Victron MPPT Solar Charge Controllers Explained

Are Victron Energy solar charge controllers better than the average solar charger? Yes. How much better? A whole lot better.

This blog explains several stand-out features that maximize efficiency, protect your battery from over or undercharging, and facilitate intelligent communication between your inverter, battery bank, and other equipment.

Fantastic battery charging

Take a look at the spec sheet for any given solar panel. It has its own performance curve and a peak performance number based on temperature and how much sun is reaching them. Finding and staying near that peak performance number dramatically improves PV output. Victron MPPT (Maximum Power Point Tracking) technology makes constant adjustments based on input current to find and collect the most power in the shortest amount of time. This built-in feature is part of what makes Victron MPPTs impressively effective battery chargers. For more perspective on the difference in performance read our article, PWM vs. MPPT Solar Charge Controllers.

Besides cloud cover and partial shading, very high or low outdoor temperatures can significantly impact how much energy we can harvest from a solar panel. Lithium-ion and lead-acid batteries are also prone to damage in very cold or hot environments. Victron MPPT chargers have a built-in internal temperature sensor that will automatically adjust absorption and float charge voltages based on either the battery temperature (for which you would need a battery monitor) or the solar charger's internal temperature.

Pro-tip: If you want to know the battery temperature but do not have a BMV-712 or SmartShunt in the system, you can use the Smart Battery Sense to monitor the temperature and voltage at the battery and relay that data back to the charge controller.

Start at a higher voltage

Victron SmartSolar and Blue Solar MPPT charge controllers allow you to bring in a higher voltage from your solar array. It is critical to design your solar array to ensure that your input voltage is 5V above your battery voltage - at a minimum. As you go up in voltage, your efficiencies will improve. 

How does coming in with a higher voltage improve PV performance? Firstly, you can now wire panels in series and reduce connections on, for example, the roof of an RV or camper, which raises the voltage and bumps the current down. Secondly, coming in at a higher voltage means less cable line loss. We can also use smaller cables. Lastly, the time window in which you're able to charge batteries during the day—even in low-light conditions in the morning and late afternoon—is greatly expanded. You can start to see how little things add up very quickly to improve the overall efficiency of a system. Watch the video below for a detailed explanation of why Victron MPPTs are designed to start at a higher voltage and the resulting efficiencies.

Note: If you simply swap out a PWM for an MPPT, you will not reap the full rewards of this upgrade. You can keep your existing array, but you will need to rewire it for higher voltage. For example, a 12 Volt solar array with 2 panels can easily become a 24 Volt solar array by changing the wiring from parallel to series. 

Safe, battery-specific charging

Solar charge controllers have a reputation for boiling (overcharging) or undercharging batteries and we know that ever time we fully discharge a battery or charge it incorrectly, we shorten its lifespan.

Like solar panels, every battery also comes with a spec sheet that identifies an ideal charge algorithm to maximize that battery's performance over time. It's not a suggestion. It's a prescription, you might say, for how to maintain the health of that battery. Being able to configure your charger for precisely what your battery requires is, therefore, very important. Victron MPPT solar chargers allow you to choose a preset charging algorithm for your battery type, such AGM, or Li-ion, or set very specific charging parameters based on your battery's unique needs to ensure a full charge, every time.

Related Video >>> Did you know: How to create a battery profile for non-Victron batteries?

SmartSolar MPPTs solar charge controllers are Bluetooth-enabled (Smart = Bluetooth), which means you can connect and change the settings via the free VictronConnect app. From the app, you can see how many Watts of power are being generated in real-time, consumption trends, and current battery voltage and state of charge.

Choosing from preset charging algorithms for your battery type will get you into the ballpark. But if you want to dive deeper, you can adjust the voltage, maximum charge current, stage duration, and more from the app. By wisely managing that charging process, that SmartSolar or BlueSolar MPPT is not only maxing out your PV performance, but it's also doing everything it can to max out the life of your battery.

For lighting and other small DC load systems, the built-in 'Load output' function on Victron MPPT charge controllers prevents damage caused by running your batteries completely dry. You can configure the exact voltage at which your SmartSolar should disconnect from a load to prevent an excess drain on your batteries. The Victron MPPT solar chargers will also run an automatic equalization charge for any battery, whether it’s lead acid, a 2-stage lithium charging, or anything in between.

Meanwhile, a SmartSolar charge controller will still attempt a 100% recharge each day. If it can't recharge to 100%, such as during periods of poor weather, the SmartSolar intelligently manages the battery charge level until it can successfully recharge your system.

In stand-alone systems, where you need the charge controller to be more than just a charge controller, all the brains built into these controllers really start to add value. On larger controllers, for example, the built-in relay is especially handy for things like starting a generator, and a whole host of other creative design options.

Recover a fully discharged battery

This is huge and unique to Victron solar charge controllers. A SmartSolar charge controller will 'wake up' and start to charge a battery—even a severely depleted battery—with PV input alone. This assumes that the cells are not permanently damaged.

