Battery Monitor/Shunt grounding question.

Converting Cargo Trailers into TTTs

Re: Battery Monitor/Shunt grounding question.

Postby flboy » Fri Feb 09, 2018 8:03 pm

onlyridepark wrote:
flboy wrote:You understood it well and have the right idea. The home run of each negative to a bus bar, then through a shunt to the negative terminal of the battery completes the circuit. On a chassis ground system... put simply, the chassis is just the bus bar.... a very large bus bar where you connect wires closest to the point of use. It just saves a lot of wire. I have a steel frame so not the issues with aluminum and galvanic corrosion.


It also seems like using the chassis ground system then having your shunt between the chassis and battery negative, you would lose some accuracy on the battery monitor. As surely not all loads would pass through it and there would be some losses, like through the tow vehicle itself and any time something was actually earthed. Probably overthinking that part and it really doesn't apply to mine since it will all be home run. Would be nice to only run half the wiring but in reality, I don't have a lot of wire to run anyway.
Thanks again for the help.


You are not thinking about the battery circuit correctly... if the shunt is the only thing connected to the battery negative terminal, and then the shunt is on chassis common (ground is really a bad word here as it means something else in the VAC world and then something different again in the RF world ), anything powered by the Positive of that battery, has to return to that battery. If something is running from another power source... it is not part of that circuit and should not (will not) be measured by that shunt circuit.

Also be careful, no matter whether you home run or use a chassis common, there are functional and reliability risks if not done correctly in either case (gage wire used... individual crimps, connections to bus bars, fuse sizes, continuous chassis vs. bolted up chassis, termination hardware, on and on we go) ... done right... either way... no more or less risks. Either is electrically the same and as reliable if done properly. "Done Properly" is the key word . Do what you are comfortable with for sure. Only you have to live with the results.
Don (Flboy)

Current Build CTC:
viewtopic.php?f=42&t=65498
Old CTC Build (sold)
viewtopic.php?f=42&t=50647
YouTube Videos of Finished Trailer:
https://www.youtube.com/watch?v=FASF-x9ofMY - Interior
https://www.youtube.com/watch?v=wb-pvBbyyBs - Exterior
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Re: Battery Monitor/Shunt grounding question.

Postby John61CT » Fri Feb 09, 2018 9:18 pm

flboy wrote:if the shunt is the only thing connected to the battery negative terminal, and then the shunt is on chassis common

I would put it as:

The shunt is the only connection between the bank terminal and the negative return buss.

That return buss may also be directly connected to one or more points of the chassis and / or to the engine block.

Then the owner can choose which consumer loads use a return wire to the buss and which are OK using the chassis.
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Re: Battery Monitor/Shunt grounding question.

Postby flboy » Fri Feb 09, 2018 9:31 pm

John61CT wrote:
flboy wrote:if the shunt is the only thing connected to the battery negative terminal, and then the shunt is on chassis common

I would put it as:

The shunt is the only connection between the bank terminal and the negative return buss.

That return buss may also be directly connected to one or more points of the chassis and / or to the engine block.

Then the owner can choose which consumer loads use a return wire to the buss and which are OK using the chassis.
Well said.

Sent from my SM-G935P using Tapatalk
Don (Flboy)

Current Build CTC:
viewtopic.php?f=42&t=65498
Old CTC Build (sold)
viewtopic.php?f=42&t=50647
YouTube Videos of Finished Trailer:
https://www.youtube.com/watch?v=FASF-x9ofMY - Interior
https://www.youtube.com/watch?v=wb-pvBbyyBs - Exterior
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Re: Battery Monitor/Shunt grounding question.

Postby NotJammer » Fri Feb 09, 2018 9:31 pm

flboy wrote:
NotJammer wrote:I agree I may home run all CTC wiring including all grounds.

:thumbsup:


QR means quick release, I made a set of jumper cables years ago for my last rig. Never used them Wire is still perfect. 25 ft with Power Pole QR and 6 ft battery ends all 1/0 welding cable.

