Solar fun! Effects of long cable runs panel to controller

[E1]

[valvecovergasket]

I've ordered from these guys before, red/black pair
$35 for 25ft of 10g


https://powerwerx.com/red-black-bonded-zip-cord
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gone, but not forgotten: '83 tdi westy - swap thread

[Sodo]

[Kombi Dad]

I too needed to park in the shade and have the panels in the sun. The ones I use are a folding set of 120W charging a 137AH AGM battery. The panels came with about 30 feet of cable of a very thin guage with the regulator mounted on the panels. I ran some experiments as at first I was going to mount the panels on top of the camper. They were about 50% as efficient as when aimed at the sun so they stayed portable. For cable I changed the original cable to a much heavier cable, the type used for connecting vehicles to caravans for charging purposes here in Australia. I also used Anderson plugs either end of the cable to help packing up. The cable is now about 75 feet in length. I am moving regulator from the panels to the battery and will use a MP3129 Powertech regulator. This gives you some idea of how far I can put the panels away from the vehicle.

[j_dirge]

[crazyvwvanman]

If the sun comes out to play today I will try the test you suggested. I have actually been doing lots of testing of different panels, different controllers, different wiring. I have tested 5 different size panels and 5 different controllers, fooling around with them when I get both the time and good sun in the middle of the day.

For most of my testing I measured volts and amps from the panel to the controller as well as volts and amps from the controller to the battery. All 4 meters were wired in so I could see all the readings at the same time. One limitation to my data is that the meters are only 3 digits, with 1 digit to the right of the decimal point. This is not precise enough for me to be satisfied with some aspects of my tests.

I am not very interested in a portable panel setup so large as to 100% fully charge my aux battery each day while I am camped. I don't need it to do that. My goal is to have a panel and long cable with me for those times when I find that I need it with the goal of extending my battery capacity for my 12volt fridge. That is it. I just want to be able to stay put for more than 3 nights and have my fridge still running. That is the same goal I had for my permanently mounted panel on my Westy roof. Our preference is for shady campsites and van orientations that are optimized for US rather than for the solar panel on the roof. That means there have been lots of times when the poptop mounted panel was nearly useless to us. If we were in a hardtop van the orientation issues would be lessened but our enjoyment would be reduced along with the headroom.

I have more controllers and panels coming. I will be doing more testing when I can. I will likely share more of the results.

[jmranger]

[4x4BNB]

Here's an interesting site....http://handybobsolar.wordpress.com

[shadetreetim]

Thanks for taking the time to do an actual test on this subject Mark. Always fun to see real test results illustrating the effects of what may seem to be simple choices. It would be interesting to have seen a comparison of the #12 and #14 cords at comparable lengths.

I used #10 on my fixed panel install, although perhaps that was influenced by the fact I already had some UV protected 10/2 cable on hand.
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'74 Jeep CJ5

[Howesight]

crazyvwvanman wrote:

This thread was only meant to help quantify how different cable lengths and wire gauges from the panel change the output of the charge controller. I did these reported tests just a few hours before I posted the results here. For my application as well as most vans the portable solar panel is going to get used only intermittently and for me that means I don't need to be very concerned with trying to attain near perfection. My concern is with general practicality. I have a DC fridge installed in my Westy and I want to be able to deploy a portable solar panel in situations where I will be staying put longer than my battery storage alone will allow. I already have a solar panel mounted on the Westy roof but that arrangement often has severe limitations when camped with the top popped. I have had it up there for 4 years and there is no doubt at all about those limitations with respect to my needs so I am going to add a portable panel. I wanted to see how long of a cable was practical and how much loss would be involved. I also wanted to see if I would be ok with just one very long cable or if multiple cables would be justified so I could run a shorter cable when that was all that was needed and thus reduce the losses unless the extra length was needed at a particular campsite. Also big coils of long heavy cable are not something I want to haul around for just occasional use so I wanted to determine what cabling gauge was actually needed. Based on my tests so far I likely won't be buying any #10 for my portable panel setups. Looks like #12 at most is all I need. More tests are needed though. The charge controller I used is these particular tests is supposedly an MPPT design. I say supposedly because at just $25 I have some doubts. I have a couple other PWM controllers that I tested side by side with this MPPT unit and the MPPT unit does appear to go through some additional output level steps each time a solar panel is connected. Also keep in mind that I mentioned having a headlight powered on by the battery during these cable length tests. The headlight was drawing power from the battery about equal to what the solar was supplying. In performing the tests I tried to keep everything consistent so I could better judge what was due to just the cabling differences. I kept the panel covered by cardboard while making setup changes. Then I uncovered the panel and let things stabilize for a couple minutes before taking readings. I also switched back and forth to do multiple tests of each combination. EDIT: I have some other controllers to try and other sizes of panel as well. I will test a smaller and a larger panel to compare the cabling needs. It looks like today will be sunny so it may happen soon. Mark

Hey Mark:

I just wanted you and everyone else reading this thread to understand that I did not in any way intend to slag you or your findings. You are the electrical guru on the Samba and I have learned a lot from your many threads.

The real-world example you gave is very helpful to many people who would zone out poring over a voltage-drop/wire gauge/wire length chart.

