorporates two RJ45 CAN connections on the bottom of the unit which are the same “ethernet style” jack that you’ll find on the VE.Can port of Victron Cerbo GX. Note: in early 2024, the formerly “white box” version of the Wakespeed regulator starting shipping with a black, plastic case. However, the Victron equipment uses a different wiring configuration than the Wakespeed so you’ll need a special Victron to Wakespeed crossover cable that has a blue connection on one end which plugs into a VE.Can port on the Cerbo GX and a black connection on the other end which plugs into one of the Wakespeed’s CAN ports. This crossover cable comes with a black resisting terminator that should plug into the other CAN port on the Wakespeed and your Cerbo GX will come with a few blue resisting terminators that you’ll put into all the empty VE.Can ports on your Victron equipment (typically one on the Lynx Smart BMS and one on the Cerbo GX).

In the example system, we illustrate how to wire up the “van harness” for the Wakespeed regulator. It has a large, main connector that plugs into the big multi-pin connector on the bottom of the Wakespeed. From there the harness has three legs which are detailed in the example wiring diagram and outlined below. If you want to see photos of the real thing on our messy work table, you can check this photo album.

Alternator Leg
This leg is the longest (about 27′) and is designed to run from the back of your van where the Wakespeed is probably installed, all the way up to the engine area where the Nations alternator will bolted onto the engine. There are two connectors on this leg: one is a black connector with green heat shrink that plugs into the temperature sensor connector coming off the Nations alternator. The other is a grey connector with a blue and a yellow wire. This connector (circled in red in the photo below) should be cut off. Then, the yellow wire that was part of that connector is not used (can be tapped off) and the blue wire that was part of that connector should be butt spliced onto the green wire coming off the Nations alternator.

Power System Leg
This leg is the shortest since the connections on this leg are typically installed near the Wakespeed which is typically located with the rest of your primary power system components. It has a connector with blue heat shrink that can be connected to an optional battery temperature sensor which we don’t use in our example system. Then there are four unterminated/bare wires:

  • The red wire should be connected to the same terminal on the DC positive bus bar of the Lynx Distributor that the Nations alternator’s DC positive charging output is connected to with an inline, 5 amp fuse.
  • The black wire should be wired up to the DC negative bus bar of the Lynx Distributor.
  • The white wire is called the “feature in” wire and it’s the one we use to send the ATC (allow to charge) signal that was discussed above into the Wakespeed to disable charging if the batteries trigger the BMS to do so. Specifically, it’s wired into terminal #9 on the multi connector of the Lynx BMS and there is a short “jumper” wire between ATC terminal #4 to the relay “common” terminal #8. This is confusing! Please see the example wiring diagram for an illustration and zoom into the detail of this multi connector’s wiring.
  • If you’re using a current shunt (recommended), the purple wire is connected to the small terminal on “alternator” side of the shunt and the grey wire should be connected to the small terminal on the “battery” side of the shunt for current monitoring.

Ignition Leg
Finally, there is a long, brown wire that is designed to be connected to an ignition-controlled circuit. This brown wire turns the Wakespeed on/off (and thus the alternator charging system). If the brown wire “sees” 8.5 volts or higher, it will turn on and enable charging. Typically you would wire this brown wire up to a circuit in your van or RV that is only on (providing voltage) when the ignition switch is enabled or the engine is running. We further recommend that you wire in a toggle switch on the brown wire circuit so that you can turn the Wakespeed/alternator charging off when desired – even when the vehicle/ignition is on.

Why This Is Awesome Example #1
Running a Mabru 12-volt Rooftop Air Conditioner Overnight with 600 Amp Hours of Battery Capacity

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 its 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 medium fan speed. That’s going to draw about 55 amps. Running for those four hours (50% duty cycle overnight) would consume around 220 amp hours from your battery bank. This means that, with no other loads,you have something like 380 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 over one hour!

Scenario #2, it’s hot but not freaking hot. In this case, you’re operating the unit in the “eco” mode drawing around 25 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 500 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 around a half hour!


