Electrical System: Build Guide for DIY Camper Van Conversion

Electrical System

Electrical System: Build Guide for DIY Camper Van Conversion

Our autonomy and comfort depend a lot on the electrical system of our DIY camper van conversion. No power means no fridge, no lights, no smartphone = no Instagram & no #vanlife as we know it! Therefore, we want our electrical system to be reliable and to work from the first time; trial-and-error is not acceptable here!

After more than a year on the road, we’re happy to report that our system works as we planned. Nice! Designing the electrical system was one of the most intimidating task of the conversion process and if you’re reading this it might be your case too…


We’re here to help. Here is how it goes:

    • PART A is where YOU grab a drink, relax and read on.
    • PART B is where WE relax and YOU do the work!





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1- What Do We Expect From Our Electrical System?

  • Power all of our “fixed” loads (fan, lights, fridge, water pump, etc) and power our “external” loads as well (phones, laptop, cameras, etc)
  • Charge from solar, van alternator and from shore power
  • Have an inverter for occasional and modest use of 120V
  • Be completely autonomous in full-sun condition and have a few days autonomy in absence of solar power and driving (no charge source)


2- Power Consumption

Our power consumption will dictate the “size” of our components (solar panel, battery, inverter, etc). Let’s make a list of our loads and calculate how much Ah (ampere hour) we will draw in total each day.


Summer Analysis
Predicted Daily Power Consumption
 LoadDescriptionMeasured Instantaneous Consumption


Calculation Assumptions Calculation Daily Consumption (Ah)
 FridgeNovakool R58104.0A24h per day @ 35% duty cycle 4.0A * 35%*24h= 34Ah
 Lights 3W LED1.3A (total 10 lights @ 100% intensity)4h per day @ 80% intensity 1.3A*80%*4h= 4Ah
 Fan Maxxfan 6200K

(10 speed settings)

0.2A@1, 0.4A@2, 0.5A@3, 0.8A@4, 1.1A@5, 1.5A@6, 2.0A@7, 2.6A@8, 3.3A@9, 4.4A@1024h per day @ 3 average 0.5A*24h= 12Ah
 Water Pump Guesstimate… 1Ah
 Sound System Guesstimate… 1Ah
 Phones Guesstimate… 1Ah
 Laptop Guesstimate… 2Ah


Reality Check:

Measured-Daily-Power-Consumption-VanLife-(Summer Time)
*Because it’s summer and there’s way more solar than we need, we can safely assume our daily yield (measured by the Victron MPPT Charger) is equal to our daily consumption.

Our summer prediction was 55Ah and we are actually consuming 59Ah on average. Pretty close! The temperatures were quite hot during the period we measured our consumption; the fridge and all the fans are working hard! It will be interesting to make more measurements in Autumn when temperatures are milder…


Winter Analysis

We predict that our daily consumption is similar for summer & winter because in winter the fridge draws less power, but it is balanced by the Webasto air heater that needs some electrical power.

LoadDescriptionMeasured Instantaneous Consumption (A)Calculation Assumptions Calculation Daily Consumption (Ah)
 FridgeNovakool R58104.0A24h per day @ 20% duty cycle 4.0A * 20%*24h= 20Ah
 Lights3W LED1.3A (total 10 lights @ 100% intensity)8h per day @ 70% intensity 1.3A*70%*8h= 7Ah
 FanMaxxfan 6200K

(10 speed settings)

0.2A@1, 0.4A@2, 0.5A@3, 0.8A@4, 1.1A@5, 1.5A@6, 2.0A@7, 2.6A@8, 3.3A@9, 4.4A@1012h per day @ 2 average 0.4A*12h= 4Ah
 Air HeaterWebasto Air Top 2000 STC Guesstimate… 20Ah
 Sound System Guesstimate… 1Ah
 Phones Guesstimate… 1Ah
 Laptop Guesstimate… 2Ah

Reality Check:

Note: As opposed to summer, we don’t have a solar SURPLUS during winter; so we can’t say that solar input = our consumption. The graph below represent therefore our solar input (not our consumption). We combined the data from summer to as a comparison purpose.

Daily Solar Input, Summer VS Winter, Van Solar Power
Solar Input (summer VS winter). NOTES: 1- Winter data gathered between January 14th to February 14th. 2- Once the battery if fully charged, there is no more solar input recorded. It means we could harvest more solar power than the graph shows during summer. 3- Winter data was gathered during an unusual stretch of “nice” weather here in the Pacific North West; it’s normally even worst…


Conclusion from this data:

The graph clearly shows that we have a SOLAR power deficiency in winter. We’re glad we installed a Sterling B2B to charge from the alternator! The Sterling is our Plan B in summer, Plan A in winter. We think the combination of solar + alternator makes a nice and balanced electrical system for people using their van for summer & winter adventures (i.e. ski. solar is probably enough for Baja or Cali winter adventures!). What about adding more solar panels instead? We think it’s not the solution for weather like PNW winter… sometimes there’s just NO sun for days. It’s nice not relying on a single source of power.


3- Battery Bank

We just determined that we will draw about 55Ah daily. Does it mean that, to have 4 days autonomy, we need a 55Ah*4days = 220Ah battery bank? No! There are more variables to take account of… keep reading the whole page and we will size the battery bank afterward…


3.1- Temperature de-rate of the battery bank

If you know someone that owns an electric car, you probably know that his/her car will do about half the mileage in winter than in summer (it might not be that bad in California, but it is in Quebec… yep, it’s cold up here!). Batteries are much less efficient in cold weather. The exact loss will, of course, depend on the battery temperature, but we will assume 30% less efficient as a general rule. For example, a 210Ah battery bank will actually deliver 210Ah*70% = 147Ah. Or, we could say that our daily consumption of 55Ah is in fact 55Ah*1.3 = 72Ah. We have to keep that in mind.


3.2- Charging a frozen battery

First of all, unlike water, a battery will not freeze at 32F (0°C). The freezing temperature of the battery depends on the depth of discharge. As the state of charge in a battery decreases, the electrolyte becomes more like water and the freezing temperature increases.  It is very important to make sure your battery stays fully charged in extreme cold weather. If a battery freezes, it can damage the plates and container leading to a potential explosion. A frozen battery must NOT be charged! Consult your battery manual.

As a guideline, this is extracted from our Rolls Battery Manual:

Specific Gravity


Depth of Discharge 

approx (%)

Freezing Temperature

C (F)

1.280100-69C (-92F)
1.26592-57.4C (-72.3F)
1.25085-52.2C (-62F)
1.20060-26.7C (-16F)
1.15040-15C (5F)
1.10020-7C (19F)




3.3- Depth of Discharge

The cycle life of a battery is directly affected by the depth of discharge. What is the depth of discharge? It is how deeply the battery was discharge during one cycle. Let’s say that a fully charge battery is 100% and a fully discharged battery is 0%. If we draw 30% of available capacity (from a fully charged battery), the depth of discharge is 70% (there is 70% of Ah remaining before the battery is 0%).

For AGM batteries, it is recommended not to go below 50% depth of discharge to maximize the battery life (it might be different for different type of batteries).

Cycle life vs Depth of discharge
Cycle life vs Depth of discharge


So, if one’s consumption is 55Ah daily and has a 100Ah battery bank, it means that at the end of the day the depth of discharge is 45Ah/100Ah = 45%? Well, not exactly… because the battery bank will get charged throughout the day by solar or by driving the van or by getting power from shore power. In fact, we observe our minimal depth of discharge in the morning just before the sunrise. Indeed, we dont have any charge source during the night. What we experienced so far is a depth of discharge of about 75-95% in the morning cause by the loads that run overnight (fan, fridge, air heater and some lights).


3.4- About battery types

There are many types of battery available. Let’s play PROS and CONS :


Flooded lead-acid


  • Cheapest battery type available


  • High maintenance (needs to be filled periodically with water and kept in a vented compartment)




  • Similar to Flooded lead-acid but the gel wont spill as easily


  • Similar to Flooded lead-acid
  • Must be charged at low rate




  • Low maintenance, good low-temperature performance
  • No need to be vented


    • More expensive than Flooded or Gel
    • Heavier than Lithium


Lithium-ion (LiFePO4)


  • Light Weight
  • No need to be vented
  • Can be discharged deeper without affecting battery life (so a 120Ah Lithium battery bank is approx. equivalent to a 200Ah AGM battery bank!)


