DIY Van Electrical Guide: Build Your Knowledge


DIY Van Electrical Guide: Build Your Knowledge

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 safe, reliable and to work from the first time; trial-and-error is not acceptable here.

After two years on the road full time, 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, you are probably looking for some guidance...


Disclosure: This post contains affiliate links, which means that if you click a product link and buy anything from the merchant (Amazon, eBay, etc.) we will receive a commission fee. The price you pay remains the same, affiliate link or not.


1- Campervan Electrical System in a Nutshell

In its simplest form, a campervan electrical system isn’t really complicated. It includes a battery bank, loads and charge sources:

Modern “off-the-grid” vans normally charge with solar power, alternator, shore power and can power 12V DC & 120V AC loads:

Camper Van Electrical System Nutshell

Makes sense so far, doesn’t it? Here is how all components work together to make a typical electrical system:

Our Wiring Diagram:

hover your cursor (desktop) or tap (phone/tablet) on each component to learn more.

Here it is in action:

Our Items List:

1- Inverter:
#ItemDescriptionQuantityView on Amazon
11000W InverterSamlex PST-1000-12 PST Pure Sine1View
2Remote Control for InverterSamlex RC-15A for 600W/1000W Inverter1View
3Cable, 2 AWG, 5 ft Black + 5 ft RedWindyNation1View
4Lugs, 2 AWG Cable, 5/16″ RingConnect to Terminal Fuse Block and Bus Bar (Pack of 2)1View
5Terminal Fuse, 175ABlue Sea (To protect inverter’s cable)1View
6Terminal Fuse BlockBlue Sea (Connects directly on the Bus Bar. Holds the Terminal Fuse)1View
2- Battery:
1LiFePO4 200 AhBattle Born LiFePO4 100 Ah
22/0 Cable in 5/16 lugs, 1 feet Red + 1 feet BlackWindy Nation Copper
3- Solar:
1350W SolarNewPowa 175W Mono Panel2View
2Extension Cables, 8 AWG, 15 ft Red + 15 ft BlackWith MC4 Connectors1View
3Double Cable Entry GlandFor 8 AWG or 10 AWG Cable1View
440A Breaker/Switch, Surface MountBetween Panels and MPPT Charger1View
5MPPT Solar ChargerVictron 100|30 SmartSolar MPPT1View
640A Breaker/Switch, Surface MountBetween MPPT Charger & Battery1View
7Heat Shrink Terminal Ring, 8 AWG Cable, 5/16″ RingConnect to Bus Bar (Pack of 3)1View
8Heat Shrink Terminal Ring, 8 AWG Cable, 1/4″ RingConnect to Breakers (Pack of 3)2View
4- Alternator:
160A Battery-to-Battery Charger (B2B)Sterling Power BB12601View
2100A Breaker/Switch, Surface MountBlue Sea 285-Series2View
3Cable, 4 AWG, 15 ft Black + 15ft RedWindyNation1View
4Lugs, 4 AWG Cable, 5/16″ RingConnect to Bus Bar (Pack of 2)1View
5Lugs, 4 AWG Cable, 1/4″ RingConnect to Breakers (Pack of 2)2View
5- Shore:
150A ChargerSamlex SEC-1250UL 12V1View
260A Breaker/Switch, Surface MountBetween Charger and Bus Bar1View
3Cable, 8 AWG, 5 ft Black + 5 ft RedWindyNation1View
4Heat Shrink Terminal Ring, 8 AWG Cable, 1/4 RingConnect to Breaker (Pack of 3)1View
5Heat Shrink Terminal Ring, 8 AWG Cable, 5/16″ RingConnect to Bus Bar (Pack of 3)1View
6- Main:
1Terminal Fuse, 250ABlue Sea (Catastrophic Fail Safe)1View
2Terminal Fuse BlockBlue Sea (Connects directly to battery post. Holds the Terminal Fuse)1View
3System SwitchBlue Sea (Main System Switch)1View
4Bus Bar (250A, 4 studs)Blue Sea2View
5Cover for Bus Bar (for 250A 4 studs)Protect the Bus Bar2View
640A Breaker/Switch, Surface MountBetween Fuse Block and Bus Bar1View
7Fuse Block (12 circuits)Blue Sea (12V Distribution Panel)1View
