The electrical system was without a doubt the most daunting task of our DIY camper van conversion. Our goal was to design and build an off-the-grid electrical system that’s safe, reliable, simple, and intuitive (yet no compromises on functionality). After over 4 years of full-time VanLife, we’re happy to report that our system is working flawlessly, nice!
Designing and building an electrical system isn’t really straightforward, there are so many concepts to grasp: solar power, alternator charging, shore power, 12 volts, 120 volts, inverter, battery bank, etc. But with our background as engineers and full-time vanlifers, we’re in a good position to make this intimidating task within your reach and help you put the pieces together with the following guide!
We’re here to help! Here is how it goes:
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. Van Electrical System In A Nutshell
In its simplest form, a campervan electrical system isn’t really complicated. It consists of a battery bank, loads, and charge sources:
Charge Source
The charge sources are the devices (solar, alternator, shore) that add energy to the battery bank.
Battery Bank
Charge sources are not available at all time! The role of the battery bank is to store energy acquired from the charge sources and release it to the loads when needed. There are typically two battery banks: the factory starter battery to start the engine and power the vehicle’s systems and the auxiliary “house” battery to power all the campervan systems (fridge, lights, fan, etc.).
Loads
The loads are the devices (fan, lights, fridge, etc.) that substract energy from the battery bank.
Modern “off-the-grid” vans typically charge with solar, alternator, and shore, and can power multiple 12V DC loads and 120V AC loads:
Whoa, components quickly add up! That’s why a comprehensive wiring diagram is a must. Indeed, to make a functional electrical system, the components are assembled together in a precise way. Overcurrent devices (fuse, breaker), adequately sized wires, and quality components make for a safe and reliable system. The “master plan”, or “assembly plan” of such a system is called a wiring diagram.
Below are the wiring diagrams we engineered for our needs. The Standard version is optimized for off-the-grid and energy efficiency (that’s the design we implemented in our first build and we are still using to these days). The High-Power version is optimized for high-power devices such as induction cooktop, microwave, etc:
Hover your cursor / click on components to learn more!
Tap on each component to learn more!Don’t worry about making too much sense of this for now… The goal of this guide is to slowly build your knowledge until you fully understand this wiring diagram. So relax, grab a drink, and keep reading. 🙂
2. Electricity for Dummies
This is not an electrician degree we’re doing here, but there is a bare minimum you must be willing to learn 🙂 This is to prevent mistakes, to feel confident about your project, but also to ensure we all speak the same language. Don’t worry, we’ll only cover the basics here, let’s go!
After reading this section, you will be able to:
- Understand the basic concepts and terminology related to electricity.
2.1. Ohm’s Law
Electricity is the movement (flow) of electrons through a conductor. The electrons always have to overcome a certain resistance when flowing through a conductor:
Potential (Voltage)
Volt (V)
Difference in charge between two points. It is the force that enables current to flow through a conductor.
Resistance
Ohm (Ω)
Opposition to current flow.
Current
Amp (A)
Flow of electrons through a conductor.
Thanks to Ohm’s law, we can calculate how much current flows through a conductor:
Ohm’s Law
Current (A) = Potential (V) / Resistance (Ω)
Ohm’s law is kind of a big deal: it lays the foundation for most calculations in electricity. And as far as we’re concerned, it allows us determine wire/cable size (cross section diameter) and to select the appropriate overcurrent device size (fuse/breaker), but we’ll get to that later.
2.2. Analogy With Water
Electricity can be a bit abstract, so we like to think of it as water (of course that’s not technically accurate, but it’s good enough to make sense of all of this!):
| ELECTRICITY | WATER | |
|---|---|---|
| Capacity | Total amount of energy available (Ah) | Total amount of water available (gal) |
| Potential | Difference in charge between positive and negative (V) | Difference in height between top and bottom (ft) |
| Flow | Rate at which energy is substracted from the battery (A) | Rate at which water is substracted from the tank (gpm) |
Capacity
AMP HOUR (A⋅h)
Amount of energy stored in a battery.
The unit of capacity is Ah (1 amp x 1 hour), not A/h (amp per hour)! It is the amount of energy resulting by allowing 1 amp of current for 1 hour. For example, a battery that has 100Ah capacity can deliver any of this:
- 100A current for 1 hour.
- 50A current for 2 hours.
- 20A current for 5 hours.
- And so on!
Example:
| ELECTRICITY | WATER | |
|---|---|---|
| Initial Capacity | 200 Ah | 20 gal |
| Flow | 4 A | 2 gpm |
| Duration | 8 h | 5 min |
| Consumption (Flow x Duration) | 32 Ah (4A x 8h) | 10 gal (2gpm x 5min) |
| Remaining capacity (Capacity – Consumption) | 168 Ah (200Ah – 32Ah) | 10 gal (20gal – 10gal) |
2.3. POWER
Power (watts, W) is the rate at which the electrical energy is absorbed (or generated). And most of the time, the consumption of a load is represented in watts (W). However, sometimes, it is defined in amps (A). Both are technically correct and can be linked by the following equation:
Power (W) = Current (A) x Voltage (V)
For example, for a given system where voltage remains the same (12V), it would be accurate to say that a fridge draw 4.4 amps or 52.8 watts. Both are equivalent:
52.8W = 4.4A x 12V
Similarly, for a 12V system, it would be accurate to say that the capacity of a battery is 100 Amp-hour (Ah) or 1200 Watt-hour (Wh):
1200Wh = 100Ah x 12V
To avoid any confusion and for consistency’s sake, we will use the following units throughout this guide:
- Load consumption (DC): Amps (A).
- Load consumption (AC): Watts (W).
- Battery capacity: Amp-hour (Ah).
Speaking of DC and AC. Electricity as we know it, provided in our house, is Alterning Current (AC), also known in North America as 110V/120V. The battery used in a van delivers Direct Current (DC), and is sold as 6V, 12V, 24V, or even 48V batteries. It is possible to use our home appliances (120V) in a van only through a power inverter.
A power inverter plays two roles:
- Convert direct current (DC) from the battery bank to alternating current (AC).
- Step up voltage from 12V to 120V.
Also, it is worth mentioning that the power (W) of a load is independent of voltage change. For example, a 1,500W (120V) hair dryer is still consuming 1,500W on the 12V side. However, the current (A) increases dramatically on the 12V side (125A) compared to the 120V side (12.5A):
1500W = 12.5A x 120V = 125A x 12V
Why should you care? Well, current is critical when sizing the wires. Indeed, a wire carrying 125A must be much thicker than a wire carrying 12.5A. Think of the water analogy: we need a much larger hose to allow a flow of 125 gpm of water, compared to 12.5 gpm… More on this in the Wires & Cables section.