With everything wired up, let’s dive into configuring the system! Given the nature of this post, we’re only going to focus on the configuration steps for enabling the secondary alternator and Wakespeed regulator. One awesome feature of this system provided with the Lynx Smart BMS is that the charge profile for the other Victron Energy chargers in our example system (MultiPlus inverter/charger and solar charge controller) is managed intelligently by the Cerbo GX using DVCC. This is possible because all of these devices are “talking” to each other digitally through the Cerbo GX. If you want to learn more about this DVCC magic you can read this section of the Cerbo GX manualBut, If your system has other chargers/devices that don’t have a data connection on them (no VE.Bus, VE.Direct, VE.Can, etc.), such as an Orion DC-DC charger, and therefore cannot be managed by DVCC, you’ll have to configure that device the “old fashioned” way with VictronConnect which is beyond the scope of this post.

We also won’t discuss all the setup possibilities of the Cerbo GX – you can check out this other post about that. Instead, we’ll only focus on what’s necessary to make it work with the Wakespeed regulator. However, we’ll be dedicating another post to the Cerbo GX including connecting it to VRM so “stay tuned” for that, or consider signing up for our email newsletter which is available at the bottom of all of our pages.

Victron Lynx Smart BMS Configuration with Victron Connect
Remember that any Victron product with the word Smart in the name means that you can configure, monitor, and control it via Bluetooth using the VictronConnect app. So, if you haven’t done so already, you’ll want to install VictronConnect. Links to download the app are available for iOS, Android, Windows, or MacOS on the VictronConnect page. Most folks find the app simple to use but you can read through the manual if you need it. To use it, you’ll need Bluetooth enabled on your mobile device or computer so that it can communicate with the various Victron products. Once you open the app, you’ll see a list of all the Victron products that are within Bluetooth range -all with their factory default names. You can easily rename each device to make it unique to your install if you’d like.

To configure (or monitor/control) a device simply click on its name from the list in VictronConnect. The first time you connect you’ll be asked to pair with that device. The default pairing PIN is 000000. We recommend you change the PIN on all your devices so that other users of VictronConnect don’t mess with your system! Keep in mind that if you find yourself in a place with other camper vans/RVs that have Victron components you might see a bunch of other devices listed in VictronConnect – basically anything that’s within Bluetooth range.

By the way, if you don’t have any of this equipment yet but are curious how it all works, you can actually use VictronConnect with “virtual” (demo) devices. In other words, you can go through the settings and screens available in VictronConnect for any Victron Smart product by using the demo library available in VictronConnect. This is a great feature to use when planning a system.

Let’s start with the Lynx Smart BMS. Connect to this device in VictronConnect. The first screen you’ll see is the “status” tab that displays the same kind of information as other battery monitors from Victron including the calculated state of charge (SOC) as a percentage and if you scroll down, a bunch of other information about the battery including voltage, current, etc. Below is a screenshot of this screen. Take note of the area circled in red: “allow to charge” and “allow to discharge”. Earlier we discussed these modes that get triggered by the batteries when they are in distress. This is where you can see if these states are triggered.

There are several other screens that we won’t detail here but you can read more about them in the manual.

Next, click on the “gear icon” in the very top right of the screen to enter the settings. You can use the following screenshot as a guide to these settings however, be sure to set the “Battery bank capacity” and “Number of batteries in parallel” to reflect what is in your particular system. These settings are outlined in red below. In the screenshot, they are set to 600Ah and 2x batteries to match the example system. The rest of the settings we show are fairly universal and typically a good starting point for your system.

Also note the “Relay mode” setting that we’ve outlined in green in the screenshot above. This is how the “white wire” (feature in wire) that we wired from from the Wakespeed harness into terminal #9 on the multi connector of the Lynx SmartBMS is interpreted by the BMS. It enables the ATC (allow to charge) relay to disable charging from the Wakespeed/Nations if the battery triggers that state.

Note: if you’ve ever configured another Victron Energy battery monitor such as the BMV-712 or SmartShunt you may notice that the settings presented here are different and, in some ways, more simple than you’d see on the other products. That’s because, in this example system, you can literally only use one single type of battery – a Victron Smart lithium battery. The batteries may be different capacities (200 vs. 300Ah, etc.) but they are the same baseline so many of the settings about the battery that you have to change/set in other systems are already known/assumed in this case.

Wakespeed WS500 Configuration
If you buy your Wakespeed regulator from us as part of a discounted secondary alternator product bundle, it will ship pre-configured based on the information we collect when you add the stuff to your cart.

However, configuring a Wakespeed WS500 regulator is pretty simple when using the Wakespeed Android app. Note, at the time we’re writing this post, there is a version of the Wakespeed app available for Apple, iOS devices but it can’t connect to the Wakespeed via USB so it can only create and manage configurations – not communicate or send them to the Wakespeed.

