Cerbo GX on a boat: do you need one?

The short answer. A Cerbo GX gathers your Victron gear in one place. It shows it on one screen, sends it to Victron’s VRM portal when the boat has internet, reads tank senders and temperature sensors, and switches two relays. If all you have is a SmartShunt and you’re happy checking a phone, you can skip it. Once you have three or four Victron parts, tanks to watch, or a boat you want to check from home, it starts paying its way.

You’ll need

• A Victron Cerbo GX MK2
• One VE.Direct cable for each VE.Direct product you connect (Victron says 10 m max, and you can’t extend them)
• A screen if you want one at the helm: Victron’s optional GX Touch 50 or GX Touch 70, or a compatible MFD. A phone or laptop on the boat’s WiFi works too
• Internet on board (a router or hotspot) if you want VRM from home
• Optional: Victron’s GX temperature sensors and your existing resistive tank senders

Let’s be straight about what it is. The Cerbo doesn’t charge, measure current or protect anything by itself. It’s the brain that talks to the gear that does. So the real question is how much gear you have for it to talk to.

What does a Cerbo GX actually do?

Victron calls it a communication centre. It runs Victron’s Venus OS and connects inverter/chargers, solar chargers, DC-DC chargers and batteries. On a boat, that boils down to four jobs.

1. One view of everything. Battery state of charge, solar input and charger status, all on one screen.
2. Remote monitoring with VRM. Online, it sends its logs to Victron’s VRM portal. You can check the boat from home and even switch the GX relay or update firmware from there.
3. Tanks and temperatures. The MK2 has inputs for tank senders and temperature sensors.
4. Relays. Two relays that can start a generator, sound an alarm or run a pump.

Which ports does the Cerbo GX MK2 have?

From Victron’s technical specifications for the MK2:

All rows from Victron’s Cerbo GX manual (sources at the bottom).

Two lines in that table matter on a boat. The first is IP20. The Cerbo belongs somewhere dry, like a nav station or a cabinet, not an engine space. The second is Bluetooth. Victron says the Cerbo’s Bluetooth is only for first setup and network setup. It can’t pick up a SmartSolar charger or other Victron gear over Bluetooth. Everything you want on the screen needs a cable.

What connects to it?

Battery monitor. A SmartShunt has a VE.Direct port, and a GX device reads it over a VE.Direct cable. That’s the data most boats want first. If you haven’t picked a monitor yet, SmartShunt vs BMV-712 vs BMV-700 goes through them.

Solar charger. The Victron SmartSolar MPPT 100/30 has a VE.Direct port that Victron’s datasheet describes as a wired data link to GX products. Plug it in and solar shows up next to the battery. For sizing the controller, see Picking an MPPT: 100/20 to 150/60 in one table.

Managed lithium batteries. Some lithium batteries talk to a GX device over a CAN bus. Victron uses BMS-Can at 500 kbit/s for these and says VE.Can and BMS-Can must not share the same bus. If you need both, it points you to a GX device with two CAN buses, and names the Cerbo GX MK2. Only use batteries on Victron’s compatibility list.

DC-DC charger: check first. The Victron Orion-Tr Smart 12/12-30 isolated is set up and monitored in the VictronConnect app over Bluetooth. Its manual mentions no VE.Direct port and no GX connection. What it does have is a two-pole remote on/off connector. So plan to watch it in the app, not on the Cerbo screen.

Tanks and temperatures

This is where the Cerbo does something your phone can’t. The MK2 has four resistive tank level inputs. Victron’s product page lists fresh water, fuel and black water as the tanks to watch. It also has four temperature inputs.

For temperature, use Victron’s GX sensor. The manual gives its range as -40 to +70 °C, and says the BMV temperature sensor accessory won’t work on these inputs. Victron also sells the GX Tank 140 for senders that don’t use the resistive type.

The relays: what they’re for

Relay 1 can be an alarm relay, start and stop a generator, run a tank pump, follow a temperature, or be switched by hand. Relay 2 does temperature or manual switching, and Victron says it needs firmware 2.80 or newer.

Mind the rating. It’s 6 A up to 30 V DC, but only 1 A up to 70 V DC. That’s enough for a signal or a small relay coil. A big load gets its own relay or contactor, with the Cerbo only giving the signal.

VRM: checking the boat from home

VRM needs internet. Victron says that with a connection, the Cerbo sends its logs to the VRM portal whenever it can. Without one, it keeps logging on the device, and you can upload the logs by hand later. Victron’s example puts storage at about 25 MB a month at a one-minute log interval.

So if your boat sits on a mooring with no WiFi or cell router, you won’t get remote monitoring. You’ll still get the local screen, tanks and relays.

Where do you look at it?

