Shunt location on travel trailer with batteries in front

[Leo3]

Right. The circuit is completed for everything - except the inverter - using the chassis.

Right now the wire going from neg battery post to chassis is about 3' long and is on the same side of the trailer as the neg bus bar chassis screw which is about 10' away. In deciding which location to place the shunt I am considering moving that battery to chassis screw to some other part of the trailer, close to where the shunt will be. What do you think the guidelines are for this? Like would it bad to move it to the opposite side of the trailer?

 

[HRTKD]

Right now the wire going from neg battery post to chassis is about 3' long and is on the same side of the trailer as the neg bus bar chassis screw which is about 10' away. In deciding which location to place the shunt I am considering moving that battery to chassis screw to some other part of the trailer, close to where the shunt will be. What do you think the guidelines are for this? Like would it bad to move it to the opposite side of the trailer?

No. But I'll qualify that by adding that you want to avoid increasing the length of the cables if you can. If you have to increase the length, then the gauge may also need to be increased. This is to avoid voltage drop.

 

[Leo3]

No. But I'll qualify that by adding that you want to avoid increasing the length of the cables if you can. If you have to increase the length, then the gauge may also need to be increased. This is to avoid voltage drop.

Yeah I just didn’t know since the chassis is doing some of the current carrying if it matters how close wires are relative to other components/wires, or can I just screw the return current wires all over the place.

 

[Zil]

I just have to address a few things I have read here, if I can remember them. Photo of shunt in #69; There are too many wires on the battery side. Are you sure you labeled it correct? Should only be one wire connecting shunt to negative battery. 105c wire; Using a voltage drop table for the AWG and ampacity table for the fuse. The cable should never get close to warm. Unless there is a short and that is why we use fuses. Running wire from the battery negative to the battery side of shunt. Properly sized. Same with the load side of the shunt. Run wire shunt to negative battery side of buss bar, or just to the original negative battery wires.

 

[HRTKD]

I just have to address a few things I have read here, if I can remember them. Photo of shunt in #69; There are too many wires on the battery side. Are you sure you labeled it correct? Should only be one wire connecting shunt to negative battery. 105c wire; Using a voltage drop table for the AWG and ampacity table for the fuse. The cable should never get close to warm. Unless there is a short and that is why we use fuses. Running wire from the battery negative to the battery side of shunt. Properly sized. Same with the load side of the shunt. Run wire shunt to negative battery side of buss bar, or just to the original negative battery wires.

Yes, it is labeled correctly. I have two batteries in my battery bank. Note, the picture is my system, not the OP.

 

[Leo3]

In my two battery system, after I connect the shunt to one battery and all negative loads to the shunt, should I put all the positive loads on the OTHER battery that the shunt is not connected to? Or does it matter?

 

[HRTKD]

In my two battery system, after I connect the shunt to one battery and all negative loads to the shunt, should I put all the positive loads on the OTHER battery that the shunt is not connected to? Or does it matter?

Just to make sure we're on the same page...

Load - <- shunt <- Battery #1 - ... (connection between batteries ) ... Battery #2 + -> Load +

As I recall you have two 12v batteries, connected in parallel.

 

[Leo3]

Just to make sure we're on the same page...

Load - <- shunt <- Battery #1 - ... (connection between batteries ) ... Battery #2 + -> Load +

As I recall you have two 12v batteries, connected in parallel.

Yes exactly I have 2 in parallel. So my pic is correct?

 

[HRTKD]

Yes exactly I have 2 in parallel. So my pic is correct?

Yes, your picture is correct.

 

[Leo3]

Just for my education, what would happen if I put the positive loads on the same battery as the shunt?

 

[Leo3]

Just for my education, what would happen if I put the positive loads on the same battery as the shunt?

I just read this: "You CAN connect your load to ONE of the batteries, and it will drain both equally. However, the preferred method for keeping the batteries equalized is to connect to the positive at one end of the battery pack, and the negative at the other end of the pack."

 

[BiduleOhm]

If you want more info on the subject Victron made a great paper: https://diysolarforum.com/resources/wiring-unlimited.2/

 

[Leo3]

If you want more info on the subject Victron made a great paper

Wow this is great! Thank you so much!

 

[Leo3]

Do you guys think the copper pipe to shunt idea is safe?

 

[chrisski]

Do you guys think the copper pipe to shunt idea is safe?
View attachment 25788

I looked at making bus are out of copper pipes or scrap copper, and decided against it. I would consider getting a copper busbar blank (don’t know they’re actually called this) that goes in a server rack and using that, because at least it has a rated capacity, but I was spending way too much time going through catalogues.

THere’s a post somewhere on this forum from a user in THailand who I guess is so remote he has little choiiice except to manufacture his own busbars.

Another thing that lead me to buying a busbar versus pounding copper tubes with a hammer or putting it in a machine press, is 9 out of 10 times whenI fab something commercially available, I spend more than I would had I just spent the money and bought it outright.

 

[John Frum]

Do you guys think the copper pipe to shunt idea is safe?

I can't really see the picture but using copper pipe to connect things can be fine if done properly.

@ghostwriter66 has lots of experience with this.

A partial list of minutia in no particular order.
1. The copper has to be thick enough to carry the current without getting too warm.
2. you need to make sure the joinery stays conductive.
That means preparing the mating surfaces and/or controlling the environment.
3. Exposed copper can be an unintended current path if something else comes in contact with it so you may have to mitigate that issue.

Do you have a drill press?
If you are considering copper pipe why not consider copper flat stock?

The devil is in the details especially when you are doing it yourself.

 

[Zil]

The shunt is on the negative. I prefer flat bar stock copper. Cut to length. Drilled with a step drill and cutting oil designed for copper. Don't ask, my buddy gave me a can full from his machine shop drum. I then tin plate using torch and "tinners flux". I found some 1/16 copper 3/4 wide copper plating anodes that work well, are easy to bend for shapes, and can be stacked for more thickness.

 

[grizzzman]

I have on my FLA bank a flattened and bent L water pipe. just like it pic including the shunt. All my buss bars are of the same construction on my LFP bank. Even running the microwave they stay cool to the touch. "L" pipe is twice as thick as the "M" pipe.

 

[Leo3]

I'm having some self doubt going on. Can you guys look at my pic and confirm the neg wire from the left battery should not be on the shunt on the right battery? Thanks.

 

[grizzzman]

yep.