Doesn't matter exactly how far but you want to mount it so there are no other lines off of the battery between the shunt and the main negative post. That way the Trimetric can count all amps going in and coming out to get an accurate % charged figure.
Keep in mind though, short the cables are then better for power transfer, less line loss. Longer you go the thicker the wires need to be.

Example:

Travis, the important thing with a shunt isn't its proximity to the battery but that it is the only thing between the battery and all loads. The other important factor unrelated to a shunt is that as battery cable lengths increase so does voltage drop through the cable. Use a voltage drop calculator to make sure your cables are of adequate size for the load and cable length. This is the one I like.

Voltage drop calculator

On charging from the alternator you will find this somewhat limited due to the small wire size found in a 7 pin wiring harness. In most cases when you attach the 7 pin from the truck to a stock camper there should be a charge to the battery when the truck is running. You will need to confirm that the trucks hot wire in the 7 pin works. I have heard some trucks require a fuse to be installed to energize that circuit. I can't recall if that was a Ford thing or a Chevy. I do know that Ram has the fuse installed. Not a big deal either way. You can test the 7 pin with a meter to see if the 12v hot is working.


There are people who add a larger cable from the tow vehicle starter battery through an ignition disconnect and to the coach battery. That can work well for better charging. There are also dc-dc chargers on the market that can make effective coach battery chargers from the alternator with adjustable voltage output. These would still require upsizing the cables between the tow vehicle and the coach batteries.

Great schematic Ray. I did install a disconnect switch in the negative coming right out of the battery to disconnect the batteries during storage. Saved my slow drain during storage. How is your new lithium battery hookup going. Can’t wait to hear?

In case you want to put the shunt closer to the batteries, here is what I did:




Here is a link to the box I used for the shunt:

https://www.amazon.com/SockitboX-Weatherproof-Electrical-Connection-Enclosure/dp/B009RX5GI2

Here is a link to the battery box:

https://www.amazon.com/NOCO-HM426-Commercial-Automotive-Batteries/dp/B003VAUG5A

. How is your new lithium battery hookup going? Can’t wait to hear? — Columbus

Great so far, got them all installed and charged up. They charge super fast. Right now I'm doing some tests, starting with a slow discharge to see how many amp-hours I get before they quit. Going to do a bunch of different tests.
Also, have a video coming out this week answering the common questions I'm getting.

Travis, looks like you're getting lots of good advice. Here's one other (different) suggestion: Be sure to consider possible future DC loads and charging sources - where they might be located and the negative wire run needed to reach the 'load' side of the shunt - before you finalize the location of the shunt. E.g. if you plan to enclose the shunt, allow for 'growth' at a later date. If a later added solar panel will be coming into the front bay from the passenger's side or you want to add an externally accessed connector e.g. to run a water pump on the driver's side, consider how that might affect the orientation of the shunt. Ray's block diagram is indeed a helpful (and for most of us, coveted) reference to have on hand. But I've found that it's when you start wrangling with wire, breakers, fuses and gaining the access you need to work them all - both now and in the future - that DC wiring can become a lot more challenging that one would think. Good luck with the project!

Jack