In addition to the Android app and device, you’ll a USB “on the go” (OTG) cable with one end matching the USB connection on your phone (most Android phones now use USB-C) and the other end having a standard, USB-A female plug such as this one. You’ll also need a short USB-A to USB-B cable. The USB-A end of this cable will pair up with the OTG cable and the other will plug into the USB port on the Wakespeed regulator that is accessed when you remove the lid. Once you have this all connected you can take a look at the following video that does a great job at introducing how to use the Wakespeed app for configuration.

Now that you know the basics of how to use Wakespeed app, below is a video of us configuring the Wakespeed regulator for this example system. Note that we’re showing 2x batteries instead of three. This is another place where your particular settings need to be adjusted to match your system’s battery count and storage capacity. In the video, we show the settings you would enable or disable depending on if you have an analog current shunt. More on that is below.

Optional Analog Shunt for Monitoring Nations/Wakespeed Current On Cerbo GX
In our example wiring diagram we show an optional Victron Energy analog shunt wired into the Nations alternator’s DC positive charging output wire. We recommend you include this in your system but it is not required. You’ll probably want to locate this shunt close to the rest of your power system components – near the “loads and chargers” Lynx Distributor. The purpose of this shunt is to measure the current flowing from the Nations alternator distinct from the “main” current shunt in this system which is one integrated into the negative bus of the Lynx Smart BMS. In other words, if you add this shunt, you’ll be able to see the current (in amps) and power (in watts) being generated by the Nations alternator when you view the Wakespeed in your system on the Cerbo GX as illustrated below. The left side screenshot is before a shunt was installed in our demo system (outlined in red) and the right side is after (outlined in green). This is pretty cool and allows you to see how much current is coming from the alternator alone without the other charging sources or loads being considered – much like you would be able to see on a solar charge controller. For instance, if your Nations alternator is charging at 150 amps and your solar array is charging at 20 amps and, at the same time, your 12 volt rooftop AC is running and using 55 amps, if you were to look at your primary battery monitor (the Lynx Smart BMS) you’d see an aggregate current readout of something like 155 amps (170 being supplied and 55 being used). Meanwhile, you could take a look at the solar charge controller specifically and see that it was charging at 20 amps alone and look at your Nations/Wakespeed and see it’s charging at 150 amps alone.

Note that the Wakespeed can be “powered” in two ways. Normally it would be powered by your van’s power system via the “brown wire” discussed above (ignition trigger wire, on/off wire). Alternatively, when configuring the Wakespeed via USB, the USB cable will supply enough power to turn the unit on. This is very handy for configuring a Wakespeed regulator prior to installation into a system.

About “Reading” the Configuration of a Wakespeed Regulator

One thing you may notice if you experiment with the Wakespeed Android app enough is that if you edit the settings in the configuration screens and send that configuration to the Wakespeed using the “configure device” and then use the “copy” feature that reads the config file from that device back into the configuration screens of the app, most of the settings you’ll see in the configuration window will NOT match what you think you had set up. The same thing can happen if you connect up to any pre-configured Wakespeed regulator using the Android app expecting to see the configuration options “match” the options in the user interface.

Why is this? When you’re configuring a Wakespeed using the app interface, what is happening “behind the scenes” is that your selections are getting “translated” into a “lower level” configuration file that looks something like the screenshot. In other words, the app is allowing you to create a config file in a user-friendly way but, at a deeper level, many of the choices you’re making are getting converted into the values and formatting the Wakespeed actually needs to be programmed. When you “copy” a current configuration of a Wakespeed, you’re retrieving this ‘lower level” file that, when opened in the app, doesn’t line up with the selections available in the user interface. Thus, when you do a “copy” you’re actually creating a brand new configuration file.


If you’re experiencing problems with your system be sure that the firmware is up to date on all the devices.

On the Wakespeed you do this from the Wakespeed app. Tap on the “home icon” at the top left and then select “device” and finally “firmware update”.  You need version 2.5.0 or higher for the system to work correctly with the Cerbo GX.

On the Cerbo GX you’ll need to have version 2.90 or higher of the Venus OS. You can check this by opening the menu, navigating to “settings” then “firmware” then “online updates” and then press on the “check and update” button.

On the Lynx Smart BMS you’ll open that device up in VictronConnect then press on the “three dot menu” in the top right part of the interface and choose “product info”. Find the “firmware” link and press update.

