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Author Topic: Solar panels on tent trailer - Worth it?  (Read 554 times)

KodiakJack

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Solar panels on tent trailer - Worth it?
« on: April 22, 2018, 10:46:55 PM »
So I just got a 2005 Viking epic tent trailer. It’s a little eight footer. It came with a “condition unknown” 12v battery. I’m playing with the idea of getting a solar panel to top it up during the day, so it got lots of juice at night.

The trailer has an inverted, LED interior lights, 3 way fridge, and furnace.

Our camping style is to abandon the site during the day for adventures abroad, then return for supper, a camp fire then bed. Our only use of the electrical system would be the LED lights at night (for maybe an hour or so if we get chit chatting), and the 120v inverted outlets for charging cell phones, or maybe inflating a mattress or something.

Would this be a good application for solar?  Where does one go to find the best deal on solar panels? Are they worth the hassle?

Here’s one on sale locally. Thoughts on it?
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xvz12

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Re: Solar panels on tent trailer - Worth it?
« Reply #1 on: April 24, 2018, 07:33:13 PM »
Just FYI, Harbor Freight has a 100W system that is very similar for the same price, Twice the bang for the buck.

Isaac-1

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Re: Solar panels on tent trailer - Worth it?
« Reply #2 on: April 24, 2018, 08:30:54 PM »
Smaller solar panels can help maintain the battery while the trailer is not in use, though to power the refrigerators control electronics, run LED lights at night, and charge the battery enough to power the furnace blower fan during cooler nights you will likely need 150 -200 watts worth of solar panels minimum if camping in the spring or fall with shorter days, if not you would still need to run a generator to keep your batteries charged while camping.

Here goes the math

Knowing the exact model of refrigerator and furnace you are using would help give a better estimate, though as a general rule an RV refrigerator will consume 5-8 watts of power for the control electronics, which would run 24 hours per day.  Lets assume on the high side so 8 x 24 = 192 watt per day, lets round that to an even 200 to keep things simple.  Lets assume you have a small Suburban brand NTQ series forced air furnace, which has an amp draw of about 3 amps while running, 3 x 12.8  = 38.4, rounding again gives us 40 watts per hour, assuming running only at night, 8 hours per night, for 30 minutes out of every hour.  40 x 8 x .5 = 160 watts per day.  LED lights should be trivial in comparison, even assume you want it fairly brightly lit, a 60 watt equivalent LED light bulb draws about 9 watts per hour, let say 3 hours per night we are still just under 30 watts per day.  This all brings us a grand total of about 400 watts per day you must replace into your battery.

For mid America average spring / fall lighting levels a fixed mount flat solar panel will generate 4 to 5 hours worth of peak output per day if exposed to open sky.  Shading can reduce this considerably, battery charge losses account for 20-25% of the total solar output.  So working with a single 150 watt solar panel with 4 hours of peak output per day we get 150x4 600 watts per day x .75 for battery charge losses, and we just about break even at 450 watts of available power added to the battery on an average day.  Of course you may want to go larger in case of cloudy weather, wanting to recharge cell phones, run radio, etc. 
2002 Safari Trek 2830

KodiakJack

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Re: Solar panels on tent trailer - Worth it?
« Reply #3 on: April 24, 2018, 09:16:23 PM »
Just FYI, Harbor Freight has a 100W system that is very similar for the same price, Twice the bang for the buck.

I appreciate the heads up, but I’m in Canada, and the nearest harbor freight is 8 hours away, then there’s currency exchange and duty...

Thanks though.
You're free to make your choices, but not free from the choices you make.

KodiakJack

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Re: Solar panels on tent trailer - Worth it?
« Reply #4 on: April 24, 2018, 09:41:49 PM »
Smaller solar panels can help maintain the battery while the trailer is not in use, though to power the refrigerators control electronics, run LED lights at night, and charge the battery enough to power the furnace blower fan during cooler nights you will likely need 150 -200 watts worth of solar panels minimum if camping in the spring or fall with shorter days, if not you would still need to run a generator to keep your batteries charged while camping.