8Fuses KitAssorted Fuses (2A 3A 5A 7.5A 10A 15A 20A 25A 30A 35A)1View
9Battery MonitorVictron BMV-712 with BlueTooth1View
10Cable, 2/0, 5 ft Black + 5 ft RedBetween battery and Bus Bar1View
11Lugs, 2/0 Cable, 3/8″ RingConnect to System Switch and Shunt (Pack of 5)1View
12Lugs, 2/0 Cable, 5/16″ RingConnect to Bus Bar, Terminal Fuse Block and Battery (Pack of 5)1View
13Cable, 8 AWG, 5 ft Black + 5 ft RedBetween Bus Bar and Fuse Block1View
14Heat Shrink Terminal Ring, 8 AWG Cable, #10 RingConnect to Fuse Block (Pack of 3)1View
15Heat Shrink Terminal Ring, 8 AWG Cable, 1/4″ RingConnect to Breaker (Pack of 3)1View
16Heat Shrink Terminal Ring, 8 AWG Cable, 5/16″ RingConnect to Bus Bar (Pack of 3)1View
17Heat Shrink Tubing Kit (with adhesive)To protect lug after crimping1View
7- Hardware:
112 AWG Black/Red Duplex Cable (12/2), Ancor Marine Grade100 feet1View
214 AWG Black/Red Duplex Cable (14/2), Ancor Marine Grade100 feet1View
3Heat Shrink Terminal Ring, 12 AWG Cable, #8 RingTo connect to Fuse Block (25 Pack)1View
4Heat Shrink Terminal Ring, 14 AWG Cable, #8 RingTo connect to Fuse Block (25 Pack)1View
5Heat Shrink Butt Connector, Ancor MarineTo connect to Loads (75 Pack Kit)1View
6Heat Shrink Disconnect, 10-12 AWG Cable, 1/4″ Tab, Female
To connect to certain loads (i.e. 12V Sockets) , to make “removable” connections (i.e. Fridge, LEDs) and to connect cable of different gauge together (i.e. LED Dimmer) (25 Pack)
7Heat Shrink Disconnect, 10-12 AWG Cable, 1/4″ Tab, Male1View
8Heat Shrink Disconnect, 14-16 AWG Cable, 1/4″ Tab, Female1View
9Heat Shrink Disconnect, 14-16 AWG Cable, 1/4″ Tab, Male1View
10Heat Shrink Disconnect, 18-22 AWG Cable, 1/4″ Tab, Male1View
113M Scotchlok Quick Splice with Gel (14 AWG stranded)We used that to parallel our LED lights (25 Pack)1View
12Split Loom Tubing, 3/8″ diameter 20 feetTo protect wire bundles1View
13Split Loom Tubing, 1/2″ diameter 20 feetTo protect wire bundles1View
14Split Loom Tubing, 3/4″ diameter 20 feetTo protect wire bundles1View
15Nylon Cable Clamps KitTo secure cable/split-loom to wood1View
16Zip Tie Mount with AdhesiveTo secure cable/split-loom to metal1View
17Nylon Zip Ties KitTo secure cable/split-loom1View
18Rubber Grommet KitTo protect wire from sharp edge (going through metal hole)1View
8- 12V Loads:
1Maxxair 6200K Roof FanSee our Installation or Review
2LED Ceiling LightsSee our Installation and Review
3Dimmer for LED (PWM), 12V, SliderTo control intensity of LED
4Blue Sea 12V Socket
5Shurflo Revolution Water Pump, 3 GPMSee our Installation
6ON/OFF Switch for Water Pump
7Webasto Air Top 2000 STC Gasoline HeaterSee our Installation article1eBay
8Propex HS2000 Propane HeaterSee our Installation article1eBay
9Novakool R5810 Fridge, 12V only5.8 cubic feet1Novakool
10Sirocco ii Gimbal Fan, 12VSee our Review
11Nature’s Head Composting ToiletSee our Installation or Review
12Propane Solenoid Shutoff ValveSee our Propane System Guide1eBay
13ON/OFF Switch for Propane SolenoidSee our Propane System

Well, that escalated quickly… If you can’t “read” the wiring diagram above, don’t give up just yet. Keep reading to build your knowledge and work your way up! Be patient, sleep on it; it might takes multiple reads before it all starts to make sense…

2- Battery Bank

Because power from the charge sources is not available at all time, a battery bank is mandatory in every van electrical system. The role of the battery bank is to accumulate energy from the charge sources, store it, then release it to the loads when needed. 

