Article: How to Choose the Right Victron MPPT Solar Charge Controller for Your System
How to Choose the Right Victron MPPT Solar Charge Controller for Your System
Our lead technician Wesley walks you through the entire process of selecting, sizing, and configuring a Victron SmartSolar MPPT charge controller — from reading the model numbers to dialing in settings in VictronConnect.
Watch the Full Video
Prefer to read? We've broken down everything from the video below.
Why This Matters
Choosing the right MPPT solar charge controller is one of the most common questions we get at Blue Marine — and for good reason. Pick one that's too small and you'll leave solar energy on the table (or worse, damage the controller). Pick one that's too large and you've overspent. The good news is that Victron makes the selection process straightforward once you know what to look for.
What You Need to Know Before You Start
Before you even look at charge controllers, gather two pieces of information:
1. Your battery bank voltage. The most common system voltages are 12V, 24V, and 48V, with 12V being the most popular in marine and RV applications.
2. Your solar panel specifications. You'll need the rated wattage, the open-circuit voltage (Voc), and the maximum power voltage (Vmp) from your panel's datasheet. If you're installing more than one panel, you'll also need to know whether they're wired in series, parallel, or a series-parallel combination — because this changes the total voltage and current the charge controller will see.
How to Read a Victron MPPT Model Number
Every Victron SmartSolar MPPT model has two numbers in its name, and they tell you exactly what the controller can handle:
The first number is the maximum PV (solar panel) input voltage the controller can accept. For example, on a 75/15, the controller can handle up to 75V from your solar array.
The second number is the maximum charge current (in amps) the controller can deliver to your battery bank. On that same 75/15, the controller can push up to 15 amps into your batteries.
Combine these two numbers with the maximum wattage the controller supports at your specific system voltage, and you have all the variables you need. That wattage figure is listed on the controller's datasheet, which you can find on bluemarine.com or victronenergy.com.
One thing to note: Victron groups several charge controllers together on a single datasheet, so you may need to look through the document to find the specific model you're considering.
Sizing Example: One Panel
Let's say you're installing a single 145W Sol-Go solar panel on a 12V system. That panel has a rated voltage of about 24.5V.
Looking at the Victron SmartSolar MPPT 75/15:
The panel's 24.5V is well under the controller's 75V maximum input. And the 145W panel is well within the 220W maximum that the 75/15 supports on a 12V system. So the 75/15 is a great fit — with headroom to spare.
Sizing Example: Two Panels in Series
Now let's say you're installing two of those same 145W panels wired in series. When panels are wired in series, you add the voltages together and sum the wattage:
That gives you approximately 49V and 290W total.
The 75/15 can still handle the voltage (49V is under 75V), but 290W exceeds the 220W maximum wattage it supports on a 12V system. So you'd need to step up to the next larger controller — like the MPPT 100/20 or 100/30.
This is the basic sizing process: check that your array's total voltage stays below the controller's first number, and that your array's total wattage stays below the controller's rated wattage for your system voltage.
A Helpful Resource: Wiring Unlimited
If you want to go deeper, Wesley recommends Victron's Wiring Unlimited guide. Written by one of Victron's engineers, it's a concise, section-by-section reference that covers everything from solar wiring to battery connections, complete with equations and best practices. We keep a link to it in our Installation Resources menu as well.
Key Features of Victron SmartSolar MPPT Controllers
Bluetooth built-in (Smart and SmartSolar models). If you see "Smart" or "SmartSolar" in the product name, the controller has Bluetooth on board. This is the easiest way to configure, monitor, and update your charge controller using the free VictronConnect app on your phone or tablet — no extra cables or dongles required.
Multi-stage charging algorithm. All Victron MPPT controllers support multiple battery chemistries, including lithium (LiFePO4), AGM, gel, and flooded lead-acid. Just make sure to select the correct battery type during setup — this is one of the most important configuration steps and one that's easy to overlook.
Overcurrent protection. Look at the second number on the controller (the max charge current) and size your fuse accordingly. For example, if your controller is rated at 50A, you'll want a 60A or 70A fuse on the output side. Check out our Victron MEGA-Fuses and MIDI-Fuses for the right protection.
Setting Up Your MPPT in VictronConnect
In the video, Wesley walks through the VictronConnect app setup on his laptop. Here's a summary of the key steps:
Connect to the controller. Open VictronConnect, go to the Local device list, and select your SmartSolar MPPT. If the controller is connected to panels in sunlight, you'll see live performance data on the main screen.
Check firmware. Tap the three-dot menu (ellipsis) in the top corner, then go to Product Info. This is where you can check for and install firmware updates — always a good idea before configuring a new controller.
Configure battery settings. Tap the gear icon to enter Settings. Here you'll set your system voltage (12V, 24V, or 48V), max charge current, and battery type. For lithium batteries, select "Smart Lithium" and verify that the charge voltages match your battery manufacturer's recommendations. You'll see the full multi-stage charging algorithm (absorption voltage, float voltage, equalization, etc.) laid out clearly.
Explore advanced features. Depending on your controller model, you may also have access to features like load output settings, VE.Smart Networking (which lets the MPPT communicate with other Victron devices over Bluetooth for coordinated charging), and streetlight mode. These vary by model, so poke around and see what's available for yours.
Lock your settings. Once everything is dialed in, VictronConnect gives you the option to lock the configuration with a PIN code. This is especially useful for boats and RVs where other people may access the system — it prevents accidental changes to your carefully configured settings.
Quick Reference: Victron MPPT Sizing Checklist
- Determine your battery bank voltage (12V, 24V, or 48V)
- Get your solar panel specs: wattage, Voc, and Vmp
- Determine your wiring configuration (series, parallel, or series-parallel)
- Calculate total array voltage and total wattage
- Confirm total array voltage is below the controller's first number (max PV voltage)
- Confirm total array wattage is below the controller's rated wattage for your system voltage (from the datasheet)
- Select your fuse based on the controller's second number (max charge current)
- Configure battery type and charge settings in VictronConnect
Need Help Sizing Your System?
If you're still not sure which MPPT is the right fit, we're here to help. Our team of certified technicians works with Victron solar charge controllers every day, and we're happy to review your panel specs and recommend the right controller for your setup.
Schedule a free consultation or give us a call at (800) 628-6306.
You can also browse our full selection of Victron SmartSolar MPPT charge controllers, solar panels, and solar cables and accessories at bluemarine.com.
