MICTUNING Heavy Duty 7 Gang Junction Box Install Help

[Jlawles2]

Lonestar If you look back at my picture in the post #30, you will see I did the home wiring style where I left a loop of wire should I need to cut the end off something. Basically all wires go to the opposing end then back to their corresponding stud. Do this from both ends and you have the ability to move wires if needed. Granted they will no longer be on the properly labeled stud in the box, but who cares if the labels are wrong if the issue is fixed.

[howson]

Howard, It's a giant CYA of the DC-DC system MFG should the charger loose ground and try to use the 7 way ground that is not designed to carry the 30 plus amps that will be required by the charger. Should the charger loose it's primary ground, the current returning through the whip cord and truck wiring COULD POTENTIALLY CAUSE AN OVERHEATING and result in everything bad you can think of.

So Keith disconnects the -12v return on the 7-way when he uses the DC-DC charger? I get the point of "CYA", but if the -12V return is disconnected on the 7-pin won't that impede other functions? Will the brake lights (on the trailer) still work? Turn signals?

How does he conveniently disconnect the -12v return connection?

Associated with the thought of "losing" the -12v return (and in my mind a risk-reduction strategy) on the DC-DC charger is to not use the truck's frame. Run a dedicated wire all the way to the battery terminal. The connectors used to join the trailer and truck must be robust--not a place to install a cheap connector.

Howard

[Jlawles2]

howson Howard, my observation from how the DC-DC system works is that the negative of the charger is pass through. I.E. it will take the load from ALL of the other items.

Someone with a DC-DC system that has the negative in the whip disconnected would need to test this with the unit only connected through the 7 way and not physically hooked to the truck (this eliminates hitch "grounding".

This is why I mentioned using a NC relay tied to the 12VDC+ on the DC-DC charger. If the charger is not plugged in, the relay stays closed and you have normal functioning ground system in the whip. When power is applied to the DC-DC charger, the relay activates and OPENS the contacts BREAKING the whip ground. YES this is extra components, HOWEVER you maintain the ability to run the trailer without the DC-DC needing to be energized.

https://www.amazon.com/ONLINE-LED-ST...s%2C123&sr=8-9

5 pin relay terminal 87a is the NC contact. I would supply ground through the whip so it will always be connected and not be tempted to cycle unintentionally. This means 86-30 are tied to the whip negative wire, 87a goes to the coach negative, 85 then goes to the DC-DC charger power feed line.

Hopefully this makes sense.

[howson]

howson Howard, my observation from how the DC-DC system works is that the negative of the charger is pass through. I.E. it will take the load from ALL of the other items.

I understand the relay system proposed, but introducing those extra components is a risk in itself.

My understanding is the reason a person would add the relay is to eliminate the "risk" of backfeeding through the 7-pin upon a loss of the DC-DC Charger -12v return. This "risk" is removed by disconnecting the -12v on the 7-pin. So now they could lose all the -12v returns (meaning all trailer light functions and possibly even brakes?) should the relay fail along with the -12v return line. Mechanical relays do fail--replaced many back in the day when I was a Sharp Corp. copier technician (before I went into the USAF).

Interesting discussion. If I get a chance I'm going to measure the continuity from a known good trailer frame point to the negative side of the Renogy without the truck hitched, but the DC-DC line plugged in. I'll check it unpowered and powered. The hypothesis is that there will be no continuity in either case. I'll then do the same tests with the truck hitched. Again, the hypothesis is no continuity in either case (powered or unpowered).

If the hypothesis is shown correct I don't think the relay is necessary--a loss of the negative on the input side of the Renogy means the DC-DC Charger just doesn't work. If the hypothesis is wrong (there is continuity) I'll have to definitely give this more thought.

Howard

[Yoda]

So Keith disconnects the -12v return on the 7-way when he uses the DC-DC charger? I get the point of "CYA", but if the -12V return is disconnected on the 7-pin won't that impede other functions? Will the brake lights (on the trailer) still work? Turn signals?

How does he conveniently disconnect the -12v return connection?

Associated with the thought of "losing" the -12v return (and in my mind a risk-reduction strategy) on the DC-DC charger is to not use the truck's frame. Run a dedicated wire all the way to the battery terminal. The connectors used to join the trailer and truck must be robust--not a place to install a cheap connector.