Flashing Orange Light

When the Wakespeed is up and running and configured correctly in this system you should see its LED light flashing a “reddish orange” color. This has alarmed some of our customers who think that the flashing LED indicated some kind of problem but, in fact, it means that the Wakespeed is being controlled by an external BMS which is exactly what you want in this example system.

Common Errors/Conditions with the Wakespeed WS500 Regulator

Error 51
If you’ve wired your Victron Lynx Smart BMS remote terminals to a toggle switch in order to be able to use the built-in “contactor” to turn the system on/off as you might with a typical main battery switch (those big red switches) you will get an error 51 thrown by the Wakespeed regulator when you use the toggle switch to turn off the system. The reason is actually good news. When you trigger the remote off function, the Lynx Smart BMS is able to send a message over the CAN bus to the Wakespeed regulator that puts it into this fault code and disables charging before it actually turns off the system (opens its internal contactor). This allows the Wakespeed to stop the Nations alternator from charging before the batteries are disconnected preventing a “load dump” which can be harmful to the alternator and your system. Think of it as a helpful “head up” prior to the disconnect. If you see an error 51 in this context, this would be the most likely reason. The only way we’ve found to reset this error is to make sure the Wakespeed is switched off (ignition/brown wire) and then the RJ45 CAN connection out of the Wakespeed regulator for a few seconds and then plug it back in.

Error 91
This error indicates that the Wakespeed has lost its connection with the Lynx Smart BMS and it will go into a “get home mode”. As soon as the communication is restored it will revert to the charging goals set by the BMS.

Error 92
The ATC (allow to charge) state has been triggered by the batteries and the Lynx Smart BMS has communicated this to the Wakespeed and, as a result, the Wakespeed has been turned off to disable charging.

Error 44
The WS500 is capable of providing a broad range of error and advisory codes, which are displayed by the LED that’s exposed via the jewel on the lid of the regulator. Error codes are preceded by two red “bursts” of flashes, followed by a two-digit display of flashes. In the case of an error code 44 (indicated by four flashes, a space, and four more flashes), the regulator has monitored an excessive voltage difference of greater than 2.5VDC between the regulator’s positive voltage sense (red w/yellow tracer) wire and positive power (solid red) wires. This may indicate an excessive voltage drop between the two wires, or the existence of a damaged fuse in one or the other wire. A full list of error/advisory codes is available in the WS500 Communications and Programming Guide, available on our website.

Powering Up and Testing

  • Power up the DC system by turning “on” the switch wired into the Lynx Smart BMS “remote” terminals thereby closing the contactor inside the BMS.
  • Confirm that the small loads like the Cerbo GX are powering up.
  • Turn on the MultiPlus inverter/charger with the power switch on the unit itself.
  • When the Cerbo GX running, try controlling the MultiPlus from the Touch 50/Touch 70 screen (switching modes from off/charger only/on, etc.). If you have issues with this, make sure the VE.Bus connection between the MultiPlus and the Cerbo GX is correct (RJ45 UTP network cable) and you’re using a manufactured (not hand-crimped) cable.
  • Confirm that you are getting 120 volt AC to your load center (from the AC output 1 terminals on the MultiPlus).
  • Confirm that you are getting 12 volt DC to your load center.
  • Configure the various Victron Smart devices using VictronConnect via Bluetooth.
  • Configure your Cerbo GX and connect to the free Victron Energy VRM cloud service.
  • Test the secondary alternator by starting the vehicle and then turning on any switch that may be wired into the “brown, ignition trigger wire” of the Wakespeed WS500 harness. Once the vehicle is running and the Wakespeed is powered up, you should see the LED light on the Wakespeed flash an orange/amber color indicating that it’s being controlled by a BMS. In this case, that’s the Victron Lynx Smart BMS.
  • Confirm that you’re getting a charge current from the alternator by looking at the battery monitor (shunt inside the Lynx Smart BMS) information on the Touch 50/Touch 70 connected to your Cerbo GX. Note, if the batteries are close to full this will be a small amount of current necessary for an absorption charge. You can discharge the batteries using a heavy load such as a heat gun or similar high-wattage appliance in order to see the alternator’s output during a bulk charge.
  • Test your shore power input to make sure that the MultiPlus syncs to the incoming 120 volt AC power and that the internal transfer switch transfers the loads to the shore/utility power. You’ll hear an audible click.

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