The Ultimate Guide to Choosing 30 Amp Solar Controller

Solar panels are the main power source for most off-grid campervans, but they can't do it alone. A solar charge controller takes the raw energy from your panels, packages it up, and sends it to your leisure batteries as a consistent, organised stream of electricity. At minimum, a solar charge controller keeps your batteries safe and extends their lifespan. The best models intelligently negotiate between panels and battery, maximising solar charging efficiency and charging your campervan solar power system in record time.

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This guide helps you choose the best solar charge controller for your system. We'll start by looking into the difference between a budget-friendly PWM charge controller and a high-efficiency MPPT charge controller. Then, we'll calculate charge controller size and cover key specs like efficiency, built-in Bluetooth, and safety features. At the end, we'll shortlist our favourite devices, including PWM models, MPPTs, combined DC-DC and MPPT units, and easy-to-install solar kits.

If you're just getting started, make sure you read our full guide on campervan solar systems. In that article, we go in-depth into how exactly solar charge controllers work, as well as how they integrate into full solar systems and how to wire them up.

Index

Our Top Picks

The Two Types of Solar Charge Controller: PWM vs. MPPT

Sizing Your Solar Charge Controller

What MPPT Charge Controller to Buy? Our Favourite Models

Final Thoughts

Shane, the founder of The Van Conversion, is a campervan professional and NCC-certified electrical installer. Since , he’s lived on the road full-time, completing several van builds along the way. He’s the author of Roaming Home and the creator of The Van Conversion Course, which have helped thousands build their own vans. Shane also writes The Van Conversion Newsletter, where he shares hands-on tips and practical insights. He’s passionate about empowering others to make their vanlife dreams reality.

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Our Top Picks

If you want to skip the details and get your solar system ordered, these are our top picks for a solar charge controller. They're both MPPTs, boasting exceptional efficiency ratings and optimising performance even when your panels are partially shaded. They're Bluetooth-enabled, which is essential for easy monitoring, and both incorporate a full set of safety features.

Best Solar Charge Controller for Small Systems

For single panels up to 250W or series setups up to about 350W (depending on configuration), the 100|30 SmartSolar Victron MPPT is an easy sell. It has built-in Bluetooth, yet beats competitors without this functionality on price. Victron's pedigree and long warranty makes it an easy sell.

Best Solar Charge Controller for Large Systems

For single panels up to about 450W and series arrays up to about 800W, you'll need more like 60A of charging current. In this size, we recommend Renogy's Rover 60. It has the same high efficiency rating as Victron's equivalent, the same partial shading algorithms, and the same safety features and temperature compensation, all at a lower price. Bluetooth dongle and ONE Portalmonitoring compatibility seal the deal.

The Two Types of Solar Charge Controller: PWM vs. MPPT

When designing your van’s off-grid power system, choosing the right type of solar charge controller is key to ensuring your solar panels charge your batteries efficiently. The two main types, PWM (Pulse Width Modulation) and MPPT (Maximum Power Point Tracking), serve the same basic purpose but operate very differently. Victron have published a very detailed document breaking down the difference, but we've summarised the key takeaways below.

The PWM Solar Charge Controller: Budget-Friendly but Limited

PWM controllers are a simple and cost-effective option. They work by connecting your solar panels directly to your batteries and gradually reducing the charging current as the battery reaches full charge (remember that a battery's voltage decreases as it charges). The catch is that a PWM charge controller can't convert between voltages, so it caps its charging current to your battery's voltage.

Let's say you're running a 12V lead-acid battery (gel or AGM), which will charge at between 13.5V and 15V. A typical 100W solar panel's voltage at maximum power (Vmp) is around 17V. A PWM solar charge controller will pull that 17V down to around 14V to match your batteries, losing power in the process. Let's see how much power we'll lose in that step-down.

Panel maximum power voltage (Vmp): 17.5V

Panel maximum power current (Imp): 5.71A

Panel nominal maximum power = 17.5V x 5.71 = 99.9W

PWM-reduced charging voltage: 14V

Panel actual charging power = 14V x 5.71 = 79.9W

That's a loss of about 20% of your panel's total power, due to the PWM controller's inability to convert between voltages. In order to not lose charging power, you'd need to be using a solar panel whose Vmp is less than 15V.

12V nominal solar panels, whose Vmp doesn't much exceed the charging voltage of 12V leisure batteries, do exist in wattages up to 150W. If you want more solar power in your system, PWM charge controllers aren't a good choice. If you’re keeping things minimal, with a small leisure battery (up to about 100Ah) and up to 150W of solar just powering lights and USB ports, a PWM controller will do the job. They're affordable, easy to install, and work well in smaller, lower-demand systems.

