Wiring question

[Rick 99037]

Originally Posted by Morich

That would be my recommendation as well but with some debate on the solder. While it can make a nice looking end when soldered, if there is much power and therefore heat, the solder can be a problem at times as it does melt at low temps and that can let it run to spots where it gets us in trouble. sometimes better to just go bare?
Kind of a cross between getting nicer looking job and avoiding trouble? Some engineers spec it different ways at different times.

I love your insights Richard, but on this one I disagree.
Solder alloys used for electrical soldering are around 60/40 Tin-Lead, which melts at 370°F. If things are getting that hot, you've got bigger problems than melting solder, but not for very much longer.
If you were really worried though, there are alloy mixes with even higher melting points too. Copper melts at about 2000°F, so higher melt points should be no problem.

[peggwn]

Would a diagonal mounting be a good compromise? At a steep enough angle, the heat would still be able to flow upward. The angle could be whatever you can get; the more the better. Just a thought. Good luck.

[Elkman]

This is a common problem as these devices are designed for use on land installations where panels are in series and the voltage is much higher and smaller gauge wire can and will be used. I have attached a smaller gauge jumper wire using copper split bolt connectors) for a secure attachment of the two different gauge wires.



Having a 8 gauge 3 inch long jumper wire is not going to cause any problems or reduce the current to the device to a measurable degree.

[AJMike]

I went to the RV the other day to try to build a wood framework to hold the wires to make sure that the torque did not pull them out of the push-and-screw slots but decided instead of take the advice of @Morich and just really bend them more than I originally thought proper. The Victron instructions tell you to apply a specific amount of torque to the screws holding the wires in, but not having a tool to measure the torque I just made sure they were really, really tight.

It all seemed to work, but the proof, as they say, is in the pudding so I will see what happens the next time we take a trip. Driving down the road causes the wires to sway and that generates the torque that originally pulled them out of the slots so I will just have to see how it goes. I also have a backup - the 40 amp Renogy DC-DC charger which does not have the same issues since it uses a different connection type, and I will take that with me just in case.

Thanks for all the suggestions.

[al1florida]

You should be able to find a torque screwdriver for not a whole lot of $ on Amazon.

[AJMike]

Originally Posted by al1florida

You should be able to find a torque screwdriver for not a whole lot of $ on Amazon.

Yes. Thanks. I did not think to look because I have never before had any need for one before, but they are available for about $100 on Amazon. Some a bit less, some a bit more. I suppose I ought to buy one just to have around if I need it, and probably will if the wires don't stay in the push-in connection.

[al1florida]

Yeah, they are more expensive than I thought. I was thinking 20-30 dollars. That's what I get for writing before checking the price. I see one for just under $50 with torque settings from 10 to 60 inch pounds.
https://www.amazon.com/Wheeler-Accur...s%2C510&sr=8-5

[AJMike]

Originally Posted by al1florida

Yeah, they are more expensive than I thought. I was thinking 20-30 dollars. That's what I get for writing before checking the price. I see one for just under $50 with torque settings from 10 to 60 inch pounds.
https://www.amazon.com/Wheeler-Accur...s%2C510&sr=8-5

Thank you for the link.

The Victron manual calls for torque of 1.6nM which seems to be the equivalent of something like 14 in-pounds if my conversion is right.

I am not very knowledgeable about this sort of thing, but I was always told that the accuracy of an analog setting like this is much lower at either end of the scale and that you are better off in terms of accuracy if the value you are measuring is in the middle of the scale. Perhaps the digital version would be better?

Of course I may be making too much of all of this since all I am trying to do is keep the wires from popping out of the set-screw slot.

[Elkman]

If you tighten by hand with a small wrench or screwdriver there is not going to be too much torque applied. It is when power tools are used to drive a screw that problems arise.

When using a socket wrench on small fasteners I grab the one with a stubby 2 inch handle as it is much more difficult to overtighten than with the standard ratchet wrench with its 6 inch handle. When I had friends with a bike shop one of the most common problems was a customer breaking off a 8mm bolt head by using too large a wrench and applying too much torque. Smaller wrenches are better for use with smaller fasteners.

I would be amazed if any Winnebago dealer or solar installer made use of a Newton torque wrench with their installions.

