Smart Shunt on 2024 R27

[DDean]

Thanks in advance all. I’ve watched what seems like hundreds of hours of YouTube on this and have searched here - I think that I have a plan to do this but there are differences between the schematics that came with my boat and what I’ve learned, and I’m hoping to clarify some items.

I have a Victron smart shunt to install into my 2024 R27. I will try to attach the factory schematic.

I have three batteries in the port lazerette - most forward is the thruster battery then two house batteries.
Forward house battery (middle battery) seems to be the rightmost battery on the schematic.
Forward house battery has three 1G neg yellow connections, one being the neg bridge to the aft battery.
Another should be negative from the gnd buss (not labeled) based upon the schematic.
The other is a neg bridge to thruster batt. The neg bridge to the thruster battery differs from the schematic (which doesn’t show a bridge), I’m guessing (didn’t look while on boat) because positive isn’t bridged.

Aft most battery appears to be the left battery of the house batteries on schematic
It has two 1G negative connections.
One is neg bridge to forward house battery neg terminal.
One is unknown (not labeled) - likely from inverter based upon schematic.
It also has small yellow wire to ACR (auto charge relay).

Questions:

Is it appropriate to mount the shunt before the aft battery? Ie, have the battery side of the shunt connected to the negative terminal of the aft most battery?

I’m taking everyones guidance and putting all the non bridge 1Guage connections to the negative terminals on BOTH batteries onto a buss, and connecting that negative buss to the load side of the shunt.
Therefore, I would attach the suspected inverter neg and suspected gnd buss neg to new bus forward of the aft battery? This combines negatives when they came separately attached to each battery stock, which causes me to pause as I’m unsure why (aside from avoiding stacking) they are initially separated).

I think that I should leave the small yellow ACR wire on negative term of aft battery?
Martin spoke about a number of different loads to put into a negative buss in his video - I do not appear to have any of those connected directly to my batteries from the factory. I have just the two suspected inverter and suspected ground buss, the ACR wire and the negative bridges. I think everything drawing from house batteries is captured by the connections going to the negative terminals of the house batteries by physics, right?

Does it matter which positive terminal I connect the shunt to?

So if I put the suspected gnd buss and inverter on a new negative buss connected to the load side of the shunt and connect the battery side of the shunt to the neg terminal of the aft house battery, with the positive shunt wire connected to the positive terminal of the aft battery….is that correct?

 

[DDean]

Closing out this item - the shunt is in and working well!

Thank you Martin for your help.

Notable items:
R27 wiring was changed from online records I could find for 2024 and aside from the neg from the inverter and the ground bus, and the neg to the ACR, I had no other negatives on the house batteries. Ive seen reports of others having to put a few other negative loads on a negative bus - my boat didnt have those.

I put the three negative loads on a new negative bus in the port lazerette. I mounted the bus and the shunt with industrial velcro. I will review this choice often and may screw them in, but for now the velcro is holding well and I dont have to worry about cracking anything.

Battery shelf was a B*tch to slide back in to the exact position where the screw holes lined up. I would encourage anyone to mark the position of the tray with a sharpie prior to moving it. Also consider if you can lift the aft battery off the tray via a bridge across the lazerette to lower the weight. Aligning that tray was not easy with the three batteries on it!

I didnt bother hooking up the thruster battery voltage as I didnt want to pull the shelf out any further and I dont have a use case for needing to know the thruster battery voltage today other than more info.