Use one or more 120 volt extension cords as a 12 volt solar panel extension cable????? Advice please.

[John E Davies]

I already have two 25 foot and one 50 foot 120 volt 10 AWG extension cords, primarily for use with my generator and Makita chainsaw. I have a Renogy 100 watt suitcase solar panel coming for Christmas with onboard 20 amp smart controller. I made a Furrion adapter cable for charging my compressor fridge inside the truck, so I already have tools, parts and a head start.....      

 

https://olivertraveltrailers.com/forums/topic/3247-how-to-external-solar-dc-power-cable-using-factory-furrion-port/.......

 

Sooooooo, hypothetically:

Remove the Renogy onboard controller, add two short pigtails to it with Anderson Powerpole 30 amp quick disconnects.

Add Anderson connectors at the suitcase panel’s 21.6 volt (unregulated) wires.

Make one male and one female three pin adapter for the 120 VAC extension cord, using only the neutral white and ground black pins. Remove (cut off) the unused (hot wire) male pin. Add a pigtail with Andersen connector to each. 
 

Connect the controller output cable directly to the exterior Furrion solar port with a 5 foot adapter cable (already made). Lay the controller on the tire, under the fender, to stay out of the direct sun and weather.

Now the adapter harnesses can be plugged into ANY 120 VAC extension cord to use it as a solar panel low voltage cord. Length would be a non issue since the controller would be located right at the trailer. I could choose 25, 50 75 or 100 feet total length of cord by connecting them together different ways.

If somebody was silly enough to plug the male end of the extension cord into a live 120 VAC socket, nothing would happen at the far end because the hot pin on that adapter plug has been removed.

If I wanted to use the controller with it directly on the panel, for use charging a car battery, for example, it would be a simple matter of installing two screws and plugging the Anderson connectors together.

Any reasons I should NOT do this? I know it might possibly freak out some folks who see a regular extension cord running from the solar panel to the trailer. I am fine with freaking out people 😜 I would rather not buy and make a long 12 volt solar extension when I have these other cords sitting unused.... 

Does anyone know the maximum distance for the solar panel, using 10AWG wire, to get a satisfactory amount of current at the controller?

Snowed in, too much time on my hands.  Please comment! Thanks.

John Davies

Spokane WA

Edited November 23, 2020 by John E Davies

[Stevon]

I can’t see any reason why this wouldn’t work. I have also been planning to remove the controller from my suitcase so it can be as close to the battery as possible. 

[Overland]

I'm not sure how much advantage you'd get, since you're talking 18v out of the panel vs 14.4 out of the charge controller.  Is 3.6 a big enough difference to effect the voltage drop much? 

Now, if you wire up the two panels in series, then you've definitely got a voltage advantage.  But then you'd need a new controller.

Edited November 24, 2020 by Overland

[mossemi]

[John E Davies]

Mike,  I don’t understand the chart, it is missing the X axis so I don’t really know how to interpret it. Really, I just need to know if 50 + feet extension with 10AWG stranded wire from an unregulated panel would be workable..... how much voltage drop is OK for the controller to do it’s thing?

I do know you have to figure both wires, there and back, as a complete circuit, when calculating voltage drop. I also (now) know that the cable from controller to batteries should be as short as possible. Or step up the wire size to compensate..... there is 3 feet of 12 AWG (?) wire that Oliver installed going from the inside of the solar port to my positive battery bus. I could increase that to say 6 AWG easily enough, so in effect the controller would be “closer” to the load.

Heck, I might even just add a dedicated controller inside the battery box, with an Anderson bulkhead feed through on the door, down near the hinge... and bypass the Furrion port entirely, which I do not trust as much as the other type.

Thanks.

John Davies

Spokane WA

 

Edited November 25, 2020 by John E Davies

[mjrendon]

John, 

100ft seems long for 10-AWG. This calculator estimates a 4V drop from 14.5 V with 20A.  

https://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=3.277&voltage=14.5&phase=dc&noofconductor=1&distance=100&distanceunit=feet&amperes=20&x=0&y=0

Edited November 25, 2020 by mjrendon

[RnA]

50 ft of 10 gage copper wire

for 17.7 volt output of the panels, 4.7 amp you'll loose 0.47 volts, 2.65%

for 14.3 volt output of the charge controller, 5.8 amp you'll loose 0.58 volts, 4.75%

there will also be some minor losses through each of the connections.

voltage drop calculator at the link below:

https://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=3.277&voltage=17.7&phase=dc&noofconductor=1&distance=50&distanceunit=feet&amperes=4.7&x=51&y=23 

not sure if this  calculator is for solid or stranded wire, you should get slightly less drop with stranded as the current tends to flows on the outer surface of the conductor and the stranded has more surface area.

 

 

 

Edited November 25, 2020 by RnA

[mossemi]

Sorry!  I butchered the picture.  To answer your question we would need to know the output of the panel.  With that number the chart will give you ballpark value or you can use the link mjrendon or RNA attached above for more accuracy.

Edited November 25, 2020 by mossemi

[John E Davies]

 

Since it is rated at 5.5 amps, I think it would give me usable power at 50 feet. I am not trying to maximize the charge current so much as to be able to get a decent amount from a sunny spot far away from where I am parked under trees or beside a building... Normally the panel would be pretty close, but if it could be fairly remote and still be putting out 4 or 5 amps in bright sun, I would be happy. That calculator gave me this, for a PAIR of 100 ft conductors:

 

Dropping the panel voltage to 16 volts still gives 14.9 volts at the controller input terminals. Is that enough?