My comments were meant only to re-iterate my oft-repeated comments on solar set ups: Start with the charging recommendations from your battery manufacturer and work backwards from there to ensure your charge controller puts out the volts and amps for the length of time your battery needs them. That means checking the charge controller output at the battery, adjusting your controller parameters setup to ensure you are at the target voltage (for me, it is 14.8 volts - - Trojan flooded) and to ensure your controller is getting sufficient current and volts to achieve its output. At a certain point, long cables of small gauge will prevent your controller from getting sufficient volts and amps.

It is important to remember that any solar setup will, if there is no draw on the battery, eventually re-charge your battery. The key is, do you want it recharged today or not. The panel size and the allowed losses due to cable length and gauge only affect how long it takes to mostly re-charge your battery. (I say mostly, because a battery like mine will not get to 100% charge without bulk and absorption phases first occurring at 14.8 volts.) The system must replace, in the available daylight hours, all the power that was removed when the solar system was not charging. The combination of panel size and wiring losses needs to be calculated to be sufficient to replace that power. So, there is nothing wrong with some line losses if you upsize the panel to compensate.

For me, I found a folding panel (100W Renogy) that would fit in my luggage rack and I therefore had to use big wire to avoid line losses that would yield insufficient total power for my power budget. I had no wiggle room to go to a bigger panel. Bonus: My cable still fits inside the folded panel!
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'86 Syncro Westy SVX

[4x4BNB]

I now carry two lengths of cable...a 50 and a 25 foot. Both are a 10g. My mppt controller is right next to my batteries but...now I must check the gauge from these controller to the batteries....
Great post!! Thanks for sharing the information....

[j_dirge]

[TequilaSunSet]

Going slightly OT... would a 100w set up be a solid choice, to recharge 2 batteries?
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[teej]

Interesting tests, thanks for sharing.

They mostly confirm what I have been seeing with our set up. We have a couple portable panels, 60w and 130w. Usually we just bring the 60w and move it for optimal solar positioning. Our extension cable is about 45' made from 14-2 landscape wire and SAE style 2-pin connectors. This setup has not much trouble maintaining our 88Ah aux battery that powers a fridge, lights, sometimes some stereo. The length of cable allows us to put the panel where the sun is in the often shaded PNW campsites.

A made a second shorter cable out of 12-2 which gets used with the 130w panel. When the longer cable needs replacing I will use 12-2.

We use a 20a SunSaver PWM controller mounted next to the battery, with 10ga run from controller to battery.

After a trip the battery gets fully charged with the big panel before storage.
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[crazyvwvanman]

This thread was only meant to help quantify how different cable lengths and wire gauges from the panel change the output of the charge controller. I did these reported tests just a few hours before I posted the results here.

For my application as well as most vans the portable solar panel is going to get used only intermittently and for me that means I don't need to be very concerned with trying to attain near perfection. My concern is with general practicality. I have a DC fridge installed in my Westy and I want to be able to deploy a portable solar panel in situations where I will be staying put longer than my battery storage alone will allow. I already have a solar panel mounted on the Westy roof but that arrangement often has severe limitations when camped with the top popped. I have had it up there for 4 years and there is no doubt at all about those limitations with respect to my needs so I am going to add a portable panel. I wanted to see how long of a cable was practical and how much loss would be involved. I also wanted to see if I would be ok with just one very long cable or if multiple cables would be justified so I could run a shorter cable when that was all that was needed and thus reduce the losses unless the extra length was needed at a particular campsite. Also big coils of long heavy cable are not something I want to haul around for just occasional use so I wanted to determine what cabling gauge was actually needed. Based on my tests so far I likely won't be buying any #10 for my portable panel setups. Looks like #12 at most is all I need. More tests are needed though.

The charge controller I used is these particular tests is supposedly an MPPT design. I say supposedly because at just $25 I have some doubts. I have a couple other PWM controllers that I tested side by side with this MPPT unit and the MPPT unit does appear to go through some additional output level steps each time a solar panel is connected. Also keep in mind that I mentioned having a headlight powered on by the battery during these cable length tests. The headlight was drawing power from the battery about equal to what the solar was supplying.

In performing the tests I tried to keep everything consistent so I could better judge what was due to just the cabling differences. I kept the panel covered by cardboard while making setup changes. Then I uncovered the panel and let things stabilize for a couple minutes before taking readings. I also switched back and forth to do multiple tests of each combination.

EDIT: I have some other controllers to try and other sizes of panel as well. I will test a smaller and a larger panel to compare the cabling needs. It looks like today will be sunny so it may happen soon.

Mark

[morymob]

I'm going to use 10guage & I have 50ft of wire to get out into sun 4 most conditions, I guessa voltage check at both ends would be needed, controller inside .

[Howesight]

[Howesight]

[jmranger]

Thanks for taking the time to experiment and sharing your results Mark.

I'm puzzled by the drop in charging voltage. Do you understand why it is dropping? Battery internal resistance? Battery or panel temperature?

Also, do you know what technology your charge controller is based on? On/off, PWM, MPPT?

Jean-Marc

[goffoz]

Interesting
My charge controller is on my panel, So any extension puts the controller further from the battery
Maybe the controller should be in the van ?