3. Battery Bank
Because energy from the charge sources is not available at all times, 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.
After reading this section, you will be able to:
- Understand the benefits and drawbacks of different battery chemistry types, in order to choose the type that better suits your needs.
- Learn the terminology and understand data sheets, in order to adequately select a battery model.
- Understand how to operate and select a battery (charge/discharge profile, temperature), in order to maximize its life expectancy.
- Understand how to combine batteries (parallel/series), in order to get the desired battery bank characteristics.
3.1. Battery Types
A battery stores energy under chemical form, then converts it to electrical energy when needed. There are many battery types (chemistry) available, and each have their pros/cons:
Flooded Lead-Acid
Pros
- Cheapest of all types.
Cons
- High maintenance (needs to be filled periodically with water and kept in a vented compartment).
gEL-cELL
Pros
- Similar to Flooded lead-acid, but the gel wont spill as easily.
Cons
- See Flooded lead-acid.
- Must be charged at low rate.
AGM
Pros
- Low Maintenance (no need to refill with water, no need to be vented).
- Performs well under most temperature range.
- Can be charged/discharged at higher rate than Flooded Lead-Acid.
Cons
- Much heavier than Lithium.
- Shorter life span than Lithium.
Lithium (lifepo4)
Pros
- Light weight.
- No need to be vented.
- Can be discharged deeper without affecting battery life (meaning a 100Ah Lithium delivers almost twice the energy of a 100Ah AGM or Flooded).
- Can be charged/discharged at higher rate than AGM.
- Low self-discharge (2-3% per month).
- Much more life cycle than any other type (not so expensive in the long run).
Cons
- Higher upfront cost.
- More sensitive than other types, they require a BMS. See below for more info.
Unless you’re on a very tight budget, we don’t really recommend flooded lead-acid or gell-cell (because of the maintenance/venting).
We will therefore put the emphasis on AGM and Lithium for the rest of this guide. In this day and age, Lithium batteries are far more common than AGM. But that doesn’t mean AGM’s are obsolete… Let’s dig a bit deeper!
Lithium/AGM Comparison
AGM batteries should ideally not be discharged below 50%, and for that reason we compare a 100Ah Lithium battery to a 200Ah AGM battery.
| LITHIUM | AGM | |
|---|---|---|
| Capacity | 100Ah | 200Ah |
| Usable Capacity1 | 100Ah | 100Ah |
| Weight | 31 lbs | 130 lbs |
| Dimensions (L x W x H) | 12.76 x 6.86 x 8.95 in | 20.6 x 9.4 x 8.8 in |
| Discharge Temperature Range | -4 to 135F (-20 to 57°C) | -4 to 135F (-20 to 57°C)2 |
| Charge Temperature Range | 25 to 135F (-4 to 57°C) | -4 to 135F (-20 to 57°C)2 |
| Charge/Discharge Profile | Simple | Sensitive |
| Self-Discharge Rate (monthly) | 3% | 30% |
| Requires BMS? | Yes | No |
| Total Life Cycles | 3000 | 1200 3 |
| Cost (upfront) | $875 | $400 |
| Cost (per cycle for 3000 cycles) | $0.29 | $0.40 |
——————
1 Assuming 50% DOD (Depth Of Discharge) for AGM.
2 If SOC (State Of Charge) is above 60%.
3 Total life cycles vary with manufacturers. 1,200 cycles is considered a general rule of thumb.
* In the table above Lithium=BattleBorn, AGM=Renogy.
AGM vs Lithium Takeaways
- Usable Capacity: Discharging AGM batteries below 50% greatly reduces its lifecycle; it is economically advantageous not to discharge below that point. That’s why we compare a 200Ah AGM battery to a 100Ah Lithium battery.
- Weight: Lithium batteries allow weight saving up to about 75%, that’s huge! That means less weight to carry around in the van (gas saving) and it reduces the risk in case of an accident.
- Dimensions: Space optimization is the name of the game in a van conversion, so each opportunity is considered. Lithium takes the win here!
- Charge Temperature Range: Lithium batteries don’t charge too well below freezing (see section below), but manufacturers now produce self-heated batteries which mitigate this weakness.
- Charge/Discharge Profile: To prevent permanent damage (capacity loss), AGM requires specific discharge profile (not below 50%) but also specific charge profile (bulk, absorption, float). Lithium are not as sensitive, they’re a little bit more “set-and-forget”.
- BMS: Lithium batteries are more sensitive to current/voltage/temperature, thus they require an BMS (Battery Management System). The BMS won’t allow charge/discharge when going out of range (temperature too high/low, too much current, etc.). Most Lithium batteries have an integrated BMS these days, so it’s “transparent” for the user.
- Total Life Cycles: Capacity reduces as batteries are cycled. For Lithium, approximately 80% of capacity remains after about 3000 cycles, while it’s only about 1200 cycles for AGM. In other words, a Lithium battery should last much longer than AGM.
- Cost: Lithium batteries upfront cost is higher, but in the long they’re actually cheaper to own than AGM (because of their total life cycles).
AGM vs Lithium: Our Experience
Back in 2016, we initially went with an AGM battery (230Ah capacity), and spent our first two years of full time vanlife with it. We then upgraded to Battle Born’s Lithium (2 x 100Ah capacity). While upgrading resulted in more usable capacity, the major difference is that we pretty much stopped monitoring and worrying about the battery getting a complete charge cycle daily. That means less effort to park in the sun (solar) or drive the extra mile to get more charge from the alternator.
Decision
In our humble opinion, Lithium batteries are definitely the way to go these days. When we upgraded from AGM to Lithium, we basically stopped to constantly monitor the SOC (because going 50% didn’t matter anymore) and stopped monitoring the charge profile (because ideally AGM require a complete absorption/float at each cycle). Lithium batteries are more “set-and-forget” than AGM.
Like most people out there, we went for the tried-and-true Battle Born Batteries. Outstanding product, warranty, and customer service. We’ve been using them trouble-free for years:
Battle Born Batteries
3.2. Specifications
Not all batteries are made equal! For example, a cheap or generic battery may not deliver as much current, causing intermittent performance problems. To prevent getting caught, always check the data sheet; it should be available on the product page. No data sheet? Consider a different brand!
Here is an example of Battle Born data/specifications sheet (click the images to enlarge):
Information is clearly shown, it’s straight-to-the-point, there is no marketing sales pitch… well done!
Terminology:
- Self-Discharge: This is the % of charge that is lost during storage. Lithium batteries have very low self-discharge rate, and can therefore be stored for long period without having to periodically recharging them.