2.1- Battery Types

A battery stores energy under chemical form, then convert it to electrical energy when needed. There are many battery types (chemistry) available and each have their pros/cons:

Flooded Lead-Acid
Lithium (LiFePO4)

Unless your budget is very critical, we don’t really recommend flooded lead-acid or GEL (because of the maintenance aspect). That brings us to our next topic:

Choosing between AGM or Lithium (LiFePO4) Battery in 2019

When we built our van in 2016 (researching and designing during 2015), AGM was the obvious choice because  it was a tried-and-true option (good performances, safe & reliable). Lithium (LiFePO4) batteries were a relatively new thing (in the van/RV world) and we were concerned about reliability & safety (and cost!). Technology advance so let’s see if, 4 years later, our concerns have been addressed:

1- B.M.S. (Battery Management System)

There are a few scenarios where it could be unsafe to operate a LiFePO4 battery:

  1. Temperature too low / too high;
  2. Voltage too high;
  3. Current too high.

To mitigate these scenarios companies like Battle Born Batteries, Trojan, Relion, Victron, now include BMS (Battery Management System) built-in their batteries. The BMS is in charge of watching if parameters (temperature, voltage, current) are within safe range. For example, the BMS will prevent charging the battery if the temperature is too low; it will also regulate the amount of power you can take out of the battery. It makes using a Lithium battery safe.

2- Lithium batteries can't be charged below 32F/0°C (more or less)

That’s quite an issue for us, knowing we use our van for skiing all winter ( An AGM battery do better in that department, but still performs better around room temperature; that’s the main reason why we installed our AGM battery inside the van. Because we live full-time in our van, we never let the interior freeze (because food/liquid/comfort) so that solves the issue for us!

Note 1: While LiFePO4 cannot be charged below freezing temperatures, they can still be discharged. So it would be possible to install a 12V heat mat to prevent the battery from freezing…

Note 2: In fact, some brand of Lithium batteries can be charge below 32F/0°C, but at a slower rate. Check your battery specification sheet!

3- AGM vs Lithium Comparison

Let’s compare our actual Rolls AGM battery (210Ah) to a BattleBorn LiFePO4 battery bank (100Ah). What really matter here is the “Actual Capacity Available” (remember that ideally an AGM should not be discharged below 50% of its capacity); so that’s why we compare a 210 AGM to a 100Ah Lithium:

  210Ah AGM 100Ah LITHIUM
WEIGHT 133.5 lbs 31 lbs
UPFRONT COST $650 $950
COST PER CYCLE $0.54 $0.32
LENGTH 21" 12.75"
WIDTH 8.5" 6.875"
HEIGHT 9.5" 9"
*Assuming a D.O.D. (Depth-of-discharge) of 50% for AGM, 100% for LiFePO4.

For full-time Vanlife (1 full cycle daily), it means an AGM will cost roughly $200 per year to operate and will last 3.5 years; while a Lithium will cost roughly $120 per year to operate and will last 8 years.

Soooo, AGM or Lithium?

If we had to start over (in 2019), we would go for Lithium (LiFePO4). Oh wait… as of June 2019 we just upgraded to Battle Born Lithium batteries (2 x 100Ah)! We LOVE staying up-to-date with technology and we enjoy testing products, so we made the leap 🙂 Our first impressions:

  • These things are crazy light weight!
  • They reach 100% SOC much faster than the AGM (absorption phase in AGM occurs quite slowly), and keep in mind we made no change to our solar & alternator charging. That means more power, faster. Nice.
  • Since we have two batteries in parallel, we can charge up to 100A if we upgrade our b2b charger (right now we have a 60A b2b charger); that could be nice for winter.
  • So far so good, highly recommended!*

*Note: We would NOT go for Lithium if our battery bank was installed outside the van (too cold during skiing season).