Here goes the math

Knowing the exact model of refrigerator and furnace you are using would help give a better estimate, though as a general rule an RV refrigerator will consume 5-8 watts of power for the control electronics, which would run 24 hours per day.  Lets assume on the high side so 8 x 24 = 192 watt per day, lets round that to an even 200 to keep things simple.  Lets assume you have a small Suburban brand NTQ series forced air furnace, which has an amp draw of about 3 amps while running, 3 x 12.8  = 38.4, rounding again gives us 40 watts per hour, assuming running only at night, 8 hours per night, for 30 minutes out of every hour.  40 x 8 x .5 = 160 watts per day.  LED lights should be trivial in comparison, even assume you want it fairly brightly lit, a 60 watt equivalent LED light bulb draws about 9 watts per hour, let say 3 hours per night we are still just under 30 watts per day.  This all brings us a grand total of about 400 watts per day you must replace into your battery.

For mid America average spring / fall lighting levels a fixed mount flat solar panel will generate 4 to 5 hours worth of peak output per day if exposed to open sky.  Shading can reduce this considerably, battery charge losses account for 20-25% of the total solar output.  So working with a single 150 watt solar panel with 4 hours of peak output per day we get 150x4 600 watts per day x .75 for battery charge losses, and we just about break even at 450 watts of available power added to the battery on an average day.  Of course you may want to go larger in case of cloudy weather, wanting to recharge cell phones, run radio, etc.

Thanks for that.

I’m still getting to know the systems. 

The fridge is a Dometic 2193. When running on propane, according to my interpretation of the manual, the propane system runs continuously without a thermostat, the temperature just being controlled by the flame setting. So I don’t think there’d be any electrical draw from it. It says to make sure both dc and ac power are switched off before using propane to cool.

The lights are just 2 dome lights in the ceiling. The previous owner has replaced the little lights inside with KEDs. They’re about the size of my little finger.

The furnace is kind of a moot point. We’re used to tenting it, so I’m pretty sure we can get by without heat. The only time I’d use it would be when moose hunting, and then we’d have a fleet of generators anyway. But for arguments sake, the furnace is a Suburban NT-12SE. I don’t see anything in the manual that depicts its draw.

So realistically, it would be pretty negligible use I think... I think.
You're free to make your choices, but not free from the choices you make.

KodiakJack

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Re: Solar panels on tent trailer - Worth it?
« Reply #5 on: April 24, 2018, 09:47:43 PM »
A couple other questions about solar in general:

Could a solar system charge a battery “all the way” or just keep it topped up?  If you had a battery that was at say 25%, could a small solar system over the course several days bring the battery back to 100%?
Or would that be bad for the battery?

Would there be any harm in mounting the panel to the top of the trailer more or less permanently? So that it’s keeping the battery topped up year round?
You're free to make your choices, but not free from the choices you make.

HappyWanderer

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Re: Solar panels on tent trailer - Worth it?
« Reply #6 on: April 24, 2018, 09:54:19 PM »
Harbor Freight solar is junk, so you're not missing anything.

With the fridge on propane and LED lights, you should be fine with a 100 watt panel. Amazon is a good source for Renergy panels and controllers. Portable is good, because you can tilt it towards the sun for greater efficiency.

Ditch the inverter for charging electronics: it has a current draw of its own. Charge the phones directly from 12 volts. No reason to convert DC to AC and back to DC for charging.
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KodiakJack

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Re: Solar panels on tent trailer - Worth it?
« Reply #7 on: April 24, 2018, 10:07:45 PM »


Ditch the inverter for charging electronics: it has a current draw of its own. Charge the phones directly from 12 volts. No reason to convert DC to AC and back to DC for charging.


Hmm. That’s a good point, but there’s no “cigarette lighter” type outlets. The only 12v outlet is the funny jack in the overhead light:  http://www.rvforum.net/SMF_forum/index.php/topic,113289.msg1024114.html#msg1024114

Is there a typical solution for this?  Aftermarket 12v “powerbars” so-to-speak? Or outlets I could install?  I’m awfully new to this world. :-/
You're free to make your choices, but not free from the choices you make.

