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Solar Wiring - No Factory Controller

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#21 ntsqd

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Posted 11 November 2020 - 02:25 PM

With our old camper I took it a step further and deliberately mounted the panel at a 0.25"/30" slope (totally arbitrary) and drilled the high end of the frame with a hole saw. All to encourage hot air escape from under the panel. That was probably over-thinking it, but I felt better having done it.


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Thom

Where does that road go?

#22 Charlie

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Posted 12 November 2020 - 05:23 AM

Hi Charlie - I really like your solar assembly.  We just bought two Renogy 175's and are looking at mounting them similarly.  Curious what thickness your z-channel is.  I've only been able to find 1/16" which seems a little flimsy.  Also, did you purchase your poly online somewhere? Last thing...we're looking for a new truck to pair with our 2005 Hawk.  How do you like your Tundra?  Care to share year, trim, etc?  I'm assuming that's a 6.5' bed?

 

Thanks!

 

My notes say that the Z-channel 1/8". We are lucky enough to have an aluminum supplier in the Denver area (Alreco), which is where I got it.

 

Likewise, I got the polycarbonate from a local plastics supplier (Colorado Plastics). I was surprised at how expensive it was, but it is a pretty specialized structural material. I've since noticed that Home Depot carries it; just search there for polycarbonate.

 

Someone posted below that that there may be a downside to not having the flexible panels fixed to a solid surface.

 

Our truck is a 2016 Tundra TRD Double Cab (6.5' bed), with towing package. I purchased it in Nov. 2018 with 29k miles, for $30k. One of the options it has is the large gas tank (38 gal., 30 gal. usable). Although I didn't appreciate it at the time, the large gas tank has been invaluable, giving us > 400 mile range.  That lets us knock around some pretty remote places without fuel anxiety. I'd say we average about 15 mpg overall with the camper on, and that's over any trip that includes interstate combined with much mileage on forest service roads. The Tundra is kinda dated in its design (interior systems), but we have been quite happy with it. The 2019 Hawk has tons of storage, and the back seat of the Tundra provides a huge amount of extra storage (true of any pickup). On a recent one month road trip, we hardly filled the back seat area half full.

 

Hope this helps.

 

Charlie


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#23 Charlie

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Posted 12 November 2020 - 05:34 AM

One thing to keep in mind is that current PV cells work better when their backside is cooler than their exposed side. With flexible panels whatever they are attached to wants to be a heat sink or at least a good thermal conductor. Not to say that they won't work if attached that is a poor thermal conductor, just that they'll work better if it is a good thermal conductor.

 

This may be a valid concern. I figured that mounting the solar panels on a frame that was attached to Yakima tracks, and thus above the roof, would provide better cooling since there was airflow underneath them. On the other hand, perhaps using the roof as a heat sink by gluing them down to the roof could actually keep them cooler. I don't know.

 

I have to report that the original panels that I bought from Renogy failed, and I replaced them under warranty a couple of months ago. We will see if the new ones hold up. The replacements do seem to be constructed differently than the original ones.

 

When I designed my system, the whole purpose was to minimize the weight, so that I could still lift the roof easily. Succeeded at that. Also, I'm not willing to drill through or glue anything to the camper roof. For some reason, I didn't even think about just replacing the struts with stronger ones. If I do it again, I may just go with rigid panels mounted on the Yakima racks, and beef up the struts.


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#24 Jsoboti

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Posted 17 January 2022 - 11:53 PM

Follow on question. I've read as many Solar posts on here as I can as well as studied many wiring diagrams (thanks to all who provide them btw!). 

 

I just ordered a Victron MPPT 100/20 Smart Solar Charge Controller. My camper is new-ish and does have the black/white "load" wires pre-wired. Understanding that the Victron MPPT has terminals for those wires, is it necessary to connect them to the MPPT? I don't plan on utilizing the "load" output functionality for any devices ( I think I understand its purpose, but honestly, who knows), so I'm wondering if the system will function as desired without connecting the load wires to the load output of the MPPT.

 

Thanks gurus!! 


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#25 Vic Harder

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Posted 18 January 2022 - 02:15 AM

You do not "need" to connect anything to the LOAD wires on your Victron MPPT.  That is an optional feature that allows you to use logic in the MPPT to turn the load on/off depending on certain conditions.  


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#26 Jsoboti

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Posted 19 January 2022 - 09:11 PM

You do not "need" to connect anything to the LOAD wires on your Victron MPPT.  That is an optional feature that allows you to use logic in the MPPT to turn the load on/off depending on certain conditions.  

 

Thanks Vic! 


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#27 ckent323

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Posted 20 January 2022 - 07:11 AM

Charlie, et. al.,

 

If you bond flexible panels down make sure you use a thermally conductive adhesive (check the manufacturers specification)

Many adhesives are poor thermal conductors and can significantly reduce the heat dissipation from the panels to the surface intended to be a heat sink thereby contributing to premature failure of the panel.


https://www.scienced...uctive-adhesive

 

 


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#28 Bikeandfish

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Posted 16 February 2023 - 05:14 AM

Attempting to do an amateur Solar job and have a silly question:

If I were to try to replicate Charlie’s wire diagram, what gauge/s wire should I use? It seems as though the wires coming in from the camper, connecting to controller and switch are smaller than the black ones connecting the shunt and switch to the batteries.

Thank you!
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#29 Vic Harder

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Posted 17 February 2023 - 02:13 AM

Well, if you think of electrical current as being similar to water currents, if you want more water to flow, you need a bigger hose/pipe.  The wires feeding the individual circuits in your camper will be 18-14awg, and those all feed into a fuse box which has to carry the aggregate of all those flows up to the battery, so the combined current will need a 12-8awg wire.  The wires between the batteries in a dual battery setup are ideally so big that that the batteries act as one bigger battery.  2awg is not unheard of.  The Victron solar gear has screw terminals that will accept 6awg, so that is a good choice.  The wires coming from the roof solar on a FWC/ATC are typically 12awg (I think?).

 

All that said, the wire size is determined by the expected current flow.  Online calculators exist to help pick the right size, which depends on many factors, such as distance (length of the wire), how well cooled the wire is, voltage, current, acceptable power losses, etc.


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