- Cycles (or Life Cycle): Number of cycles before the battery’s end of life.
- Maximum Discharge Current: That’s the current the battery is able to deliver continuously. Power inverters draw HUGE amount of current, so make sure to size your battery bank so that its discharge current is greater than the inverter’s draw! (as a general rule of thumb, 1000W inverter = 100Ah battery bank, 2000W inverter = 200Ah battery bank, etc.)
- Recommended Charge Current: Charging a battery too fast decreases its lifecycle, so choose a battery charger that charges within that range! (0.5c means 0.5 x battery bank capacity; e.g. for a battery bank comprised of 2 x 100Ah Battle Born Batteries connected in parallel, “0.5c” = 0.5 x 200Ah = 100A)
- Maximum Charge Current: Never exceed that value.
- Voltage (absorption, float, equalization) and Time: That’s called the “charging profile” and we explain it later 🙂
- Temperatures: Lithium/AGM have different specifications. Different brands of the same chemistry have different range as well.
3.3. Maximizing life cycle
Batteries don’t last forever. If you’re going for the long run, there’s a pretty high chance you will have to replace your battery bank in your van at some point. Life expectancy of batteries is highly influenced by the conditions of operation; that means YOU can take precautions to increase life expectancy and protect your investment. Let’s see how!
But first, some terminology:
Cycle
A cycle is completed when you’ve used (discharge and then recharged) an amount that equals 100% of the battery’s capacity. This doesn’t have to happen in a single charge! For example, if you use 70% of the battery’s capacity one day, recharge it fully, then use 30% the other day, you’ve completed one cycle (over two days).
Life Cycle
As the number of cycles increases, a battery looses it’s ability to return to its initial capacity. The life cycle is the number of cycles that the battery can complete before loosing too much capacity. As a rule of thumb, the end of life cycle is reached when it cannot hold more than 75%-80% of its originial capacity.
State Of Charge (SOC)
The state of charge (SOC) is defined as “how fully charged” the battery is.
100% SOC: fully charged.
25% SOC: 1/4 capacity left.
0% SOC: empty.
The life cycle varies greatly with battery chemistry (as seen previously). But it’s also influenced by the charge profile, discharge profile, temperature, and long term storage. Keep reading!
3.4. Charge Profile
An adequate charge 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 brands (Battle Born, Trojan, Renogy, etc.) require different charge profiles.
Typical Charge Profile:
(Consult the data sheet of your brand/model to find its recommended charge profile!)
AGM
Stage 1: Bulk
- SOC: Between 0% and 85%.
- Current: BIG! As much as the charger can “push” into the battery! (battery’s recommended charge current)
- Voltage: Increases with time.
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…
STAGE 2: ABSORPTION
- SOC: Between 85% and 100% of the charge.
- Current: LOW. Decreases with time.
- Voltage: Fixed (around 14.7V)
Near 85%, the battery becomes 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
- SOC: Once the battery is fully charged.
- Current: VERY LOW. (typically lower than 1A)
- Voltage: Fixed (around 13.8V)
The float stage prevents self-discharge and can be maintained indefinitely.
Lithium
STAGE 1: BULK
- Current: BIG! As much as the charger can “push” into the battery! (battery’s recommended charge current)
- Voltage: Increases with time.
The bulk stage is terminated when the absorption voltage is reached (around 14.4V).
STAGE 2: ABSORPTION
- Current: LOW. Decreases with time.
- Voltage: Fixed (around 14.4V)
The absorption stage is terminated when current decreases below approximately 5% of the battery capacity (approx. 5A for a 100Ah battery).
STAGE 3: FLOAT
- Floating a Lithium battery is unnecessary, but it won’t hurt it.
- Voltage: Fixed (around 13.6V)
Good to know:
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!
The SOC reached during a charge cycle, and completing all stages is quite important for the life cycle of lead-acid batteries (AGM). On the other hand, Lithium batteries are not as impacted by the SOC reached during a charge cycle.
Takeaway points to maximize life cycle during charge:
AGM
- Charge rate: Typically 20% of capacity (0.2c).
- Charge profile: Completing all stages is critical to the life cycle. It is therefore important to design a system that allows a complete charge cycle frequently (e.g. by having solar + alternator chargers, and sizing them adequately).
Lithium
- Charge rate: Typically 50% of capacity (0.5c).
- Charge profile: Completing all stages is not that critical; no need to monitor frequently and go crazy with this.
3.5. Discharge Profile
How a battery is discharged also affects its life cycle. The depth of discharge and discharge rate are of our interests here:
Depth Of Discharge (DOD)
The depth of discharge (DOD) is defined as “how deep” the battery is discharged (it’s the opposite of SOC…):
25% DOD: 1/4 of total energy available was used (75% SOC).
75% SOC: 3/4 of total energy available was used (25% SOC).
100% DOD: Fully discharged (0% SOC).
The DOD is quite important for lead-acid batteries (e.g. AGM). Indeed, discharging an AGM battery below 50% DOD greatly reduces its life cycle and is not economically advantageous:
On the other hand, Lithium batteries are not as impacted by the DOD. That’s why we generally consider that nearly 100% of capacity is usable on a Lithum battery.
Discharge Rate
The discharge rate is defined as how fast a battery bank is discharged (current).
For lead-acid batteries (e.g. AGM), the discharge rate affects not only the life cycle, but also the available capacity. As discharge rate increases, the battery’s available capacity decreases (for a given cycle, this is not permanent). This is called Peukert’s law, and that explains why lead-acid batteries have several ratings for their capacity.
For example, let’s take the capacity rating of a Roll’s 12V 230Ah AGM battery:
| Hour Rate | Capacity | Current |
|---|---|---|
| 100 Hour Rate | 230Ah | 2.3A |
| 20 Hour Rate | 210Ah | 21A |
| 10 Hour Rate | 189Ah | 18.9A |
| 5 Hour Rate | 172Ah | 34.4A |
- If this battery is completely discharged in 100 hours (at a slow rate of 2.3A), it can deliver 230Ah capacity.
- If discharged in 20 hours (at a faster rate of 21A), it can deliver 210Ah capacity.
- And so on…
On the other hand, Lithium batteries are not subject to Peukert’s law! The discharge rate don’t affect the usable capacity.
Takeaway points to maximize life cycle during discharge:
Lithium
- DOD: No significant impact.
- Discharge rate: No significant impact.
AGM
- DOD: Life cycle is impacted at DOD over 50%.
- Discharge rate: Life cycle and usable capacity is impacted as discharge rate increases.