Replace Rolls AGM with Battle Born Batteries Lithium
New Battle Born Batteries ready for installation!
Renogy 50/100/170Ah Lithium (LiFePO4) 12V Battery
(2000 cycles life, 100A COntinuous Discharge Current)
Battle Born Batteries 100Ah Lithium (LiFePO4) 12V
Trojan 110Ah Lithium (LiFePO4) 12V
(4000 cycles life, 110A continuous discharge current)

Quick interruption: Our Opinion About Product Quality

"You get what you pay for"

What differentiate the “cheap” products (unbranded, very cheap products on Amazon & eBay) from the “Budget” products:

We took our chance with cheap products on non-critical components (radio unit, inclinometer, electrical connectors when we ran out of the good ones –> we replaced them with good ones afterwards!) and the result is always the same: product doesn’t last long, it’s buggy and has to be replaced soon enough. Even if the low initial cost is very appealing, we will NEVER recommend a cheap product for the electrical system (or else); we’re not rich enough to constantly replace our stuff.


This is our entry-level. To save cost, budget products typically don’t use the best internal components and consequently don’t show the best performance and durability. We recommend products within that category if budget is your priority.

Brands that fall into that category:

This is our mid-level and most components in our van stand within that range. We don’t mind paying more initially if the product delivers good performances and last in time. We think it’s the best bang for the buck.

Brands that fall into that category:

This is the “pro-level”. Products within that range deliver the ultimate performances. It’s pricey but for critical components of our electrical system, there’s no price for peace of mind.

Brands that fall into that category:
OK we're done, thanks for listening!

2.2- Specifications

Not all batteries are made equal! A cheap battery won’t be able to give as much current as a high-quality battery… it is YOUR responsibility to make sure you’re not going overboard, so read the spec sheet! Any reputable brand should publish one for each of its product. Cheap products often don’t publish spec sheet; that a good enough reason not-to buy their products!

Here is  an example of how a spec sheet should be (click the image to view the pdf):

Relion Specification Sheet (1 of 2)

Information is clearly shown, it’s straight-to-the-point, there is no marketing sales pitch… well done Relion! More examples: Trojan, BattleBorn (they really need to step up their game…), Rolls.

Information to look for:

2.3- 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.

For example, adding two batteries of 12V/100Ah (50A charge rate / 100A discharge rate) in parallel results in a battery bank of 12V/200Ah (100A charge rate / 200A discharge rate).

photo credit:

For example, adding two batteries of 6V/200Ah in series results in a battery bank of 12V/200Ah.

photo credit:

2.4- Charge Profile

Charging a battery is NOT like filling a car with gas…

  • With a car, bringing the fuel gauge up to 100% is all that matters. Then, maintain your car periodically (oil change) and it’ll be running smooth for a long time 🙂
  • With a battery, how you bring it up to 100% really matters: you are filling it and doing the maintenance simultaneously!

An adequate charge cycle goes through multiple stages; each stage has specific current/voltage parameters. The combination of these stages is called the charge profile. Different battery chemistry (AGM, Lithium, etc) and different brand (Rolls, Trojan, BattleBorn, etc) requires different charge profile.  Why you should care about charge profile:

Lead-Acid (Flooded, Gel, AGM)
Typical Charge Profile
Stage 1: BULK

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 results in a large current; in other words most of the energy is transferred during that stage. 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…


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. That’s why a proper absorption stage is so important! It prevents hard deposits (sulfuration) and therefore prevents loss of total capacity memory.

Stage 3: FLOAT

The float stage prevent self-discharge and can be maintained indefinitely.

Lithium (LiFePO4)
Typical Charge Profile

Lithium batteries don’t suffer from sulfuration, so charging with the wrong charge profile is not as bad as with lead-acid batteries. Charging with the wrong profile could prevent reaching 100% charge, but that won’t hurt the battery in the long term. Good to know: Most Lithium batteries are OK to charge with an AGM profile!