PWM Charge Controllers and Lithium Batteries

The story is reversed with lithium batteries. These typically have a charging voltage that starts at ~13.5V and tops out at ~14.5 as the battery approaches full charge. Below these voltages, lithium batteries won't charge at all. Because a PWM solar charge controller can't convert between voltages, your solar panels need to be producing at least 14V for your lithium batteries to charge. On hot days when panel voltage drops, or when charging power is very low, a PWM might not be able to hack it. For this reason, it's hard to recommend a PWM solar charge controller for any lithium battery setup.

The MPPT Charge Controller: Smarter, More Efficient Charging

MPPT charge controllers are more sophisticated. Rather than simply matching voltages, they use a DC-to-DC conversion system that tracks the solar panel’s optimal power output (maximum power point) and converts any excess voltage into additional charging current. Remember that power (W) = volts x amps: Because an MPPT can convert between voltages, it can take the solar panel's full power output, convert it to the voltage the batteries want, and supply it at a higher amperage.

Any solar panel above ~150W will have a higher Vmp than what leisure batteries can take. Wiring multiple panels in series also adds up their output voltage, easily putting you above this threshold. Finally, cold temperatures naturally increase a solar panel's output voltage. A MPPT charge controller is comfortable in all of these cases, dynamically converting its output voltage and current to suit your batteries.

Additionally, MPPTs have no problem stepping up their output voltage to match a lithium battery's charging threshold. This means that even on hot days or when charging power is low, an MPPT can fully charge your lithium battery.

MPPT Charge Controller vs. PWM: Which Should you Choose?

Ultimately, your decision comes down to how big your system is, your battery chemistry, what voltage your solar panels produce, how much you're willing to invest upfront.

Nick at Cleversolarpower has done a great video summary of the difference between PWMs and MPPTs:

Sizing Your Solar Charge Controller

Undersized controllers can overheat or fail, while an oversized one might be an unnecessary expense. Let's break down how to size your controller correctly.

1. Match the battery voltage

First, ensure the controller's voltage rating matches your battery bank:

• 12V battery bank: Use a controller rated for 12V.

• 24V battery bank: Use a controller rated for 24V.

• 48V battery bank: Use a controller rated for 48V.

Some solar panel controllers, like Renogy's Rover and Rover Lite series, are compatible with multiple voltages, but always confirm this in the specifications.

2. Calculate the maximum current

Solar charge controllers are sized according to two key figures: charge current and charge voltage. To size for current, determine the maximum current your solar panels can produce and ensure the controller can handle it. Use the formula:

Current (A) = Total Solar Panel Wattage (W) ÷ Battery Charging Voltage (V)

For example, if you have 400W of solar panels and a 12V battery bank that charges at 14.7V:

400W ÷ 14.7V = 27.21A

In this case, you'd need a controller rated for at least 30A to provide a safety margin.

3. Calculate the open circuit voltage (Voc)

To size for voltage, we need to look at your solar panel's open circuit voltage and choose a charge controller that can handle this Voc. If you have multiple panels wired in series, their Voc is added up. For example:

If you have two 100W solar panels wired in series which each have a Voc of 21.5V:

21.5V x 2 = 43V

4. Account for temperature variations

Solar panel voltage increases in colder temperatures. To prevent overvoltage, ensure the controller's maximum input voltage exceeds the panel's open circuit voltage (Voc) adjusted for cold conditions. A common practice is to multiply the total Voc by 1.25 to account for temperature:

Adjusted Voc = Total Voc × 1.25

Using the previous example:

43V × 1.25 = 54V

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Ensure your controller can handle at least this voltage.

In this case, our campervan solar power system needs a charge controller rated for 30A and 54V. Victron's BlueSolar 100|30 would do nicely: it's rated for an open circuit voltage of 100V and a current of 30A.

Renogy's Rover Li 30 would also be a good choice: it's rated for 30A and up to 100V.

By carefully matching your solar array's specifications with the appropriate charge controller, you ensure efficient and safe operation of your van's electrical system. To simplify these calculations, check out our MPPT sizing calculator.

Our handy tool does all these calculations for you based on your solar array, and even recommends charge controllers that fit the bill.

Key Features of Solar Panel Controllers

Now that you have your solar charge controller sized, you can start looking at specific models. What matters here is efficiency, connectivity, and safety. Let's take a look.