3.6. Effect of temperature
Generally, batteries perform better near room temperature. For example, take electric cars: their range in a 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
Lithium (LiFePO4)
We often hear that a lithium battery cannot be charged below 32F (0°C); In fact, Lithium batteries can be charged 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.
- Some Lithium batteries are self-heated to allow lower temperature operation.
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 electrolytes become 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!
As a guideline, this is extracted from Rolls Battery User Manual:
| Specific Gravity (SG) | State of Charge approx (%) | Freezing Temperature |
| 1.280 | 100 | -69°C (-92F) |
| 1.265 | 92 | -57.4°C (-72.3F) |
| 1.250 | 85 | -52.2°C (-62F) |
| 1.200 | 60 | -26.7°C (-16F) |
| 1.150 | 40 | -15°C (5F) |
| 1.100 | 20 | -7°C (19F) |
Charging a battery at high temperature
Charging a battery at high temperature generally affects its cycle life (lifespan). For example, here is the Trojan Trillium Lithium Cycle Life VS Temperature:
3.7. Long Term Storage
Not planning on using your van for a while? Here are the storage parameters we recommend to maximime a battery’s life cycle:
SOC
- Lithium: 50-70%. No need to recharge periodically (low self-discharge!)
- AGM: 100%. Recharge periodically to maintain 100%.
Temperature
- Lithium and AGM:
- Ideal: 60F (15°C)
- Recommended: 32F to 86F (0°C to 30°C)
- Acceptable (may affect life cycle): -4F to 140F (-20°C to 60°C)
Depending on the climate you live in, batteries may be removed from the van and stored inside. We personally leave them in our van, with the following configuration:
Long Term Storage Mode
Lithium:
AGM:
Recap (of Section 3.3.): Maximizing Life CYcle
Now that we better understand the factors that affect the life cycle of a battery, let’s do a quick summary of how life cycle can be maximized:
| LITHIUM | AGM | |
|---|---|---|
| Life Expectancy | 3,000 cycles | 1,200 cycles |
| Charge Rate | 0.5c | 0.2c |
| Charge Profile Importance | Medium. Aim for 100% recharge, but it’s not critical. | High. Ideally each charge cycle should complete bulk/absorption/float. |
| Discharge Rate | 1c | Higher discharge rate does not arm, but at the detriment of usable capacity (Peukert’s law) |
| Depth Of Discharge | ~90% | 50% |
| Charge Temperature | 25F to 135F (-4°C to 57°C) | -4F to 135F (-20°C to 57°C) [if SOC is kept above 60% when temp < 32F (0°C)] |
| Discharge Temperature | -4F to 135F (-20°C to 57°C) | -4F to 135F (-20°C to 57°C) |
| Storage SOC | 50% to 70%. | 100%. Recharge periodically. |
| Storage Temperature | Ideal: 60F (15°C). Recommended: 32F to 86F (0°C to 30°C). | <- Same as Lithium. |
3.8. Combining Batteries
Batteries can be connected together in parallel or in series:
Parallel
To increase total capacity
- Capacity (Ah): Adds up.
- Voltage (V): Same.
- Charge & Discharge Rate (A): Adds up.
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).
Series
To increase voltage
- Capacity (Ah): Same.
- Voltage (V): Adds up.
- Charge & Discharge Rate (A): Same.
For example, adding two batteries of 6V/200Ah in series results in a battery bank of 12V/200Ah.
In both cases, follow these recommendations:
- Cables: Always use identical cables (length/diameter) so they offer the same resistance, ensuring all batteries work equally together.
- Mixing batteries: Do not mix batteries of different brand/models. Do not mix batteries of different age if using lead acid (AGM, gel, etc.). It is acceptable to mix batteries of different age (no more than two years old) if using Lithium (see Battle Born FAQ).
3.9. 12V vs 24V Battery Bank
12V electrical systems have been around for a long time in campervans, RVs, cars, boats, so we know for a fact they that are efficient and reliable. But 24V and 48V systems are getting increasingly popular, and are often the subject of heated discussions on social medias.
Cost saving is the number one reason why people choose 24V over 12V, smaller wires are cheaper after all. However, as you’ll see in our cost analysis, saving on wires does NOT translate in 24V systems being necessarily cheaper…
Reading the comments on social media, the race for “more volts” kind of reminds us of the race for “more pixels” with digital cameras (way back, when it was relatively new). The number of pixels were used as the main (and often only) selling point, while actually there are other important variables in the equation to be considered.
12V vs 24V vs 48V electrical systems require an in-depth analysis which you’ll find below. After reading this fact-based guide, you will be able to make an informed decision and decide which of 12V, 24V, or 48V electrical system is the best for YOUR needs.
4. Charge Sources
Now that we understand the importance of charging a battery with an adequate charge profile, let’s see which charge sources are available!
After reading this section, you will be able to:
- Understand how an external power source can be converted to a proper charge profile.
- Identify which charge sources (solar/alternator/shore) applies to your needs.
4.1. Creating a proper charge profile
External power sources (e.g. solar panels, alternator, 120V outlet, etc.) don’t provide an adequate charge profile from the get go; the voltage and current are “random” and not suited to charge a battery. To make an external power source usable, a device (typically called a “charger” or a “controller”) is installed between the charge source and the battery. The role of the charger is to take the “random” voltage and current, and to convert it to a charge profile (voltage/current) suitable for a specific battery type:
4.2. Solar Power
Harvesting power from the sun feels a bit like cheating to us; this is the exciting part of the electrical system!
