One common question that we get asked here at Tiny Build Electrics is in relation to series and parallel. Batteries in parallel? Solar array in series? Pros, cons?

This is a key stage in your Tiny Build and something you definitely want to get right! In this article we are going to break it down into small, manageable chunks to make it easy to understand.

---

Batteries in parallel

“In parallel the battery voltage remains constant and the amp hours increase”

Put simply, you connect the positive to positive, negative to negative. Easy, right? Well.. kind of!

The diagram below is why this type of connection is called ‘parallel’. The positives and negatives remain parallel to each other at all times. They never touch or connect, this is a parallel wiring format.

Every time a battery is added to the bank the voltage remains the same but the amp hours increase

So, you understand the basic layout of a battery bank connected in parallel, but the electrical principles are also worth understanding. Again, we can keep this simple.

Every time we add a battery to the bank the voltage remains the same but the amp hours increase by the size of the added battery.

Here, you can have a look at a real life example of this, as the batteries in our own Tiny Build Electrics example are wired in a parallel configuration.

The system above comprises of two individual 100ah lithium-ion batteries connected in parallel.

Here we have a total of 200ah at 12V. The common mistake here is to double the voltage and not the amp hours. In parallel the battery voltage remains constant and the amp hours increase.

Connecting your batteries in parallel is not just as simple as connecting all the reds and all the blacks. You also need to consider balancing the system.

How can you do this?

Instead of connecting both the positive and negative at one end of the bank via one battery, we connect the positive to the load at one battery bank and the negative to the load from the other end of the battery bank.

The diagram to the right depicts a battery bank correctly connected in parallel.

See how the negative has been taken from the last battery to the installation, whilst the positive has been taken from the first battery to the installation. The bank is now working as one unit. The current being drawn from the battery bank will now be equal across each battery and the bank will receive charge equally across all its batteries.

This way the charge and discharge is evenly spread throughout the entire battery bank. This way of wiring increases the likelihood that the manufactures specified life cycles will be met. If this is not adhered to you are in danger of damaging your batteries and depleting their lifecycles.

Common mistakes when connecting batteries in parallel

When connecting your batteries in parallel you must balance your battery bank as discussed above. This is a crucial step and often overlooked during the installation stage.

This diagram shows a common way in which parallel battery banks are incorrectly connected. The way in which these are connected puts strain on the primary batteries and is considered unbalanced.

As you can see in the diagram the battery closest to the installation, let’s call this the primary battery, is the first in line to be discharged and is also the first to receive a charge current.

Each set of connecting cables, between each battery, creates a resistance. Electricity will always take the path of least resistance, like water flowing in a river. The path with the least resistance always wins. In the diagram shown, the primary battery is the first power source which has least resistance and therefore this one takes the biggest hit.

This will then happen in reverse when the battery bank is being charged. The primary battery gets a largest amount of charge current, with every set of interconnecting cables the charge current depletes from one battery to the next leaving the last battery with very little charge current.

Useful Definitions

Resistance: A measure of the opposition to current flow in an electrical circuit.
Charge Current: A flow of electrical charge carriers

Batteries in series

“In series the battery voltage increases and the amp hours remain the same”

Batteries wired in series are different. The principles are in reverse to a parallel setup. Instead of the voltage remaining the same and the amp hours increasing, the voltage increases and the amp hours remain the same.

Keep in mind, if you plan to wire multiple batteries together in series, each battery needs to have the same voltage and capacity and rating, or you can end up damaging the batteries.

This may seem irrelevant as I’m sure, like most people, you plan on having a 12v system in your camper van.
But, with older vans and vehicles becoming ever more popular to convert into tiny builds, their onboard electrical systems may surprise you.

A lot of big lorries and buses are being converted into tiny homes and they often have a 24V or 48V systems. Something to definitely bear in mind to ensure you purchase the correct equipment for your system.

4 x 12v 100ah batteries in series 48V 100ah Battery Bank

Series & Parallel Wiring for Solar Panels

Each solar panel has a positive and a negative. A series connection is created when one panel’s positive is connected to the negative of another.

