question

neil-feliciano avatar image
neil-feliciano asked

BMV 712 negative bus wiring in boat with two engines and 3 batteries

Hello.


I have a BMV-712 installed in the house battery on my boat and it measures load well, however, it is not measuring charge from the two engines alternators. Here is the current diagram.


I believe that the issue is that the negative of the alternators are connected directly to the start batteries and no way for the shunt to see what goes "in" into the battery. Correct?


What would be the best way to correct this? Move the negative jumper that connects Start Battery 2 to House Battery to the Negative load side of the shunt? Any implications on doing this that might damage the system?


The shunt measures the charge when connected to the on-shore charger since the negative lead of the charger is connected to the load side of the shunt.

final.gif

BMV Battery Monitor
final.gif (194.4 KiB)
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
klim8skeptic avatar image
klim8skeptic answered ·

@Neil Feliciano you will need to move the negative from the start batts to the house batt negative bus bar.

All charging and load negative cables have to be on neg bus for the shunt to measure current entering / leaving the house battery.

house-batt-soc.png


house-batt-soc.png (337.7 KiB)
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.

mvas avatar image
mvas answered ·

To measure charging amps ... The only connection to the 3 battery bank negative terminals must be the shunt. All other black / ground wires must connect to the other side of the shunt. Each battery should have its own neg cable directly to shunt bus bar bat(-).

Or have you considered three BMV 712's, one for each battery neg terminal?

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.

neil-feliciano avatar image
neil-feliciano answered ·

Thanks. I rewired just like you said and now i can see the charge going into the house battery.

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.