I may as well use it. Maybe I'll just set it up as I planned. Connect the short end permanently to the TV battery with QR by outside front bumper. Store the rest in the cab.

Run 8 gauge from underhood battery isolator to CTC with QR at rear bumper. On F15o0forum there is talk of smart OE battery cables on the truck, that somehow don't like the extra battery system.

I got time, I will study up.

My lifetime hobby was motorcycles. I have owned several hundred, lost count. Buy, fix, ride, sell and repeat for 51 years so far. I have 2 bikes now and it feels like zero. I usually had 15 in various conditions. All kinds, I like em all, tiny and big. But I got sick about 10 years ago and couldn't walk or drive my 2 stick shift vehicles. Wheelchair, crutches. Sold all bikes, but one. Sold the cars. Got a van. I never got out of it, too much pain. Then I started getting better. Now I am pretty darn good at 67. Had to learn to ride differently as I still had bad vertigo, which needs a different way of riding a bike! Heart attack fixed that with a stent in my biggest heart artery. My brain was not getting blood until the stent. What a difference.

However, i also decided I needed an old man hobby. I did have to study for the Ham test. I passed, but then realized I don't like to chat like they do. All my life I have listened to Shortwave, especially when camping. Long wire, a tree and a little radio. Campfire.

So I went nuts on old time photography. Huge 100 year old cameras shooting X-Ray film. I enjoy it and plan to do some field work with the CTC. Here's a 1929 Deardorff 11X14 made for making Sears catalogs. It's 6 feet long, 10 ft in the air. Originally it could go 20 ft up, It can spin the whole thing upside down and shoot at 2" off the floor. 500 made in Chicago. Maybe 100 left. Maybe way less. Image1929 S11 Deardorff by moe.randy, on Flickr

I need a better HT. Any suggestions around $250 or should I just get a removable mobile? Can't put a mag mount antenna on my aluminum F150...

I get the feeling we may have a real SHTF in my lifetime. It's why I moved out of Chicago last year and into a rural area. Now, where is my shovel!
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Re: Battery Monitor/Shunt grounding question.

Postby onlyridepark » Fri Feb 09, 2018 9:43 pm

flboy wrote:You are not thinking about the battery circuit correctly... if the shunt is the only thing connected to the battery negative terminal, and then the shunt is on chassis common (ground is really a bad word here as it means something else in the VAC world and then something different again in the RF world ), anything powered by the Positive of that battery, has to return to that battery. If something is running from another power source... it is not part of that circuit and should not (will not) be measured by that shunt circuit.

Also be careful, no matter whether you home run or use a chassis common, there are functional and reliability risks if not done correctly in either case (gage wire used... individual crimps, connections to bus bars, fuse sizes, continuous chassis vs. bolted up chassis, termination hardware, on and on we go) ... done right... either way... no more or less risks. Either is electrically the same and as reliable if done properly. "Done Properly" is the key word . Do what you are comfortable with for sure. Only you have to live with the results.


DC wiring is mostly new to me. I'm learning as I go on this entire build. I've bought quality marine wire, crimps, lugs, etc. I've sized all my wire to be less than 3% loss as per the charts. As well as fusing all circuits appropriately. I'm comfortable with the system I've designed to work properly. I guess I have just never seen an electrical system that wasn't tied into the chassis somehow. But I guess that makes sense if things are grounded to the chassis, then the battery negative would also have to be to complete the circuit. I was thinking in terms of earthing like in an AC system, which stopped making sense when I put the shunt into the equation. I think I am pretty clear now. I don't want to just throw something together and hope it works. I am doing my best to fully understand everything I am doing.
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Re: Battery Monitor/Shunt grounding question.

Postby KTM_Guy » Fri Feb 09, 2018 10:24 pm

NotJammer wrote:
flboy wrote:
NotJammer wrote:I agree I may home run all CTC wiring including all grounds.