Both series and parallel wiring formats can also be applied to solar panel arrays. There are pros and cons to both methods. This is something you should consider carefully before starting your build.

When you wire multiple panels in series, their output voltages add together and their output currents remain the same. Conversely, when you wire numerous solar panels in parallel, their output currents add together, but their output voltages stay the same.

Series Solar Panel Wiring

Each solar panel has a positive and a negative. A series connection is created when one panel’s positive is connected to the negative of another.

Total Voltage: 22v x 3 = 66V
Total Current: 4.52A
Total Power: 300W

*These calculations do not include resistance losses caused by the panels and the cables. These numbers are for example purposes only.

From the calculation above you can see that the voltage has been multiplied by the three panels to give us 66v, the current remains at 4.52 amps. The total power (watts) is also accumulative of the three panels. This accumulates to 300w.

So, what are the Pros to wiring in this series over parallel?

Pros to series wiring format

• Higher voltage gives the MPPT controller (maximum power point tracking) more range when adjusting its charge current.
• MPPT Charger requires 5 volts more than the battery voltage in order to start charging. This works well with the series wiring as it creates a higher voltage and the charger is able to charge from earlier in the day and later into the evening extending the daily charge period.
• On cloudier days the solar arrays output voltage is reduced, but due to the higher voltages produced by the series wiring format, the MPPT is still able to create a charge current. Whereas a parallel array would drop below the MPPT’s minimum PV voltage and switch off.
• A lot simpler to wire
• Uses less cable than parallel

Cons to series wiring format

• If any shade covers even a single cell on a panel, it will reduce the whole system’s power output. For example parking under a tree will seriously impede your output charging current. In simple terms, the array likes to be balanced, it likes to see the same amount of light over every cell and when it gets this, its incredibly effective.
• Each panel and every cell within that panel are critical in a series format.
• Any spots of dirt over any of the cells will impede how the system charges. Therefore if your panels are in series they will need to be kept clean to maintain a optimum charge current. In series you cannot connect different size panels together. The power (watts) from the first panel passes through both the second and the third to make the accumulation, they all must be equal in size.

Two solar panels wired in series fitted to the top of a camper van.

The panels themselves have two cables each, so 4 cables altogether, but by connecting the positive of one to the negative of the other we essentially create one giant panel. That then leaves a positive from one panel and a negative from the other. These are the two cables we send down to the electrical control panel to connect to the MPPT controller. As seen this in the photo.

Parallel Solar Panel Wiring

A parallel connection is created when the positive of one panel is connected to the positive of another, and the negatives are connected to each other.

Total Voltage: 22V
Total Current: 4.52A x 3 = 13.56A
Total Power: 300W

*These calculations do not include resistance losses caused by the panels and the cables, These numbers are purely for example purposes.

From the calculation above the voltage now remains the same, a constant 22v. The current is 13.56A (that’s the current of each panel multiplied by 3).

A solar array in parallel is fantastic if partially shaded. In simple terms, if a few cells were covered by an overhanging tree, the rest of the array would pick up the slack and still give a reasonable charge current.

Pros to parallel wiring format

• One of the biggest pros to wiring in parallel is you can mix different size solar panels together. If, up on top of your campervan or motorhome roof, you have fans, surfboards, wifi boosters and therefore only have room for a 100w, a 50w and a 25w, they can be configured in different orientations around your equipment. Although this can be done, we at TBE do not advise this as it is very inefficient.
• When in optimal conditions parallel can give a very good, strong charge current.
• When shade hits any part of a solar array wired in parallel, the power output from that panel reduces significantly. BUT, any other panels in the configuration are unaffected.

Cons to parallel wiring format

• The parallel setup needs a certain amount of power from the solar panels in order to create a charge current.
• During the winter months, when the sun is low in the sky, the parallel format will struggle to produce enough voltage to initiate a charge.
• Requires a lot more cabling to wire a parallel format therefore your cable costs will be higher.