Having the controller sitting  in the shade, or hard mounted inside with my batteries, should help significantly because one sitting out in the sun, baking at 120+degrees F, is not going to be very happy.

I haven’t read any articles or forum threads about a long distance panel with a close in controller; if somebody has a link I would really appreciate seeing it. I don’t mind doing R and D but would feel stupid if somebody has already done it for me.😳

Thanks.,

John Davies

Spokane WA

 

 

Edited November 25, 2020 by John E Davies

[RnA]

it will work better with the controller close to the batteries.  i would not locate it in the battery compartment though.  a pulse type controller will pulse the output to match the the voltage needs of the battery.  the duty cycle of the pulses will be driven by the amount of current and voltage on the input.  thus as the voltage and the current, drops the frequency of the pulses spread over time.  there is probably some minimum input voltage dependent on the specific controller where it all falls off a cliff and the controller won’t output.  i think 14.9 volt input would be more than enough though.

obtw.  an mppt controller will give the voltage output your batteries need but drop the current giving a more constant current flow not pulses of energy to the battery.

make sure you fuse the lines.

give a try.  you can always make cord shorter if need be.

 

[RnA]

more simply, the voltage output of the controller is optimized for the battery state.  if the controller is at the panels the voltage drop will be more over the long run of wire and less than optimum for the batteries.

[John E Davies]

RnA, why should the controller not be located inside the battery compartment? I will be switching from four bad AGMs to two 100 AH lithiums, there will be plenty of room. I was actually thinking of mounting it and an inline fuse upside down on the door itself, so it would drop down out of the way when opened, to allow the tray to slide out. With the door open you would have easy access to the controls and be able to view the display. Does this present problems? I don’t need to see it other times since I have a Victron Connect app that will show me what is going on at the battery bus.

OTH It would work just as easily in the electrical compartment just forward of there. BUT I was hoping to not drill any extra holes through the outer hull; holes in the battery door could be remedied by a simple door replacement, if a future owner was unhappy with it for some reason....

John Davies

Spokane WA

 

Edited November 25, 2020 by John E Davies

[RnA]

agm batteries still have a potential to vent hydrogen, particularly if overcharged.

here’s a good link with an explanation of the rvia position:  

https://rvnerds.com/2017/11/01/electrical-myths-part-4-agm-batteries-dont-need-venting/ 

“The Recreational Vehicle Industry Association’s Low-Voltage similarly requires venting for all battery locations, whether or not batteries are actually installed, and prohibits installation of other potentially spark-producing equipment in the same compartment (e.g. inverters, charge controllers, disconnect switches):.....”

regarding Li, i wouldn’t want any electronics (fire potential) co-located.

[John E Davies]

39 minutes ago, RnA said:

 

“The Recreational Vehicle Industry Association’s Low-Voltage similarly requires venting for all battery locations, whether or not batteries are actually installed, and prohibits installation of other potentially spark-producing equipment in the same compartment (e.g. inverters, charge controllers, disconnect switches):.....”

regarding Li, i wouldn’t want any electronics (fire potential) co-located.

Thanks, I was aware of that link, and about venting. I personally would have zero concerns with a controller plus lithium batteries. But I suppose a future buyer might not be as accepting of a code violation. I guess this is a good reason to mount the parts inside the hull itself. I do plan to cover those vent holes though, and insulate the door itself.

John Davies

Spokane WA

 

Edited November 25, 2020 by John E Davies

[RnA]

5 hours ago, John E Davies said:

BUT I was hoping to not drill any extra holes through the outer hull; 

Why not use the Furion 10amp exterior connector straight from the solar panel?  Are you planning on going beyond 100watts?  If you use that connector could then locate the controller under the aft dinette seat.  My setup has wires from the outside Zamp connector direct to the batteries (through a 10amp in-line fuse).  You could install the controller between the port and the fuse. 

 

When using the extension cord you need to be careful of powering the male plug from either batteries or solar panels.  If male is at the panel end with an adapter (with an inline fuse) to the panels I think ( but you need to check on your specific charge controller) the charge controller should have diodes to prevent current flowing back out to the panels (this is done to keep your batteries from discharging back into the panels at night).  With the extension cord male end at the other end, you risk damage your panels with an accidental short of the plug.  Your idea of using only the ground and neutral is a good one to keep from putting 120 ac into your controller.  Just make sure the ground is 10awg also.  A Furion connector to male  plug would complete the trailer side. 

[John E Davies]

I will start with the Furion port, but I really do not like the design, and I am already using it as a 14 volt power source for my fridge inside the truck. So I would have to share that connection. I may end doing that.

But really like the Power Pole connectors, they provide a much stouter/ reliable connection and will handle way more current too.

Thanks for all the comments.

John Davies

Spokane WA

[Geronimo John]

On 11/23/2020 at 7:13 AM, John E Davies said:

Does anyone know the maximum distance for the solar panel, using 10AWG wire, to get a satisfactory amount of current at the controller?

I was on the phone with Renogy today exploring home made  extension cords for my suitcase next summer project.  I asked what the maximum distance I could run my extension from the Solar Charge Controller to the panels was?  Answer Given:  40 feet using #10 AWG wire.  For #12 AWG it was 15 to 20 feet.  

I like your idea as it means I can get double duty from my existing #10 AWG and #12 AWG Generator extension cords!