HappyWanderer

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Re: Solar panels on tent trailer - Worth it?
« Reply #8 on: April 25, 2018, 07:56:25 AM »
Get one of those multi-outlet accessory cords and cut off the lighter plug. Put a fuse on the end and connect directly to the battery. Instant charging station.
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KodiakJack

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Re: Solar panels on tent trailer - Worth it?
« Reply #9 on: April 25, 2018, 10:22:05 AM »
Get one of those multi-outlet accessory cords and cut off the lighter plug. Put a fuse on the end and connect directly to the battery. Instant charging station.

What size fuse should one install? 10a? 

Could be used for charging phones... maybe a little 12v air pump for blowing up mattresses and beach toys... bicycle pump... fan... whatever.

You're free to make your choices, but not free from the choices you make.

HappyWanderer

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Re: Solar panels on tent trailer - Worth it?
« Reply #10 on: April 26, 2018, 07:21:59 AM »
10 amps sounds right.
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KodiakJack

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Re: Solar panels on tent trailer - Worth it?
« Reply #11 on: April 27, 2018, 06:01:30 AM »
10 amps sounds right.

Went amazoning, and stumbled across this one.  Thoughts?

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Kevin Means

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Re: Solar panels on tent trailer - Worth it?
« Reply #12 on: April 27, 2018, 11:19:28 AM »
Could a solar system charge a battery “all the way” or just keep it topped up?  If you had a battery that was at say 25%, could a small solar system over the course several days bring the battery back to 100%? Or would that be bad for the battery?

Would there be any harm in mounting the panel to the top of the trailer more or less permanently? So that it’s keeping the battery topped up year round?
When boondocking, our solar array is our primary method of recharging our house batteries, so yes... solar can be used to fully recharge batteries. However, our array is fairly large, we're able to tilt our panels toward the sun and we're located in Southern California. Those things have a significant impact on the effectiveness of solar. Our array wouldn't be nearly as effective in Canada. The sun is much lower in the sky, especially in cooler months when RVers rely more on solar power.

A lithium battery would be fine if it were repeatedly discharged to 25% but repeatedly discharging a lead/acid battery anywhere near that far would shorten its life considerably. FWIW, I don't let our battery bank get below 75% and our last set of batteries lasted seven years.

When a lead/acid battery gets deeply discharged, it should be fully recharged as quickly as possible. A solar array may, or may not be able to do that, depending on the size of the array compared to the AH capacity of the battery bank, available sunlight, shading and draw on the system.

If the panel was approved for outdoor use (some smaller panels aren't) it should be fine to mount it on the roof... as long as it was installed correctly.

Kev
2011 Winnebago Tour 42QD
Towing a Jeep Rubicon Unlimited LJ
RVI Brake 2, Minder TM-66 TPMS, 960 watts of solar
(Can't wait to spend more time RVing)
Lakeside, California

KodiakJack

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Re: Solar panels on tent trailer - Worth it?
« Reply #13 on: April 27, 2018, 07:10:24 PM »
Thanks gang!
You're free to make your choices, but not free from the choices you make.

pip

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Re: Solar panels on tent trailer - Worth it?
« Reply #14 on: Today at 02:57:12 PM »
I appreciate the heads up, but I’m in Canada, and the nearest harbor freight is 8 hours away, then there’s currency exchange and duty...

Thanks though.

Just throw fly down in that quest, and stash it in the belly.  Problem solved.   ;D

John From Detroit

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Re: Solar panels on tent trailer - Worth it?
« Reply #15 on: Today at 03:42:11 PM »
If you have LED lighting, then yes. a solar panel may do well

If the fridge is 3-way.. DO NOT USE THE 12 volt SETTING,, EVER, Pull the 25 amp fuse (HINT the fuse needs to be that big for a reason).

Leave the 3 and 5 amp fuses in place.

Just for accent lighting I use LED's amazing how much light you get with a solar panel not much bigger than a special commerative postage stamp   (Like 1x2 or 2x3 inches)

Newer LED's.. I have two flashlights. COB led's my measurement 3 watts.  Advertised 1200 Lumens. a 100 Watt Lamp is 1200 LUMENS.. That's a whole lot of light for 3 watts of draw  3 watts is 1/4 amp at 12 volts  20% of a 100 amp hour battery would last you .. Several days.
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