How do I determine if DC-DC charger is necessary?

[uncle_bob]

Originally Posted by kmrice

Steamy1, thanks so much for the outstanding wiring diagram. It does an excellent job of helping those with limited experience in electronics (like me) understand things.

If you are still following this thread, I have a few questions:

How does the Jack connect to the DC negative? I only see a cable to the positive terminal of the battery.

Why does the Jack not run through the Shunt?

What is the B+ Shunt Wire running from the shunt to the positive DC Buss Bar? Is that how the Shunt gets power to run itself?

Thanks again for your great contribution to this very helpful thread.

Karl

Hi

The jack typically grounds to the frame of the trailer. The frame is always connected to DC negative. There are a number of "jumper points" in the trailer that do this.

The shunt needs a 12V power source. You typically run it straight to the battery so it can read out exact battery voltage.

Bob

[Tyler2you]

Originally Posted by kmrice

Why does the Jack not run through the Shunt?
Karl

Ideally, it should. Otherwise, you've got a "leaker".

[richard5933]

The jack is used very little in relation to the overall scope of things, and for us it's usually while either still connected to the TV or while the solar system is keeping things topped up. While ideally everything should go through the shunt, as long as jack manufacturers are using the mounting flange to get the negative connection is will be difficult run it through the shunt. Yes, it's possible to isolate the jack from the chassis when mounting, but I doubt the benefit will outweigh the effort.

[kscherzi]

Why not run the frame grounding wire through the shunt?

[Tyler2you]

And I assume you have the same problem if you have power stabilizer jacks (grounded at the mount/frame interface).

[Tyler2you]

Originally Posted by kscherzi

Why not run the frame grounding wire through the shunt?

Guessing you'd have to open up the jack and cut the wire from the flange to the motor ground and splice in a new connection to go to the shunt? Probably not worth the hassle.

[richard5933]

Originally Posted by kscherzi

Why not run the frame grounding wire through the shunt?

This might be the answer. Depending on how you set up the negative bus bar it would put everything on the shunt.

[Wazbro]

Originally Posted by kscherzi

Why not run the frame grounding wire through the shunt?

From everything I've read that is the way it is supposed to be done, otherwise many things would not be monitored.

[kmrice]

Thanks for all of the information which is helping this novice understand. After reading it, I'm thinking that the jack, as shown on the diagram, IS running through, and being tracked by, the shunt.

As I understand it, the jack is getting to the negative terminal of the battery by being grounded to the frame. If so, the frame must be connected to the negative terminal of the battery. On the diagram, the only cables going to the negative terminal of the battery connect to the shunt, so it seems to me that the frame is connected to the negative terminal somewhere on the other side of the shunt (as suggested by kscherzi). If so, it would seem that anything grounded to the frame, including the jack, is going through the shunt, and is therefore being counted when the shunt tracks power in and power out.

Am I missing something or have I finally got it right? I believe my shunt is wired similarly to the way shown on the diagram. There are no cables connecting to the negative terminal except the one running to the shunt.

Thanks again for all the information.

Karl