Efficiency and Charging Algorithms

Most modern controllers utilize a multi-stage charging process; typically bulk, absorption, and float stages, to efficiently and safely charge your batteries. This approach helps maximize battery lifespan and performance. Some chargers automatically detect your battery's chemistry and change their settings accordingly, whilst others need to be set manually. Either way, make sure you look for a charge controller that works with your battery type.

Conversion efficiency is the stat that solar charge controllers trade on. The best solar charge controllers, like a BlueSolar or SmartSolar Victron MPPT or a Rover Li Renogy MPPT, are 98% efficient, meaning that 98% of the gathered solar energy is transferred to your batteries.

Safety Protections

A good solar charge controller incorporates safety features to prevent dangerous malfunctions. My van's electrics are installed under my bed; I'd never be able to sleep at night had I installed components that didn't have the following protections:

• Overcharge protection: prevents my batteries from being overcharged, which causes overheating and impacts their lifespan

• Over-discharge protection: Stops my batteries from discharging beyond safe levels, again preserving their lifespan

• Short circuit and overload protection: Safeguards why whole system against dangerous electrical faults

• Reverse polarity protection: Protects my controller and connected devices if I accidentally connect anything incorrectly

In addition to these core safety protections, my 40A Renogy Rover Li also has good temperature compensation performance. I use my van year-round, and temperatures vary a lot. Temperature compensation adjusts the way my MPPT manages charging, maximising safety and efficiency as my system's temperature fluctuates. Look for a charge controller with its own temperature sensor and a compensation rating of -3mV to -5mV per °C per cell or –18mV to –30mV per °C total.

Display, Monitoring, and Connectivity

It's important to know what your charge controller is doing. You need to be able to tell, at a glance, how much solar power you have coming in, how much is going to your batteries, how charged they are, and how quickly they're discharging. Faults need to be clearly indicated and easy to understand. The more information, the better.

The first cheap, no-name charge controller I installed in my van had a really basic screen, and I could never tell exactly how well my solar system was working. It was incredibly frustrating, and trying to fiddle with the solar charge controller settings was even worse. I eventually replaced it with a 40A Renogy Rover Lithat has a big, backlit screen, which is easy to navigate and tells me everything I need to know at a glance. I'd never go back. I later added a BT-2 Bluetooth module, which allows me to do all of this from my .

We're putting a 150|60 Victron SmartSolar MPPT in Shane's new van. Victron MPPTs don't have screens, but the SmartSolar models have built-in Bluetoothmodules. This allows you to monitor them and change their settings from your or PC. Being able to check up on your solar system on a big screen with a fully-featured app is a real pleasure, and makes changing settings and monitoring performance over time a dream. If you go with a non-Bluetooth BlueSolar, consider adding a VE.Direct Smart Dongleso you don't miss out on remote connectivity.

Read more about Victron's GX monitoring ecosystem here.

What MPPT Charge Controller to Buy? Our Favourite Models

We'll be recommending Renogy and Victron charge controllers here. I have a Renogy, and Shane has a Victron. We find these brands hard to beat on price considering their excellent efficiency ratings and advanced feature sets. Shane went with Victron for the slightly longer warranty and GX integration, whilst I went with Renogy because they're slightly lighter on the wallet. Both of us went with MPPT over PWM, as we live in our vans full-time and we're happy to pay a bit extra for maximum efficiency. MPPTs from competitors EP Solar and PV Logic have comparable efficiency ratings, warranties, and safety features, but don't manage to compete on price, so they're hard to recommend.

The Best PWM Charge Controller

For anyone installing a budget, low-capacity electricity system, a PWM charge controller can be the right choice. EP Solar's 10A Landstar PWM charge controller would work well for solar arrays up to 120W. It has comprehensive safety features, works for all lead-acid battery types, and even has a built-in USB port, so you can charge your directly from your solar panels.

The Solar Charge Controller for Small Systems

For single panels up to 250W or series setups up to about 350W (depending on configuration), the 100|30 SmartSolar Victron MPPT is an easy sell. It has built-in Bluetooth, yet beats competitors without this functionality on price. You also get impeccable 98% efficiency, robust temperature compensation, compatibility with Victron's GX monitoring suite, and top-of-class performance with partially shaded panels thanks to the BlueSolar algorithm.