  • Expensive
  • More sensitive to high/low voltage or current and high/low temperatures*
  • Cannot be charged below 0C (32F)*

*Some modern LiFePO4 batteries come with a built-in Battery Management  System (BMS). In a nutshell, the BMS will cutoff the battery if the voltage/current/temperature is out of range for safe charge/discharge. This is the case with the BattleBorn LiFePO4 batteries: they come with a BMS, have a 10 year warranty and are built in Reno (Nevada). It’s safe to say they’re super popular these days among the DIY van crowd. This is what we would use if we were to go lithium. Check them on Amazon: amzn.to/2M2q0bz


3.5- Combining Batteries

While we prefer to use a single battery, batteries can be wired together in parallel or series. In both cases:

  • You should always use identical batteries (brand/capacity/age) so they work equally together.
  • You should always use identical cables (length/diameter) so they offer the same resistance, ensuring all batteries work equally together.


  • Same voltage (V)
  • Capacity is doubled (Ah)
  • For example two 100Ah 12V batteries wired in parallel = 200Ah 12V
photo credit: enerdrive.com


  • Voltage is doubled (V)
  • Same capacity (Ah)
  • For example two 200Ah 6V batteries wired in series= 200Ah 12V
photo credit: enerdrive.com


3.6 – Charging Profile

In the upcoming sections, you’ll hear about “nice charging profile”, “3 stage charge” or “smart charger”; that’s not just marketing B.S. or buzzwords, it’s actually a big deal if you want your battery to keep working for years (and avoid capacity loss, a.k.a. sulfuration)! Providing a “good” charge is important; let’s see why.


3.6.1- Lead acid batteries

Lead acid batteries (flooded, gel, AGM) are filled with electrolyte. During use, small sulfate crystals form. That’s OK and that’s reversible, except if the battery is deprived of a full charge for a prolonged period then the sulfate crystals deposit on the negative plates permanently. These hard deposits are not “usable” and therefore, the battery cannot provide as much energy as before (less capacity). To prevent sulfuration, a frequent 3 stage charge should be performed:


Stage 1: Bulk

Bulk stage happens until the battery is charged to approximately 85%. During that stage, the battery doesn’t offer much resistance to charging; it’s easy for the charger to push energy into the battery so a low voltage (below 13V) results in a large current; in other word the battery charges FAST! As the battery charges, it offers more and more resistance; it’s much more difficult for the charger to push energy into the battery. If only bulk stage is used, the battery cannot be fully charged…

Note: during the bulk stage, the current is constant (for example 30A for a 30A charger, 60A for a 60A charger) and the voltage increases gradually (but generally not more than 13V).


Stage 2: Absorption

Near 85% the battery become much more resistant to charging… to keep pushing energy into the battery, the charger raises the voltage. You can clearly observe that on your battery monitor (high voltage, low charging current). It’s kind of like switching to first gear on your car: it’s more powerful, but slower. During that stage, the high voltage results in gassing inside the battery; this gas stirs the electrolytes and helps dissolve the small sulfate crystals. See? That’s why a proper absorption stage is so important! It prevents hard deposits (sulfuration) and therefore prevents loss of total capacitymemeor.

Note: during the absorption stage, the voltage is constant (about 14.7V for AGM) and the current lowers and lowers as the battery approaches the full charge.


Stage 3: Float

Near approximately 98%, the charger switches to float stage. During that stage the voltage is lowered and current is very low. The float stage brings the battery to a full charge and maintain it that way.

Note: during the float stage, the voltage is constant (about 13.6V for AGM) and the current is very low (below 1A).


3.6.2- Lithium (LiFePO4)

LiFePO4 are different than lead acid batteries; they don’t have a sulfuration issues. We’re comfortable speaking of lead acid, but honestly we’re still learning about LiFePO4; so we leave you this quote from BattleBorn batteries: “The bulk and absorption voltages typically vary between 14.0 and 14.8 V and the float can vary between 13.2 and 13.8 V. The 12V Battle Born batteries sit comfortably right in the middle of these ranges. We recommend a bulk and absorption voltage of 14.4V. A float is unnecessary, since Li-ion batteries do not leak charge, but a floating voltage under 13.6V is fine.” More here: https://battlebornbatteries.com/charging-battleborn-lifepo4-batteries/.


4- Charge Sources

Now that we understand how to properly charge a battery, let’s see our charge source options: solar, alternator and shore power.


4.1- Solar Power

Harvesting power from the sun feels a bit like cheating to us; this is the exciting part of the electrical system! It is free to use, but it is not exactly cheap to setup at first.

First of all, do you really need solar power in your system? If you’re thinking on charging only from the alternator, keep in mind that while the bulk charge is relatively fast, it takes a long time to complete the absorption stage (even if you have a powerful charger). So unless you like to drive A LOT everyday, solar power will ensure you get a full charge and will increase your battery life!


4.1.1- The Panels

How many watts?

As a general rule of thumb, a 100W solar panel can generate about 5A/hr at peak power, that’s about 25Ah per day (sunny, summer day, best-case scenario).

We calculated previously that we will draw about 55Ah per day; it would be nice if the solar panel could provide at least that amount of power… We need 55Ah\25Ah*100W = 220W solar panel(s) to compensate exactly for our loads draw. Well, a bit more actually if we account for cold temperature de-rate & cloudy weather. However, solar power is not our only power source! When driving the van we will get some power from that as well; we have to keep that in mind…


Monocrystalline or Polycrystalline?

We read quite a bit about that and came to the conclusion that, these days, the quality of the solar panel (manufacturer) is more important than the type of the panel. If you want to learn more about that, Google is your friend! To start, here is a good article.


Should we use 1 large panel, or 2 smaller panels?

At the time of our research, we could buy one 300W or two, let’s say, 160W panels for 320W total. The cost of the 300W is generally higher than two smaller one, but is it really if you account that you need additional hardware to connect the two panels together (cables, connectors, junction box, etc…)?

One larger panel instead of two smaller ones:


  • Simple to install (no junction box and connectors)
  • Higher working voltage = lower amperage = minimize loss


  • Large physical size
  • Higher working voltage = use of MPPT charge controller recommended


Partial Shading is Evil!

Blocking a single cell (leaf, bird crap, etc.) from a solar array can completely bring your solar output down to ZERO! That’s right, bear with us…


Solar Panel Construction

Solar panels are made of multiple solar cells all connected together in series; blocking one of the cell totally kills the output of the solar panel. Think of the old Christmas tree lights: if one of the bulb blew, the entire thing would go off. Meh. Below, this single leaf totally “kills” the solar panel output:

This panel gives 0% output (no bypass diode)


Solar Array

What if the solar panel above is part of an array connected in series? The resulting total power is ZERO. See the water analogy below:

photo credit: blog.aurorasolar.com
photo credit: blog.aurorasolar.com


Bypass Diodes

Fortunately, modern solar panels have built-in bypass diodes that helps with partial shading. In such solar panel, cells are split in 2 or 3 groups; if one cell is blocked, only the group comprising the blocked cell is “killed”. Other groups bypass the killed group:

Here, the panel give 50% output thanks to the bypass diode.


Don’t celebrate too fast: even with bypass diodes, a solar array (in series) total power will be considerably reduced:

In the example above,

  • the total power (without shading) is: 57V x 9A = 513W
  • the total power (with partial shading) is: 57V x 4.5A = 257W
  • (In a series configuration, total voltage x lowest current = total power)


In our exemple above, because of a leaf blocking a single cell, the power of the entire array is reduced by 50%!


OK here we are, hold your breath for the sensational revelation of this discussion: MORE PANELS DOES NOT EQUALS MORE POWER!