:thumbsup:



So I went nuts on old time photography. Huge 100 year old cameras shooting X-Ray film. I enjoy it and plan to do some field work with the CTC. Here's a 1929 Deardorff 11X14 made for making Sears catalogs. It's 6 feet long, 10 ft in the air. Originally it could go 20 ft up, It can spin the whole thing upside down and shoot at 2" off the floor. 500 made in Chicago. Maybe 100 left. Maybe way less. Image1929 S11 Deardorff by moe.randy, on Flickr

One of the photographers I worked with in Chicago 30 years ago had a 11X14 Deardorff. Not practical for jobs but we did shot so B&W negs and contact printed them on to 11X14 paper. I have put 1000's of sheets of 8X10 Ekachrome through Deardorff's in my photo days. Good times.

Todd
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Re: Battery Monitor/Shunt grounding question.

Postby McDave » Sat Feb 10, 2018 12:26 pm

onlyridepark wrote:
flboy wrote:You are not thinking about the battery circuit correctly... if the shunt is the only thing connected to the battery negative terminal, and then the shunt is on chassis common (ground is really a bad word here as it means something else in the VAC world and then something different again in the RF world ), anything powered by the Positive of that battery, has to return to that battery. If something is running from another power source... it is not part of that circuit and should not (will not) be measured by that shunt circuit.

Also be careful, no matter whether you home run or use a chassis common, there are functional and reliability risks if not done correctly in either case (gage wire used... individual crimps, connections to bus bars, fuse sizes, continuous chassis vs. bolted up chassis, termination hardware, on and on we go) ... done right... either way... no more or less risks. Either is electrically the same and as reliable if done properly. "Done Properly" is the key word . Do what you are comfortable with for sure. Only you have to live with the results.


DC wiring is mostly new to me. I'm learning as I go on this entire build. I've bought quality marine wire, crimps, lugs, etc. I've sized all my wire to be less than 3% loss as per the charts. As well as fusing all circuits appropriately. I'm comfortable with the system I've designed to work properly. I guess I have just never seen an electrical system that wasn't tied into the chassis somehow. But I guess that makes sense if things are grounded to the chassis, then the battery negative would also have to be to complete the circuit. I was thinking in terms of earthing like in an AC system, which stopped making sense when I put the shunt into the equation. I think I am pretty clear now. I don't want to just throw something together and hope it works. I am doing my best to fully understand everything I am doing.


You've got a good handle on it. I agree with Don about removing the term "ground" from DC lexicon. For those of us who work with AC and DC daily it doesn't seem confusing so it is just a lazy man's way of saying "common". "check your grounds" or "do you have a good ground?" comes from using the chassis as common, as there is no earth ground in this case. One advantage to home run wiring is you can earth ground chassis for AC purposes, but all trailer DC wiring should be home run in that case. That kind of stuff will drive GFCI's crazy! I'll just slip this in here, if your air conditioner trips the breaker feeding your trailer, check that circuit for GFCI's BEFORE installing any sort of hard start kit. Air Cond.'s require a slowblow and GFCI's are NOT that. Most of your exterior outlets are GFCI or the breaker is GFCI. Same goes for generators and their GFCIs.

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Re: Battery Monitor/Shunt grounding question.

Postby NotJammer » Sat Feb 10, 2018 2:32 pm

McDave wrote:
You've got a good handle on it. I agree with Don about removing the term "ground" from DC lexicon. For those of us who work with AC and DC daily it doesn't seem confusing so it is just a lazy man's way of saying "common". "check your grounds" or "do you have a good ground?" comes from using the chassis as common, as there is no earth ground in this case. One advantage to home run wiring is you can earth ground chassis for AC purposes, but all trailer DC wiring should be home run in that case. That kind of stuff will drive GFCI's crazy! I'll just slip this in here, if your air conditioner trips the breaker feeding your trailer, check that circuit for GFCI's BEFORE installing any sort of hard start kit. Air Cond.'s require a slowblow and GFCI's are NOT that. Most of your exterior outlets are GFCI or the breaker is GFCI. Same goes for generators and their GFCIs.