[Morich]

If you are still thinking this over, perhaps it is better to take a look at alternate plans?
There are times when space is a real problem or there are reasons to use a smaller guage wire at the last few feet/inches and if we keep it to a minimum length, it rarely is any problem.
I don't see what gauge wire you are speaking of but how about using some straight splices to do two things that ight help. If you are place where you need to make a ninety to fit the opening on the connection better as well as need a smaller wire, I would propose using some of these to do that as well as give you a chance to make a bit more slack to relive the pressure from the wire pulling too hard.
This type of splice added a little bulk when space is short but if the splices are staggered, adding three splices might help to solve future problems:
https://www.zoro.com/ideal-splice-ki...RoC8YIQAvD_BwE

I did not look for overall best price as that varies so much and you may be able to find a much better price if picked up locally.

[AJMike]

Originally Posted by Morich

If you are still thinking this over, perhaps it is better to take a look at alternate plans?
There are times when space is a real problem or there are reasons to use a smaller guage wire at the last few feet/inches and if we keep it to a minimum length, it rarely is any problem.
I don't see what gauge wire you are speaking of but how about using some straight splices to do two things that ight help. If you are place where you need to make a ninety to fit the opening on the connection better as well as need a smaller wire, I would propose using some of these to do that as well as give you a chance to make a bit more slack to relive the pressure from the wire pulling too hard.
This type of splice added a little bulk when space is short but if the splices are staggered, adding three splices might help to solve future problems:
https://www.zoro.com/ideal-splice-ki...RoC8YIQAvD_BwE

I did not look for overall best price as that varies so much and you may be able to find a much better price if picked up locally.

The last thing I did was to really bend the 6 gauge wire I am using, more than I thought was best, to see if that fixes the issue. If it does not, then I will try replacing the 6 gauge wire with 4 gauge wire (which is what I probably should use, considering the distance) and splicing on a short piece of a smaller gauge wire for the actual connection.

But I do have a question. The link you posted showed a splicing sleeve with screw connections. Normally I would splice using a crimping sleeve. Is there any reason to use one over the other?

[Morich]

When at home, I tend to work with less tools and that makes the screws more logical but if at work and there were the far better crimpers on hand, the crimp might be as good and quicker. I would consider either much the same if the crimp is done with the good tools so a really good crimp is done but when at home, it seems like the screws biting into the wire might make a connection less prone to pulling out.

I've seen this more than actually done it with my own hands other than one famous screwup on buried cable! I found I could actually find an underground wire while standing twenty feet from a trailer and do it without even looking and only using a 1/2 inch ground rod!

[Elkman]

Every MPPT charge controller that I have looked at had terminal connections for 8 gauge or smaller wires. Adding a jumper wire that can connect to the MPPT controller and then continuing the run with a larger gauge wire is the best solution. Key is using the split bolt connectors when connectiong two different gauge wires - it is why these are made for use by electricians. Current loss will be negligible and the mechanical connection will be stronger and less stress on the MPPT device connection.

Even the Victron charge controllers that are designed for use in RVs take 6 gauge or smaller wiring and so a jumper section is often going to be needed. The Zamp controller used by Winnebago takes 8 gauge or smaller wire for connections to it.

http://circuitwizard.bluesea.com/

Useful online calculator to wire gauge selection

[AJMike]

Originally Posted by Elkman

Every MPPT charge controller that I have looked at had terminal connections for 8 gauge or smaller wires. Adding a jumper wire that can connect to the MPPT controller and then continuing the run with a larger gauge wire is the best solution. Key is using the split bolt connectors when connectiong two different gauge wires - it is why these are made for use by electricians. Current loss will be negligible and the mechanical connection will be stronger and less stress on the MPPT device connection.

Even the Victron charge controllers that are designed for use in RVs take 6 gauge or smaller wiring and so a jumper section is often going to be needed. The Zamp controller used by Winnebago takes 8 gauge or smaller wire for connections to it.

Circuit Wizard - Blue Sea Systems

Useful online calculator to wire gauge selection

I have tried to make sure all the connections I made were covered in some way to prevent shorts or people accidentally touching the live wires. I know that they are only 12 volts, but they carry a lot of current. Is there some way to enclose those connectors?

[al1florida]

Originally Posted by AJMike

I have tried to make sure all the connections I made were covered in some way to prevent shorts or people accidentally touching the live wires. I know that they are only 12 volts, but they carry a lot of current. Is there some way to enclose those connectors?