Don’t get us wrong… there’s not much you can do about a fallen leaf. But our point is that, too often, we see vans with a ton of solar panels installed (more power!!) around the fan, A/C, rack, etc. These appliances create partial shading on the solar array and we now understand the consequences… It would be wiser (and cheaper) to install less solar panels, but to better locate them. For example:

  • 3 panels with partial shading (coming from the roof fan): 57V x 4.5A = 257W
  • 2 panels without partial shading: 38V x 9A = 342W


That’s why we located our panels far apart from our roof fan; to minimize the partial shading effect. Indeed, the sun is low angled most of the time: morning, evening, fall, winter and spring:

Cleaning the solar panels 2


Series VS Parallel

Researching through the web you probably found that, if using a MPPT charge controller, connecting solar panels in series is more efficient than in parallel right? We agree, except when we take partial shading into consideration… Indeed, when solar panels are connected in parallel, the current coming out of each panel has a “direct” path toward the charger and is not “blocked” by other panels. The previous sentence is actually an oversimplification, but here is what we would get (approximately) if we connected the 3 panels from our example in parallel:

  • Parallel: 18V x (9A + 4.5A + 9A) = 400W
  • Series: 257W (remember, we calculated that previously)
  • (In a parallel configuration, average panel voltage x total current = total power)


Conclusion on partial shading

When planning your roof layout, take partial shading into consideration! If you MUST install your solar panels near your fan, A/C, etc., then consider connecting your panels in parallel.


Panel Orientation

A panel will deliver more current if oriented perpendicular to the sun. On large commercial solar plant, the panels are mounted on a motor-driven device that will optimized the orientation of the panel automatically throughout the day. Obviously there is no such device for a van roof (until when?), but with some out-of-the-box thinking you can build your own system:

900W of tilted solar panels! Credit: Rayoutfitted.com


We reached out to Ray at Rayoutfitted and he claims his tilt system can increase solar input up to 50% in winter. Pretty good!

Adding a tilt kit will obviously add weight, raise the panel(s) and have a negative impact on fuel consumption. If we were to park for extended period of time at the same place, we might consider a tilt kit. But with our lifestyle we generally move a few times each day, so we personally don’t feel like it’s worth the hassle.


Our Pick

We chose to install two panels of 160W each, for a total of 320W. This is quite a lot of power, but we’re not messing around here! (note: there was no 175W panel available when we built our van, but this is what we would choose now if we had to start over!)


From now on, we will use 320W solar power in our calculationThis should provide 320W\100W*25A (remember, each 100W gives about 25A per day) = 80Ah of charge per day during summer, 30 Ah of charge per day during winter (guesstimate, time will tell for winter).


4.1.2- The Charge Controller

How many amps?

Charge controllers are rated based on the amount of amperage they can process from the solar panels.

Solar Panel Max. Watts / Solar Panel Max. Voltage = 320W / 18.5V = 17.30A

AMPS x Surge factor = 17.30A x 25% = 21.62A

Therefore a charge controller of at least 22A is required.



MPPT are the latest thing in solar charge controllers. They are more efficient than PWM in cold temperature, partially sunny day and if the voltage of your solar panels are superior to the voltage of your battery bank. However they consume a small amount of power for themselves (it’s almost nothing really) and are more expensive than PWM. The debate rage about the MPPT efficiency over PWM, but it is believed to be around 10%-20% more efficient depending on the conditions.

MPPT VS PWM, What Others Have to Say:

  • See Bogart Engineering take on MPPT vs PWM charge controller debate here (see FAQ “C1″)
  • MorningStar MPPT vs PWM comparison.
  • Victron MPPT vs PWM: Which solar charger to choose?
  • Side-to-side, real world testing of MPPT vs PWM charge controller here.


MPPT VS PWM, What We Have to Say:

  • We first installed a PWM charge controller (Bogart Engineering) and then upgraded to a MPPT (Victron SmartSolar).
  • While we can’t exactly quantify the improvement, we immediately noticed more charging current; we observed 24A with the Victron while the most we got with the Bogart was 16A.
  • We also noticed more power earlier in the morning and during overcast weather.
  • OK we’re sold to the Victron!!


Our Pick:
Victron SmartSolar MPPT 100/30:

Victron SmartSolar MPPT 100_30
Victron SmartSolar MPPT 100/30. Buy from Amazon.
The Victron SmartSolar is sweet because it can be setup and monitored from an iPhone or an Android phone! It’s also possible to see day-to-day historical data about the system performance, love it!




Here you will find our review about the Victron MPPT SmartSolar Charger, Battery Monitor and VictronConnect App. We also go through the installation, initial setup and operation process. We have a bunch of cool screenshots and things to say about the Victron so go read the article 🙂


A note about operating/installing the solar charge controller:

A charge controller should always be connected to the battery first. It’s easy to remember if you can see it that way: the controller needs “somewhere” to “dump” the power from the solar panels. Therefore:

  • Connection order: Connect battery then connect the solar panels.
  • Disconnection order: Disconnect solar panels then disconnect the battery.


4.2- Charging while driving

Do you need alternator power in your system? It depends:

  • If you live full time in your van, we say it’s a must. Energy is a basic need, it’s not cool worrying about running out of it…
  • If you take your van for adventures in summer only, you can probably live without it.
  • For fall and spring adventures, we highly recommend it as the solar days get shorter and weaker. Alternator power is a good way to quickly go through the bulk charge, then solar power can complete the absorption stage.
  • For winter there’s no question about it, our opinion is that you want it.


4.2.1- Battery-to-Battery charger (B2B)

This option is quite popular these days as it provide many advantages:

  1. It’s a Smart Charger, meaning it provides a multi-stage charge adapted to the battery type (Gel, AGM, etc). That’s important, because it will keep your house battery healthy and maximize it’s lifespan ($$).
  2. It’s plug-and-forget. The B2B will automatically activate/deactivate when driving to keep the house battery topped up.


  1. It’s not cheap, but since it extends the lifespan of the house battery, it can be considered as a long-term investment!




4.2.2- Automatic Charging Relay (ACR)

An ACR parallels (combines) the van & the house batteries during charging (alternator or solar).


  1. Simple and compact
  2. Cheap!



  1. The house battery will get whatever charging profile the alternator provides; it works, but it’s not ideal for the house battery health in the long run.
  2. Inadequate for lithium LiFePO4 batteries.


Blue Sea ACR 7622
Blue Sea ACR with Manual Control (up to 500 amps alternator). Buy from Amazon.


4.2.3- Accessing Battery Power on the Ford Transit

Please check this official Ford SVE Bulletin on how to use the battery power  (alternator) on SINGLE or DOUBLE battery(ies) variant: SVE Bulletin Q-226 (.pdf)


4.3- Shore Power

Do you need shore power in your system? We think it’s a good option if:

  • You spend extended time in campgrounds with full service.
  • You use your van to chase the snow. Indeed, it takes a LONG drive to complete a full charge so it’s sometimes required to plug in for the night.


4.3.1- Battery Charger / Converter

A smart Battery Charger / Converter will:

  1. Charge the house battery from a 120V source by providing a multi-stage charging profile adapted to the battery type (Gel, AGM, etc).
  2. Provide power to 12V loads. This means using 12V loads (refrigerator, lights, etc) won’t discharge the battery when the charger/converter is plugged in.
Our Pick:
Samlex SEC-1250A 12V Smart Battery Charger / Converter on Amazon


4.3.2- Inverter / Charger

An inverter / Charger is a battery charger AND an inverter combined into one device. It is quite convenient because it simplify the installation (one device instead of two), but it’s more expensive (between 1000$-2000$ for high-quality ones) than installing a separate inverter and a battery charger…

Magnum-MMS-1012 Inverter Charger 1000W
Best Quality: Magnum-MMS-1012 Inverter Charger 1000W on Amazon
Renogy Inverter Charger 1000W
Best Value: Renogy 1000W Pure Sine Inverter Charger (Buy from Amazon)


5- System Monitor

A system monitor is not mandatory, but we strongly recommend it. Depending on your model, it will display the house and van battery voltage, amperage coming in/out of the house battery,  % battery left, amperage used since last charge, etc, etc. You will learn a lot from the monitor on: 1- the impact of shade on solar (and help you choose the right parking spot) 2- the impact of your load(s). This will help you better manage your energy. A popular option out-there is the Bogart Engineering Trimetric TM-2030; this is what we installed first, but we then upgraded for the Victron BMV-712 because the Bogart is not exactly user friendly to setup and operate and because it looks like it’s 1968…

Our Pick:
Victron BMV-712 System Monitor:

Victron BMV-712
Victron BMV-712 Bluetooth System Monitor. Buy from Amazon.
The Victron BMV-712 has bluetooth inside and current status (and historical data) can be displayed on an iPhone or Android phone!