*These calculations do not include resistance losses caused by the panels and the cables, These numbers are purely for example purposes.

Real world results

These two screenshots above were taken on exactly the same day under the same conditions. The difference being that one set of panels is wired in parallel and the other wired in series.

The main difference you can see is that the parallel system has around 18v to optimise the best charge current, whereas the series system has between 28V-70V. So, in the example above, the MPPT has dropped the voltage to 29.38V in order to increase the charge current to 5.2A.

The parallel system is just about managing a charge current but its very weak.

Where the parallel system shines is if the solar panels were suddenly to become partially shaded by a tree, for example. The series system would dramatically reduce while the parallel would be little effected as the panel which isn’t partially covered is still able to produce its power, the series system requires all cells to be clear to effectively create a charge current.

If you plan to travel in all seasons then series solar wiring is the better format for those conditions with less sunlight. The series wiring combined with an MPPT controller maximises your chances of getting a healthy charge current even on those overcast days.

Although you may suffer more losses during the optimum operating conditions, series can produce a high enough voltage to charge the batteries from dawn to dusk.

If you travel in a camper van or motorhome that has a roof full of vents and fans and the only option is to fit panels in here, there and everywhere, then parallel will provide you with the option of having multiple, different sized panels together on your roof but remember, the panels need to have the same voltage to maintain efficiency.

Diagram above demonstrating solar panels wired in series with a Victron Energy MPPT Controller

Our recommendations at Tiny Build Electrics

• Wire your campervan solar setup in series.
• Wherever possible, use the same size solar panels throughout the entire array.
• If you must mix panels then try to get their specification as close as possible.
• Pay attention to anything on your roof that could cast a shadow onto your solar panels, including maxxair fans, TV dishes and sports equipment.
• Avoid parking in the shade or under trees to maximise performance.
• Keep your solar panels really clean.
• Use an MPPT controller when wiring in both series or parallel to maximise performance

To carry out on your campervan conversion electrical system.

In this article we will cover some basic tests that you can carry out on your own self built electrical system within your van conversion or tiny build. These very simple tests can be the difference between a safe or dangerous installation. They help to identify loose connections and ensure that you take some time to check over your system upon completion, a stage that many miss.

---

Safe isolation of your campervan’s DC system

For the purpose of this article and the discussion of basic testing, we consider the reader to have a basic understanding of their electrical system and a basic arsenal of tooling and test equipment.

Before you start, it’s always wise to safely isolate the circuit(s) in which you wish to test. To do this you will require a device which can measure voltage, it will need to be capable of measuring direct current (‘DC’). This is the setting you will use to see the voltage in your system.

Firstly, you need to fully isolate your campervan’s DC system via your main isolator. If you do not have a main isolator for your DC system, we highly recommend that one is installed, as should an emergency arise, you need to be able to shut the entire system down quickly and efficiently.

If your system contains solar panels, please use your solar panel isolator to isolate the PV array. If there is sunlight hitting your panels the PV system will produce a voltage and therefore needs to be isolated so that we can test in a safe manner.

Once your main isolator is in the off position you can then perform the basic test of switching on lights and other DC equipment. These should, of course, not turn on.

Just because these devices do not turn on, does not mean your system is safely isolated yet, for this we need to use our test equipment.

You can then take your voltage tester and test across your positive (+) and negative (-) at any point after the main isolator. The reading should be 0v. For the purpose of the installation specified in the photos, we tested from the positive busbar to the negative busbar. Another good place to test for voltage is on any devices that have exposed terminals, such as a solar charge controller (pictured right), here you can test for both your system voltage and your solar panel voltage, because both isolators are in the off position, these should both read 0v. Once you have read 0v from both your system voltage and PV voltage the isolators must remain in the off position. This now gives you a safely isolated DC system which you can test.

