Filters
What do you want to measure?
From battery state-of-charge to cabin temperature, here's the gear that tells you what your system is actually doing — on your phone, a gauge, or your GX screen.
Swipe the table sideways to see every column →
| You want to know… | Reach for | Good to know | From |
|---|---|---|---|
| Battery charge & history | SmartShunt or BMV monitor | Shunt-based % state of charge, time-remaining, Bluetooth | $85.85 USD |
| Whole-system DC + main fuse | Lynx Shunt VE.Can | Busbar, battery monitor and main fuse in one | $295.30 USD |
| AC energy, grid or genset | Energy Meters + AC Current Sensor | kWh and load metering; needs a GX device to display | $47.80 USD |
| Battery temperature | Smart Battery Sense or temp sensor | Temperature-compensated charging; some send voltage too | $39.10 USD |
| Solar controller at a glance | MPPT Control Display | Plug-in readout for SmartSolar / BlueSolar MPPTs | $51 USD |
| Cabin, fridge, freezer, bilge | RuuviTag or Roam hub | Wireless temp/humidity (Ruuvi) or cellular bilge & battery (Roam) | $39.49 USD |
| Raw high-current measurement | Measurement Shunt | Bare 50mV shunt, 500–6000A, for custom gauges | $22.10 USD |
Comparing the battery gauges in detail? See battery monitors. For RuuviTag wireless sensors and the Victron Cerbo/Ekrano integration, see Ruuvi Tags. Most meters and CTs report through a GX device.
Three things worth knowing first
What a shunt is, what needs a GX to read it, and how the wireless options differ.
Battery monitoring runs on a shunt
A shunt is a precision resistor wired in the battery's negative path; the monitor measures the tiny voltage across it to count every amp in and out. That's how a SmartShunt or BMV gives you a true % state of charge and time-remaining — far more honest than reading voltage alone.
Some sensors need a GX to display
The SmartShunt, BMV, and Smart Battery Sense show up on your phone over Bluetooth. Energy meters, current transformers, and the AC current sensor feed data to a GX device (Cerbo or Ekrano) rather than having their own screen — so plan a GX if you want grid or AC-load metering.
Wireless: Ruuvi vs Roam
RuuviTag sensors are tiny Bluetooth tags for temperature, humidity and movement — great for the fridge, freezer, engine bay or cabin, and they can feed a Victron GX. The Roam hub is cellular: it watches bilge, battery and GPS and texts you, even with no one aboard and no Wi-Fi.
Why buy your monitoring from Blue Marine
True Blue Victron distributor
Warranty and setup support handled by us, not a ticket queue.
ABYC-certified advisors
We help you pick the right shunt size and sensors for your bank and wiring.
Free US shipping over $49
Fast shipping from Seattle and 60-day returns on non-lithium items.
Real people, real boats
Call (800) 628-6306 Mon–Sat.
Not sure what to monitor?
Tell us what you want to keep an eye on — battery health, energy use, temperature, the bilge — and we'll spec the sensors and any GX you need to see it all.
Meters & sensors FAQ
What's the difference between a SmartShunt and a BMV?
Both are shunt-based battery monitors. The SmartShunt has no display of its own — you read it on your phone or a GX screen — while the BMV-712 adds a round panel gauge plus Bluetooth. Pick the SmartShunt if you already watch things on a phone or Cerbo; pick a BMV if you want a dedicated readout at the panel. We compare them in detail on the battery monitors page.
Do these sensors need a Cerbo or other GX device?
It depends. The SmartShunt, BMV and Smart Battery Sense talk over Bluetooth on their own. The energy meters, current transformers and AC current sensor are designed to report into a GX device, so plan on a Cerbo or Ekrano if you want AC or grid metering on a screen.
What exactly is a shunt?
It's a precision low-value resistor installed in the battery's main negative cable. Current flowing through it creates a tiny, predictable voltage (these are 50mV shunts), and the monitor reads that to count amp-hours in and out. It's the most accurate way to track state of charge.
RuuviTag or a wired Victron temperature sensor?
A wired Victron temp sensor reports battery temperature to a BMV or GX for temperature-compensated charging. RuuviTags are wireless Bluetooth tags you can place anywhere — fridge, freezer, engine bay, cabin — and read on a phone or feed into a GX. Many boats use both: wired at the battery, wireless everywhere else.
Which energy meter — ET112, ET340, EM24, EM540 or VM-3P75CT?
The short version: ET112 is single-phase; the ET340, EM24 and EM540 are three-phase; and the VM-3P75CT is a compact three-phase option using current transformers. In North American single-phase setups the ET112 or VM-3P75CT covers most needs. Tell us your service and what you're measuring and we'll point you to the right one.
What's a current transformer (CT) for?
A CT clamps around a conductor to measure the current in it without breaking the circuit. The Victron CTs here pair with the MultiPlus-II to sense PV or AC input, and the AC Current Sensor lets a GX read AC loads. They're measurement accessories, not protection.