Running heavier wire for solar panels

Sorry for the derail but there seems to be some solid misinformation floating around on voltage drop (and how important it is prior to a PWM controller) which factors into the reality of why this would even need to be done (in my opinion it wouldn't). But in the end chasing the wire through the roof would be the harder part after than its behind paneling you can unscrew.

EDIT: no guarantee how FWC does it now but older ones looked similar to how ATC does it, see this post: http://www.wanderthewest.com/forum/topic/8078-building-our-new-camper/?p=89274
 
You might consider replacing just the more accessible wire from the folding lift panel to the controller with larger wire. At least, run the numbers to see if that drops your losses adequately.

Paul
 
PaulT said:
You might consider replacing just the more accessible wire from the folding lift panel to the controller with larger wire. At least, run the numbers to see if that drops your losses adequately.

Paul
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Paul that is the section that is a bit of a mystery. The section from the ceiling box to the front wall runs thru a channel and feels like it slides pretty easily up there. From the front wall behind the folding lift panel back underneath the bed platform -- that is the section I am not sure how it runs. Any thoughts? I have not heard back from Brenda.
 
pods8 said:
Sorry for the derail but there seems to be some solid misinformation floating around on voltage drop (and how important it is prior to a PWM controller) which factors into the reality of why this would even need to be done (in my opinion it wouldn't). But in the end chasing the wire through the roof would be the harder part after than its behind paneling you can unscrew.

EDIT: no guarantee how FWC does it now but older ones looked similar to how ATC does it, see this post: http://www.wanderthewest.com/forum/topic/8078-building-our-new-camper/?p=89274
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I apologize if my response came off the wrong way. I appreciate the time you took to respond and I am probably nowhere near as knowledgeable as you are on solar. There is a ton of conflicting info out there on solar voltage drop so it is hard for someone new coming into this to know which is right. Based on a fair amount of experience in wiring other stuff however, its common sense that the bigger the pipe, the less resistance there is. I figured that if I ever wanted to expand the system down the road, a smaller wire gauge would be preferable.

Cheers
 
kmacafee, I've dug into a few of these. Typically the wires run behind the front lift panel and then into the large cabover aluminum framing. Pull the mattresses out and take a look at how to pull off the thin plywood cover. Usually its just a few screws. Good luck.
 
kmacafee said:
I apologize if my response came off the wrong way. I appreciate the time you took to respond and I am probably nowhere near as knowledgeable as you are on solar. There is a ton of conflicting info out there on solar voltage drop so it is hard for someone new coming into this to know which is right. Based on a fair amount of experience in wiring other stuff however, its common sense that the bigger the pipe, the less resistance there is. I figured that if I ever wanted to expand the system down the road, a smaller wire gauge would be preferable.

Cheers
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Just look at the numbers, if you have a question ask. What is the worst case expansion you imagine? I'll run the numbers if you want.

Voltage drop between a charging source and a battery is definitely something to pay attention to. In the realm of wires to upgrade the ones between your truck and camper is an area where there is certainly room for improvement since there really isn't extra voltage to loose and still have a good motive voltage to charge since the alternator isn't putting out a higher value. Solar panels are putting out higher voltage than what is needed at the battery so there is some wiggle room between the panels and controller (after the controller you need minimum loss again) and really very little difference if 1% or 5% is lost in the grande scheme in that section of wiring. That is certainly not the case between the truck and camper though, you really do need to keep the losses very low there if you want decent charging ability.
 
Ok. Just went out to my Hawk to see what I could see. There is good news and bad news. The good news is that FWC did a masterful job of bundling the wires under the cabinet to avoid rat's nests and ensure that the wiring doesn't easily get snagged, come loose or otherwise cause issues. Of course, that is also the bad news.

It appears that the solar wiring comes out of the exterior wall near the top of the underside forward corner of the cabinet, follows the upper corner under the counter top and forward vertical end panel to the interior vertical panel then rearward to the Zamp controller. Short of opening up the cabinet or removing the counter top, I can't see how one might replace the solar panel wires.

An alternative approach might be to have new wires exit the camper exterior wall and drop underneath the driver side wing and follow the flexible conduit of the truck alternator wiring and re-enter the camper near the battery/voltage isolator area. It would work especially well if you were planning to replace the solar charge controller in the future as you could mount the new controller within the battery compartment. Otherwise, just continue the wires to the back of the Zamp charge controller.

The tough decision there would be where to put a hole to exit the camper and attach some type of surface mount conduit to protect the wires from the exit hole down to underside of the camper wing.

As a former President used to say, "I feel your pain." :)

Paul
 
pods8 said:
Often the calculators ask for one way distance, 100watt from the panel for 25’ in 10ga is about 1.7%, I have no idea why you would call that marginal.
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Unless they're doubling the distance behind the scenes they giving erroneous results. From what I saw in a qwik look most of the online calculators are also for AC. FWIW my measured length, overall, was over 30 feet. 10ga. was barely acceptable making 12 ga. marginal.






pods8 said:
This makes no sense, you are saying you'd be forced to abandon the PWM controller to go MPPT because there was too much drop, right?
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No, not right. Forced into a MPPT because of series panel voltage exceeding a PWM's input voltage limit. At least that is true for any that I have seen after looking for one.
 
ntsqd said:
Unless they're doubling the distance behind the scenes they giving erroneous results. From what I saw in a qwik look most of the online calculators are also for AC. FWIW my measured length, overall, was over 30 feet. 10ga. was barely acceptable making 12 ga. marginal.
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Correct, the caculators that have you only put one way voltage run the complete circuit on the back end. I often use this one which does DC just fine, I run altenator charging calcs at 14V and solar panel to controller calcs at 18V which are both close: http://www.nooutage.com/vdrop.htm

