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!
- PART A: THEORY
- 1- What Do We Expect From Our Electrical System?
- 2- Power Consumption
- 3- Battery Bank
- 4- Charge Sources
- 5- System Monitor
- 6- Battery Bank Sizing
- 7- Electrical Wire
- 8- Fuses and Breakers
- 9- Loads
- 10- Short Term and Long Term Storage
- 11- Our Electrical System
- PART B: YOUR TURN TO SHINE!
- Customization Wizard
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PART A: THEORY
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.
|Predicted Daily Power Consumption|
|Load||Description||Measured Instantaneous Consumption|
|Calculation Assumptions||Calculation||Daily Consumption (Ah)|
|Fridge||Novakool R5810||4.0A||24h per day @ 35% duty cycle||4.0A * 35%*24h=||34Ah|
|Lights||3W LED||1.3A (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@10||24h per day @ 3 average||0.5A*24h=||12Ah|
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…
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.
|Load||Description||Measured Instantaneous Consumption (A)||Calculation Assumptions||Calculation||Daily Consumption (Ah)|
|Fridge||Novakool R5810||4.0A||24h per day @ 20% duty cycle||4.0A * 20%*24h=||20Ah|
|Lights||3W LED||1.3A (total 10 lights @ 100% intensity)||8h per day @ 70% intensity||1.3A*70%*8h=||7Ah|
(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@10||12h per day @ 2 average||0.4A*12h=||4Ah|
|Air Heater||Webasto Air Top 2000 STC||Guesstimate…||20Ah|
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.
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:
|Depth of Discharge |
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).
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 :
- 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
- 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!)
- 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
- Voltage is doubled (V)
- Same capacity (Ah)
- For example two 200Ah 6V batteries wired in series= 200Ah 12V
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
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:
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:
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:
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:
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.
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:
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.
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 calculation. This 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.
PWM or MPPT?
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!!
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:
- 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 ($$).
- It’s plug-and-forget. The B2B will automatically activate/deactivate when driving to keep the house battery topped up.
- 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).
- Simple and compact
- 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.
- Inadequate for lithium LiFePO4 batteries.
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:
- Charge the house battery from a 120V source by providing a multi-stage charging profile adapted to the battery type (Gel, AGM, etc).
- 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.
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…
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…
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!
We also considered:
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
The inputs are:
- Nominal Circuit Voltage (hint: it’s 12V)
- Average Current (it’s normally written in the owner manual of the load)
- 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)
- Allowable Voltage Drop % (critical VS non-critical loads, see section 7.1.2)
The outputs are:
- Recommended wire diameter
- Maximum current capacity of the wire (for reference)
Let’s select the correct wire diameter for the Maxxair Fan.
What we know:
- We measured that the fan pulls 2.8 amps at maximum speed (faroutride.com/maxxfan-review/#Specifications).
- The manual recommend a 5 amps fuse.
- The length of the duplex wire from the fuse box to the fan is: 16 feet
We head to circuitwizard.bluesea.com and enter the following inputs:
- 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:
- 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:
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:
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.
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.
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:
*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.
Quality tools = safe and durable electrical system. Do not use pliers as you will get poor connections = safety and reliability issues.
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:
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:
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
9.1- 12V Loads
These are all the 12V loads that we installed:
LED Light (Dimmable)
Installation and wiring: faroutride.com/led
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):
Shurflo Revolution Water Pump, 3 GPM
Novakool R5810 Fridge 12V
Webasto Air Top 2000 STC Gasoline Heater
Propex HS2000 Propane Heater
Sirocco ii Gimbal Fan, 12V
9.2- 120V Loads
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:
Or instead of charging your phone, cameras, etc., using a 120V charger, use a 12V charger:
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.
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!
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.
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:
- easier to understand (see our new Interactive Diagram AND new tutorial “From Blank Page to Wiring Diagram in 15 Steps”)
- easier to install (more intuitive design and less components to install)
- easier to use (Plug-and-forget, monitoring via Android or iPhone)
- 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.