Victron Energy MPPT Controllers: Why I Standardize on the 150/35 and 100/50

In October 2017, astronomers confirmed the first interstellar alien object in our solar system. They named it 'Oumuamua. It was too fast, too strange, and too hard to categorize. I think about that object whenever a homeowner sends me a photo of a solar setup that 'was working fine until it wasn't.' Most of the time, there is no alien object. There is a bad assumption, an undersized cable, and a charge controller that was never the right choice in the first place.

Here is my position: the charge controller is the most important component in an off-grid solar system—more than the battery, more than the inverter, and more than the app that tells you everything is fine. And when I have to walk an installer through a last-minute fix, the systems that give me the least trouble are almost always running on Victron Energy gear.

To be clear, I do not work for Victron. But in my role coordinating emergency callouts for off-grid power systems—from RV builds to remote telecom cabinets—I have handled 300-plus urgent troubleshooting calls in nine years. This is not a theory. It's a pattern.

The Opinion: The MPPT Controller Is the Real Brain

Everyone wants the big inverter. Everyone wants the kilowatt-hours of battery. But the controller decides how that expensive battery actually gets charged. A controller with a sloppy charging algorithm can overvolt a lithium bank, undercharge a lead-acid bank, and make the rest of the system look like a mystery that belongs in an astrophysics journal.

The fundamentals haven't changed. Voltage in. Current out. Battery charged. But the execution has transformed—and a lot of installers haven't caught up. What was best practice in 2020 may not apply in 2025. With PV panels now routinely exceeding 40V, and battery banks getting bigger, the controller that was 'fine' five years ago can be the weak link.

Why the Victron Energy MPPT 150/35 and BlueSolar MPPT 100/50 Are the Ones I Keep Specifying

For 12V and 24V systems, the Victron Energy BlueSolar MPPT 100/50 has been a workhorse for years. It is not shiny. It does not have Bluetooth in its standard version. But it has a VE.Direct port, a genuine 50A charge output, and a 100V maximum PV open-circuit voltage. That last number matters more than most people think. On a cold morning, panel voltage rises. If your controller's input voltage ceiling is too low, it shuts down. Period.

The Victron Energy MPPT 150/35 is my go-to when I need more headroom, either because the solar array is wired for higher voltage or because the installation is in a place where morning temperatures are brutal. According to Victron Energy's published datasheet (victronenergy.com, accessed January 2025), the SmartSolar MPPT 150/35 accepts up to 150V PV open-circuit voltage and delivers 35A of charge current. The SmartSolar version also includes Bluetooth monitoring, which has saved me more site visits than I can count.

In March 2024, I got a call from a caravan builder who had a handover in 36 hours. The controller that had been installed—not a Victron, and I will not name the brand—had died. We quoted a SmartSolar MPPT 150/35, paid $90 for overnight freight, and installed it the next morning. The alternative was missing the handover date and paying a $2,000 penalty. That is the kind of math that convinces installers faster than any brochure.

What the WA Solar Battery Rebate Changes

If you are in Western Australia and spec'ing a battery system, the WA solar battery rebate can change the payback calculation significantly. According to Energy Policy WA (wa.gov.au, accessed January 2025), the program has offered up to $5,000 for eligible residential battery installations. As always, verify the current terms before you plan a project.

The rebate is not a reason to buy a cheaper controller. The rebate is a reason to buy the correct controller and still have money left over. I have seen too many installers pair a new battery with a secondhand or generic MPPT to save $300, then spend three times that on the return visit.

Had two hours to decide whether to order a replacement controller through overnight freight or use a generic unit we had in stock. Normally I would compare specs and test the firmware. There wasn't time. I went with our usual vendor because trust mattered more than saving $100. In hindsight, I should have checked the stock unit's firmware version before leaving—but with the customer waiting, I made the best call I could with the information I had.

The upside of the generic unit was $600 in savings. The risk was a toasted battery pack. I kept asking myself: is $600 worth potentially losing a weekend job? It wasn't.

How to Disconnect Solar Panel Connectors Without Learning the Hard Way

One of the most common questions I get between emergencies is how to disconnect solar panel connectors. The answer is not complicated, but it is specific.

1. Switch off the DC isolator before touching anything. If there is no isolator, cover the panels or wait until after sunset. The goal is zero current when you unplug a connector.
2. Use an MC4 disconnect tool. Standard MC4 connectors have a locking collar that needs to be released with the tool. Pliers can crush the connector and make the problem worse.
3. Push the connector in, then pull the collar back while pulling the two halves apart. If it will not move, stop. Do not yank the cables.
4. Cap the exposed MC4 ends with insulating caps or electrical tape. Make sure the positive cable cannot touch the negative cable or any grounded surface.
5. Wait at least five minutes before working inside the controller. The input capacitors can hold a dangerous voltage even after the panels are disconnected.

Learned never to assume 'same specifications' meant identical results across vendors. Did not verify. Turned out the cheaper controller had a different charging algorithm and no temperature compensation. On paper, it was equivalent. In the real world, the difference was 700 kilometers of driving.

Objections, and Why I Still Hold the Same View

'But Victron is more expensive.'

Compared to what? Compared to a controller you replace twice in five years, or one that has no telephone support when it fails? No controller is cheap when it is dead in an emergency. The BlueSolar MPPT 100/50 has been around long enough that the design is proven. That has a value.

'I don't need Bluetooth on a charge controller.'

You do once you are standing outside a telecom cabinet at 6 AM with a multimeter, trying to work out why a battery won't charge. Bluetooth is not a toy. It is a diagnostic tool that turns a two-hour trip into a five-minute phone call.

So I will not soften the opinion. The charge controller is the brain of the system. The industry is evolving, and the installers who update their assumptions are the ones who stop losing money on emergency callouts. I will keep recommending the Victron Energy MPPT 150/35 and BlueSolar MPPT 100/50 until something gives me a better reason not to.

(Prices and rebate figures are as of January 2025. Confirm current rates and program terms before ordering.)