Battery monitor wiring

[RogerWo]

I am going to be installing a battery monitor system which requires the use of a battery shunt in the negative side. Instructions state that all negative wiring should be passed thru the shunt. As provided from the factory with on board generator, the negative terminal has two connections, one for the generator and one for the trailer systems. My question is if there is any reason why I can't pass the trailer wire through the shunt and leave the generator wire connected to the battery? It would seem to me that the battery monitor will still indicate battery condition? Am I missing something here?

[TowPro]

depends on what kind of meter you are running. if its one that does Coulomb counting to know state of charge you need to have the all power draw go through the shunt.
that Negative cable to generator is for starting the generator, its power consumption.
Also make sure you buy a large enough shunt. The Bogart system I use will work with a 100a shunt, will cause your meter to show .01a precision and the 500a shunt which cause your meter to have .1a precision. I have only used 500a shunts but watching the meter show the load jump around I have thought I would hate to have .01 reading on amps because even .1 jumps around as you watch the load.


Here is a tip. I take a piece of 1/2" copper pipe a couple inches long and flatten it with a hammer on anvil. than drill 2 holes in this pipe on each end that fit the battery bolt and bolt on Shunt.

use this flat pipe as a buss bar to connect the battery to shunt, plus it holds the shunt in place on top of the battery .

[babock]

With the shunt, only one connection should be on the negative terminal of the battery and it needs to go to the shunt. All other connections are on the other side of the shunt.

If you leave the generator cable on the battery, you won't keep track of the current being drawn by the generator starter.

[Bama Rambler]

If it's a huge pain to run both negatives through the shunt or if you need to buy a bigger shunt to run the genny negative through it, I don't see the need to run it through the shunt. It won't affect the state-of-charge reading greatly and I figure that if you're running the genny it will recharge the battery when it's running, so you'll be back to 100% SOC. Unless you're just running it to exercise it and in that case you're probably plugged into shore power anyway.

[babock]

Agreed. The amount of power you will miss measuring will be minimal.

Originally Posted by Bama Rambler

If it's a huge pain to run both negatives through the shunt or if you need to buy a bigger shunt to run the genny negative through it, I don't see the need to run it through the shunt. It won't affect the state-of-charge reading greatly and I figure that if you're running the genny it will recharge the battery when it's running, so you'll be back to 100% SOC. Unless you're just running it to exercise it and in that case you're probably plugged into shore power anyway.

[RogerWo]

Thanks for the responses. I will be monitoring an external battery so I am thinking that I should mount the shunt in a more or less watertight enclosure close to the battery. Due to space constraints I think using a separate shunt box is the best solution. If I were to keep the generator negative on the battery it would make the install a bit easier. I will be using a 500 amp shunt. Have any of you attempted an external shunt mounting, and what are your thoughts on a watertight mount? Thanks