5 Best 24V Marine Solenoids For Larger RV Systems For True Off-Grid Power

You’ve spent thousands on lithium batteries and a monster 24V inverter for your rig, but how are you going to safely disconnect it all with the flip of a switch? A simple mechanical switch that can handle 200+ amps at 24 volts is massive, expensive, and impractical to run into your living space. This is where the humble solenoid becomes the unsung hero of any serious off-grid RV electrical system.

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Why 24V Solenoids Are Key For Large RV Power

Moving to a 24V system is a smart play for larger rigs. It lets you run bigger inverters and solar arrays while using smaller, cheaper, and lighter gauge wiring compared to a 12V setup. But with that power comes the need for robust control. You can’t just use any old switch to handle the massive amperage that a 3000W or 5000W inverter can pull.

A solenoid, also called a contactor or relay, is simply an electronically operated switch. A small amount of power sent from a simple dashboard switch energizes a coil, which creates a magnetic field that closes a heavy-duty internal contact, completing a high-amperage circuit. This lets you safely control a massive electrical load from anywhere in your RV with small, easy-to-run wires.

For an RV, you absolutely want a marine-grade solenoid. These are built to withstand constant vibration, moisture, and temperature swings. They are also typically ignition protected, meaning they are sealed to prevent any internal sparks from igniting potential fumes (like propane) in a storage bay—a critical safety feature.

The most important distinction to understand is continuous duty versus intermittent duty. Intermittent solenoids are for short, high-draw tasks like starting an engine. They’ll overheat and fail if you leave them on. For connecting your house battery bank to your inverter and other loads, you must use a continuous duty solenoid designed to stay energized for hours or days on end.

Blue Sea Systems ML-RBS: Remote Battery Switch

If there’s a gold standard for RV battery control, the Blue Sea ML-RBS (Magnetic Latching – Remote Battery Switch) is it. This isn’t just a solenoid; it’s a complete battery management tool. Its standout feature is the magnetic latching mechanism. Unlike traditional solenoids that need constant power to stay closed, this one uses a pulse of energy to switch on and another pulse to switch off.

The benefit is huge for off-grid power conservation. When it’s on (or off), it consumes zero power. That constant 0.5A draw from a traditional solenoid might not sound like much, but it adds up to 12 amp-hours every single day. The ML-RBS eliminates that parasitic drain entirely.

With a 500A continuous rating, it can handle virtually any inverter you’d realistically install in an RV. It also features a bright yellow manual control knob. If your control switch or wiring ever fails, you can walk to the unit and physically turn it on or off, ensuring you’re never left without power or a way to shut things down in an emergency. It’s expensive, but for a primary battery disconnect, the reliability and efficiency are unmatched.

Cole Hersee 24213-01: Heavy-Duty Continuous Use

The Cole Hersee 24213-01 is a classic for a reason. It’s the rugged, reliable workhorse you’ll find in commercial trucks, marine applications, and industrial equipment. There are no fancy features here—just a rock-solid, 200A continuous duty 24V solenoid that does its job without complaint. It’s fully sealed against dust and water, making it perfect for mounting in an RV’s underbelly storage bay.

This is an excellent choice for tasks like combining two separate 24V battery banks or creating a sub-panel disconnect for a bank of high-draw DC appliances. Its 200A rating is more than enough to handle most 24V inverters up to about 4000W. If you need simple, proven reliability for a secondary circuit, this is a fantastic and cost-effective option.

The main tradeoff compared to the Blue Sea is that this is a standard electromagnetic solenoid. It requires a small but constant current (around 0.4A) to hold the contacts closed. While not ideal for a main disconnect in a power-sipping build, it’s a perfectly acceptable compromise for circuits that aren’t energized 24/7.

Victron BatteryProtect: Smart Solid-State Option

For those who prefer modern electronics over mechanical relays, the Victron BatteryProtect is a compelling alternative. It’s not a solenoid in the traditional sense; it’s a solid-state switch using MOSFETs. This means there are no moving parts to wear out or arc, offering potentially higher reliability and a completely silent operation.

The "smart" part is its primary function: it’s a programmable low-voltage disconnect (LVD). You can set a precise voltage at which it will automatically disconnect your loads, protecting your expensive battery bank from damaging over-discharge. It can also be controlled remotely by a switch or, more powerfully, by the BMS of a lithium battery for intelligent, integrated protection.

