Where do I put my Shunt?

[smac999]

Originally Posted by OS2Dude

I've read many items that say the battery negative should go to a bus bar where all the other major grounds connect (including the engine.) It is recommended that the engine block NOT be a part of the negative circuit.


A side question: Why a shunt in the negative side? Does it matter? On our vessel the shunt is in the positive side. I guess if you want the alternator output to be apart of the meter the negative side would be easier. If that is the case, wouldn't having the shunt between the alternator and loads be the correct position? (Given the engine block is a part of the negative circuit.)

if you put the shunt on the pos side, both of the small shunt wires need to be fused. where as the ground wires do not. so it's safer on ground side. and less things in the connection to mess up the reading. even a tiny voltage drop in the meter fuses would make a big difference when the meter is reading mv

some gauges may only work with it one way or the other.

some places you can only measure on the pos. like most alternators.

a battery monitor shunt goes in A

I would reroute the main panel neg to the battery (load side of shunt) and not through engine block.

[CatNewBee]

Disconnect negative from the battery and mount all wires disconnected to the shunt, make a new cable from the shunt to the battery negative and do not connect anything else to the negative pole of the battery.

That makes sure all current to and from the battery must pass the shunt.
If the shunt has also a voltage sensor board, connect the small plus wire via a separate fuse directly to the battery plus, the fuse as near as possible to the battery.

[Zil]

With the shunt at point 'A' all the current to and from the battery will be measured, even if the alternator negative is to the block. The block negative returns to the battery through point 'A'.

Many heavy duty, even OEM, alternators have a separate negative lug on their case. That can go to the block or directly to the battery negative.
If you are only using the shunt for a amp meter and not a battery monitor, I guess a small amount of current from the alternator to the panel could be missed. Someday I will draw this out and see how.