Howard

Howard
I have not disconnected the negative return at the king pin and probably wont when I finally upgrade to Lithium. I am leaving that all stock. I have a dedicated negative return for the DC-DC back to the truck battery through an in bed Anderson connector. See this thread. https://gdrvowners.com/forum/operati...project/page17

Now in a discussion with my Ford service manager he looked up and found the RV charge circuit is protected for trailer back-flow or excess voltage. Its fused too.
Second the voltage output from the alternators can be 15-16V depending where measured so he doubted the higher charge voltage for Lithium would hurt anything.

Last - there is not a frame ground on the DC-DC unit and as installed it is protected on both sides by circuit breakers in case of a major short.

So in a nut shell I am leaving the stock king pin wiring as is including the negative return to the truck and not changing anything.

I did verify there is no frame ground anywhere in the king pin area. There is a 10AWG white wire headed towards the front bay of the trailer - that could be the frame ground connection - don't know yet.

Now I did find a mystery pair of wires cumming from the trailer (Black and dark green) that are tied together and not tied to the 7 pin cable.. No clue what they are for - maybe break away power. Ill get some pictures and post

[Yoda]

Well I think I solved the mystery of the Black pair of wires. The second wire is black, not dark green.

On the left is the black pair in question (red wire nut) Theses wires do not attach to the 7 pin cable. Center red wire nut has a black from the 7 pin cable tied to a red with white stripe. Now far right in the knife splice is the brake wiring, one blue is for the 7 pin cable and the other blue is from the brake trailer wiring. The center black is to the break away switch. So where does the break away switch get it constant power? That the black pair on the left. One wire goes to the front bay the other to the breakaway switch.

I went back and found a picture of the power distribution bar in my front bay

To the right the large loom runs to the front king pin.. You will see the black wire is tied to the constant hot positive buss bar ad runs into that loom, Now interesting enough below that on the other connection to the circuit breaker is the red/white stripe wire, So that is the charge line from the king pin box. Also below in the negative return frame bar I added, There is a 10 awg white wire running into the loom headed to the kin pin box, so it should be easy to ohm out to see if I am correct. Thanks Scott and Joseph for suggesting this was the case.

So now that I have identified all the wiring I think I am ready to move over to the other box.

Keith

[Jlawles2]

Keith, IIRC the 2 black wires tied together are the ones for the break away. As you note they are the same size and type.

The question is if the DC Charger is pass through negative or not. If it's pass through as suspected, that is why they say to kill the 7 way negative. If not, then you will loose lights and brakes.

howson Without a connected negative in the 7 way you are required to hook up the DC charger every time to provide the necessary return. Again suspect that the DC charger negative is pass through.

[howson]

Jlawles2 and Yoda

Finished my preps for departure (we leave in the morning) so did a few quick checks.

Keep in mind the output of the Renogy in my camper is wired to the Multiplus. (It has two sets of inputs meant for two strands of 2/0 wire. I used one 4/0, so an input was available which I used with the Renogy.) This wiring effectively connects the output of the Renogy to the battery bank. What that means is the negative side of the Renogy's output would have continuity to the frame of the trailer. The question is what about the input side? Is that negative also tied to the frame (through the Renogy)?

The Tests

1) Verified voltage on output (the battery voltage) and found none on input as expected. Renogy's input was not connected to the truck.



2) With the Renogy still disconnected from the truck and not powered on, checked for continuity between output negative and input negative. OL as expected.



3) Connected truck (but did not power on Renogy) to trailer through cable for Renogy (not hitch--camper not ready for that!) and reran tests. Same result. No continuity.

4) Powered on truck and engaged Renogy. Verified voltage on input (from truck). Checked for continuity between input and output negatives and again got OL (infinite resistance).

This appears to me to verify the hypothesis stated in an earlier post.

Howard

[Jlawles2]

howson

Then how do the lights work if there is not a negative pass through on the DC-DC charger? Is Renogy expecting the lights to ground (negative 12vdc) through the hitch? Is your negative still connected in the whip? When you have time, can you do the same test with the negative disconnected and check the lights on the trailer for function?

This worries me that a MFG is telling people to disconnect a vital component in the safety equipment of the trailer. The negative being critical to the function of the brakes and all lights.

[Yoda]

howson

Then how do the lights work if there is not a negative pass through on the DC-DC charger? Is Renogy expecting the lights to ground (negative 12vdc) through the hitch? Is your negative still connected in the whip? When you have time, can you do the same test with the negative disconnected and check the lights on the trailer for function?

This worries me that a MFG is telling people to disconnect a vital component in the safety equipment of the trailer. The negative being critical to the function of the brakes and all lights.

