question

Ignace avatar image
Ignace asked

Cerbo Gx & BVM712

i intend to install a config as follow on my boat, with 2 start batteries & 1 household battery:

1 pce Cerbo GX

1 pce GX Touch 50 + Wall mount

3 pces BMV-712 Smart ( or maybe the Smart shunt, without display)

3 pces Temp sensor for BMV (measuring the batteries temperature)


i intend to connect 2 room temperature sensors, 1 for the engine room, 1 for the cabin

i intend to use digital inputs for bilge alarm & door alarm

i intend to use 1 digital output, used for remote switch-on the cabin heating

i intend to connect 2 resistive tank sensors


i want to have remote access to my boat by using my pc, smartphone , by using the VRM portal.

when moored in the "home" marina, i can connect to the marina wifi. Maybe, i buy a 4G internet wifi router, usable when travelling for different purposes. But i did not decide on that.


my questions:

- is my config ok?

- it is not clear to me, where to connect the battery temperature sensor. is it wired to the BMV712? Or to the shunt?

- do i need other items?

- i assume the 3 VE direct ports on the Cerbo are used for connecting the BMV712's. Imagine i want to add a Victron charger/invertor later? how to do that, as 3 VE ports are occupied.

- what are the specs for the room temperature sensors?


cerbo gxBMV Battery Monitor
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2 Answers
wkirby avatar image
wkirby answered ·

Three battery monitors. This can be done, three will show up on the devices page of the Cerbo and VRM device list , but only one of them can be assigned to be the system battery monitor. Only the assigned one shows on the tiles page and the dashboard page in VRM. This is because only one battery bank can be the system battery bank. You'd most likely assign the BMV connected to the household bank to be the system battery monitor.
A BMV for each start battery is a bit excessive, it'll only show consumed and charged energy at cranking time and then for re-charge for a few minutes afterwards. Aside from this the only useful information will be the Voltage of the start batteries. SOC will not be counted because no current will be flowing through the shunt when the engine is off.

The temperature sensor for the BMV-712 connects to the shunt. See figure 13 of the quickstart guide here:
https://www.victronenergy.com/upload/documents/BMV-712-quick-installation-guide.pdf

If you can do without the display of the BMV-712, then perhaps the Smartshunt will be a better option for you.

If you need more VE.Direct ports in the future, then you'll need to use the VE.Direct-USB interface and use one of the USB ports on the CerboGX:
https://www.victronenergy.com/accessories/ve-direct-to-usb-interface

Not sure what specifications you need regarding the temperature sensors. The ones that you might use for the rooms would connect directly to the CerboGX (which are different sensors to the ones which connect to the shunts) have isolated tabs and used for normal ambient environmental conditions.

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Ignace avatar image
Ignace answered · 
Thank your for the answer. I intended to install 3 pces BMV, because the bow thruster is connected to the starbord starting battery, and the anchor winch to the other one. They are big consumers, and i think that starting batteries are important. If you can not start in full sea, it can be quite dangerous.  But of course, voltage is the main indicator.

how do you think about chargers? Should i select a charger with 3 independent circuits? Not only isolated, bit also with independent regulation.


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wkirby avatar image wkirby ♦♦ commented ·

Now you mention the thruster and windlass it now makes sense to me to have three BMV's.

If you require independent regulation from chargers, the it would be best to go with separate chargers for each.

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