If you're building a Victron-based 48 V boat system, the Cerbo GX is the device that pulls it together. It isn't a charger, an inverter or a battery monitor. It's the coordinator that lets the chargers, inverters, MPPTs, BMS and shunts work as one system, and it gives the helm a single screen showing what the electrical system is doing.
The name now covers three versions. The original Cerbo GX was followed by the Cerbo GX MK2, which Victron's manual describes as "almost identical to the Cerbo GX, but with two VE.Can ports". The current datasheet lists the MK2 alongside a newer Cerbo GX MK3, which is "three to four times faster than the MK2". This page sets out what each difference means on a boat, from Victron's own documents.
If you're configuring a multi-unit Victron array and just need the Cerbo step, see Configuring a three-phase Victron charger array.
What a Cerbo does on a boat
Everything in the system reports to the Cerbo:
- Inverter/chargers (MultiPlus-II, Quattro) over VE.Bus
- MPPT solar controllers over VE.Direct, VE.Can or USB
- The BMS over VE.Can (Lynx Smart BMS, Lynx BMS NG) or BMS-Can (managed batteries such as BYD and Pylontech)
- Battery monitors such as the SmartShunt over VE.Direct
- Tank senders, temperature sensors and digital inputs on its own terminals
It then shows the whole system on a GX Touch screen, a browser or Victron's VRM portal, and coordinates charging through DVCC. With DVCC, the BMS publishes charge voltage and current limits once, and compatible chargers and inverter/chargers follow them. The Lynx Smart BMS NG guide covers DVCC on a propulsion bank, and the Cerbo motor drive guide covers putting the propulsion motor on the same screen.
The one difference that decides it on a boat: CAN ports
A Cerbo talks to two kinds of CAN network, at different speeds:
- VE.Can, at 250 kbit/s: Victron's own CAN devices, including the Lynx Smart BMS, Lynx BMS NG and VE.Can MPPTs
- BMS-Can, at 500 kbit/s: managed lithium batteries from makers such as BYD and Pylontech
Victron's manual is explicit: "VE.Can and BMS-Can must not share the same bus". If you need both, use "a GX device with two separate CAN buses (e.g. Cerbo GX MK2 or Ekrano GX)".
- The original Cerbo GX has only one fully functional VE.Can port. Its BMS-Can port is limited.
- The MK2 and MK3 have two VE.Can ports, one isolated and one not, and either can be set up for BMS-Can.
So if your boat combines VE.Can devices with a battery that speaks BMS-Can at 500 kbit/s, an original Cerbo can't run both on full VE.Can ports. An MK2 or MK3 can.
MK2 vs MK3, from the datasheet
| Feature | Cerbo GX MK2 | Cerbo GX MK3 |
|---|---|---|
| Speed | — | 3–4× faster than the MK2, depending on load |
| VE.Direct ports | 3 | 3 |
| Maximum VE.Direct devices (direct + USB) | 15 | 25 |
| VE.Bus | 2 paralleled RJ45 sockets | Same |
| VE.Can | VE.Can 1 isolated, VE.Can 2 non-isolated | Same |
| Bluetooth | Yes, for setup and networking | Same |
| WiFi | Built-in, 2.4 GHz | Same |
| Ethernet | 10/100 | Same |
| USB | 3 host ports | Same |
| Tank / temperature / digital inputs | 4 / 4 / 4 | Same |
| Relays | 2, NO/NC: 6 A up to 30 V DC, 1 A up to 70 V DC | Same |
| Supply voltage | 8–70 V DC | Same |
| Power draw, no screen | 2.8 W at 12 V | Same |
| Dimensions | 78 × 154 × 48 mm | Same |
| Protection | IP20 | Same |
The device limit is the one practical difference. Victron says the 15- or 25-device ceiling is "mostly bound by CPU processing power". Most boats connect a handful of VE.Direct devices. A large catamaran with many MPPTs and shunts, or a system that runs heavy add-ons on the Cerbo itself, is where the MK3's headroom earns its place. For the MK3 on its own — the processor change, Node-RED and Signal K, and how to tell the two apart — see Cerbo GX MK3 vs MK2.
Things that matter on any version
- Mount it somewhere dry. IP20 means no protection against water. Put it in a dry locker, not the engine space or a damp bilge.
- Power it so it can't flatten a battery. It draws only 2.8 W without a screen, but that runs continuously. On a 48 V propulsion bank it's within the 8–70 V supply range, so it can run from the bank the BMS protects, through a fuse.
- Bluetooth is for setup only. Victron notes that it's "intended to be used to assist with initial connection and networking configuration". It doesn't connect the Cerbo to other Victron Bluetooth products.
- Relay 1 is the programmable one. It can be an alarm relay, generator start/stop, tank pump or temperature relay. Relay 2 is limited to temperature control or manual switching.
Which to buy
- New build or refit: an MK2 or MK3. Choose the MK3 if you expect many VE.Direct devices or plan to run demanding software on the Cerbo, and the MK2 otherwise.
- You need VE.Can and a 500 kbit/s BMS-Can battery together: an MK2 or MK3, not the original.
- You already have an original Cerbo that does the job: keep it, unless you need the second full VE.Can port.
Prices vary by dealer and country, so get current quotes.
Sources
Checked on 7 November 2026:
- Victron Energy — Cerbo GX & GX Touch datasheet: MK2 and MK3 specifications, the MK3 speed claim, VE.Direct device limits, relay ratings, power draw, dimensions, IP rating, Bluetooth note
- Victron Energy — Ekrano GX, Cerbo GX, Nucleo GX manual: the MK2 description, VE.Can and BMS-Can speeds, the rule that they must not share a bus, the original Cerbo's single full VE.Can port, relay functions
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