---

Visually inspecting your campervan’s electrical installation

A visual inspection of your campervan’s electrical installation is crucial. It is good practice to sit and run your eyes over the system, thinking of the flow of electricity like the flow of water through pipes. Ensuring that all the right cables are making their way correctly from A to B to C to D. This a not only a good way of ensuring that your system is correctly connected but also a good way of understanding your system and how it works.

This is also a great stage of the inspection process to reference your wiring digram (schematic) that you used during the installation process. Follow the diagram like a flow chart and ensure all devices are in the correct sequence and have the correct cables running to and from them.

A visual inspection of your cable management is also a key aspect here. All cables should be secure and protected from external influences. Cable trunking is a good example of cable management. It protects the cable from any external damage from the likes of surf boards and mountain bikes thrown in the back of the campervan at the end of the day.

The trunking also provides the cable with some air flow, enabling the cables to dissipate any heat effectively and operate at their designed specification.

Visually inspecting how your cables enter enclosures such as control panels and jointing boxes is also another key way of ensuring system longevity. Cables entering via sharp edges can cause potential damage to the cable over time. Here we must ensure that the cables are protected whilst the vehicle is moving and vibrating. Over time the sharp enclosure edge could slice into your cables and cause substantial issues, so you can make a quick wiggle check, ensuring the gland or grommet is holding our cable firm and protecting it as it enters the enclosure.

---

Tug testing your campervan’s electrical system

If the cable pulls out during a tug test then it was never going to stand the test of time.

Tug testing is an extremely basic electrical test but a critical one. Too many people forgo this step and issues that later on arise could have been solved by simply tugging on a cable to reveal a loose connection. 
Tug every single termination that you have made, yes every single one, there are probably hundreds, but do this! 
For terminations using lugs, these have more than likely been fixed using a nut and bolt method, a wiggle of the lug will suffice.

Checking that the lug is secure, creating a good, solid face to face connection and also that the copper within the lug is crimped tightly and that no strands of copper protrude the lug from the side in which the cable enters.

Key areas for tug and wiggle testing are at the fuses and protection devices. A loose connection here can cause a high resistant joint, the high resistance joint will ultimately result in a higher current being pulled though the loose joint and this could result in arcing, which can potentially lead to a fire.

If you have used through crimps, boot lace ferrels or, the ever popular, WAGOs in your installation then these can also be tug tested. Remember if the cable pulls out during a tug test then it was never going to stand the test of time. When you start taking your campervan down those bumpy lanes to get to the best surf location these connections need to be solid. Finding these loose connections is what tug testing is all about, you would rather find it now at this point than when your miles from home enjoying your travels.

---

Identification of cables within your campervan’s electrical system

Identifying your cables is a really good way of future proofing your installation.

Buy a labeller and label everything! You’ll be on your travels, an issue will arise and the labelling process that you undertook will save you hours.

Labelling all your DC circuits is the key to identifying which cable is supplying which piece of equipment in your tiny build.

You should also label every isolator. Knowing which isolator you’re turning is crucial. If your van sits for a period of time you may want to isolate certain aspects of the installation. This is a great way of knowing exactly what is isolated and what is not.

Labelling your individual fuses is also a must, this can save a whole lot of time fault finding another day. Knowing what part of the system has failed and then knowing where said components are is crucial to any installation.
Ensure your cable colours are correct. This is crucial in any good installation. Using a red colour for your DC positive and black for your DC negative is a good place to start. If you have a plain black cables, such as cables coming from your solar panels, its always a good idea to label your positive and put a little red band or heat shrink around the neck of the cable.

---

Basic continuity testing of your campervan’s electrical system

Once you are satisfied with your visual and tug testing you can then move onto some basic continuity testing.

Continuity testing is simply ensuring that the start of your cable is connected to the end of your cable.

As an example, you will have a cable that is connected at your battery or busbar (origin), and will run to your 12V DC distribution panel (load), to power your lights, fridge and fan.

Now, that cable should be continuous, from the origin to a fuse and then from the fuse to an isolator and from the isolator to your distribution panel.