Victron BMV-712 Monitoring



Here you will find our review about the Victron MPPT SmartSolar Charger, Battery Monitor and VictronConnect App. We also go through the installation, initial setup and operation process. We have a bunch of cool screenshots and things to say about the Victron so go read the article 🙂


6- Battery Bank Sizing

Back on the battery topic; we still haven’t choose our battery size…

Remember we predicted that we would draw 55Ah daily; so if we want to last 4 days without any charge (bad weather happens, like it or not!), we need a battery bank of 55Ah per day x 4 days = 220Ah, right? Not so fast! An AGM battery should, ideally, not be discharged below 50%, so we actually need… 440Ah. That a LOT (of money, space and weight). Fortunately we have a wildcard: charging while driving. If weather is really crappy, we can go for a drive. We (arbitrarily) decided we don’t mind driving every other day, so we need a battery bank of 55Ah per day x 2 days   = 110Ah x 2 = 220Ah to stay above 50%. We just saved 220Ah of battery bank! Nice, the B2B charger paid for itself!


We finally went for a 210Ah AGM battery.


Did we choose well? Here’s a reality check (September 2018, 1 year full time in our van):

  • In summer, we can get a daily full charge (bulk + absorption) from solar only (the charge is generally complete in early P.M.). Maybe our “4 days of bad weather in a row” was a bit aggressive, but Squamish was exceptionally dry that summer (no rain at all for about 2.5 months)… We can recall that, back home, 4 days of rains do happen sometimes!
  • In fall and spring, the full charge is achieved with the help of the alternator (bulk) and solar (absorption). If we had solar only, we wouldn’t run out of juice, but we probably wouldn’t get a proper absorption stage (not good for battery health).
  • In winter (which was spent chasing snow north of USA and Canada), forget about solar. We have to drive to charge. The problem is that the bulk phase is relatively fast, but the absorption stage take a while to complete. A quick drive to the nearest Tim Hortons is not enough. That’s where the shore charger is handy: we sometimes visit friends and leave the charger plugged in for the night. We managed to keep the battery above 50% most of the time, but that means driving almost everyday.


As you can see, there is no single formula to calculate your battery size. There are many variables to take into consideration: charge source, local weather, seasons, how often and how long you drive, etc. Hopefully our “reality check” above helps you take your decision!


Our Pick:
Rolls S12-230 AGM Battery
Rolls S12-230 AGM Battery SPEC SHEET
 We also considered:
Highest Quality:

Marine Lifeline 255Ah AGM Battery. Buy from Amazon.

Renogy AGM Deep Cycle 200 ah
Renogy 12v 200ah AGM. Buy on Amazon.


7- Electrical Wire

7.1- Wire Diameter (AWG)

Selecting the correct electrical wire diameter is crucial for the system performance and safety. The maximum current and the voltage drop need to be taken into account to select to appropriate diameter.

7.1.1- Maximum Current (capacity)

For a certain wire diameter, there is a maximum current carrying capacity of a wire. Going over that capacity would create a safety issue (i.e. bigger current requires bigger wire diameter).

7.1.2- Voltage Drop

There is a loss of energy (voltage drop) as current moves through passive elements (wires, terminals, etc) of an electrical system. The wires are a big contributor to the voltage drop and this should be taken into account when designing the electrical system. How? By selecting the appropriate diameter; the bigger the diameter, the smaller the voltage drop. Generally, wire diameter should be selected to provide a maximum of 3% voltage drop for critical loads (panel main feeder, inverter, electronic) and 10% maximum voltage drop for non-critical loads (lightning, fan, etc).

7.1.3- Selecting the correct wire diameter

Now, really, how do you selected the correct wire diameter? Let’s keep it simple and use the BlueSea Calculator (circuitwizard.bluesea.com):

Blue Sea Calculator
Blue Sea Circuit Wizard, use it! circuitwizard.bluesea.com


The inputs are:

  1. Nominal Circuit Voltage (hint: it’s 12V)
  2. Average Current (it’s normally written in the owner manual of the load)
  3. Length of the Wire Run (Wire Run = positive (red) + negative (black)! For example, a load using 10 feet of duplex wire has a Wire Run of 20 feet)
  4. Allowable Voltage Drop % (critical VS non-critical loads, see section 7.1.2)

The outputs are:

  1. Recommended wire diameter
  2. Maximum current capacity of the wire (for reference)


7.1.4- Example

Let’s select the correct wire diameter for the Maxxair Fan.

What we know:


We head to circuitwizard.bluesea.com and enter the following inputs:

DC Wire Selection Example


  • Circuit Voltage: It’s always 12V…
  • Load Current: For simplicity sake, we use the fuse capacity instead of the average load. By doing so our system will have slightly oversized wires, but it’s actually a good thing: there is less voltage drop and the wires are more robust. (if you decide to use the average current that’s OK, just make sure the wire capacity is greater than the fuse selected)
  • Length of Conductor: We measured 16 feet of duplex wire, but for calculation it’s always the positive wire + negative wire that must be used. So 16 feet of positive + 16 feet of negative = 32 feet



  • The calculator recommends: AWG 18.
  • AWG 18 is capable of taking current up to 20 amps (read the small prints below the Recommended Wire) which is greater than the 5 amps fuse we’re using; we’re safe!
  • BUT, AWG 18 wire is really small and fragile. Vibration and sharp edges will damage it in the long run; for this reason anything smaller than AWG 16 is not recommended.
  • We could use AWG 16 but, to save cash, we bought a big roll of AWG 14 wire; therefore we will use AWG 14! It’s OK to use bigger wire (but it’s NOT OK to use smaller wire).


7.2- Wire Type

Electrical wire is made of a conductor inside an insulator. There are two types of wire depending on how the conductor is made:


Solid Wire Pros:

  • Cheaper
  • Smaller diameter for same conductibility
  • More resistant to corrosion due to decreased surface area

Solid Wire Cons:

  • Not intended to be flexed (more difficult to route)
  • Not resistant to vibration (will break in the long run)


Stranded Wire Pros:

  • Very flexible (easier to route)
  • Resistant to vibration

Stranded Wire Cons:

  • More expansive
  • Less resistant to corrosion, that’s why some marine-grade wire is tinned


Solid wire is commonly found in houses, not in moving vehicles (car, RV, boat). Because of the vibration and tight turning radius (when routing), the conductor in solid wire will most likely break in the long term. Therefore, it is mandatory to use stranded wire. We like the marine-grade Ancor wire as it’s tinned and will last longer without corrosion issues:

Ancor Marine Duplex Wire 14AWG
Ancor Marine Grade Duplex Wire. Buy from Amazon (many length and diameter available; make sure to select the appropriate wire for YOUR application!)


7.3- Wire Crimping (connecting wire)

There are many ways to connect wires together or to a terminal. We will go straight to the point here, the best way to do it is crimping. Crimping will deform the connector into the wire and ensure a solid permanent mechanical connection with low resistance. To crimp, you need quality crimping tools and quality crimp connectors. 


7.3.1- Crimp Connectors

There’s 3 types of material:


– Vinyl/PVC

One word: CHEAP. With this type of crimp, the wires remain exposed to the elements and can corrode. Moreover, the insulation can become brittle and crack over time. The vinyl/PVC are single-crimped and it’s not great against pull-out. We pass.


– Nylon

Like the Vinyl, the wires remain exposed to the elements. However, the nylon is more durable than the vinyl and is double-crimped, which provides more tensile strength and strain relief against pull-out.


-Heat Shrink

The connector is crimped (single-crimp, because double-crimp might damage the insulation) and then heated to shrink the insulation around the wire and the melting adhesive adheres to the wire insulation. This provides a waterproof and permanent connection. Heat shrink connectors are more expensive, but there’s no price for safety and peace of mind!


We recommend the Ancor, marine-grade connectors:

Terminal rings are commonly used to make connections to the fuse block, battery, etc.

Ancor Terminal Rings
Ancor Heat Shrink Terminal Rings. Buy from Amazon
Butt connectors are commonly used to make a permanent connection to an appliance.

Ancor Heat Shrink Butt Connectors
Ancor Heat Shrink Butt Connectors. Buy from Amazon.
Disconnects are commonly used to make “non-permanent” connections (i.e. to our fridge which we periodically pull-out to clean the back) and to connect to certain appliances (i.e. 12V Sockets, switches, etc).

*Hint: Female disconnect should be on “hot” side of the wire (that’s the wire closest to the battery), male disconnect on the side of the appliance. This is to prevent short circuit when manipulating the “hot” wire.