There are two key considerations. First, solid-state switches have a small internal resistance, which creates a minor voltage drop under heavy load—more than a high-quality mechanical relay. Second, while robust, they can be more sensitive to catastrophic short circuits than a beefy mechanical contactor. It’s an excellent choice for protecting sensitive loads, but for a main inverter disconnect, many still prefer the raw current-handling ability of a top-tier mechanical solenoid.

Trombetta 114-2411-020: The Bear Contactor

Trombetta is another major name in the industrial and heavy-equipment world, and their "Bear" series of contactors are built tough. The 114-2411-020 is a popular 24V model known for its compact, sealed design and durability. It’s an electromagnetic, continuous-duty solenoid that provides a great balance of performance and value.

With a continuous current rating of 150A and an intermittent peak of 800A, it’s a versatile player. It’s beefy enough to serve as a main disconnect for systems with inverters up to around 3000W. Its compact size and sealed housing make it easy to tuck away safely in a battery compartment.

Think of the Trombetta Bear as a direct competitor to the Cole Hersee workhorse. The choice between them often comes down to availability, price, and form factor. Like the Cole Hersee, it has a constant coil draw when energized, making it a simple and effective component for controlling specific circuits rather than being the absolute main battery disconnect where zero parasitic draw is the goal.

PAC-500 Relay: High-Amp Isolator Performance

Sometimes you just need to switch a massive amount of current. The PAC-500, while popular in the high-end car audio scene, is a beast of a relay that’s perfectly at home in a large RV power system. As the name implies, it boasts a 500-amp continuous rating, putting it in the same league as the Blue Sea for pure power handling.

This is the tool for the job if you’re running a massive 24V inverter (5000W or more) or need to parallel multiple large battery banks. It’s designed for one thing: switching huge DC loads reliably. It’s a simple, powerful, and relatively affordable way to get a very high amperage rating.

The PAC-500 is a no-frills, electromagnetic solenoid. It requires constant power to its coil to stay engaged and lacks the smart features or manual override of its more expensive counterparts. But if your primary concern is safely and remotely switching a circuit that pulls between 200A and 500A continuously, it’s one of the strongest options available.

Choosing Your Solenoid: Amperage & Duty Cycle

Don’t just guess when selecting a solenoid. The decision comes down to two critical factors: amperage rating and duty cycle. Get either one wrong, and you risk component failure or even a fire.

First, calculate your maximum continuous amperage. For an inverter, a conservative formula is (Inverter Watts / Low Battery Voltage) * 1.25. For a 3000W inverter with a 22V low-voltage cutoff, that’s (3000 / 22) 1.25 = ~170A. You need a solenoid with a continuous* rating higher than that. The intermittent rating only matters for brief surges, like an motor starting up.

Second, as we’ve covered, you must use a continuous duty solenoid for any load that will be on for more than a minute or two. A starter solenoid used as a battery disconnect will overheat in under an hour and weld itself shut or burn out completely. The component’s datasheet will always specify its duty cycle. If it doesn’t say "continuous" or "100% duty cycle," assume it’s intermittent and don’t use it.

Proper Solenoid Installation and Wiring Safety

Where and how you install your solenoid is just as important as which one you buy. A great component installed poorly is a dangerous liability. Keep it as close to your positive battery terminal as possible. Every inch of unfused, high-amperage cable is a potential point of failure.

Use correctly sized cable and high-quality, properly crimped lugs for all connections. Loose connections create resistance, which generates immense heat under heavy load—this is a primary cause of electrical fires in RVs. Use a torque wrench to tighten the nuts on the solenoid terminals to the manufacturer’s specification. Don’t just guess.

Finally, and most importantly: a solenoid is not overcurrent protection. You must install a catastrophic fuse, like an ANL or Class-T fuse, in the positive cable between the battery and the solenoid. If there’s a dead short downstream, the fuse is what saves your wiring, your batteries, and your rig. The solenoid just switches the power; the fuse provides the safety.

Ultimately, the right solenoid is the invisible guardian of your electrical system. It provides crucial control and a layer of safety, allowing your complex 24V system to operate with the simple flick of a switch. By matching the component’s amperage, duty cycle, and features to your specific needs, you build a more reliable, safer, and more capable off-grid home on wheels.