maryfilen
I have a 2019 193. I'm looking for a solar panel to help recharge my trailer battery. Does anyone have any recommendations?
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mikes
Renogy sells decent, inexpensive ones. You _must_ also have a charge controller. Without more info on your needs/wants, not much more can be said.

You need to provide more info on how much energy you use daily, how long you need to be self-sustained, where you camp (open sunny, or shaded by trees), and what your budget is.
Mike
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maryfilen
Well would like to be able to recharge our battery every other day. Hope to get a long cord so the panel can be moved to the sunlight.  Not sure how much power I need in the solar panel
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mikes
You need to be more specific. How big a battery? How much do you discharge it each day? What are you powering each day, and for how long (furnace? lights (are they LEDs)? fans?). There is no simple "you need x amount" answer. Math is involved. Some of what follows isn't technically correct, but the concepts are.

You first need to understand some basic electrical stuff. For RV solar systems, amp-hours is the most basic measure. Think of amps as how much power something uses. Hours, how long you use it each day. So something which uses 2 amps when on, which you use 5 hours per day, would use 10 amp-hours per day. Watts are amps times volts, so that also comes into play, because that's how solar panels are rated.

We have 200 watts of panels (200W/12V ~= 16 amps in full sun) to charge 2 6V golf cart batteries (~220 amp-hours). The common group 27 "deep cycle marine/RV" batteries dealers commonly install are good for about 80 amp-hours. For good battery life, you don't want to discharge them below 50% on a regular basis.  These are the current draws I've measured:

Refrigerator ~.680 A constant when on gas
LPCO alarm ~.050 A constant
Water pump ~6.5 A running
Furnace ~2.1 A running
MaxxFan 0.3-3.0 A, depending on speed
Bath Fan 1.6 A
TV Antenna 0.1 A
TV 1.0 A
LED "bulbs" .2 - .36 A, each

So, if we use 2 dual LED fixtures for 6 hours/day, that's about (.36 A x 2 x 2 x 6 =)  8.64 Amp-hours. The MaxxFan is usually running a step or two above low constantly, so (.5 x 24 =) 12 Amp-hours. Refrigerator runs constantly, so (.68 x 24 = ) 16 Amp-hours. That adds up to about 36, add the small stuff and occasional use of other stuff, maybe 40 Ah typical, 50 amp-hours per day max. So, we can go a couple of days without draining the battery more than 50% with no charging. We can do much better by consciously conserving if we need to.

The typical "RV" battery mentioned above would only be good for a day (or 2, with a shortened lifetime). If you have incandescent bulbs, well, they draw 3-5 times as much power as LEDs, so either use them sparingly or better yet, replace them with LEDs.

On clear, sunny days, you can figure about the equivalent of 5 hours of full charging, so that's 1000 watt-hours for 200 watts of panels, (divided by 12 V =) 83 amp-hours, more than enough on a daily basis, usually but not always enough for every other day. But we usually "off-grid" at festivals, where there's little shade, so unless it's overcast for days, it keeps up. Panels are mounted on top, so no worry about theft when we're away, no need to store them somewhere, no need to set them up, they're charging while driving (just being hooked to a vehicle doesn't provide much charging), and they keep the batteries in good shape while in storage. I'll probably add another 100W panel when I get around to it, just to add more charging in overcast/partial shade.
Mike
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mikes
You need to be more specific. How big a battery? How much do you discharge it each day? What are you powering each day, and for how long (furnace? lights (are they LEDs)? fans?). There is no simple "you need x amount" answer. Math is involved. Some of what follows isn't technically correct, but the concepts are.

You first need to understand some basic electrical stuff. For RV solar systems, amp-hours is the most basic measure. Think of amps as how much power something uses. Hours, how long you use it each day. So something which uses 2 amps when on, which you use 5 hours per day, would use 10 amp-hours per day. Watts are amps times volts, so that also comes into play, because that's how solar panels are rated.