Stage 1: BULK

The bulk stage is terminated when the absorption voltage is reached (around 14.4V).


The absorption stage is terminated when current decrease below approximately 5% of the battery capacity (approx. 5A for a 100Ah battery).

Stage 3: FLOAT

Consult the specification sheet of your battery brand/model to find its specific charge profile!

2.5- Discharging Batteries

We’ve just seen how charging a battery impact its life cycle & performance. Discharging a battery has similar implications; let’s see how!


State Of Charge (SOC)

It is defined as “how fully charged” the battery is.

Depth Of Discharge (DOD)

It is defined as “how deep” the battery is discharged. (it’s the opposite of SOC…)


In a typical usage, a battery starts fully charged (100% SOC), then goes down to a certain level (e.g. 80% SOC), back to fully charged (100% SOC). This is defined as a cycle

A cycle is independent of calendar, so there could be multiple cycles per day or one cycle per week… But typically, a campervan/RV battery cycles once per day because of solar power.


The life span of a battery (how long it will last) is mostly defined by the number of cycles… in a similar way that mileage defines the life cycle of cars.

As a battery ages (cycles), it holds less and less energy. Generally, manufacturers consider that a battery has reached its end of life when it cannot hold more than 70% of its initial capacity (i.e. eventually, a 100Ah battery becomes a 70Ah battery).

Charge/Discharge Rate

It is defined as how fast (current) a battery bank is charged/discharged. 

“0.2C Rate” means 20% of the battery bank capacity; “0.5C Rate” means 50% of the battery bank capacity; and so on. For example if the battery bank is comprised of 2 x 100Ah Battle Born Batteries, “0.5C Rate” =0.5 x 200Ah = 100A.

Discharge Current Rate

1- Its Capacity:
Features / Setup / Installation / First Impressions:
(credit: BattleBorn Batteries)

A Lithium battery (black curves) is able to deliver pretty much the same amount of energy regardless of how fast it’s being discharged, as opposed to a lead acid (red curves).

2- Its total life cycle:
Trojan Trillium LiFePO4 Life Cycle
(credit: Trojan)

Discharging a battery more rapidly will reduce its total life cycle (AGM or Lithium).

Depth Of Discharge (D.O.D.)

Trojan Trillium Lithium (LiFePO4):
Rolls AGM:

For full-time Vanlife, a battery will typically sees 365 cycles per year. But keep in mind that while cycle life plays a major role in the life span of the battery, calendar also has an impact as materials (used to chemically store energy) degrade over time. Many factors influence degradation, temperature being one of the most important. 

2.6- Temperature

Generally, batteries perform better near room temperature. For example, take electric cars: their range in cold climate is greatly reduced during winter! That’s another reason why we installed our battery bank inside the van; exterior temperature has less impact on our battery that way.


Charging A Frozen Battery

Lead-ACID (Flooded, Gel, AGM)

First of all, unlike water, a battery will not freeze at 32F (0°C). The freezing temperature of the battery depends on the state of charge. 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


State of Charge 

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)
Lithium (LiFePO4)

We often hear that a lithium battery cannot be charged below 32F (0°C); In fact, some brand of Lithium batteries can be charge below 32F/0°C, but at a slower rate. Check your battery specification sheet!

Take a look at Trojan Trillium LiFePO4 battery for example:


Good to know: the built-in BMS in high-quality batteries will take care of cutting-off the current if temperature gets too low.

Charging A Battery At High Temperature

Charging a battery at high temperature generally affects its cycle life (lifespan). For example, here is Trojan Trillium Lithium Cycle Life VS Temperature:

3- Charge Sources

Now that we understand how to properly charge a battery, let’s see our charge options:

3.1- 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!

3.1.1- In a Nutshell

For example, here is a screenshot from our Victron solar charge controller ( Notice how the voltage/current coming out of the panels are different from the voltage/current going into the battery:

3.1.2- Monocrystalline or Polycrystalline?