Solar panels catch energy from the sun and convert it into electricity (about 10-20%) and heat (about 80-90%). The % of the energy converted to electricity is called the efficiency of the solar panel (module). The voltage and current coming out of the solar panels are not ideal to charge a battery, and therefore a solar charge controller convert it to an adequate charging profile:
4.2.1. Rigid vs Flexible Solar Panels
Both rigid and flexible solar panels have their pros and cons, and which one’s best depends on your needs and priorities. Here are the key characteristics of both:
| RIGID | FLEXIBLE | |
|---|---|---|
| Efficiency | 15-20% | 7-15% (more surface required for same output as rigid) |
| Durability | Maintains its efficiency longer. | Looses efficiency faster over time. |
| Strength | A sturdy frame and tempered glass prevent damages to the panel. | Prone to scratches and cracks. |
| Weight | About 3x heavier than flexible. | About 1/3 lighter than rigid. |
| Thickness | Thicker, less aerodynamic. | Lower profile = gas saving. |
| Installation | Limited to flat surfaces. | Adapt to curved surfaces and various configurations. |
| Life Span | 25 years | 5 years |
| Cost | Cheaper upfront and in the long run. | Higher upfront and in the long run. |
4.2.2. Monocrystalline vs Polycrystalline Solar Panels
Most of the solar panels on the market can fit into two categories: monocrystalline or polycrystalline. The key takeaways are pretty straightforward:
| MONOCRYSTALLINE | POLYCRYSTALLINE | |
|---|---|---|
| Efficiency | 17-22% | 15-17% |
| Temperature Degradation | Efficiency less affected by temperature | Loss of efficiency as temperature rises |
| Aesthetics | Uniform black-ish (more attractive for most) | Speckeld blue (less attractive for most) |
| Cost | Higher | Lower |
That being said, the quality of the solar panel is more important than the type of the panel! So we’d rather recommend a good polycrystalline panel than a cheap monocrystalline…
4.2.3. Series vs Parallel
Solar panels can be combined in parallel or in series, with the following characteristics:
| SERIES | PARALLEL | |
|---|---|---|
| Voltage | Added | Same |
| Current | Same | Added |
| Voltage Drop | Minimize voltage drop (allow to use smaller cables). | Increase voltage drop (use thicker cables to compensate). |
| Partial Shading | Higher output degradation. | Less impacted by partial shading. |
| Installation | Easier (no adapter required). MPPT solar charger only.* | Adapter required (See on Amazon). MPPT or PWM solar charger.* |
| Performance | More efficient early/late during the day and at high temperature. | More efficient in partial shading situations. |
* See MPPT vs PWM section below.
Series
Solar panels in series results in a high voltage, low amperage array. Ideal for long cable runs and MPPT solar charger. Panels depend on each others, so partial shading could take down the whole array; not recommended when permanent partial shading cannot be avoided (e.g. roof accessories).
Parallel
Solar panels in parallel results in a low voltage, high amperage array. Mandatory for PWM solar charger. Panels operates independently from each others, so partial shading output deterioration is mitigated.
4.2.4. Partial shading
Solar panels are made of multiple solar cells all connected together in series; blocking one of the cells totally kills the output of the solar panel. Think of the old Christmas tree lights: if one of the bulbs blew, the entire thing would go off! Fortunately, most modern solar panels have built-in bypass diodes that helps mitigate partial shading. In such solar panels, 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 panels connected in series can get the output of the entire array down to 0% because of partial shading! Back to the water analogy:
Connecting the solar panels in parallel is a bit like adding bypass diodes; each panel operates independently and total output is not completely blocked:
Total output:
- No Partial Shading: 513W
- Partial Shading | Bypass Diode | Series: 257W
- Partial Shading | Bypass Diode | Parallel: 400W
Partial shading conclusion: Try to install your panels so they are not located in the shade of other roof accessories (roof rack, fan, etc.). If this is inevitable, connect your panels in parallel.
And that explains our roof layout:
4.2.5. Orientation
A panel will deliver more current if oriented perpendicularly to the sun. On large commercial solar plants, the panels are mounted on a motor-driven device that optimizes 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. With our lifestyle, we generally move a few times each day, so we personally don’t feel like it’s worth the hassle.
4.2.6. Installation
We personally went for a simple DIY installation (faroutride.com/solar-panels-installation) on our 2016 Transit, but upgraded to a FlatLine Van Co. roof rack on our 2021 Transit:
Flatline Van Co Roof Rack
- Modular: you can shuffle the cross bars around to fit your custom roof layout (e.g. solar panels/roof fan/etc).
- Low profile: a bit more stealth and aerodynamic than the tubular aluminum “overland-style” roof rack.
- Easy installation: it’s attached to the van’s roof with the factory mount points (no-drill!), and because they are modular they ship flat packed in a box and they are easier to install (less bulky).
- Easy to install gear and accessories: the cross bars are 80/20 aluminum extrusions, so you can get creative and attach pretty much anything in any possible way: solar panels, decking, awning (Fiamma F45S direct-mount, no drill), light bar, etc.
- Vans: Transit, Sprinter, ProMaster.
For more info (features, specifications, installation, ordering, etc.):
4.2.7. Solar charge Controller
A solar charge controller is responsible of delivering an adequate charge profile to the battery bank. In other words, it regulates the voltage and current coming from the solar panels and going to the battery bank.
MPPT vs PWM solar charge controller
The two types of solar charge controller available are MPPT and PWM. In a nutshell, MPPT will ouput 10-20% more power than PWM depending on the conditions. For this reason, MPPT has become the most popular option despite its higher cost.
MPPT
(Maximum Power Point Tracking)
The high voltage coming from the panels is dropped to a lower voltage, and this voltage reduction is converted into higher current.
- Efficiency: About 10-20% more efficient than PWM, especially in non-ideal conditions (cloudy, low temperatures, etc.).
- Panels/Battery Voltage: Works best when panels voltage is much higher than battery (panels combined in series).
- Cost: Higher.
- Best for: Larger systems where getting the most out of the panels is a priority.
PWM
(Pulse Width Modulation)
The high voltage coming from the panels is dropped by quickly turning the charge controller ON and OFF (10,000 times per second). This method of lowering the voltage does NOT produce more current (as opposed to MPPT).
- Efficiency: Not as efficient as MPPT.
- Panels/Battery Voltage: Panels voltage must be near the battery voltage (panels combined in parallel).
- Cost: Lower.
- Best for: Smaller systems where low cost is a priority.
MPPT vs PWM: Our Experience
Back in 2016 we initially went with a PWM solar charge controller (Bogard Engineering), then upgraded to a MPPT charger (Victron). We immediately noticed the difference: more current was going into to battery despite the fact that we didn’t change our solar panel setup. We also noticed more power earlier during the day and in overcast weather. Nice!
How to select a solar charge controller
Most MPPT solar charge controllers are defined by the maximum open circuit voltage and the maximum charge current:
1. Select a solar charge controller that is rated for your battery bank voltage (12V, 24V, etc.).
2. Make sure the Maximum Open Circuit Voltage rating (Voc) of the solar charge controller is higher than the maximum open circuit voltage of the solar array:
- Panels in series: Voc(array) = Voc (single panel) x Number of panels x T°factor
- Panels in parallel: Voc (array) = Voc (single panel) x T°factor
A note on T°factor: Voc is typically rated for 77F (25°C) and as temperature decreases, Voc increases. Because we’re mobile and our home-on-wheels will most certainly face cold temperatures at some point, we use 1.2 as T°factor.
3. Make sure the Maximum Charge Current rating of the solar charge controller is higher than the maximum charge current of the solar array:
- Maximum Charge Current = Max Power (array) / Battery Charge Voltage (14.7V or 29.4V)
Example:
In the example above:
- The solar charge controller is rated for a 12V battery bank.
