question

kodax avatar image
kodax asked

Voltage on both the house bank and starter batteries when replacing BMV with Lynx Shunt?

I have a BMV-712 today in my boat, reading the voltage for both the house bank and the starter battery. (These batteries are separated with a Cyrix-Li-ct.)

Since I have Lynx Distributors, I am looking at replacing the BMV with a Lynx Shunt, so that I can get power to the Lynx Distributors and monitor them through my Cerbo GX.

However, I do not see that the Lynx Shunt can read the voltage on both the house bank and the starter batteries, and I guess it is not possible to have the Cerbo GX to read the voltage directly from the starter battery.

Is the only solution to keep the BMV in addition to the Lynx Shunt, or can I provide the voltage for the starter battery to the Cerbo in another way?
If I have to keep the BMV, do I have to use the aux input to read the voltage on the starter battery, or can I use the "main" reading on the BMV for the starter battery? (Will this confuse the Cerbo?)

cerbo gxBMV Battery Monitorlynx shuntlynx distributor
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

3 Answers
pwfarnell avatar image
pwfarnell answered ·

If you have a Lynx Shunt and a BMV installed you have to choose one monitor as the Battery Monitor in the Cerbo and only that one is used for the battery display and SOC calcs, the other can be seen but is taken as an entirely separate battery. This will not confuse the Cerbo.

There are a couple of other things you could consider.

1. Connect the BMV negative to the start battery negative with a small wire and the positive to the starter battery so it only works as a voltage sensor. A bit of a waste really.

2. If I were doing this I would change the BMV to a DC energy meter on all the house battery that are not measured internally. Victron inverters and MPPTs know what current they take, but your pumps, lights, nav equipment that run on DC could be metered. This would need the BMV rewiring. When used as a DC energy meter you can still monitor the starter battery voltage.

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

kevgermany avatar image
kevgermany answered ·

If it's just to power the LEDs on the distributors, you can supply 5V from a USB adapter. Not a supported solution and unofficial.

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

kodax avatar image
kodax answered ·

Thanks guys!
I guess I'll go for the simplest/cheapest option; buying a 12V to 5V converter and connect the RJ10 to it. I see it is documented here:
https://www.victronenergy.com/media/pg/Lynx_Distributor/en/features.html#UUID-56b38917-a174-17f7-0a17-2bb9b0ae80dd

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.