McDave


Read my mind. Last night I discovered I have 3 wire 120 VAC to my overhead vent. No fan or AC at this moment, but I am concerned that the 3 AC wires are not in any conduit or sheath. They are solid core and rub on my all aluminum superstructure. Meaning after some miles they will short out...This might be OK if the trailer was stick built, but...

My first thought was adding GCFI. My 3rd thought was rewiring it.

What do you guys think?

I think I should install conduit on the walls, room side, which is what we have been doing in Chicago for Art studios and workshops. Makes it easy to change.
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Re: Battery Monitor/Shunt grounding question.

Postby hankaye » Sat Feb 10, 2018 8:56 pm

Howdy All;

I tend to stay out of the electrical conversations as my know how is non-existent.
So, when I find something from a true expert in the field I try to post it so y'all can
read it , perhaps learn from it, or refute it if you find it to be not trust worthy.

Here is a link to a series of articles written by Mike Sokol, who does have a long list
of credentials There were 12 of them focused on RV electrics so it may or may not
be helpful to folks that may have a question or 3 or 4. We have some truly share minded
folks that would help, if asked nicely, for further enlightenment. Here's the link, enjoy.

http://noshockzone.org/rv-electrical-sa ... ge-strips/

This is a gateway link, the rest of the articles are reached from the list in the upper Right corner.

hank
Striving for a less complicated life since 1949 ...
Every day I beat my own previous record for number of consecutive days I've stayed alive.
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Re: Battery Monitor/Shunt grounding question.

Postby McDave » Sat Feb 10, 2018 9:09 pm

AC should at least be in smurf tube and DC as well if you think there will be contact wear. Air Cond. wiring is only AC wiring I have running to rear of trailer. I used a lot of zipties and ties with an eyelet for screw and the harness runs in a chase so it is all accessible. But just in case the master cut off switch, main breaker and fire extinguisher are all located just inside the man door, extinguisher mounted to door. I try to remember to turn everything off except fridge when I leave. Learned the hard way about the pump switch.

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Re: Battery Monitor/Shunt grounding question.

Postby McDave » Sat Feb 10, 2018 9:42 pm

Excellent information Hank. I was not able to see the images but the author does a very good job of breaking down the systems and possible reasons for failures and diagnostic procedures. Nice find. I am saving that stuff for sure. At first reading I have found nothing to disagree with.

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Re: Battery Monitor/Shunt grounding question.

Postby NotJammer » Sun Feb 11, 2018 4:02 pm

hankaye wrote:Howdy All;

I tend to stay out of the electrical conversations as my know how is non-existent.
So, when I find something from a true expert in the field I try to post it so y'all can
read it , perhaps learn from it, or refute it if you find it to be not trust worthy.

Here is a link to a series of articles written by Mike Sokol, who does have a long list
of credentials There were 12 of them focused on RV electrics so it may or may not
be helpful to folks that may have a question or 3 or 4. We have some truly share minded
folks that would help, if asked nicely, for further enlightenment. Here's the link, enjoy.

http://noshockzone.org/rv-electrical-sa ... ge-strips/

This is a gateway link, the rest of the articles are reached from the list in the upper Right corner.

hank


Thanks, Hank, good thing I read about the Honda generator issue. That would have baffled me. The lightning discussion was good also.

I now plan to rewire almost everything, except the electric brakes, unless I find something wrong there. So far the 7 way and electric brakes are working perfectly.

Rewiring using Liquidtight Conduit and Cantex as appropriate.

The only plumber/mechanic/electrician I trust is myself. I won't ride a brand new motorcycle until I check everything, I was once Suzuki trained wrench, and I have seen some real deadly mistakes.
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