[Here's another that allows the specific exact voltage, IE say 14.4V off the alternator, etc. Again it wants one way distance, not round trip: http://www.calculator.net/voltage-drop-calculator.html]

What criteria are you using for acceptable and marginal??? At 30' 12ga is ~3.2% and 10ga is 2%, both of those are perfectly fine and not even coming close to marginal for PWM input, IE your voltage is still well over 16V if your panel outputs 17V.

ntsqd said:
No, not right. Forced into a MPPT because of series panel voltage exceeding a PWM's input voltage limit. At least that is true for any that I have seen after looking for one.
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I have no idea where you are headed with that thought, why on earth would you series up two "12V" 100watt panels on a PWM controller? Two 100watt panels outputing 17V in series is 34V but still at 5.8amp, you only get MAX of 5.8amps to the batteries, the second panel is completely wasted, the voltage just gets chopped down. Now putting them in parrellel would work just fine even with that 10ga wire running 30', the drop is about 4%, again still well over 16V to the controller which is more than PWM needs.

Nothing you described (two 100watt panels and 10ga wire running 30') forced/required you to go MPPT specifically.
 
Four pages, wire size is turning into an engine oil thread on a motorcycle website. We live in a great time where we can get fairly inexpensive solar. The question for me is what do I need (not want). My 100w panel on the roof feeding a 30amp PWM controller kept my 2 batteries charged on my trip to the east coast. Even parked for a week in Baltimore with compressor fridge running, yes it was cold there. Driving daily may have kept my batteries full, I was never below 12.5 volts in the morning. Disclaimer I have 6 gauge wire from truck to camper. I do need to go some where warm, park for a week and set up my 120w solar in a bag to see if my batteries stay full.


Needs:
  • Enough solar to keep batteries full and compressor fridge running.
  • Voltage meter to monitor battery.

Wants:
  • High efficiency solar system. Big wire and MPPT.
  • Trimetric meter to monitor all amps and voltage.

Both system will work if sized correctly. I purchased my 100w panel and 30amp PWM controller for less that the cost of the Trimetic monitor or the cost of a 30amp MPPT.

Another disclaimer. I really want a Trimetric monitor.
 
billharr said:
Four pages, wire size is turning into an engine oil thread on a motorcycle website.
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:p Well I'm showing the basis of my statements here in hopes calculated numbers are useful to review the situations folks are actually in vs taking recommendations from other systems (ie a big RV with more solar and a longer wire run which could quite easily warrant a 6ga min). I'm more than happy to admit if someone flags where I'm off base. At the moment though I'm seeing some false assumptions driving a critiquing of the manufacturers and an unneeded desire for modification.
 
As I stated our system IS 10 ga., but not because I wanted it to be. I'd have gone with 8ga. to further reduce the voltage drop. That a PWM doesn't care above some particular voltage is news to me and comes after the 8 ga. decision. I'll need to research what ours specifically wants or maxes out at.

I would go series with multiple panels to allow the use of a smaller wire. That in turn drives using an MPPT.

The tone of your posts, to me, is that you're so eager to prove me wrong that you're not really reading what I'm saying and are jumping to conclusions based on your assumption of an erroneous logic. I don't care any more.

To the OP: If you came to me and asked "Is 12ga. big enough?" I'd say no, it should be at least 10ga. and if your peak amperage justifies it probably one or two steps bigger.
 
Folks, this thread seems to be coming to the point where it would be best to 'agree to disagree' and move on.

I would suggest taking futher discussion off-line via PMs.
 
I'll PM ya, I'm seriously trying to clear up confusion. My only defensiveness was the thread had folks calling out manufacturers without merit, in my opinion.
 
FYI, I had reached out to Morningstar wondering what minimum voltage they’d recommend as input for their SS-20L-12V PWM controller to still output a full 14.4V. I just got an email back and they said 15.2V was their recommendation. Gives you a target idea when deciding how much voltage drop is acceptable when feeding a PWM controller. [To have full amps you’ll have full sun so voltage with be 17V+, 30’ of 12ga wire will carry 19amps in that case which is 300+watts of solar panel.]

Hopefully the OP finds that useful.
 
To the OP. I've thought about this on my Eagle and if I decided to heavy up the wiring I think I would personally run it exposed on the exterior of the camper. Most of it would be hidden between the truck and camper. I'd use very fine strand marine cable that is very flexible. Put it in UV protected black wire loom and enter the camper under the wing at the front like the truck wiring does. Any place possible I'd pull a couple of corner/trim screws and put them back in through either cable clamps or zip ties with a screw eyelet. There is only a few inches of "loose" wiring that has to flex as the camper opens and closes. I think any flapping or unwanted movement of this ( if it exists) could easily be dealt with by a small length of shock cord on the loop when closed.

I've run wiring on my bass boat like this above deck with no ill effects from the sun or weather for several years. Done well I don't think appearance is a problem. No more so than exposed lift struts. If you have those (lift struts) you could possibly zip tie part of the loose cable section to one of them.
 
Not to add complexity to the question but what about heat produced? I would think thicker wire would help in that area but then again, maybe the original 12 gauge wire didn't get that hot but how could they know what your solar configuration might be?
 
In my 2012 Eagle, it will be fairly easy to run heavier gauge wire for all but about 6-8 feet. The section in the roof from the box to the front of the camper is buried in the ceiling and I'm going to leave that alone.

From there, it runs alongside the sleeping platform and down thru the drivers side cabinet and along the top of the water tank to the battery box. That run is probably 12-15 feet if you factor in all the twists and turns it will take which will reduce the voltage drop some, especially if I add additional panels in the future.

My plan is to run 8 gauge wire and I will post photos of the project when I get it all done.

Cheers
 
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