The Solar Charge Controller for Large Systems

For single panels up to about 450W and series arrays up to about 800W, you'll need something bigger. Among 60A charge controllers, we recommend Renogy's Rover 60. In these higher capacities, the price difference between Victron and Renogy becomes apparent. Renogy's offering has the same high efficiency rating, the same adaptive algorithms for partial shading, and the same safety features and temperature compensation. It's Bluetooth compatible with a dongle and integrates with Renogy's own monitoring suite, ONE Portal.

The Best Solar Charge Controller - Combined MPPT and DC-DC Charger

As we discussed in our DC-DC charger buying guide, a combined MPPT and DC-DC charger unit promises one box, one fuse set, and less wiring, saving money and simplifying your installation. It's a good option, but be wary of the way the double duty is handled. The device caps solar and alternator inputs at 25A each when both are active. This means that if your engine's running, your solar input is capped at 25A even if your panels could supply more. By contrast, with the engine turned off, your solar panels are free to supply the full 50A.

A 25A MPPT can take the input from up to about 400W of solar, which is still a lot. If you've got a solar array in this range, a smart alternator, and want to simplify your electrical system, a combined unit is worth a look. We recommend Renogy's 50A Combined DC-DC charger and MPPThere. Both the DC-DC and the MPPT component have decent efficiency ratings (though not as high as standalone units); built-in Bluetooth sweetens the deal.

The Best Campervan Solar Kit

Your charge controller and your panels are only one part of the whole solar system. Besides the panels, you need a solar charge controller, fuses, busbars, cables, and mounting equipment for the panel. Overwhelmed? This is where campervan solar panel kits come in.

Buying your whole solar system in a kit ensures your MPPT is sized correctly to your panels, and gives you all the wiring, connectors, fuses, and mounting hardware you'll need for the installation. We can easily recommend this 450W solar kit. It's generously sized for most use cases, powered by Eurener's excellent half-cut solar panel and a SmartSolar Victron MPPT with built-in Bluetooth.

Final Thoughts

You should now be fully equipped to choose among the best solar charge controllers, matching your panels and complimenting your solar system. For an overview of the other components you might need, check out the dedicated section in our solar panels buying guide. When you're ready to take the plunge, check out Victron's SmartSolar MPPTs for their overall balance between supreme quality and affordable price. Alternatively, Renogy's Rover series is a good option at in higher capacities. Or, take the hassle out of sizing and matching components altogether with a solar panel kit.

If you need more information, don't forget to take a look at our comprehensive article on campervan solar systems.

Don't forget to subscribe to The Van Conversion Newsletterfor everything you need to get started with your own van conversion (we'll send you a free wiring diagram when you join).

If you're looking for some guidance with your van conversion, you might be interested in our book Roaming Home, or in our online course The Van Conversion Mastery Course. You'll learn directly from our founder Shane how to convert a van into your dream home - no prior experience needed. Shane also offers one-to-one consultations, where he'll help you with any aspect of your build in a face-to-face video call. All consultations come with a free copy of Roaming Home and our Diagram Pack.

Finally, our Van Conversion Ultimate Guide lays out the whole van conversion process in easy-to-follow sections with tools, materials, and step-by-step instructions. It's the perfect companion for your van build.

A solar charge controller is a regulator for your solar battery that prevents it from overcharging. Batteries are rated for reasonable volts and voltage capacity, and exceeding that voltage can lead to permanent battery damage and loss of functionality over time. Solar charge controllers act as a gateway to your battery storage system, making sure damage doesn't occur from overloading it.

Charge controllers are only necessary in a few specific cases. Most commonly, you will want to look into charge controllers if you are trying to install an off-grid solar system – from rooftop systems to smaller setups on RVs or boats. If you're a homeowner looking to install a solar array with a battery that is connected to the electric grid, there's no need for a charge controller – once your battery is full, excess energy will be directed to the grid automatically instead, helping you avoid overloading your battery. This is known as load control.

To help you find the best match, we created a list of the best portable solar products of . Many of these include built-in solar charge controllers for ease of use.

For the majority of solar shoppers, there's no need to worry about charge controllers. Rooftop or ground-mount solar installations with a battery backup are almost always linked to the electric grid, and in the case that your battery is completely charged, your excess solar energy will automatically reroute there.

If you're interested in installing a small off-grid solar energy system with battery backup, you might need to look into a charge controller to ensure that your battery is safely charged. For relatively small batteries paired with low-output 5-10 watt (W) solar panels, a PWM charge controller should do the job. For more complex DIY solar projects with higher output panels, you may want to consider an MPPT charge controller.

If you want to use solar to go completely off-grid, there are two types of charge controllers to consider: PWM controllers and MPPT controllers.