Ancor Heat Shrink Disconnect. Buy on Amazon.


7.3.2- Tools

Quality tools = safe and durable electrical system. Do not use pliers as you will get poor connections = safety and reliability issues.

Ancor Crimp Tool
Ancor Double-Crimp Tool (for nylon insulated connectors). Buy from Amazon
Ancor Single Crimp Tool
Ancor Single-Crimp Tool (for vinyl & heat shrink connectors). Buy on Amazon.


Hydraulic Crimper 5 Ton 00-12 AWG
Hydraulic Crimper for 2/0-12 AWG. Buy on Amazon.
Wire Cutter Stripper
Stripper / Cutter for 8 – 16 AWG Stranded Wire. Buy on Amazon.


Heat Gun
Heat Gun for heat shrink. Buy from Amazon
Digital Multimeter. Buy on Amazon.


Electrical System Installation Van Conversion (4)
You shall crimp with grace


7.4- Wire Installation

For safety sake, the wires should not be installed loose and unprotected; as opposed to a house, there is a lot of vibration and movements that will damage the wires in the long run.

The wires should be routed through Split Loom Tubing (make sure to buy several diameters) attached with zip ties:

Split Loom Tubing
Split Loom Tubing. Buy from Amazon.
Zip Ties
Zip Ties. Buy from Amazon


The Split Cable Loom should be secured with Nylon Cable Clamps on wood:

Nylon Cable Clamps Kit
Nylon Cable Clamp. Buy from Amazon
The Split Cable Loom can be secured with Zip Ties Mount Adhesive on metal. Make sure the surface is cleaned (isopropyl alcohol works great) and warm enough.

Zip Tie Adhesive Mount
Zip Tie Mount Adhesive. Buy from Amazon


8- Fuses and Breakers

Fuses and breakers are essential in any electrical system! It will protect the circuit wires and the components against over current and ultimately fire. If you blow a fuse during your system installation (we did a few times), it means that you just avoided a potential failure or fire! Nice!

Each load should be fused according to it’s current maximum normal draw. Consult the owner manual of the load. This is achieve through a fuse box such as:

Blue Sea Fuse Box
Blue Sea fuse box. Buy from Amazon


The fuse will drive the wire diameter selection. For example, if wiring a load that draw 5A and a fuse of 15A is used, you should choose a wire capable of (more than) 15A! This is safety matters.


Breakers are similar to fuses, except that if it blows it is possible to reset it without replacing it. Fuses generally blow faster than breakers and therefore fuses are preferred for sensible electronics. We added a few 40 amp breakers in our system. Why? First, to avoid having to use big electrical wires. Indeed, our fuse block is capable of 100A; even if we know that we will never draw 100A, we need to size our wires for 100A ($$$). By adding 40A breakers, we can size our wires for 40A. We can also turn off portion of the system by switching a breaker off (for example, turn off solar panels to display on our system monitor the draw that the loads are pulling. Or the opposite to display the charge that the solar panels are providing).


Here is a more complete article about this topic: http://www.12voltplanet.co.uk/fuses-guide-uses.html


9- Loads

9.1- 12V Loads

These are all the 12V loads that we installed:


Maxxair 6200K Roof Fan

Installation: faroutride.com/fan-installation

Review: faroutride.com/maxxfan-review

Maxxfan Roof Fan. Buy from Amazon.
LED Light (Dimmable)

Installation and wiring: faroutride.com/led

acegoo Recessed Ceiling Light LED 12V 3W, Warm White (Silver)
Warm White, Silver Finish. Buy from Amazon.


12V Socket

We decided to install 12V sockets all over the van instead of USB chargers. Why? Because this is the most universal plug (we can charge everything: phone, laptop, camera, etc.) and it’s not likely to evolve in the future (as opposed to USB standards). We went for a high quality, marine-grade Blue Sea 12V socket (15A capable):

Blue Sea Systems 12 Volt Dash Socket
Blue Sea Systems 12 Volt Dash Socket. Buy from Amazon.
Most appliances plug directly into the 12V socket, but for phones or other USB gear we use this:

USB Car Charger
Buy from Amazon.


Shurflo Revolution Water Pump, 3 GPM

Installation: faroutride.com/pressurized-water-system

Water 12V Pump
Shurflo Revolution Water Pump. Buy from Amazon.
Novakool R5810 Fridge 12V

Installation: faroutride.com/fridge-electricity-cabinet

NovaKool 12V Refrigerator
Novakool R5810 12V Fridge. Manufacturer Website.


Webasto Air Top 2000 STC Gasoline Heater

Installation: faroutride.com/air-heater-installation

Webasto Air Top 2000STC. Gasoline Model or Diesel Model
Propex HS2000 Propane Heater

Installation: faroutride.com/propex-install

Propex HS2000 (300x252)
Propex HS2000 Propane Heater. Dealer Locator.


Sirocco ii Gimbal Fan, 12V

Review: faroutride.com/sirocco-fan-review

Sirocco 3-axis Gimbal Fan 12V Black
Sirocco 3-axis Gimbal Fan. Buy from Amazon.
Nature’s Head Composting Toilet

Installation: faroutride.com/composting-toilet-installation

Review: faroutride.com/natures-head-review

Nature's Head Composting Toilet Standard Handle
Nature’s Head Composting Toilet. Buy from Amazon.



9.2- 120V Loads
9.2.1- Inverter

The role of the inverter is to convert the voltage from 12V DC to 120V AC. Just remember that there is a loss of around 15% efficiency during the conversion from DC to AC, so it is better to reduce the use of an inverter. For example, get a universal 12V power adapter to power your laptop if possible:

90W 12V adapter on Amazon.com. (make sure it’s compatible with your laptop)


Or instead of charging your phone, cameras, etc., using a 120V charger, use a 12V charger:

USB Car Charger
Buy from Amazon. (make sure it’s compatible with your gear)


Now there are some appliance that must use 120V AC such as microwave, gaming laptop, milk frother, blender, coffee machine, etc. In that case, you will need an inverter. You should size your inverter according to your most demanding appliance; check the owner manual or check online to find out how much Watt an appliance draw. If you can’t find the info, you can use a Kill-a-watt. The Kill A Watt is plugged into the 120V outlet (of your house), then the appliance is plugged into the Kill A Watt and then the consumption will be displayed.

Kill A Watt. Buy on Amazon


And remember that a microwave rated for 1500W will most likely draw more than 1500W… so get a 2000W inverter.


9.2.2- Modified VS Pure Sine Inverter

There are two types of inverter: modified and pure sine inverter. There is a good explanation here. This is a must-read if you need to choose between the two. Did you read it? Yes? Good, then we all agree that a pure sine inverter is the way to go!


Our Pick

You will find same very cheap inverter on Amazon or ebay; stay away from them if you don’t want to toast your 120V appliances and for safety sake. We like Samlex; they make good quality products and are reasonably priced:


  • Samlex 1000W Pure Sine Inverter, Buy on Amazon.
  • Samlex 300W, 600W, 1500W or 2000W Pure Sine Inverter, Buy on Amazon (make your selection in the Amazon store).


10- Short Term and Long Term Storage

Not planning on using your van for a while? Then it’s important to properly put your electrical system into “storage-mode” to maximize your battery lifespan! For either short-term storage (weeks) or for long-term storage (months), here are our recommendations.


10.1 – Loads

All the loads should be disconnected to prevent draining the battery. In the electrical diagram we propose (see below), all the loads are turned off by flipping the breaker (between the bus bar and the fuse block) to OFF position. The battery monitor can be disconnected simply by removing the UTP cable from the shunt (as it uses minimal amount of power), but we prefer to leave it ON to be able to monitor the SOC of the battery over time. (disconnecting then re-connecting the battery monitor won’t give you the correct SOC…)


10.2- State Of Charge (SOC)
10.2.1- Lead Acid Batteries (flooded, gel, AGM)

Lead acid batteries should be put into storage fully charged to prevent sulfuration. They self-discharge over time, so give them a good charge when approaching 85% SOC. Lead acid batteries can be left into float mode indefinitely so if you have solar power, leave it ON as it will maintain the battery fully charged over time (assuming your solar charge controller float voltage is correctly set for your battery type).

10.2.2- Lithium Batteries (LiFePO4)

Lithium based batteries should be put into storage at 40-50% SOC to prevent permanent capacity loss. They do not really self-discharge, so disconnect the solar power.

