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 > Routing Solar Wires Through Fridge Vent

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f150camper

Oregon

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Posted: 05/20/19 01:14pm Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:

That one 250w panel is probably way cheaper than two or three 100w panels.


Any suggestion for a good 250W panel, and maybe a source (link)?


Nights camped 2011: 13 (4 in the old popup) ">
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BFL13

Victoria, BC

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Posted: 05/20/19 01:32pm Link  |  Quote  |  Print  |  Notify Moderator

EDIT--no idea for panel buying there. Try to get one you can pick up yourself as they are big and heavy so shipping cost is high.

Big thing is to check your controller specs with panel wattage. I use a 20 amp with my 255w, but would need a 30 for a bigger panel. On that, watch out if the spec wattage you are looking at for what the controller can handle is at 24v or at 12v!


The Renogy ISTR is a Tracer by EPSolar, and is a decent controller. I have a 20 amp Tracer MPPT for my 255w panel. I get around 16 amps to the battery with that set-up.

I got the same amps to the battery with my three 100w panels array whether I used PWM with them in parallel or whether I used them with the Tracer with the panels in series or in parallel.

The controller does get warm and needs air cooling--they have big slots in back so when wall-mounted air can get by in behind them. I doubt the controller getting warm will add any to heating the RV.

There is a lot of bogus info out there about MPPT. Main thing is the panel heats up in the sun and loses 10% of its power (watts) right there from that. Amps to the battery is controller output power in watts divided by battery voltage. So if your power out is 200 watts, then amps to the battery will be:

200/12v = 16.7 amps
200/13v = 15.4 amps
200/14v = 14.3 amps

So the salesman always uses the amps expected at low battery voltage, but fails to mention that your battery voltage during the day will be over 13 and rising to 14.5 ish

* This post was edited 05/20/19 01:45pm by BFL13 *


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f150camper

Oregon

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Posted: 05/20/19 01:42pm Link  |  Quote  |  Print  |  Notify Moderator

Thanks BFL13!
One thing is that with the PWM controller, you could not wire the panels in series, and therefore reducing the current that needs to be wired to the controller, right? Does the PWM controller support trickle charging / battery maintaining?

BFL13

Victoria, BC

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Posted: 05/20/19 01:57pm Link  |  Quote  |  Print  |  Notify Moderator

f150camper wrote:

Thanks BFL13!
One thing is that with the PWM controller, you could not wire the panels in series, and therefore reducing the current that needs to be wired to the controller, right? Does the PWM controller support trickle charging / battery maintaining?


With a 12v battery system the array must be 12v too with PWM. A PWM can do two 12v panels is series if it is a "12/24" controller, but then the battery bank must also be 24v.

PWM or MPPT controllers can do battery maintaining etc IF they have adjustable voltage for their "stages" and some even have timers. Plain Jane PWMs that cost $25 usually don't have adjustable voltages. Some like my Solar30 PWM has adjustable voltage, no timer.

But even the nice Tracer MPPT which is lower cost than many MPPTs has a fixed charging profile. You can get the extra gizmo for it (a remote) that has a way so you can make adjustments. The latest thing seems to be where some let you adjust their parameters using your cell phone!

ajriding

st clair

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Posted: 05/20/19 06:02pm Link  |  Quote  |  Print  |  Notify Moderator

Expect to pay near $100 for a MPPT controller. Don't get the $25 ones.
They need some airflow, but on my last camper I put the controller under the dinette seat with all the food goods. Not a big space and no vents, and things were fine. Just dont put it in a shoebox. Anywhere it can get air is fine.
I use a Morning Star brand. It has some heft to it unlike the cheap plastic ones, I never noticed it getting hot.

The MPPT controllers, I could have told you all about them at the time I did the research, are the good ones, multi-level stage charging as opposed to your alternator that just sends out voltage blindly. It will help keep your batteries in good condition and last longer.

My solar panels, and I have had many over 5 campers, put out about 18 volts each. 18 is fine to use with a 12 volt controller and is common and expected numbers.

No need to double the voltage and try to get the controller to step it down. Stick with the voltage range you need. Wire is expensive, but not so much that you need to get crazy to save a few bucks.

Don't ask the dealer for advice. There are so many dealers who know nothing except how to push you into buying something.

side story:
I was talking to a salesman at a random event. He said how great RV fireplaces are, and I commented they are useless as a TV and wasted space.
Oh, no, they are a great heater he said.
I said, arent they just a giant electric heater?
He tried to argue that it is better and heats better. Well, it does because it is 3 times the wattage as a plug in electric heater… Then he went on to babble about how you plug into shore power and the "camper inverter turns the power to make it work" .
Umm, what? I asked…
Yea, its the converter and thats why it is such a great heater…
OK, thanks for telling me this, I have to go now.
Amazing how little he even knew about the most basic things in an RV.

BFL13

Victoria, BC

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Posted: 05/20/19 06:32pm Link  |  Quote  |  Print  |  Notify Moderator

"
My solar panels, and I have had many over 5 campers, put out about 18 volts each...."

NO they didn't! (except if you had MPPT and it was in Bulk) Your basic 12v panel has a Voc of about 22 volts and operates at battery voltage (12-15 volts) with a PWM controller.

It could have a Vmp of about 18 volts, which it will be set at by an MPPT controller during its Bulk stage. Vmp has nothing whatever to do with operating using a PWM controller.

See the set of IV curves for any 12v panel.

dougrainer

Carrolton, Texas

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Posted: 05/20/19 06:38pm Link  |  Quote  |  Print  |  Notify Moderator

Use silicone. Dicor is self leveling and kind of hard to install on the SIDE of something. It will just run off and not stay in the hole. Doug

f150camper

Oregon

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Posted: 05/20/19 06:51pm Link  |  Quote  |  Print  |  Notify Moderator

dougrainer wrote:

Use silicone. Dicor is self leveling and kind of hard to install on the SIDE of something. It will just run off and not stay in the hole. Doug


There is self leveling and non-self leveling Dicor.

bpounds

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Posted: 05/21/19 04:06pm Link  |  Quote  |  Print  |  Notify Moderator

I found the fridge vent was nowhere near where my CC or my batteries were, and it would have involved a lot more wire fishing than it would to just drill a hole through the roof. Once you get over the fear and decide to just drill, your options open up wide.

Some will scoff at this, but below is what I did. I used sheathed cable (solar and UV rated), which avoids a leak path that you would have between two individual conductors. Just drilled a hole a little bit bigger than the width of the sheath. This one is next to a sewer vent, but that's just because that is in a partition wall and I followed that path to the basement. It could have been anywhere. It was a short easy wire fish job.

Formed what is called a drip loop, then slathered it all up with Dicor, including securing it to prevent flexing in the wind. No box needed. Just off to the left in this pic is the first MC4 connector.

I might have to hit it with more Dicor in the future, but we should all be up there inspecting all the roof penetrations yearly anyway, so it's just one more of those.

[image]


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BFL13

Victoria, BC

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Posted: 05/21/19 04:38pm Link  |  Quote  |  Print  |  Notify Moderator

With some (all?) of those roof vents, the rain cover comes off. You can drop a solar pair of wires down the vent pipe and cut a hole in the side of the pipe in the "basement" (where it is above the tank it vents).

Fish out the wires into the basement and afterwards, seal the hole in the vent pipe where the wires now come out.

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