Monocrystalline used to be more efficient than polycrystalline, but it’s not so true anymore. The quality of the solar panel (manufacturer) is more important than the type of the panel. Here is a good article if you want to learn more about that: Pros and Cons of Monocrystalline vs Polycrystalline solar panels.

Renogy 100W Solar Panel 12V
Newpowa 175W Solar Panel 12V
Renogy 300W Solar Panel 24V

3.1.3- Combining Multiple Panels

No adapter required.
Parallel adapter required.

Partial shading is not a myth, but unfortunately professional solar installers (or DIYers) seem to ignore that a lot, judging from how solar panels are installed relative to the fans/roof racks… Take the time to read the next section!

3.1.4- Partial Shading

Blocking a single cell from a solar array can completely bring the 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. Typically we see roof racks or fans creating partial shading (this is totally avoidable!):

This panel gives 0% output (assuming it has 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:
photo credit:
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:

Solar Panel Blocked Cell bypass diode
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:

Total Power Without Partial Shading
0 Watts
(57V x 9A)
Total Power With Partial Shading (Series)
0 Watts
(57V x 4.5A)
Total Power With Partial Shading (Parallel)
0 Watts
18V x (9A + 4.5A + 9A)
Conclusion on partial shading

And that explains our roof layout:

Cleaning the solar panels 2

3.1.5- 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:

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.

At last, having several panels with dissimilar orientation has a similar effect as partial shading. If you must have dissimilar orientation, consider connecting your panels in parallel.

3.1.6- Solar Charge Controller


MPPT are more efficient than PWM in cold temperature, partially sunny day and if the voltage of your solar panels is 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 MPPT!!

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 🙂

Choosing the size of the Charge Controller

All Victron solar charge controllers are denoted by MPPT XXX | XX:


Choosing the size of the charge controller is also covered in our “Victron Review” above 🙂

3.2- Alternator

When driving, the alternator role is to convert mechanical energy (engine) into electrical energy. This electrical energy is delivered to all the vehicle’s electrical components (lights, radio, etc.) and to charge the starter battery as well. It’s possible to “borrow” electrical energy from the alternator to charge the house battery…

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.
3.2.1- Isolator / Automatic Charging Relay (ACR)

Isolator and ACR combine the starter battery and the house battery together during the charge and disconnect them during discharge. They’re good at “bulk-charging” the house battery, but they’re not so good at finishing the charge properly because the house battery is not getting an adequate charge profile. That’s not great for the cycle-life of lead-acid batteries (flooded, gel, AGM) and they tend to overwork alternators, so we prefer the B2B option.

Blue Sea ACR with Manual Control (up to 500 amps alternator).
Lithium Battery Isolation Manager (Up to 225A)
To prevent overworking the alternator, this device cycles 15 minutes "ON" then 20 minutes "OFF".
3.2.2- Battery to Battery Charger (a.k.a. "B2B" or "DC to DC")

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, LifePO4, etc). That’s important, because it will keep your house battery healthy and maximize its lifecycle (especially for lead-acid batteries “flooded, gel or AGM”).
  2. It acts as current limiter to prevent overworking the alternator (choose between various models: 30A, 60A or 120A).
  3. Easier to install: no need to wire to the vehicle ignition.
  4. It’s plug-and-forget: the B2B will automatically activate/deactivate when driving to keep the house battery topped up.
Renogy DC to DC charger
(20A or 40A)
(20A or 80A with Smartpass. Also acts as solar charge controller)
Sterling Power Pro Batt Ultra
(30A, 60A or 120A)
3.2.3- Accessing Battery Power (alternator 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 variant: SVE Bulletin Q-226 (.pdf)

3.2.4- Accessing Battery Power (alternator power) on the Mercedes Sprinter
Sprinter Power Tapping Option 2 (page 1)
Sprinter Power Tapping Option 2 (page 2)


3.3- 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, solar is VERY weak in winter and it takes a LONG drive to complete a full charge so it’s sometimes required to plug in for the night.
3.3.1- 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.
Samlex 12V Smart Battery Charger / Converter.
3.3.2- 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…

Renogy Pure Sine Inverter/Charger (2000W).
Victron MultiPlus Compact Pure Sine Inverter/Charger (2000W).
Magnum Pure Sine Inverter/Charger (2000W).