10.3- Temperature

Even if a battery is stored at the correct SOC, a permanent capacity loss occur over time and it’s directly related to storage temperature. The ideal storage temperature is around 10-15C (50-60F) for all battery types. The higher the temperature, the more non-recoverable permanent capacity loss.  The battery should not be allowed to freeze (remember freezing temperature of a battery depends on SOC; see “Charging A Frozen Battery” in the article above).


11- Our Electrical System

Before going any further, we draw a logical diagram and a wiring diagram. We did not want to waste time on that at first, but we are so glad we did it. When doing the actual physical installation of our system in the van, we realized how important it was to prevent messing up. Things will not clarify during the installation… the physical installation is quite overwhelming and referring to the diagram gave us a lot of confidence. When we first turned the switches on, we were not afraid to blow everything up 🙂 To this day, we printed a copy and leave it in the van at all time.


We’re very proud to introduce our new Wiring Diagram! What’s wrong we the previous one? Nothing, it passed the test of time and it works exactly as it should! Then why change it? We realized many people are just replicating it (which we think is great!), so we wanted to make it:

  1. easier to understand (see our new Interactive Diagram AND new tutorial “From Blank Page to Wiring Diagram in 15 Steps”)
  2. easier to install (more intuitive design and less components to install)
  3. easier to use (Plug-and-forget, monitoring via Android or iPhone)
  4. easier to adapt to anyone’s need (many features can be deleted/modified for different needs/budget. See our suggestions.)

It’s the result of the ultimate question: “If you had to start over, what would you change?”. Answer: we deleted some features we never used in the real world and we updated some components because we like to stay up-to-date with the latest technology.


11.1- Logical DiagramFaroutride Logical Diagram V2 (800px)


11.2- Wiring Diagram
11.2.1- Interactive Wiring Diagram

180 thoughts on “Electrical System: Build Guide for DIY Camper Van Conversion”

  1. First off, can’t tell you how much all of this information ha helped in my planning so thank you! There were a couple discrepancies I was hoping you could clear up for me.

    I noticed on your 6 stud negative bus bar there are 7 wires connecting to it. How does that work?

    Also in your wiring diagram there is a native wire running from the bus bar to the B2B charger and a negative wire running from your bus bar to the alternator. In the B2B installation manual is appears that they recommend running a wire from the B2B charger to the starter battery and then a wire from the starter battery to the house battery. Just wondering what your thinking was here?

  2. Hi Antoine
    your website and information has been incredibly helpful to work through our van conversion design. I’ve downloaded your wiring diagram and am finding that our requirements are going to be very similar. I have a pretty basic question about your electrical build-out: where did you put the electrical component box and what are the dimensions. I know every build will be different, but this will give me a starting point.


  3. Thanks for this incredibly well presented electrical diagram.
    I’m planning on following your diagram with solar, shore, and B2B power sources with a LiFePO4 battery. Do you disconnect the various power sources depending on your situation, or do you have them all on at the same time? As I read about the bulk, absorption, and float phases, I’m wondering how that would work with three different controllers working on the same battery bank? Do they interfere with one another, or will they independently realize which phase the battery needs to be in, and any timing differences are too small to matter?

  4. Hey Guys. I am have used your diagram with everything EXCEPT the shore power.

    I have a question on the main switch. is it correct that one wire from the switch goes to the bus bar, and the other side is attached to the fuse which is then attached to the positive of the starter battery?

    To clarify – – – – this set up allows me to break the power off to the whole system (if i’m not using the van for a while). But, if I just want to turn off the fuse box / solar, I would just flip the breakers.


    • That’s correct!
      The breakers act as switches as well; so you can use the main switch to turn everything OFF OR use the breakers to turn sections of the system OFF.


  5. Hey there! Love the site and it’s been super useful for me.

    I have a quick question on the position of your “system switch” / battery isolator. In your diagram you have it as an I/O switch for the battery, whilst power from the “shore” side will still enter the system via the positive bus bar. Can I understand why?

    Is the purpose to completely isolate the battery from any power input or to isolate the system from any power? I set my system up as you pointed out, with power then coming from the shore power, MPPT, or split charger if the battery is isolated. So your system is set up to just stop power coming from the battery, right?

    I’m trying to think if it would be wise to isolate the entire system, so nothing is drawing from any power source. Having said all this, I may be completely misunderstanding it all.

    I’m waiting to hear back from the guys whom I bought my shiny lithium battery from but was curious as to your take on it. I’ll share what they say when I get feedback.

    Phil 🙂

    • Hi Phil,
      The main switch isolate the battery from everything (input (charge) / output (loads)). If you want to isolate the loads from the charge sources, you can do so by flipping the 40A breaker to “OFF” position; it acts as a switch as well. Make sense?


      • Yeah… I think I realised what it was all about after a third read and a chat with my battery supplier…

        The knowledge one gains by attempting to build a camper hey?! Jeez… It’s awesome though 🙂

        Thanks again for the inspiring site and I know it’s helping a bunch of folk I’ve passed it on to. I think for my next trick I’ll do my second build in Canada and have one there for the Americas and one here for Europe 😛


        Thanks Antoine… you guys are stars… happy travels 🙂

  6. Hey there – thanks for the detailed write up! Quick question: does your battery monitor allow you to see the amp draw from your inverter? For some reason, I don’t think I can with my set-up, so I won’t be able to directly see what the 120v appliances are pulling except vs. estimating based on how the battery is doing.

  7. Hey guys! This is incredible! So so so helpful. I’m recommending it to everyone I see asking about electrical on other forums.

    Quick question. I’m looking at my charge controller (Victron 100/50), and I see it has a grounding screw on the left side. I see that you grounded everything to your negative bus bar, but I was wondering if I should ground that screw to my bus bar, or if the negative line running to the bus bar works as a ground?

    Thanks for everything!

    • Awesome, thanks for recommending us!! 🙂

      Per manual: “Chassis grounding: A separate earth path for the chassis ground is permitted because it is isolated from the positive and negative terminal.”

      We didn’t ground ours and most people don’t…


  8. Hey antoine!
    Question about your wiring diagram for the Sterling battery to battery charger. I’m looking at the documentation that came with the Sterling it looks like they recommend connecting the negative terminal of the house to the negative terminal of the starter battery. They indicate that the system will have improved efficiency with this connection. Your wiring diagram does not appear to have this connection. Is there a reason for this?

    • Mike!
      It does! Look for the black (4 AWG, 12 feet) wire running from “Alternator” to the negative Bus Bar: this connection makes the van + house battery common. Maybe you downloaded an older version of the diagram? It was a bit confusing at first so we updating it for better clarity; if your diagram is different than the following one, you can download it again (use your existing link or buy again for 0$): https://www.thinglink.com/scene/1043905602801106946

      Hope that makes sense!
      On your side, you could help us by sending some cold air here in Mt. Baker!! It’s raining mid-mountain all week 🙁

      • Ah-hah! That was it, I do have an older version! Thanks!

        Sorry about the rain! We are getting absolutely buried! Looks like 10+ feet foretasted on this storm cycle and it keeps going up by the day! Now if I only could get rid of this cold!


  9. Hello you two!

    Another question about grounding! In Sterling’s manual, it recommends a ground running from B2B to Van Battery to House Battery, but you guys went from B2B to House Battery to Van Battery. I don’t know a lot about electrical yet, but is there any difference between those two configurations? It seems like a LOT less wire running it the way you guys did – is that why you chose that configuration instead?

    Thank you!

    We appreciate the time and effort you used up to create this website!

    Bailey and Jake

    • There’s not difference; since all grounds are common (parallel). In other word all grounds are connected to our Negative Bus Bar (per diagram).

      Hope that helps!

  10. Hey Guys,

    Thank you for this invaluable diagram. I have been all over the interwebs the last few months, and your page has BY FAR been the most helpful. You spent your time very generously providing us with this information, Thank You!!

    If you have time, I do have a question regarding the grounds. My understanding is that when you were installing your B2B charger, you wired your house/starter batteries grounds together at the chassis grounding point?

    I also read that you grounded your inverter, did you run a heavy gauge wire all the way to that same grounding point, find a closer grounding point, or make your own?