In my white wiring bundle at the king pin there is a frame ground 10awg connection back to the trailer (post #66), so if there is no connection to the truck everything works.I believe this was done so the breakaway switch works and can power the brakes when disconnected from the truck. I remember verifying this when I was testing out the 7 pin trailer plug with jumper wires to power the lights during a test a while back.

howson

Did you happen to check input and output voltages when on?. Even with the negative lines being connected at all times through the DC-DC did you see higher voltages on the truck side? I suspect it was the trailer side. Tomorrow I will be calling Renogy and asking a few questions. I don't remember anything in the install instruction to disconnect the TV negative wire on the larger DC_DC units.

This has all been a very educational discussion
Keith.

On edit - here is the manual https://www.renogy.com/content/RNG-D...060-Manual.pdf
No mention of disconnecting the negative wire in the 7 pin.

[Jlawles2]

Thanks Howard for the search information many threads back. Found this using the duckduckgo.com searching "disconnect AND negative AND renogy site:gdrvowners.com"

https://gdrvowners.com/forum/operati...-dc-dc-charger post #7 disconnect 12V+ charge wire in the 7 way.

I vaguely remember this being discussed several months back. As I am not running the DC charger system, it's stored in the open sieve files of the brain where little remains.

I may not be remembering the instructions as to what needed to be disconnected fully.

[Yoda]

DOH !!!!!!!!!!!!!!!!!!!!!!!!!!! it the 12v+ that is the issue, not the negative

BTW I called Renogy this morning. The young lady in teck support could not answer my questions, tough to understand here with he speaking ability, and thier engineers are not taking phone calls. She could not comprehend my question, and even gave me wrong information on the amperage draw for the charger - said it was just 60A. Also said I should have hooked it directly to the alternator and not the battery. I had to enplane that 60A the max output, but it could pull code to 90A in the input side.

Keith

[Jlawles2]

Yoda Again Keith, you could wire a NC relay into the 12V line on the whip with the activation power coming from the DC charger power. Put a fuse there also. If there is any question on the relay being bad, pull the fuse.

[BWSTGDS]

Adding my pigtail junction box re-wire to an already very useful and detailed thread.

On my truck, the pigtail receptacle is in the bed ahead of the rear axle. The trailer pigtail is too short to reach, and the connector is pretty worn. I probably should move the receptacle near the rear of the bed, but don't want to drill another hole.



I decided to replace the pigtail with a 12' cord, and redo the junction box under the pinbox. This is how the junction box looked as installed, and a link to the pigtail I went with. Conntek is the brand of the one I removed, so stayed with that.
Conntek 12' pigtail



It's tucked up there inside the pinbox. I had not seen the guidance to use the Mictuning box before I did this, and purchased this Cheemuii version.

7way junction box
Ring terminal kit
Crimp tool

Really like how this turned out. Makes it easy to replace a pigtail in the future as well. Here getting ready to install 2 more strain relief clamps and button it up. The cable coming in at the upper left has breakaway switch wires and disc brake actuator wires (brake/+12V/breakaway trigger)

[Yoda]

Adding my pigtail junction box re-wire to an already very useful and detailed thread.

On my truck, the pigtail receptacle is in the bed ahead of the rear axle. The trailer pigtail is too short to reach, and the connector is pretty worn. I probably should move the receptacle near the rear of the bed, but don't want to drill another hole.



I decided to replace the pigtail with a 12' cord, and redo the junction box under the pinbox. This is how the junction box looked as installed, and a link to the pigtail I went with. Conntek is the brand of the one I removed, so stayed with that.
Conntek 12' pigtail



It's tucked up there inside the pinbox. I had not seen the guidance to use the Mictuning box before I did this, and purchased this Cheemuii version.

7way junction box
Ring terminal kit
Crimp tool

Really like how this turned out. Makes it easy to replace a pigtail in the future as well. Here getting ready to install 2 more strain relief clamps and button it up. The cable coming in at the upper left has breakaway switch wires and disc brake actuator wires (brake/+12V/breakaway trigger)

Jeff
Not to side track this, but is you AUH hitch rotating? In the first picture hooked up the red AUH connector is pointed forward and at a very odd angle. Could be the Rotoflex, but I sure don't think it looks right. In the last picture unhooked the red AUH is pointed rearward.. It was my understanding the red head was not supposed to move and had set screws to keep it from rotating. Just wondering.

You wiring looks good - a lot neater than I can do.