Victron Smart Shunt conflicting instructions.

[hjohnson]

Originally Posted by wholybee

The starting battery negative needs to be connected to the load side of the shunt. If it is connected the the battery side with the house battery, then any current going into or out of the starting battery would be totaled with the house battery, and throw off the SOC calculation.

Actually it wouldn't, thanks to Kirchoff's Current Law. As long as the engine negative is directly connected to the starter battery, the circuit from the starter motor, engine et al, will never flow through the shunt.

If the starter loads are connected to one side of the shunt, and the battery to the other, then you have an issue, but as long as there is only a single point of connection between the starter system and the smartshunt (for the negative side) the shunt will not see any current. Now, there is a potential for the voltage to be slightly out, as the voltage is referenced to the negative side of the shunt, but at most that will be 50mv out.

[goboatingnow]

It theory it doesn’t matter , in neither case will the main starter currents flow through the shunt. In practice there are some sneak paths that may throw the shunt off

In most installs the second is most common in my experience.

[CharlieJ]

The start current is not flowing through the shunt in the second document (nor in the first document).

In general, there is no intent to measure the 1 to 2 Ahrs that it takes to start a marine diesel.

It appears that we are in violent agreement.

What is the special case shown by the second document?

Measuring the voltage of the second battery would require the same zero reference point achieved as shown on the second diagram.

I think that the illustration was added just for that reason: both batteries have to have the same zero referenced for the readout to be meaningful. Remember that, for all intents and purposes, the 50mVDC/500A shunt is pretty low resistance so in the scheme of things which side of the shunt that the starting battery is landed is not really very important. What is important is that the battery B- is on one side of the shunt and all loads and sources are on the other side.

I have been correcting owner installed mistakes where this simple detail has not been followed for years.

[wholybee]

Wow. I can only suggest that the OP contact Victron support. This is really simple. The SOC coulomb counting of the house battery will only work if the house battery is the only thing connected to that side of the shunt. If anything else is connected to that side, another battery, loads, etc. then that current will be totaled as well(noting that seldom is the starter the only thing connected to a start battery), and the SOC measurement will be wrong.

Attached, are the drawings from both Bluesea and Balmar, which show, like the drawing from the Victron instructions, that the starting battery negative is connected to the load side. The drawing that shows the starting battery connected to the battery side is wrong. But like I said, call Victron support if you think that the Victron manual, the Bluesea manual, and the Balmar manual are all wrong.

[Wotname]

Originally Posted by wholybee

Wow. I can only suggest that the OP contact Victron support. This is really simple. The SOC coulomb counting of the house battery will only work if the house battery is the only thing connected to that side of the shunt. If anything else is connected to that side, another battery, loads, etc. then that current will be totaled as well(noting that seldom is the starter the only thing connected to a start battery), and the SOC measurement will be wrong.

..............

This comment is only partly correct. Yes, any current flowing through the shunt will be measured.
BUT... connecting the negative of the start battery to the load side of the shunt as shown in the Victron image does not generate any start battery current flowing through the shunt.

[wholybee]

Originally Posted by Wotname

This comment is only partly correct. Yes, any current flowing through the shunt will be measured.
BUT... connecting the negative of the start battery to the load side of the shunt as shown in the Victron image does not generate any start battery current flowing through the shunt.

Yes, but you are making an assumption that the starter current is the only current involved. Almost always, there will be other chargers and loads connected to the start battery. For example, the OP mentioned a VSR. There is also often an A/B switch. Sometimes the alternator is connected to the house bank(but through the engine grounded with the start battery). In all of these cases, the start battery negative must be on the load side.

In the rare case there are no other loads or charge sources involved, then yes, either could work. But it's very confusing to not just always connect it properly.

[mrlorin]

I have received a response from my local Victron Dealer. He says the second diagram (from the video) is not correct:

Quote:

"The manual entry and diagram have been updated to show the correct connection. Please follow the latest manual information."

https://www.victronenergy.com/media/...b-7f807edfb62f

The start battery negative should connect to the shunt load minus NOT the battery minus.

Thankyou everyone for the lively debate on my first post. This forum is awesome!

[Wotname]

Thanks for the update. It is aways good to hear the end result of these questions!

[Kolchac]

I do not see any conflict. You just are not careful enough.

In both picture and video your shunt "Load Minus" goes to your Starter minus (you have to break the original connection). Your shunt "Battery Minus" goes to the Battery minus.
Simple.
Your batteries Minus are hard connected before the shunt, your batteries Plus are connected by a switch when you want to start the engine. You monitor the real current in the negative wire. Two tiny red wires are just for electronics. Simple.

[smac999]

technically the picture is actually not incorrect as it is drawn, however no boat (or rv / van) is wired like that. as soon as you add an ACR, dc to dc charger, or parallel battery switch the shunt becomes wrong. which every boat will have at least one of those between house and engine,

as pictured no current will ever flow on the wire from the engine battery to the shunt, so it's location is meaningless. it's only purpose is a ground for the volt meter to read the 2nd battery.

[AKA-None]

The pix in 3.4.1 shows no way to charge or consume power from the second bank only how to monitor the voltage of said bank