- The solar charge controller maximum open circuit voltage rating is higher than the array (100V > 47.6V).
- The solar charge controller maximum charge current rating is higher than the maximum charge current of the array (30A > 21.8A).
This MPPT solar charge controller calculator should make things a bit easier:
MPPT SOLAR CHARGE CONTROLLER CALCULATOR
1. SINGLE PANEL SPECIFICATIONS:
(CHECK DATASHEET OR MANUFACTURER’S WEBSITE)
| MAXIMUM POWER (Pmax): | W |
| OPEN CIRCUIT VOLTAGE (Voc): | V |
| SHORT CIRCUIT CURRENT (Isc): | A |
2. SOLAR ARRAY:
| SERIES: | |
| PARALLEL: |
| BATTERY BANK VOLTAGE: | 12V |
| 24V |
TOTAL POWER:
0 W
OPEN CIRCUIT VOLTAGE:
0 V
MAX CHARGE CURRENT:
0 A
3. RECOMMENDED MPPT SOLAR CHARGE CONTROLLER:
* This calculator assumes a temperature correction factor of 1.2.
You'll find the open circuit voltage (Voc) and the maximum power on your solar panel's datasheet:
4.3. Alternator
The role of the alternator 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 “steal” electrical energy from the alternator to charge the house battery. Similarly to solar power, we need a device to regulate the voltage/current coming from the alternator:
4.3.1. Accessing alternator power
Modern vehicles equipped with smart alternators (and regenerative braking) have finicky BMS (Battery Management System) and connecting anywhere into the system might confuse the BMS into thinking that the power used to charge the house battery is a "leak". Therefore, it is recommended to follow manufacturer's recommendations.
How to tap into alternator power is specific to each van's brand/model/variants... We can't possibly show all the possibilities, especially knowing it keeps on changing over the years! To prevent duplicate information (and mistakes), all the information we gather will be centralized and shared in this page: faroutride.com/b2b-review.
We're pretty familiar with the Ford Transit, so here's how to access alternator power:
Ford Transit 2020 & up | Dual Batteries
Since 2020, the Transit with dual battery configuration comes with two CCP (Customer Connection Point) located on the driver seat pedestal (on the door side). The CCP2 is rated for up to 175A, so it’s an ideal connection point recommended per the BEMM. Below is a photo of how we're connected to CCP2 in our Transit; it's a work in progress at the time of writing these lines and we'll update with the final photo soon! The photo shows the CCP2 location as well as how we mounted the breaker to protect the branch circuit (more info about that in Fuses & Breakers section).
4.3.2. DC-DC CHarger
(Aka DC-to-DC, Battery-To-Battery, B2B)
A DC-DC charger is the way to go these days, as it provides many advantages over the traditional isolator/ACR:
- It’s a smart charger, meaning it provides a multi-stage charge adapted to the battery type (AGM, Lithium, etc.). That’s important because it'll keep your house battery healthy and maximize its life cycle.
- It acts as a current limiter to prevent overworking the alternator. An alternator is a mechanical device and using it over its intended capacity can affect life expectancy.
- Easier to install: no need to wire to the vehicle ignition.
- It’s install-and-forget: the DC-DC charger will automatically activate/deactivate when driving to keep the house battery topped up.
- Modern DC-DC chargers are programmed to handle smart alternators and their highly variable voltage, ensuring a continuous and uninterrupted charge.
There are a few good DC-DC charger options out there:
Victron Orion (30A)
- The ISOLATED Victron Orion has two separate negative port, for when the installation does not share a common negative path (e.g. fiberglass boat).
- The NON-ISOLATED version is suited for installations sharing common negative path, and that is actually our case (i.e., starter & house battery share common ground).
Sterling Power (60A)
To select the correct DC-DC charger size, we have to:
- Not exceed the house battery bank charge rate (typically 0.5c for Lithium, 0.2c for AGM, per Charge Profile section above).
- Not exceed the alternator's available current (varies with van brand/variant).
- Take the features into account (bi-directional charge, voltage sensing, vibration sensing, smart alternator compatibility, fan noise, etc.).
A full analysis (products/brands comparison, sizing, pros, cons, dimensions, output, features, etc.) is out of the scope of this page, but we do have a dedicated page about DC-DC chargers. Going through this page will help you make the right choice:
4.3.3. Isolator and Automatic Charging Relay (ACR)
Isolators and ACRs combine the starter battery and the house battery together during the charge (engine on) and disconnect them during the discharge (engine off). They do not regulate the voltage or current. 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. They're definitely cheaper upfront, but on the other hand, they are not great for the life cycle of batteries, and they tend to overwork alternators. For these reasons, we highly recommend the DC-DC charger option.
4.4. Shore
Shore power is a fancy name that means getting power from the grid, such as a house's 120V outlet or a campground's 30A/50A hookup. It's an expression borrowed from the marine's world which means providing electrical power from the shore to a ship while it's docked.
Similar to solar and alternator power, shore power requires a device to regulate the voltage and current. But unlike solar and alternator power, the current must also be converted from alternative current (AC) to direct current (DC). Let's get into it!
4.4.1. Battery Charger/Converter
The role of a battery charger/converter is to convert 120V AC coming from the shore into 12V DC and provide a multi-stage charge profile adapted to the battery type (AGM, Lithium, etc.).
We personally went for a Samlex America battery charger/converter, because of the brand's reputation of using high-quality components into their products. And as it turns out, it's been working trouble-free since day 1.
Samlex America
*Samlex literature don't mention compatibility with Lithium batteries, but both Battle Born Batteries and Samlex have confirmed this charger works well with Lithium when using the AGM charge profile. Indeed, the recommended charge profile of the Battle Born Batteries (14.2-14.6V absorption, 13.4-13.8V float) falls right into this charger's AGM profile (14.4V in absorption, 13.5V in float).
4.4.2. Inverter/Charger
An inverter/charger acts as a battery charger/converter and as a power inverter. The functions of an inverter/charger are:
- Charge the battery bank. It converts 120V AC coming from the shore into 12V DC and provide a multi-stage charge profile adapted to the battery type (AGM, Lithium, etc.).
- Power the 12V DC loads. In our wiring diagram, the current coming from the battery charger/converter can "bypass" the battery and go straight to the loads.
- Power the 120V AC loads. It converts 12V DC coming from the battery into 120V AC to power the 120V loads (see Power Inverter section).
- Transfer switch. Some inverter/chargers also feature a built-in transfer switch (see Transfer Switch below).