We have 200 watts of panels (200W/12V ~= 16 amps in full sun) to charge 2 6V golf cart batteries (~220 amp-hours). The common group 27 "deep cycle marine/RV" batteries dealers commonly install are good for about 80 amp-hours. For good battery life, you don't want to discharge them below 50% on a regular basis.  These are the current draws I've measured:

Refrigerator ~.680 A constant when on gas
LPCO alarm ~.050 A constant
Water pump ~6.5 A running
Furnace ~2.1 A running
MaxxFan 0.3-3.0 A, depending on speed
Bath Fan 1.6 A
TV Antenna 0.1 A
TV 1.0 A
LED "bulbs" .2 - .36 A, each

So, if we use 2 dual LED fixtures for 6 hours/day, that's about (.36 A x 2 x 2 x 6 =)  8.64 Amp-hours. The MaxxFan is usually running a step or two above low constantly, so (.5 x 24 =) 12 Amp-hours. Refrigerator runs constantly, so (.68 x 24 = ) 16 Amp-hours. That adds up to about 36, add the small stuff and occasional use of other stuff, maybe 40 Ah typical, 50 amp-hours per day max. So, we can go a couple of days without draining the battery more than 50% with no charging. We can do much better by consciously conserving if we need to. But when camping, I prefer not to have to stress over running out of power.

The typical "RV" battery mentioned above would only be good for a day (or 2, with a shortened lifetime). If you have incandescent bulbs, well, they draw 3-5 times as much power as LEDs, so either use them sparingly or better yet, replace them with LEDs.

On clear, sunny days, you can figure about the equivalent of 5 hours of full charging, so that's 1000 watt-hours for 200 watts of panels, (divided by 12 V =) 83 amp-hours, more than enough on a daily basis, usually but not always enough for every other day. But we usually "off-grid" at festivals, where there's little shade, so unless it's overcast for days, it keeps up. Panels are mounted on top, so no worry about theft when we're away, no need to store them somewhere, no need to set them up, they're charging while driving (just being hooked to a vehicle doesn't provide much charging), and they keep the batteries in good shape while in storage. I'll probably add another 100W panel when I get around to it, just to add more charging in overcast/partial shade.

TL;DR;

200 watts of panels will probably work for you, making what are probably invalid assumptions like you'll have clear days with full sun when you charge every other day, and plan on replacing the battery every 3-4 years.
Mike
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maryfilen
Thank you so much for the information.

On Sat, Jan 25, 2020, 8:13 PM Riverside RV Forum Retro White Water and Mt.
McKinley <noresponse@websitetoolbox.com> wrote:
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richardtc17
We have what I would consider a minimum. Two Renogy panels/200 watts on our roof and a 105 amp hour battery. Running only the minimum from mikes list was not enough to keep us charged this past fall over three consecutive cloudy days in some shade in low 40s nighttime temps (thermostat set to 63 F at night). We might have been able to maintain charge had we not been in the shade. Portable panels are a hassle, but the ability to move them and direct them is a significant benefit. I will be more conscious of parking in the shade with cloudy forecasts from now on. It will be interesting to see if that makes the difference.
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maryfilen
Do you have two 200-W panels or two panels equaling 200 w
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richardtc17
Two 100 watt panels.
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efranzen
I have one 100 watt panel, controller and a 20ft cable that let's me chase the sun around. It puts out over 5 amps and charges my single Interstate battery up during the day. I also changed all the light bulbs to LED. Crazy how much juice the standard ones pull. 6 LEDs pull less amps than just one incandescent bulb.
Solar Panel: $150
Controller: $60
Cable: $20

Lost-Dutchman.jpg 
2015 177
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maryfilen
Thank you so much!  We will check the kind of bulbs we have. 
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maryfilen
Narrowed down my search to portable Renogy starter kit (either 150 or 200 W) The panel is about 40 lbs. That got me looking at newer flexible, lightweight panels that are touted as effective. My concern is that they are so lightweight they may not stay in place (blow down with the
wind). Anyone have experience with such panels?

Also wondering how people secure their portable panels to prevent theft.
If you set them 15 feet from your trailer for the day, what would prevent someone from taking them??

*Mary Filen*





*Business Systems Development and Consulting, LLC*
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mkevenson
Mary, I have Renogy, suitcase 100W style. They work just fine to keep my Lithium battery charged, assuming we have some sunlight for a few hours each day.
As far as security goes, I hope for the best. I have seen some folks who chain and lock their panels to the trailer, I don't. Odds are I will keep my panels for a while . Impossible to lock up everything! 
Happy Camping!
Mark
Please buy Made in USA
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cadal99
Anyone use the Harbor Freight 100W system: https://www.harborfreight.com/100-watt-solar-panel-kit-63585.html ?  $189, but use one of their 20% off coupons just about $151 plus tax - seems like it is well reviewed - but like to get first hand reviews if there's anyone here that's actually used it.
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