4- 12V DC Loads

Installing appliances and devices that work on 12V DC is efficient, because there’s always a loss when converting to 120V AC. Here are all the 12V loads we’re running in our van:

Shurflo Revolution Water Pump, 3 GPM
Novakool R5810 12V Compressor Fridge
Webasto Air Top 2000 STC Gasoline Heater
Propex HS2000 Propane Heater
Sirocco II Gimbal Fan
Propane Solenoid Shut Off Valve

5- 120V AC 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 try to avoid it when possible. For example, get a 12V power adapter to power your laptop, phone, camera, etc:

Laptop Car Charger
(make sure it's compatible with your laptop)
Phone Car 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.

Kill A Watt

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

Modified VS Pure Sine Inverter

There are two types of inverter: modified and pure sine inverter. This short but comprehensive article makes a good job at explaining the differences and there’s a list of appliances that might not work with a modified sine wave inverter:

In a nutshell:

Modified Sine Wave

In a modified sine wave, the voltage rises and falls abruptly, the phase angle also changes abruptly and it sits at 0 Volts for some time before changing its polarity:

Pure Sine Wave

In a pure sine wave, the voltage rises and falls smoothly with a smoothly changing phase angle and also changes its polarity instantly when it crosses 0 Volts. 

About Power Rating

Normally inverters are rated for the power they can continuously deliver on the 120V AC side. But remember that because there is an efficiency loss (around 15%), more power is draw on the 12V DC side (battery). For example, a 1800W inverter will draw more than 1800W on the DC side:


We had really good luck with our Samlex pure sine wave inverter (and our Samlex charger as well!) and highly recommend it. It’s been running great since 2016. 

Renogy Pure Sine Inverter
Xantrex Pro Power Inverter 1000W 1800W
Xantrex Prowatt SW Pure Sine Inverter
Samlex Pure Sine Power Inverter

High Current!

Remember that inverters draw HUUUUGE amount of current (i.e. a 3000W inverter draws over 300 amps!) and are the most “dangerous” component of your electrical system. Make sure that your connections are p-e-r-f-e-c-t (and won’t loose over time/vibration) or else, enjoy the fireworks. In doubt, ask a professional to install/verify it for you.

6- Battery and System Monitoring

6.1- Battery Monitor

A battery 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 battery 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. We tested and recommend the Victron BMV-712 because it’s a modern, high-quality monitor:

Victron BMV-712 System Monitor

The Victron BMV-712 has bluetooth inside and current status (and historical data) can be displayed on an iPhone or Android phone!

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 🙂

6.2- System Monitor

The Simarine Pico system monitor enables to monitor much more than just the battery. It can also monitor the consumers (current consumption of individual loads), tank levels (fresh, grey, Nature’s Head, propane, etc), temperatures (interior, exterior, fridge, etc) and pitch/roll (inclinometer to park level). We installed it recently and we’re blown away by the quality of that thing! Not to mention it is VERY sexy and looks much better in our van than any other monitor 🙂

Simarine Pico System Monitor: Installation, Setup and Review

7- Electrical Wiring

7.1- Wire Diameter (AWG)

Choosing the correct wire size (AWG) is essential for SAFETY (fire hazard due to ampacity) and PERFORMANCE (intermittent problems due to voltage drop) of your electrical system.

7.1.1- Ampacity

The ampacity is the maximum current that a wire can carry continuously without exceeding its temperature rating. For example: if a wire ampacity is 60A (AWG 10) and there is a continuous current flow of 61A, the wire will overheat and the insulation could melt, creating a fire hazard. An overcurrent protection device (fuse/breaker) prevents going over the ampacity rating of the wire (the fuse/breaker size should always be smaller than the wire ampacity).

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). That being said, we personally like to use around 3% voltage drop for everything in our van.

7.1.3- Selecting the correct wire diameter

Now, really, how do you selected the correct wire diameter? It can be done manually by following ABYC standards (ABYC E-09 1990 pdf), but to make your life easier we designed this WIRE GAUGE CALCULATOR:


Wire Gauge (AWG) Calculator