This capability to initiate a charge on a fully discharged battery has proved a huge help to our friends at Explore.org, who set up wildlife camera systems in hard-to-reach locations with heavy snowfall that can completely cover the system for months at a time. When batteries go down, you need them to come back, and you need them to do that on their own. The fact that they do is a total game changer and a welcome surprise for old-time solar installers like ourselves. 

Remote monitoring: How did we ever live without it?

Like many Victron products, your solar installation can be connected to the Victron Remote Management Portal (VRM) using a GX device. VRM provides access to rich data on the incoming watts of PV (from your solar panels), the charge state, battery voltage, current yield, and past yields. It's impossible to emphasize how satisfying and helpful this is. As a troubleshooting tool, there's nothing better. Suppose I'm concerned that my batteries aren't charging or that my panels are not producing enough power due to the shadow cast by a big tree on my property. In that case, it's easy to pull up the last 30 days of performance data in one clean-looking graphic to see how much power the batteries have taken in, what my trends in power consumption are for this week, and to make decisions and adjustments from there. No mysteries, just good data for decision-making in a visual format that anyone can understand. 

Curious minds want to know…

What kind of battery monitor is used with a Victron solar charger?

Victron makes several different types of battery monitors. The Smart Battery Sense is a battery voltage and temperature sensor with a wireless connection to the rest of the Victron "Smart" products. Used together with a solar charge controller, it acts to measure the battery temperature, as well as the battery voltage and sends this information via Bluetooth to the solar charger. Information on the battery's temperature facilitates more precise charging as the solar charge controller will adjust the charge based on that real-time temperature data. Likewise, if the battery monitor detects a voltage drop, it will tell the charge controller to increase the voltage to compensate and protect the battery. 

Other Victron battery monitors include the BMV-712 Smart or a SmartShunt (which now comes in an IP65 rated model); both provide Bluetooth access to settings and stats with a Temperature sensor for BMV. Lynx smart shunt, and of course, if you're using Victron Smart lithium batteries, then a Lynx Smart BMS also monitors SOC and much more.

Is it Ok to oversize your charge controller?

Sure. Solar panels are constantly changing and improving. The SmartSolar 450/100, for example, is designed so that if you add more solar panels in the future, you already have multiple PV input options. However, you might get the best result by matching an MPPT to your solar system as it is now and adding a second MPPT in the future. 

Installing a larger solar controller for future expansion can be risky unless you're confident you can obtain the same solar modules you have now. I often advise my customers to either A.) Add new solar panels that closely match their existing ones or B.) Add a second charge controller specifically for the new modules. In short, given the rapid rate of change in the solar module market, it's better to buy a second controller in the future for new and improved modules.

Thankfully, the communication between Victron Energy solar charge controllers is very good, such that they act like one large controller, even if the solar arrays are very different. 

When should you add more than one charge controller?

Remember that Maximum Power Point Tracking (MPPT) solar chargers are highly efficient because they find and stay close to that peak performance number, the point on the curve at which they can harvest as much energy from the sun. If two panels are mounted on the roof of a house - one facing East - and one facing West, they should be wired independently. Otherwise, they will fight to determine where that peak performance number is. The MPPT cannot find that peak number when it receives conflicting information. 

Similarly, imagine solar panels atop the roof of an RV or camper van. They may be tilted in different directions. One may be fully or partially shaded when parked. If you don't isolate them into separate charge controllers, your performance off of any one panel will suffer significantly. 

Lastly, whenever you add a very different type of panel into a solar array or mix and match panels because what you bought previously is no longer being manufactured, you'll want the new or different solar panel wired to its own solar charge controller. 

How do I make sure multiple charge controllers work together? 

Victron's products are designed to communicate and work together. If you have a Victron Cerbo GX, enable the DVCC functionality. That will ensure that all your charge controllers talk and function as one big solar charger, regardless of what they receive.

If you don't have a Cerbo GX, you can use the VE network option in every Bluetooth-enabled solar charge controller to sync to the other charge controllers in your system. Again, they will create a network, collaborating as if one controller. This prevents them from competing with each other and maximizes the system's overall performance. 

Can you charge batteries without a charge controller?

Yes, but you don't have a way to regulate the voltage, and you'll likely damage your battery. Batteries, often the most expensive part of a solar system, can be damaged over time because they have been repeatedly over-changed or undercharged. We would only - cautiously - recommend a system without a charge controller if you had a panel that matched the ideal charging voltage of your battery and if the panel was sufficiently small so that you couldn't overcharge your battery. A simple PWM charge controller can be as little as $25 and can protect a system worth thousands of dollars over many years. An MPPT offers the same protection and the ability to max out the efficiency of any system, large or small.

Have a related question or need help choosing the right Victron solar charger for your application? Just shoot us a message here.