    I am just a little confused about whether I should have ANY of my auxillary setup grounded to the vehicle chassis, or if it is OK to have the system isolated completely from the vehicle chassis. Please note that my setup includes ONLY solar, no alternator/shore power.

    Cheers, happy travels and enjoy the pow!

    • The house/van batteries are common, that’s correct. Because of the B2B. We routed a 2/0 cable from the chassis ground point (between driver/passenger seat) down to our negative bus bar.
      We grounded our inverter (per manual) to a ground point located in the back of the van (per BEMM).

      If you only have solar, you don’t need to ground your system to the chassis! Except for the inverter; I believe it’s required for safety sake (secondary path?). What does the manual of the inverter says?

  11. Wow, just wow. What you have provided here is just so incredible, I am going to have to read it a few more times! I’ve spent so much time researching and learning, only to arrive here and realize it’s a one-stop-shop!! I can’t thank you enough for your generosity.

    One question that has been nagging me is about the fridge. I have seen a lot of van builds that just use a dorm-style 110V mini-fridge – I can understand why, since they are $1000-2000 cheaper than the AC/DC boat/RV fridges! Of course they use a lot more electricity, but then I ask myself if it’s not cheaper to buy more solar panels and batteries to compensate.

    I don’t mind to spend more money if it makes sense, but I haven’t found a satisfying answer that makes me feel really good about spending thousands more dollars – how did you arrive at your decision?

    Thank you again so much for your amazing contribution <3

    • Hi Annalise, thanks for the kind words 🙂

      Reality check: depending on where you travel, sun is not always shining! Sometimes it’s overcast for days, sometimes you’re parked under the trees, sometimes there is snow on the panels… therefore more panels probably won’t be enough. When off the grid, energy is a precious resource. Also small dorm fridges aren’t built for high vibration and the door don’t have a lock device.

      So I’d rather spend the money on a good 12V fridge than oversize the electrical system.

      Hope that helps!
      Good luck 🙂

    • Can you address any health concerns sleeping over the electrical systems? I have noticed most conversions have them “hidden” under the bed and am planning my design to have them located elsewhere which is inconvenient but seems to be potentially safer.

  12. Hi – thanks for the detail! I found your electrical diagram especially helpful.

    One question – do you recommend shutting off the battery switch when you aren’t using your van for a week or more to avoid parasitic drain and more cycles on your batteries?

    • Yeah, turning all load to OFF is definitely a good idea to prevent battery drain. That’s the purpose of the main switch. You want to keep your battery fully charged, so leave solar ON as a lead acid battery can be left to “FLOAT” mode indefinitely (the solar charge controller will take care of that automatically). However if you have a lithium battery, turn solar OFF (a lithium battery doesn’t self-discharged).


  13. This site is incredible and has been an fantastic resource for me in my Transit build. The approach you have taken to design your electrical / mechanical services is very well done and thorough! I have spent many years in the commercial mechanical / electrical world (engineering, construction, etc), and your design and execution is on point and professional level (not just your everyday DIY regurgitation of thing you have read other people say). Additionally, you have done an amazing job of making this technical information very consumable and user friendly.

    I love what you have built here, not only in the van, but in the community and on this website.
    Massive Kudos to you.

    With much respect, thank you for your efforts and contribution.

    • Justin,
      Thanks for taking the time to write these words, this is much appreciated, really! We’re glad the information make sense, cause we’re not fans of “oversimplification”; taking a decision is never black & white, there are always trades-off and a design is never perfect… Our goal with the website was to give as much info as possible (so people understand what’s going on), while still keeping things relatively simple and “fun” (people’s attention-span is short these days…).

      Anyway, thanks again and good luck with your build! 🙂

  14. How did you connect a fuse to your starting battery terminal for the cable to the B2B? I could have sworn I saw a photo of it somewhere once but can’t find it now.

  15. Salut!
    Sans votre site, nous n’aurions pas acheté notre van! Merci!
    I purchased the electrical diagram, but from the website, I think you connected your B2B charger directly on the second B+ connector since you have the 2 batteries option, right?
    I am trying to figure out how to connect my B2B (60A) charger from Sterling Power to my Transit single battery. Ford tells us to use the CCPs (Customer Connection Points) for trucks with single batteries. Sterling Power recommends a 70A fuse.
    Given that I have the 60A B2B charger and that the CCP incorporates a 60A fuse, what should I do?
    If I connect the charger directly to the single CCP (60A fuse) wouldn’t I risk blowing the 60A fuse? The 70A fuse wouldn’t be usefull right?
    Should I combine two CCPs together (2x60A) and put the 70A fuse recommended by Sterling Power?

    Thank you so much for your help!

    Merci !

    • Oui, te connecter au CCP tel que tu l’as décrit devrait fonctionné; certain l’ont fait sur fordtransitusaforum.com . Si tu optes pour cette méthode, utilise des cables de diamètre et longueur identique pour que le courant passe “également” dans chaque circuit de 60A.

      Laisse-moi savoir le résultat! Bonne chance,

  16. Hi,
    I noticed on your web page it says you bought a 30 amp charge controller but your interactive diagram says 50 amp.
    Which did you go with and how did you decide how many amps for the controller?

    • Hi Rob,
      We went with the 30A because we have 160W solar panels; now that 175W panels are available, we would go with that along with a 50A controller (the 30A is borderline with 2 x 175W panels).

      Have a good one!

  17. Hey Antoine! I notice that you have the 250amp “catastrophic failure” fuse connected directly to the battery. I haven’t seen many diagrams with this element. I have been advised going from the battery positive terminal to a 90 amp circuit breaker (200amp battery with a max 90amp charging current) to a switch. Any reason you use the 250amp fuse versus a circuit breaker at the max amp output for the battery?

    • Hi!
      Yeah a 90A circuit breaker is fine, as long as you won’t charge or draw (inverter?) more than that! We use a 250A for more flexibility (inverter up to 2000W and multiple charge sources). A 250A circuit breaker is much more expensive than a 250 fuse 🙂

      Have a good one!

  18. Hey, great work providing an amazingly detailed and useful source of information!
    I wondered if you could offer any advice please?…
    I’m trying to achieve a (small) battery system which is easily removed from my camping car (VW Touran) and primarily charged from the alternator.
    Ideally using a wooden box which contains all main components (B2B charger, AGM battery, fuse box and all necessary fuses, battery switch, battery monitor).

    Do you think it would be feasible to have this box easily disconnect from the cables connecting to the alternator?
    So possibly the cables wired from the alternator first go through an inline fuse close to the alternator, then terminate at an inline circuit breaker fixed in the rear of the car; the battery box cables, i.e. the B2B, could then be connected/disconnected as necessary to the inline breaker (possibly with the use of quick release clamp, quick connect plug https://www.amazon.com/AURELIO-TECH-Universal-Connector-Electrical/dp/B0129E1KF8 or coupling latch like this https://uk.rs-online.com/mobile/p/automotive-connectors/7242440/)?
    The circuit breaker would provide a way of safely stopping the signal when the battery box is not connected.
    Perhaps I should also house it in a plastic box with opening lid to give an extra layer of protection when not in use?

    Many thanks,

  19. Hey, awesome website.

    Here’s a challenge for you since you’re up north: Stay in the Southwest part of the US during the summer months when sunlight is the most intense and the heat is excruciating and log data from your solar setup and see if there’s a difference. Also, I live in the Southwest and added your webpage to an email message I have for stuff like this, so I’m interested in seeing an equation of yours in power consumption for an indoor portable AC unit ran during the night (or day or both) with the long exhaust hose running from the back of the AC unit to your Maxxfan hole and it pulling air from the inside of the van to atmosphere to help push the hot air from the exhaust hose to atmosphere. I don’t have a choice as to where I can stay for school related purposes and work as well as van dwelling reasons. A lot of people say units that use that kind of power drain the hell out of your AC, but there’s websites that review units that use low power consumption for indoor units.

    I’ll never get a window unit. I’ve read reviews about them that say that they’re nowhere near as efficient as the portable indoor ones you plug to a wall and mount the exhaust hose to the window. I work as a CNA at a nursing skill facility and the majority of patients at my unit, in their rooms, have portable AC units with the 4 wheels and the hose going out the window with some stuff surrounding the open space around the hose so stuff doesn’t come in.

    • Challenge REJECTED! Sounds awful 😛 We don’t like hot temps, so we stay north in summer!