Pulse width modulation solar charge controllers

PWM solar charge controllers are the standard type of charge controller available to solar shoppers. They are simpler than MPPT controllers and generally less expensive. PWM controllers work by slowly reducing the amount of power going into your battery as it approaches capacity. When your battery is full, PWM controllers maintain a state of "trickle," which means they supply a tiny amount of power constantly to keep the battery topped off.

With a PWM controller, your solar panel system and your home battery need to have matching voltages. In larger solar panel systems designed to power your whole home, panel and battery voltage aren't typically the same. As a result, PWM controllers are more suited for small DIY solar systems with a couple of low-voltage panels and a small battery.

Maximum Power Point Tracking solar charge controllers

MPPT solar charge controllers are a more expensive and complex charge controller option, often coming with items like lcd displays and bluetooth. They provide the same switch-like protection that a PWM controller does and will reduce the power flowing to your home battery as it nears capacity.

Unlike PWM controllers, MPPT charge controllers can pair non-matching input voltages from panels and batteries. MPPT controllers adjust their input to bring in the maximum power possible from your solar array and can also vary their output power to match the attached battery. This means that MPPT charge controllers are more efficient than PWM controllers and more effectively utilize the full power of your solar panels to charge a home battery system.

If efficiency were the only concern in purchasing a controller, an MPPT controller would be the best choice every time. But it's not always practical. Selecting the right solar charge controller involves several factors beyond just efficiency.

PWM vs. MPPT solar charge controller comparison

To determine what controller is right for you, answer these questions:

What type of panels do you have?

Most off-grid solar panels are 36-cell panels designed for 12-Volt battery charging current and amperage ratings of typically around 30 amps. These systems work well with PWM controllers and lithium batteries. 60-cell and 72-cell panels are typically used with a grid-tie solar panel system and have a higher voltage (24-volt systems or more), thus requiring an MPPT controller.

How big is your system?

A PWM controller works with any system size as long as the voltage between the solar power system and home battery are matched, even at low voltage —though typically, they don't match in larger systems, making a PWM ideal for smaller setups. MPPT controllers are less efficient unless your array is at least 170 W.

What temperatures can you expect?

MPPT controllers work better than PWM controllers when it gets colder. As the temperature drops, the voltage increases, and an MPPT controller can capture the excess voltage. In warm climates where the temperature doesn't typically get very low, there isn't extra voltage and an MPPT controller isn't necessary. Temperature sensors are another additional feature that could be added.

What is your budget for a controller?

In general, MPPT charge controllers are more expensive than PWM controllers due to their higher charging efficiency. An MPPT controller can reach up to 20 percent higher efficiency – this is due to its four-stage charging method, which is healthier for your battery life. PWM solar charge controllers are more versatile and more easily installed, but their lower efficiency usually means lower prices.

Renogy

Renogy produces DIY-friendly products for off-grid projects of all sizes. Their offerings include solar panels, batteries, inverters, and more. Their line of charge controllers is ideal for small projects that require a PWM charge controller or larger projects that need the more robust MPPT charge controller. Each type of charge controller comes in different sizes, so you can match your system's requirements.

BougeRV

BougeRV is a reliable resource for RV travelers and others seeking off-grid power solutions. Both their PWM and MPPT chargers are well-rated and have size and compatibility options to make them work with your system. BougeRV also develops other outdoor appliances and power solutions, which is great if you are concerned about overall system compatibility.

Victron Energy

Victron Energy offers a wide range of off-grid energy supply and storage solutions. The company has been in the industry for 45 years and continues to develop new products to meet changing consumer needs. The amp MPPT charge controller linked above is just one of many they have at different sizes and price points to suit your system requirements.

On the EnergySage Marketplace, you can register your property to begin receiving quality quotes for solar installations. If you are interested in storage solutions to pair with your panels, you can simply indicate your interest on your profile for installers to see. Connecting your solar project to the grid (even with battery backup) is a smart move, as it provides a second backup for your system, and in the case that your battery storage capacity isn't enough, you won't simply run out of power to use.

While going completely off-grid with a DIY solar project may work in some cases, if your main concern is saving money, hiring a qualified installer to help you go, solar is still a sound financial decision. What's more, having a professional installer work on your solar project ensures that you are getting the expertise you need to have a functional and effective solar system. Installers also offer warranties and protections for their products that you can't always get with a DIY project. If you want to see how much you can save by going solar, check out our Solar Calculator for an instant estimate based on your unique property.

For more Amorphous Solar Panelinformation, please contact us. We will provide professional answers.