Sounds obvious when said, but by the time you get to the end of your build these cables will be covered by your cable management, buried in walls and hidden behind kitchen cabinets and shower rooms so they can no longer be seen in their entirety.

Once your test equipment is on the continuity setting (see pictures below) you can simply touch the ends of the probes together and you should either hear a beep, get 0.00ohms or sometimes both (diagram above left). You are simply creating a loop. Your meter is sending out a signal on one probe, it touches the other probe and returns said signal to the test equipment.

Remember: Lower number = Lower resistance & Higher number = Higher resistance

You are doing exactly that, but the probes will be at each end of your cable. Your cable becomes part of the loop, this is how you test for continuity, you are ensuring your cable is continuous and has no breaks.

At this basic level of testing you are simply listening out for a beep or looking for a low value. Just bear in mind that values will vary due to the differences in the length of cable, fuses, switches and thickness of the cable.

Every joint that you make adds a level of resistance the the circuit. That is what you are measuring with your test equipment. A thick piece of cable with no joints will produce the lowest reading whilst a thin piece of cable with plenty of joints, fuses and switches will create a higher reading as there are more obstacles in the way, that is what we call resistance.

You can run through a scenario with the diagram below.

You first, touch one of the probes (it doesn’t matter which) on to the positive busbar(1), (if your system doesn’t have a busbar, the nearest positive terminal to the dead side of the isolator will suffice).

Once the probe is firmly on the positive busbar, you can then put the other probe onto the next connection in the diagram, which is at one end of the fuse(2). Here, if the cable is uninterrupted and continuous you should hear beep from your multimeter and, or a low reading.

You now know the cable between the busbar and the fuse is continuous.

You can then move to the fuse itself, put the first probe on one side of the fuse(2) and the second probe on the other side of the fuse(3), beep/low reading! This confirms to you that your fuse is intact and has not been broken or has blown.

Next you take a probe, put it on the outgoing side of the fuse(3) and connect the second probe to the positive connection on the lamp(4), beep/low reading!

You have confirmed that from the busbar, the origin of the circuit, you have continuity to the load, the end of our circuit and therefore the electricity can freely flow along this route without any issues.

*Note, your test leads may not be long enough to reach end to end of every circuit. You can make a longer bit of cable which will help you reach other parts of the installation, this is known in the electrical industry as a wandering lead.

*Not all cables need to be continuity verified, I appreciate this takes time and if you can see the cable in its entirety then you can be 100% sure this cable is entire and connected at both ends.

This is a really good way of proving you have good connections and your circuit is entire. If this is your first installation I recommend doing as many cables as you possibly can. If you are more experienced you can apply diversity factor and do a random selection.

---

Summary

We at Tiny Build Electrics believe the words “electrical testing” can seem daunting. You may think it involves complicated procedures and equipment, and sure, it can do, but, we believe by doing some small, basic tests like the ones that we have discussed here in this article it is certainly better than none at all. If during your testing process you find one slightly loose cable or a mislabelled fuse then it was worth it.

Visually testing, tug testing and carrying out basic levels of continuity testing does not need to be complicated nor scary. By carrying out these basic, yet important, tests you can safely sleep in your home on wheels knowing the fundamentals of your installation are correct.

Whether you’re testing a van conversion, boat, motorhome, log cabin or any other tiny build electrical system, these basic, yet important procedures can be applied to all electrical installations, big and small!

*For the testing of your 230v systems, we advise contacting a qualified electrician to test and inspect this part of the installation. The tests conducted require more complex equipment and a portion of the testing is carried out live and therefore needs to be conducted by competent person(s).

If you’re a vanlifer, you know how important it is to have reliable access to power while on the road. Whether you need to charge your phone, run a laptop, or power small appliances, a campervan inverter is an essential component of your electrical system.

But what exactly is an inverter, and why is it so important?