      You would need a massive battery bank to run an AC, that being said it’s probably possible.


  20. I did not realize that there was so much to take into consideration when looking at the electrical systems of an RV. However, I must admit that I am especially surprised to learn that solar panels can very easily added to them. Of course, I imagine that you would need some kind of electrician to handle the rewiring in order to hook them up.

  21. Hey thanks for an awesome electrical write up! Can’t tell ya how many times I’ve been here while is study up electric stuff… My question is, how did you wire your b2b, is it connected to the ccp provided by ford? or did you connect it to the alternator?

  22. Your postings are very much on point for us We hope to be chasing snow et al. I had a couple of questions.

    1) i was initially planning to go with aux alternator to quickly charge lithium house batteries. esp. in cold cloudy areas. After reading your plans I am rethinking my plans. Does high idling charge your house battery, or do you have to drive ? if so how long? I assume this would an issue in sustained cloudy weather
    2) i believe i read your transit is a 250. How do you feel about that decision (re 250 v 350).

    • Hi!

      1) We drive. The battery will charge fast up to approx. 85-90%, then the last 10-15% is slow (because the smart charger switch to absorption phase). So it’s hard to reach 100%, you have to drive a few hours.
      2) We’re almost at GVWR (we’re at 8800lbs), so 250 is OK but 350 would be better. The problem with the 350 is I believe there is a sway bar and that reduces the ground clearance…


  23. Thanks for your helpful diagram! I was wondering what MPPT charge controller you would recommend for an AGM battery bank of 700 Ah (two 350 Ah batteries wired in parallel at 12V) and 600 Watt of solar (two 300 Watt panels wired in parallel at 12V)?

  24. Hi Antoine! I bought the plans and cannot say how helpful your information has been — I don’t know what I would have done without it! I do have a quick question — you mention that the size of the terminal fuse and the size of the wires connecting the battery to the main switch, bus bars, etc. should be driven by the size of the inverter since that is typically the largest load. However, my inverter is tiny – 300W – and the manual recommends a 40A fuse and 8AWG wire. Given that, in my case it seems like the size of the terminal fuse and those wires should actually be driven by the B2B charger (I got the same one you have – so a 70A fuse and AWG 4). Would you agree?

    Seriously thanks again. This resource is invaluable.

    • Hi, glad the website is helping 🙂
      I would use the “no inverter” scenario (as noted on the diagram): 150A fuse, AWG 4. So when the B2B + Solar are charging simultaneously, the 70A fuse doesn’t blow.


  25. I see in your most recent diagram that there are no “ground” connections to the vehicle. I’m aware there is no true earth ground when connecting to a chassis. The negatives on the battery and the inverter are simply connected to the negative bus bar, does this represent the extent of the grounding in your diagrammed system?

  26. Hi Antoine, thanks for all the great advice. The Sterling B2B only has one spot for a negative cable, so how do I connect it to the alternator ( the ground between the front seats) and at the same time to the negative bus bar?
    Thanks much

  27. Is there a reason you don’t have a breaker on the positive wire coming into your inverter?

    You have a breaker/fuse between the positive bus bar and all the other components, so I was wondering your logic behind that.

    Thanks so much, this has been a MASSIVE help!


    • The fuse at the battery positive pole is driven by the inverter size; if there’s a failure with the inverter, that fuse will blow.

      We install smaller breaker (or fuse) for others appliances because they “need to blow” at smaller amp. (for example 70 amp for the B2B charger)

      Hope that make sense!

  28. Antoine, I recently came upon your excellent site and at the exact moment I am beginning to add the electrics to my custom camper project. I have bought your electrical schematics and purchased thru Amazon most of the items on your shopping list. One thing is unclear to me: you specify several breakers ranging from 40 to 70 amps. However I don’t see a breaker box or any suggestion about mounting or employing those breakers. Can you give me some direction here? Thanks very much. I admire the choices you and Isabelle have made and the way you are realizing your dreams!

  29. I’m back!!! Things are getting serious over here.

    I initially bought 2 – 350ah batteries. I was planning on putting 540 watts of solar on the roof, but then after researching more, it appeared that I would need an extra panel or more like 700 watts of solar to adequately charge those batteries. FYI I also have a blue seas ACR, and Victron MPPT. I’m a traveling cinematographer and I guestimated I would use 120AH on a heavy work/shoot day. I want to hear your opinion on that number as its almost double yours, and probably very high. I have all the same appliances plus about 40 feet more of LED strips, a 2000 watt inverter/charger, a microwave (would use sparingly – less than 3 minutes a day), and my camera batteries (http://www.red.com/store/products/red-brick-153wh) which are each 153wh/10.4 ah, and charge at 4 amps. So if I’ve done my math correctly to charge 1 of these batteries it will take 3 hours x 44 ahs = 130 AH + my 120AH use – 250AH. I’m not sure if I’m calculating that correctly though. charger (http://docs.red.com.s3.amazonaws.com/955-0038/Power%20Operation%20Guide/Content/6_Chargers/RED_BRICK_Charger.htm)

    The issue is that I’m installing a sailboat hatch in the rear and don’t have the space to put 4 panels so here is my question.

    Option 1: Stay with 3 panels totaling 540 watts and keep both batteries for a bank of 700AH. The bank should never get below 60% SOC

    Option 1: Stay with 3 Panels totaling 540 watts and return one of the 350AH batteries. This would balance out the system and potentially save me some money, except I think after shipping the battery back (160 pounds) I would only save a few 100 dollars max. On a heavy work day with camera charging, I’d be at 40% SOC.

    Option 3: ditch the rear hatch and add another panel to get 700 watts. Don’t really want to go here.

    • Hi Matt,
      First be aware that those LED strips draw a lot of current! We have a 10 feet strip in the garage and it draw roughly 2 amps when on. So 40 feet will draw quite a lot. A few Light pucks draw much less.

      If one battery has 10.4Ah capacity, then it will take about 10.4Ah to charge (OK a little more to account for some loss, so more like 15Ah). So charging a battery doesn’t draw much current, but your computer setup might draw more.

      Option 1 (driving a little will speed-up the charge) or option 2 would be OK, but 700Ah seems like a LOT of battery bank…

      Good luck!

  30. Hey guys, one quick follow up. On your materials list, you’ve linked to the Blue Seas bus bar 150 amp 4 stud with cover, but in the interactive diagram, it’s a 250 amp 6 stud no cover. Any reason to go with the 250 amp with more studs for positive and negative (that’s a difference of about $50)? Bear in mind that I don’t have a Samlex battery charger and I have a 2000w inverter, but all other aspects of my build follow your design exactly.

  31. Hi guys, thanks so much for all the info. It has been indispensable in my own build out. I’ve just donated to get the PDF because I have been planning an electrical system pretty much exactly the same. I’m using your affiliate links to do a major purchase but I am wondering about a few finer details.

    1. The solar leads in your diagram start as 12 AWG and then move to 10. I am assuming this is because you wired them in parallel. If I plan to wire two GS 180W in series, do you know if I can I still use the 15ft 10AWG Amazon product you recommend?

    2. Did you purchase all of your wire from amazon? I can see buying two 100ft spools of the marine duplex for most 12V loads (one 10 AWG and one 14AWG) to save money, but where did you source your single lengths of larger wire (00, 6, 8).

    3. I see you recommend buying various types of crimp connectors. I know that I would need quite a few ring-style connectors, but what are the butt and “Nylon Disconnect” types of connections used for? How many would you say are necessary?

    4. Do you have any AC outlets in the van coming from the inverter? If so, how did you wire the outlets up from the 3 prong connections in the back of the inverter?


    • 1. The extension we recommend is 8AWG; you can use that for sure!
      2. We went to our local shop, it’s called Battery Expert (it’s in Canada, not sure it that exists in the States). You could probably ask in Auto Parts shop and they will direct you to a local shop.
      3. You’ll need butt connectors for permanent connections (light dimmer, to extend a wire too short (shit happens), etc… the quick disconnects are used to connect to the 12V outlet, light switch, water pump (or you could use butt for a permanent connection). Best advice is have a bunch of them of different size; it SUCKS having to stop everything because you don’t have it handy…
      4. We have one AC outlet. We used a heavy-gauge (don’t know the exact diameter) extension cord that we cut. But any triplex wire should be OK (I think they have some at Home Depot or Lowes).

      Hope that helps, good luck!