Victron lists plenty of ways to see it:

• A GX Touch 50 or GX Touch 70 screen (optional, sold separately)
• A compatible boat MFD. Victron’s page says it integrates with MFDs and NMEA 2000
• Remote Console in a web browser
• VictronConnect on a phone, over the boat’s network
• The VRM portal from anywhere with internet

You don’t need a Cerbo GX if…

• You have one Victron part. A SmartShunt on its own reads fine in VictronConnect on your phone.
• You don’t want to watch tanks or temperatures. Those inputs are a big part of what you’re paying for.
• The boat has no internet, and you don’t want a screen. Without both, the Cerbo has little to show you.
• Your DC-DC charger is the main thing you watch. On an Orion-Tr Smart, that stays in the app anyway.

It earns its place when you have a shunt, solar and an inverter/charger together. Or tanks you’re tired of guessing. Or a boat you want to see from your couch.

How to fit a Cerbo GX MK2: step by step

Here’s how. It’s mostly plugging in cables, and you can take your time getting it neat.

1. Pick a dry spot. It’s IP20, so a nav station or dry cabinet. Wall mount, or DIN rail with Victron’s adapter.
2. Run the VE.Direct cables. One from the SmartShunt, one from the MPPT. Keep each one 10 m or under.
3. Wire tank senders and temperature sensors to the inputs, if you have them, and switch them on in the Cerbo’s settings.
4. Wire a relay if you want an alarm or generator start. Keep inside the relay rating.
5. Power it from the battery. Use the supplied power cable. Victron fits it with an inline 3.15 A slow-blow fuse. The supply range is 8-70 V DC.
6. Connect a screen or the network. GX Touch, MFD, or the boat’s WiFi.
7. Register on VRM once the Cerbo is online, and check your gear shows up.

If a product doesn’t show up, check its cable first, then its firmware. Victron’s manual notes that some older MPPT units can’t connect at all.

Does this guide fit your setup?

This applies if: – Your system runs at 12V, 24V or 48V (the Cerbo takes 8-70 V DC). – You have, or plan to have, Victron gear with VE.Direct, VE.Can or VE.Bus ports. – The Cerbo can live somewhere dry.

This doesn’t apply if: – Your gear isn’t Victron and isn’t on Victron’s supported list. Check Victron’s manual chapter on non-Victron products first. – Your system runs above 60 V. Victron says the Cerbo then counts as a built-in product, with its terminals kept out of reach, so plan that install with a qualified installer. – You only want to watch a DC-DC charger. See above.

Products used in this guide

Prices show live from the store. Monitors are in Battery monitors.

Bundles for this job: Victron smart system bundle

Quick answers

Is a Cerbo GX worth it for a SmartShunt alone? Usually not. The SmartShunt already reads on your phone in VictronConnect. The Cerbo adds value once you have more gear, tanks to watch, or want VRM from home.

Does the Cerbo GX need internet? Only for VRM. Victron says it logs locally when offline. The screen, tanks and relays work without internet.

Can the Cerbo GX read my Victron gear over Bluetooth? No. Victron says its Bluetooth is only for setup and can’t connect to products like SmartSolar chargers. Use VE.Direct, VE.Can or VE.Bus cables.

Can the Cerbo GX MK2 read boat tank levels? Yes. It has four resistive tank level inputs. Victron’s GX Tank 140 covers 4-20 mA and 0-10 V senders.

Will my Orion-Tr Smart show on the Cerbo? Don’t count on it. Its manual names no VE.Direct port or GX connection. It’s monitored in VictronConnect and has a remote on/off connector.

Sources

• Victron Cerbo GX manual, Introduction: https://www.victronenergy.com/media/pg/Cerbo_GX/en/introduction.html
• Victron Cerbo GX manual, Technical specifications: https://www.victronenergy.com/media/pg/Cerbo_GX/en/technical-specifications.html
• Victron Cerbo GX manual, Installation: https://www.victronenergy.com/media/pg/Cerbo_GX/en/installation.html
• Victron Cerbo GX manual, Connecting Victron products: https://www.victronenergy.com/media/pg/Cerbo_GX/en/connecting-victron-products.html
• Victron Cerbo GX manual, VRM portal: https://www.victronenergy.com/media/pg/Cerbo_GX/en/vrm-portal.html
• Victron Cerbo GX product page: https://www.victronenergy.com/communication-centres/cerbo-gx
• Victron SmartSolar MPPT 100/30 & 100/50 datasheet: https://www.victronenergy.com/upload/documents/Datasheet-SmartSolar-charge-controller-MPPT-100-30-&-100-50-EN.pdf
• Victron Orion-Tr Smart DC-DC Charger Isolated manual: https://www.victronenergy.com/upload/documents/Orion-Tr_Smart_DC-DC_Charger_-_Isolated/34439-Orion-Tr_Smart_DC-DC_Charger-pdf-en.pdf
• Victron SmartShunt datasheet: https://www.victronenergy.com/upload/documents/Datasheet-SmartShunt-EN.pdf