For 12V power to cause a problem there needs to be a good connection between the 12V and a ground. Something like metal (rings on fingers, metal watch band). However it has to have a direct connection from the 12V to the ground. Just touching the 12V with your finger and having your other hand on a ground doesn't cause a problem. Screw connectors on the back of a charger are usually somewhat recessed making them hard to make good solid contact with.

Now if there is a 1/2 inch or inch of bare wire exposed where something metal could drop on to it and the other end touching a ground that is different. Or a place where a metal watch band or ring on a finger could bridge the gap between 12V and a ground, that is a very dangerous problem. The high current caused by a direct connection with a watch band or ring will create high heat and very nasty burns.

The direct connection issue is why you always remove the negative lead from a battery first instead of the positive lead. Bridging the wrench or screwdriver from the negative lead to ground is not a problem. However disconnecting the positive lead and bridging the wrench to ground can weld the wrench from the terminal to ground.

[Morich]

When in doubt, it's good to cover things. One way to do it is heat shrink as it comes in every size from tiny up to several inches. If you piece out the cables and the connections are close, I would go for heat shrink and then while about it, push the sleeve as far forward to cover as much as practical.

You don't need anything specific to shrink it, just heat of some sort, even a hot light bulb!
For small stuff I use a soldering iron but that takes so long, a torch works better if it is something big and out in the open.

A can of "liquid tape" is another good one.

[AJMike]

Originally Posted by Morich

When in doubt, it's good to cover things. One way to do it is heat shrink as it comes in every size from tiny up to several inches. If you piece out the cables and the connections are close, I would go for heat shrink and then while about it, push the sleeve as far forward to cover as much as practical.

You don't need anything specific to shrink it, just heat of some sort, even a hot light bulb!
For small stuff I use a soldering iron but that takes so long, a torch works better if it is something big and out in the open.

A can of "liquid tape" is another good one.

I was specifically referring to the split bolt connector referred to by @Elkman. The ones that I found on Amazon (like this) seem to be fairly large and all metal and I was thinking about something that would insulate that from accidentally touching something metal while driving.

All of the insulation I have used so far (shrink tubing, plastic covers and the like) have been designed for specific tasks and would not fit anything shaped like the split bolt connectors at the link I provided. I assumed there is something that would work for it.

[Morich]

Yes, they are a problem and not something that I would want in confined spaces. They are way too bulky and too many sharp points to cut through any type insulation.

[Elkman]

A compartment with a charge controller is not what I would view as a confined space for using split bolt connectors. When you have a 4 gauge wire connecting to a 6 gauge jumper to connect to a charge controller the split bolt is the most mechanically secure way to do this without attaching a couple of terminal blocks to the wall. There may be plenty of space in some motorhomes and trailers this definitely not the case with Class C motorhomes.

Adhesive shrink wrap is a good idea if it is cut long enough so when it shrinks it does not expose the copper core. With the battery leads done by Winnebago on my 2021 Navion this was overlooked and I decided to put 10 wraps of electrical tape around the end of the shrink wrap where is was too short.

Worrying about the fin orientation is OK but also think about what else is in an unvented compartment and producing heat. With my last RV I bought metal vent plates and made 2" holes at the bottom and top of a compartment to allow for passive circulation of the heated air inside.

[AJMike]

Originally Posted by Elkman

Adhesive shrink wrap is a good idea if it is cut long enough so when it shrinks it does not expose the copper core. With the battery leads done by Winnebago on my 2021 Navion this was overlooked and I decided to put 10 wraps of electrical tape around the end of the shrink wrap where is was too short.

I have been using electrical tape, wrapped several times around the connections. I prefer the old friction electric tape but all I can find now is the new plastic electric tape. I suppose it still works, but the old friction tape seemed more substantial somehow.

Originally Posted by Elkman

Worrying about the fin orientation is OK but also think about what else is in an unvented compartment and producing heat. With my last RV I bought metal vent plates and made 2" holes at the bottom and top of a compartment to allow for passive circulation of the heated air inside.

The compartment used to be unvented but I put 2 holes in it, one on each side, to provide for ventilation, and then installed a 2" muffin fan to make sure the air is actually moving, so there is now plenty of air movement across the heat sink fins.