Simply put, an inverter is a device that converts direct current (DC) power from your vehicle’s battery into alternating current (AC) power, which is the type of power used by most household appliances and electronics. Without an inverter, you would not be able to use or charge your devices while driving. In addition to charging your devices, an inverter can also be used to power small appliances such as a microwave, coffee maker, or mini fridge. This can be especially useful if you’re staying in a remote location with no access to electricity.

Types of Inverters

There are two main types of inverters: modified sine wave inverters and pure sine wave inverters.

1. Modified sine wave inverters are the more basic and inexpensive option, and they work well for most basic, non-sensitive devices such as chargers and tools. However, they may not be suitable for more sensitive electronics, as the power output is not as clean as with a pure sine wave inverter.
2. Pure sine wave inverters, on the other hand, provide a more accurate representation of AC power and are suitable for use with sensitive electronics such as TVs and audio equipment. They are generally more expensive than modified sine wave inverters, but they offer better performance and compatibility with a wider range of devices.

Sizing an Inverter

When choosing an inverter for your campervan, it’s important to consider the total cumulative wattages of your appliances and electronics. You’ll need to select an inverter that can handle the combined wattage of all the devices you plan to use. For example, if you have a laptop that requires 60 Watts and a phone charger that requires 10 Watts, you’ll need an inverter with a minimum deliverable power rating of 70 watts. This is why you also need to consider inverter efficiency, (most entry level inverters start at around 85% efficiency, with higher quality models reaching 93-94% efficiency). Other considerations include the size and weight of the unit, as well as any additional features such as remote control.

Installing an Inverter

Installing an inverter in your campervan is a relatively straightforward process, but should be approached with due diligence.

First, you’ll need to choose an appropriate location for the inverter. It should be easy to access, in a well-ventilated area to prevent overheating, and should ideally also be mounted on a non-combustible surface. Under no circumstances should an inverter be installed directly above Lead-Acid batteries. Under significant load, or when approaching sulfation, Lead-Acid batteries can off-gas, meaning gas is released from the battery. This gas could be drawn through the fans of the inverter and result in fire! So, once an appropriate location has been confirmed, next you’ll need to connect the inverter to your auxiliary battery using the correctly sized cables, paired with an correctly sized overcurrent protective device.

Lastly, your local regulations may require a true neutral. In some cases, where the inverter is not fitted with a Neutral to Earth Bond, one of the AC output wires must be connected to the chassis, and the chassis must be connected to a reliable ground. Reason being that a true neutral is needed to ensure correct operation of an earth leakage circuit breaker (RCCB / RCD / GFCI)

Maintaining an Inverter

Once your inverter is installed, it’s important to maintain it to ensure it stays in good working order.

1. This includes cleaning the terminals and checking the battery connection regularly. By taking good care of your inverter, you can ensure that you have reliable access to power while on the road.
2. It’s important to manage your power usage carefully. This includes turning off appliances when they’re not in use, unplugging chargers when they’re fully charged, and avoiding using high-wattage appliances at the same time.
3. It’s also important to properly maintain your auxiliary battery to ensure that you have a reliable power source for your inverter. This includes keeping the battery charged, cleaning the terminals, and in the case of VRLA batteries, checking fluid levels.

Here are some potential pros of using an inverter in your campervan:

• Convenience: An inverter allows you to use and charge your electronic devices while on the road, providing a convenient source of power.
• Compatibility: Inverters are compatible with most household appliances and electronics, so you can use them to power a wide range of devices.
• Safety: A quality inverter will have built-in safety features such as short circuit protection and thermal shutdown to help prevent accidents or damage to your tiny home.
• Versatility: In addition to charging your devices, an inverter can also be used to power small appliances such as a microwave or coffee maker, making it a versatile power source.
• Durability: With proper care and maintenance, an inverter can last for many years, making it a reliable and long-lasting power solution.

In conclusion, a campervan inverter is an essential component of any vanlifer’s electrical system. Whether you’re using it to charge your devices or power small appliances, an inverter will allow you to enjoy all the comforts of home while on the road.

So if you’re building or upgrading your campervan electrical system, be sure to include an inverter in your plans.