Interrupted charger output

[al1florida]

I have been using this 12V muffin fan I bought on Amazon for over a year at up to 14.4V w/o a problem.

https://www.amazon.com/gp/product/B0...0?ie=UTF8&th=1

I bought the 140MM size which looks like it is no longer available in 140MM but there are smaller ones available.

This type of fan come with a 3 or 4 pin connector. I just cut the connector off and wired the red & black wires to 12V.

[AJMike]

Originally Posted by al1florida

I have been using this 12V muffin fan I bought on Amazon for over a year at up to 14.4V w/o a problem.

https://www.amazon.com/gp/product/B0...0?ie=UTF8&th=1

I bought the 140MM size which looks like it is no longer available in 140MM but there are smaller ones available.

This type of fan come with a 3 or 4 pin connector. I just cut the connector off and wired the red & black wires to 12V.

Thanks for the comment and the link. When I looked at the description of one of the fans I browsed on Amazon I noticed the comment about anything over 12.8 volts or so greatly shortening the life of the fan and that was why I asked about the voltage issue.

[AJMike]

Well, probably is.

I have been doing more testing on this Renogy DC-DC charger as I have been able to, and it appears that @Morich was right. The issue is heat and I suspect that the internal fan in the charger is just not working or, at least, not working enough to cool the unit.

What I did was relocate the unit from the cabinet it was originally installed in to a more open cabinet and so extended the existing wires (the wiring instructions called for 6 gauge wire for that distance so I used wire from a 6 gauge jumper cable. I am not sure that is good enough for long term. Any suggestions?) and wired a muffin fan to the 12 volt connection, making sure that it was blowing air into the input side of the unit where the fan is supposed to be. I then went for a 45 minute drive and saw no repetition of the sawtooth operation so I assume that the problem is heat and the charger is failing. That is, this on-off operation was not part of its normal functionality, and it was not the alternator.

The charger is currently in the cabinet under the dinette seat and I left the top (that is, the actual seat itself) off so there was good circulation. Next I will have to have holes drilled into the sides to provide for air input and output and mount the fan at the input. That should also help to take care of the noise from the fan. I would not have thought that a small muffin fan would make so much noise.

[Morich]

Kind of lost track of this discussion, so missed the question on powering the fan. I've also lost most of my deep thinking on designing a power supply to cut the power from 13.7 to 12.0. I'm not sure it is a big problem to worry me as techie folks who do computer are often far more concerned about power differences than folks who just think fans. But if it was a bug to you, adding a resister inline with the power is one way to reduce the voltage to the fan. That's where I've lost the theory /formula for voltage dropping resisters. Ohms law is the base but I have not used it and designed anything in years and never found it too often used other than understanding the why of it.
One reason for the noise, might be the overpower and over speed with higher voltage?
A variety pack of resisters might be one way to just go with testing. Since it is low voltage as well as low current, maybe just clipping or twisting in a few for trial and error would do the job as it is not going to damage things if it is totally the wrong size resister and makes it too slow. It can't make it faster, for sure!
I may have a different thought on airflow as I feel I get better use of the fan if I use it to pull air across the equipment, rather than push it over. Seems the pushing causes more blocking of the airflow actually moved out of the cabinet than if I can arrange to have the fan near the output vent and pulling air in over the item.
Where I feel things may be going off is that the onboard cooling fan can't actually move the air out of the cabinet, so when pulling air in it is hot air that it has moved out the other side. Air moved out of the equipment is then adding heat to the air then pulled in again so that we never really get fresh cool air but tend to warm the same air which is passed over again and again until it is too hot. Kind of like using a fan in a room to move air but it just keeps getting hotter but works great if we can use the fan to pull air in through a window?
I once had an RV with a ton of electronics gear to cool and went this way on that RV layout. Not likely to have the same on yours but possible to set up a different airflow to match layout you have? This put the fan and noise in the bathroom as sound does follow air to some extent as well as moving it much further away from the drivers section where I was. This drew the coolest, newest, air into the equipment by pushing old out the vent in the bath.
Also prewarmed the stool for my comfort!!!