It combines a charger/converter and a power inverter into a single device, and somewhat simplifies the system. The drawback is that if a failure is to happen, more functionalities are lost simultaneously.
Victron's Multiplus inverter/charger packs a lot of features in a high-quality product, it's definitely a crowd's favorite. Going through all of this would be a bit much here, so we have a dedicated page that covers the features and configuration:
4.4.3. sizing shore power
To select the correct shore charger, we have to:
- Not exceed the house battery bank charge rate (typically 0.5c for Lithium, 0.2c for AGM).
- That being said, it's not necessary to go all the way up to 0.5c for Lithium. For example, a 200Ah Lithium battery bank can accept up to 100A charge, but it's OK to select a 50A charger if you don't mind the extra time it'll take to fully charge the batteries.
4.4.4. Automatic Transfer switch (ATS)
An automatic transfer switch (ATS) is a priority switch that allows only one input at a time (typically shore power or generator on big RV) in order to prevent backfeeding or overload. On RV's, the ATS normally prioritize the generator input:
On top of that, RV are typically wired so that the AC distribution panel can only be fed by one input at the time (priority given to shore/generator):
Let's hook up a battery charger in there, and things start to look a bit complex:
An inverter/charger combines the inverter and the battery charger and simplifies things a little:
At last, most vans have modest power needs compared to motorhomes, so a generator is typically not required:
That's better 🙂
4.4.5. Shore hookup types
Here in North America, there are 3 types of outlet/hookup you may encounter. The usual 120V outlet (15A), and the campground's 120V hookups (30A and 50A):
15 Amp
3 prongs: 120V positive ("hot"), negative ("neutral"), ground ("earth").
30 Amp
3 prongs: 120V positive ("hot"), negative ("neutral"), ground ("earth").
50 Amp
4 prongs: 2 x 120V positive ("hot"), negative ("neutral"), ground ("earth").
4.4.6. Shore power inlet
15 Amp
This 15A shore power inlet does not require hardwiring, an easy solution for our Standard Wiring Diagram.
30 Amp
A 30A shore power inlet should be sufficient for most vans, ideal for our High Power Wiring Diagram. (Installation instructions PDF)
50 Amp
A 50A shore power inlet is typically seen on larger motorhome. (Installation instructions PDF)
Ford Transit Shore Power Entry Box (No-Drill / No-Screw)
For years we simply routed the shore power cord through the rear doors or through the D-Pillar cutout (we had to crawl under the van and fish the cord every time). It worked, but it wasn't ideal. For our next van we started looking for a solution, but of course most options require to make a hole in the van.
As you might know by now, we go the extra mile to avoid drilling/cutting our van when we can... So we came up with this stealth "Entry Box" that allows to install a Shore Power Inlet without having to make a hole/drill into the van. It simply snaps under the D-Pillar cutout and then the power cord is routed inside the van through existing openings, neat!
The Entry Box accepts the 15A NOCO (shown above) or 30A Furrion inlets and works on 2015+ Transit vans. We added it to our Store in case that's something you could use as well:
4.4.7. Shore power Cord
Shore power cord design varies (15A, 30A, 50A), so make sure to select a power cord that matches with your system:
15 Amp
30 Amp
50 Amp
4.4.8. Pigtail Adapter (Dogbone)
A pigtail adapter (aka dogbone) allows to connect to a different power configuration. For example, for connecting your 15A charger to a 30A outlet. You can also connect your 30A shore power inlet to a 15A "regular" house outlet, but you will be limited to 15A because that's the maximum it's capable of delivering. To prevent tripping the breaker on the 15A side, you have to limit the power input on the Multiplus inverter/charger (procedure described in our Victron Multiplus Guide).
Pigtail Adapters
This listing contains all types of pigtail adapter:
Note that installing an AC Main Breaker after the shore power inlet is highly recommended, in order to protect yourself from current surge and reverse polarity. Such as the Blue Sea AC Main Breaker 30A or 50A, which can be enclosed in a surface mount box:
4.5. Generator
One of our favorite things about being off-the-grid is to feel close to nature and enjoy the silence. Generators don't get much love around the Vanlife community, as they very effectively spoil the vibe and provide a frustrating experience for the others around. If you do have a generator, a good etiquette is to run it in the middle of the day to charge your batteries, then turn it off during the evening/night/morning.
Fortunately, vans have modest power needs and with proper planning generators are normally not needed. An exception to this would be air-conditioning, because A/C is by far the most power-hungry appliance you can run. Running A/C off-the-grid is possible though, but you'll have to invest a lot in the electrical system. We do have a full article about that:
In a stationary scenario (no help from alternator or shore charging), it's almost impossible to sustainably run an A/C for extended period. A massive battery bank will buy you more time, but solar alone can't fully recover the energy and top up the battery bank. In that case, a generator may be needed. For vans, a portable generator connected to the shore power inlet should suffice (in other words, the generator acts as the shore power source):
You should know that your battery charger (or inverter/charger) is sensible to voltage fluctuation. If you plan on using a generator with a Multiplus, make sure to read this to learn how to choose a generator and how to program the Multiplus: Multiplus Generator FAQ.
Also, getting the Digital Multi Control Remote (more info in our dedicated Victron Multiplus page) to limit the Multiplus input current may be a good idea, to prevent overloading the generator.
A high-quality generator will provide a stable voltage, run quieter and will be more fuel efficient:
Honda EU1000i
For (very) small power needs (definitely not A/C).
Honda EU2200i
Probably the best choice for vans. Best compromise on size/power/price. Should be able to power a 120V air-conditioning (but not more) when paired with a Soft-Start.
Honda EU3200i
Honda's latest offering. More power, but bigger and at a higher cost.
| EU1000i | EU2200i | EU3200i | |
|---|---|---|---|
| Maximum Output (surge) | 1,000W | 2,200W | 3,200W |
| Continuous Output | 900W | 1,800W | 2,600W |
| AC Output @120V | 7.5A | 15A | 21.7A |
| Displacement | 49.4cc | 121cc | 130cc |
| Fuel Tank Capacity | .55 gal | .95 gal | 1.2 gal |
| Length | 17.8" | 20.0" | 22.5" |
| Width | 9.5" | 11.4" | 12.0" |
| Height | 14.9" | 16.7" | 17.8" |
4.6. Wind
Using a wind turbine while driving is a proposition that resurfaces occasionally on online forums. We'll keep it short: the additional drag caused by the wind turbine will increase the gas consumption and overall, there's more energy lost than gained. Better invest in a DC-DC charger!