[AJMike]

Originally Posted by Morich

Kind of lost track of this discussion, so missed the question on powering the fan. I've also lost most of my deep thinking on designing a power supply to cut the power from 13.7 to 12.0. I'm not sure it is a big problem to worry me as techie folks who do computer are often far more concerned about power differences than folks who just think fans. But if it was a bug to you, adding a resister inline with the power is one way to reduce the voltage to the fan. That's where I've lost the theory /formula for voltage dropping resisters. Ohms law is the base but I have not used it and designed anything in years and never found it too often used other than understanding the why of it.
One reason for the noise, might be the overpower and over speed with higher voltage?
A variety pack of resisters might be one way to just go with testing. Since it is low voltage as well as low current, maybe just clipping or twisting in a few for trial and error would do the job as it is not going to damage things if it is totally the wrong size resister and makes it too slow. It can't make it faster, for sure!
I may have a different thought on airflow as I feel I get better use of the fan if I use it to pull air across the equipment, rather than push it over. Seems the pushing causes more blocking of the airflow actually moved out of the cabinet than if I can arrange to have the fan near the output vent and pulling air in over the item.
Where I feel things may be going off is that the onboard cooling fan can't actually move the air out of the cabinet, so when pulling air in it is hot air that it has moved out the other side. Air moved out of the equipment is then adding heat to the air then pulled in again so that we never really get fresh cool air but tend to warm the same air which is passed over again and again until it is too hot. Kind of like using a fan in a room to move air but it just keeps getting hotter but works great if we can use the fan to pull air in through a window?
I once had an RV with a ton of electronics gear to cool and went this way on that RV layout. Not likely to have the same on yours but possible to set up a different airflow to match layout you have? This put the fan and noise in the bathroom as sound does follow air to some extent as well as moving it much further away from the drivers section where I was. This drew the coolest, newest, air into the equipment by pushing old out the vent in the bath.
Also prewarmed the stool for my comfort!!!

This effort was simply a "proof of concept" in that all I wanted to do was test the idea that relocating the charger and running a muffin fan would take care of the problem, and it was not intended to be a final fix.

To do this test as simply as possible I connected the fan to the input connection on the charger but I assume that is not a good location for a final fix as the voltage is higher than the 12 volts it should be. The cabinet has both a 12 volt (the old cigarette lighter) and usb power connection and I suspect that the best thing to do would be to hook into one of those. They should be 12 volts, not 13.7, and perhaps the fan will be quieter when run at its designed voltage.

The real issue for the fan is that there is no voltage source that I have available that will only be "live" when the engine is running so I will have to install an on/off switch to turn the fan off when the engine is not running and that sounds a bit "kludgy" to me. But all power sources in or near the cabinet are always on and I don't see another choice.

I did think of adding a resistor to the line as that should cause a voltage drop at the fan itself, but that meant that I had to figure out the resistance of the fan, buy a resistor pack and a soldering iron and try to remember if I ever was able to make anything other than a cold solder connection. The 12 volt outlet seems like a better bet even if it requires an on/off switch.

The main reason for the post was to share what I had learned about the source of the issue and to give you the credit you deserved for being right from the get-go. Thanks.

Do you have any thoughts about whether a 6 gauge wire cut from a jumper cable is as good as a 6 gauge wire bought at an auto store? I would think that 6 gauge means 6 gauge but I am not familiar enough with high current wires to feel knowledgeable about something like this.

[Morich]

Six gauge in either should carry the same current with the main difference being stranded six is more flexible but somewhat larger diameter than solid six gauge. Stranded is good for jumper cables, etc. that we move but if we want smaller size to fit into clamps, etc. the solid is good. Some difference in issues with corrosion as the stranded does get some corrosion down between strands and solid does make a little neater connection if we put it under a screw clamp, but I would consider it a tossup if I wanted to junk a jumper cable. But then six solid is pretty easy to get from places like Home Depot who sell it by the foot. I might go for the solid as a neater look?
For powering the fan, I looked at a couple of salvage and they show like .55 amp current so, I would not blink at using any 12 volt wire I could find. I wire them for fish tank use with leftover 22 gauge telephone wire! That puts it into a deal where I don't mind running the wire a lot further to get to the connection I might like best. RV have lots of little nooks and crannies to sort out whether close or easy is better!
Sometimes the decision is the harder part as I spent far more time figuring how to wire in a couple little voltmeters than I did actually putting the wire in!
On the credit for suggestions, I figure you can buy me a cup of coffee the next time we meet and I'll buy you one for keeping my mind from going to silly putty while trapped at home.

[al1florida]

The #6 jumper cable wire is much more flexible than the stranded #6 wire bought at the big box hardware store. That stuff is pretty stiff. Solid #6 would be even harder to run.

As Morich wrote, #6 is #6 wire and all will carry about the same amount of current.