For a permanent camp, it could be considered. But wind turbines are big and bulky, not really suited for a nomadic lifestyle. Solar is much more convenient. Here is a more in-depth page on BattleBorn website: Can a wind turbine power my RV?
4.7. charge sources you actually need
We've seen several ways to obtain power from external sources: solar, alternator, shore, generator, and wind (🤨). That doesn't mean you need all of them! But there's a reason why most vans are equipped with solar, alternator, and shore power. More options mean flexibility, resilience and peace of mind. The upfront cost is higher, but it's an insurance your electrical system will work in every scenario: long stretch of driving, stormy days, rest days, etc. Definitely recommended for:
- Full time Van Life.
- 4 season vans.
- All-electric vans (no propane, high power needs).
- AGM battery banks (need frequent full charge).
- Better resale value.
Our Experience
We realized that it's difficult to plan how Vanlife will unfold. You dream of sunny days or driving for hours into the unknown... but the reality can be quite different. Here are a few real-world anecdotes:
- We spent over a week In Oaxaca (see our Mexico Vanlife Guide), and we were fortunate enough to find a campground with a roof above us to protect us from the sun (it was HOT!). We used public transport over there, so that van was stationary. Our only charge source was shore power.
- We spent our first two winter chasing the snow (see our Winter Vanlife Guide). With short days and low angled sun, solar is pretty much useless in this scenario. So, alternator power was our main charge source.
- Covid was a weird period to live in a van. At some point, travel was restricted here in Canada, so we parked in the mountain and took the opportunity to work on this website for a few days. Solar power was definitely our main charge source.
These are just a few random examples to show that things don't always go as planned. Better be prepared!
All of that being said, it all depends on your own needs. For example, some people build van without solar because they know they will drive long stretches every day. Discarding a charge source can be a way to cut on costs, so evaluate your needs and build accordingly!
5. 12V DC Loads
After reading this section, you will be able to:
- Understand why you should prioritize 12V loads (or, more broadly, loads with same voltage as battery bank) over 120V loads.
- Identify typical 12V loads found in vans/RVs.
5.1. 12V DC loads are more efficient
Any voltage conversion comes with energy loss. The energy loss from converting 12V DC to 120V AC is typically around 10-15%. Whenever you can, choose loads with the same voltage as the battery bank to increase the efficiency of your electrical system.
You should know that many appliances are actually DC, even if we take it for granted that they are 120V AC. For example, most smartphones require an input of 5V DC. So, using a 120V outlet to charge a phone will result in a double-conversion (12V DC -> 120V AC -> 5V DC):
5.2. 12V DC loads in our van (and more)
Maxxfan Roof Fan
Sirocco II Gimbal Fan
12 Volt DC Socket
Phone Charger
LED Lights (Dimmable)
LED (With Built-In Switch)
Reading Light
Water Pump
Novakool Fridge
Propane Solenoid
Air Heater (Gas)
Air Heater (Propane)
Composting Toilet
6. 120V AC Loads
After reading this section, you will be able to:
- Understand the role of inverters and inverter/chargers.
- Learn the difference between pure sine and modified sine inverters.
6.1. Power Inverter
A power inverter plays two roles:
- Convert direct current (DC) from the battery bank to alternating current (AC).
- Step up voltage from 12V to 120V.
Pure Sine vs Modified Sine Inverters
Electric current is defined as the flow of charge (movement) of electrons.
- Direct current (DC) is an electric current that flow in one direction.
- Alternating current (AC) is an electric current that reverses direction periodically.
In DC, voltage is constant, while in AC, it oscillates between its positive and negative peak. When plotted on a chart (Voltage over time), AC voltage takes the shape of a sine wave:
Power inverters can be found as modified sine wave inverter or pure sine wave inverter. The difference lies in the ability of the inverter to reproduce the shape of the AC:
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:
- Any device that uses a control circuitry that senses the phase (for voltage/speed control) or instantaneous zero voltage crossing (for timing control) will not work properly: fridge, microwave, clock, power drill, dimmer, fan, etc.
- Produces enhanced radio interference, higher heating effect in motors/microwaves, and produces overloading due to lowering of the impedance of low frequency filter capacitors/power factor improvement capacitors.
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:
- Inductive loads like microwaves and motors run faster, quieter, and cooler.
- Reduces audible and electrical noise in fans, fluorescent lights, audio amplifiers, TV, fax, and answering machines.
- Prevents crashes in computers, weird print outs, and glitches in monitors.
Pure sine inverters cost more, but as we now understand, they are definitely worth it.
Energy loss
Remember that there is an energy loss of around 10%-15% during the conversion from DC to AC, so it’s better to avoid the inverter when possible (e.g., by charging your phone from a USB outlet).
Power Rating
Inverters are normally 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 drawn on the 12V DC side (battery):
High Current!
Remember that inverters draw a HUUUUGE amount of current (e.g. 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 loosen with time/vibration). In doubt, ask a professional to check your installation.
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
(Budget)
Samlex America
(High-End)
6.2. Inverter/Charger
An inverter/charger combines an inverter and a battery charger. More info on this page:
6.3. Power Meter
To correctly size your inverter, you need to know the power consumption of the appliances you'll be taking with you in the van. You can normally find that information in the owner's manual, or you can use a Power Meter to find the real-world power consumption:
Power Meter
7. Monitoring
A battery/system monitor is optional, but we highly recommend it. You'll learn a lot about your power consumption, the actual status of your battery, and the impact of your charge source(s). For example, you can immediately see the effect of partial shading on solar and move to a better spot as required. In the end, it'll make you better at managing energy and optimizing the usage of your electrical system.
After reading this section, you will be able to:
- Understand the role and functions of battery/system monitors.
- Learn how monitors help managing your power.
7.1. Battery Monitor
A battery monitor function is to calculate and display real-time and historical data:
A shunt enables the battery monitor to make the measurement. It is typically installed between the battery bank and the negative bus bar:
We tested and recommend the Victron BMV-712 battery monitor, as it's a high-quality monitor with an excellent smartphone (BlueTooth) interface:
Victron BMV-712 Shunt & Display
Victron Smart Shunt
Smartphone App
Here you will find our review about the Victron MPPT SmartSolar Charge Controller, the Battery Monitor, and the 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 🙂
7.2. System Monitor
The Simarine Pico system allows you to monitor much more than just the battery. It can also monitor the current draw of individual loads, tank levels (fresh water, grey water, Nature’s Head, propane, etc.), temperatures (interior, exterior, fridge, etc.) and pitch/roll (inclinometer to park level). We installed it recently and we were blown away! The installation is more involving than a simple battery monitor, but here we have the full write-up (review, installation, etc):
