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Author Topic: solar panel charging batteries  (Read 1233 times)

Scott Hagen

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solar panel charging batteries
« on: April 27, 2019, 01:21:03 PM »
Anyone have advice on charging the battery on a popup with solar panels? My main issue would be ,is there enough in one panel to charge the battery after using the heater at night. It does draw a lot from the battery when using it and am wondering if it would charge up on a sunny day

Gary RV_Wizard

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Re: solar panel charging batteries
« Reply #1 on: April 27, 2019, 01:51:05 PM »
Panels come in many sizes, so yes there are panels big enough to do what you wish. Assuming you are camper in full sun, of course. A 200 watt solar panel can produce 10-13 amps per hour, so can replace50 Amp-Hours (AH) or more on a sunny afternoon. A typical small RV has a single battery that has a usable capacity of about 35-50 AH. The question would be whether you have room on the pop-up roof for that panel, which is maybe 2 ft x 4 ft in size. There are also portable panels that could be set out on the ground and angled toward the sun.

If you were perhaps thinking of the little 18" panels often advertised for cars or camping, they probably aren't worth the effort at all.
« Last Edit: April 27, 2019, 01:53:22 PM by Gary RV_Wizard »
Gary
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Mark_K5LXP

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Re: solar panel charging batteries
« Reply #2 on: April 28, 2019, 08:58:27 AM »
It comes down to where you want to put your time and resources - camping, or engineering and managing a solar power system.  You can absolutely put together a solar system that could allow your popup to run autonomously.  I had a portable panel for my popup that kept the lights on but I didn't have a heater, so your loads are a bit heavier.

Step one would be to characterize the load.  For the heater specifically you measure how much power it draws when it's running, then either log or estimate how many minutes per hour it runs overnight.  That, plus whatever other loads you have will dictate how big a battery you need.  It could be assumed that the battery that came with the camper is big enough to run it for 24 hours but depending on what you run for how often you need to know how much excess or deficit you have. 

To replace those amp hours used is the mission.  What make solar a less than ideal charging source is there's only a few hours a day panels are putting out anything useful, and it only takes one cloud to stop the show.  If your panels are mounted to the camper roof they're not at an optimum angle to get the most energy, plus unless you like your camper to roast in the sun all day, they'll be shaded and won't put out much at all.  If you use portable panels you have to lay them out, run wires and move them around from time to time to keep them facing the sun.  Then either watch them or lock them together so they don't walk away.

A battery monitor that counts amp hours will really help to know if you're filling up or coming up short.  It can also help you economize by knowing what you're drawing and cutting back on a few things if necessary so you don't have to wonder if you'll make it through the night.

All it takes is one cloud to render your solar capacity useless.  If you're OK with the idea solar is more supplemental power than primary, things are a bit easier.  If you want to be 100% solar you need a lot of panels to maximize your charge opportunities and a large battery bank to carry you through the clouds and night time.  My approach to solar is I get what I get during the day, then using a generator around dinner time to make up the difference.  If you have enough panels and the day remains sunny you may not need any generator.  With my popup I used the power from the 7-pin trailer plug to charge the battery, just let the tow vehicle idle for a while around dinner time if it needed it.   But again I only had lights and a radio so solar was usually enough.  Living in NM with 300 sunny days a year helps.

My advice would be to start with what you're comfortable spending on it, then setting it up at your house with the battery and a few loads to get comfortable with the day to day operation of the system.  You can always add more panel and batteries later if you want but the lessons you learn with a small system are the same.

Mark B.
Albuquerque, NM

HappyWanderer

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Re: solar panel charging batteries
« Reply #3 on: April 28, 2019, 09:33:02 AM »
You could put a portable panel on the roof before cranking it up, pointed in the optimal direction. It doesn't need to be elaborate to work.
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Gary RV_Wizard

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Re: solar panel charging batteries
« Reply #4 on: April 28, 2019, 10:30:23 AM »
Yeah, I think a simple solution works for this situation, so a portable panel on roof or nearby on the site is probably a good choice.  However, you still have to do some arithmetic to figure out how much power (amp-hours) gets used and therefor e needs to be replaced daily.  Most people don't have a clue about how much power their battery can hold or how much of it they use overnight. Maybe don't need to be as rigorous as Mark suggests, but it can't be just guesswork either.

And then there is the definition of a "sunny site".  Back in the day when we owned pop-ups and camped in New York's Adirondack region, what we called a "sunny site" would produce few, if any, solar amps.
« Last Edit: April 28, 2019, 10:34:50 AM by Gary RV_Wizard »
Gary
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Drewd

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Re: solar panel charging batteries
« Reply #5 on: April 28, 2019, 10:56:03 PM »
A trimetric battery monitor will tell you how much your usage was and give you an idea of how to size your system.  As a typical rule of thumb, I like at least 100 watts of solar for every 100 amp-hours of battery capacity. 

Gary RV_Wizard

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Re: solar panel charging batteries
« Reply #6 on: April 29, 2019, 08:24:33 AM »
Remember we are talking about a pop-up trailer.  A large battery bank or sophisticated (and pricey) monitoring system is probably overkill, even for one of the larger models.
Gary
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Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

Kevin Means

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Re: solar panel charging batteries
« Reply #7 on: April 30, 2019, 12:39:34 PM »
I think a 100 watt suitcase solar system would be a very practical setup for the OP's needs, and while I love our Trimetric BM, I think the OP would be better off to invest in a catalytic heater before buying and installing a BM for a pop up.

A catalytic heater would significantly reduce propane consumption, and eliminate battery consumption altogether. In most cases, a catalytic heater should be more than enough heat for a pop up. In decent (or even fair) sunlight, a 100 watt solar panel would likely be all that's needed to fully recharge the battery. My two cents

Kev
2011 Winnebago Tour 42QD
Towing a Jeep Rubicon Unlimited LJ
RVI Brake 2, TST 507 TPMS, 960 watts of solar, SolaRVector tilt
Lakeside, California

Isaac-1

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Re: solar panel charging batteries
« Reply #8 on: April 30, 2019, 09:50:41 PM »
I know I am a bit late here, but I wanted to mention Renogy is running a big "earth day" sale today until midnight, midnight pacific time tonight or maybe 1 am, which includes a 100 watt panel for $99.
2002 Safari Trek 2830

Drewd

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Re: solar panel charging batteries
« Reply #9 on: April 30, 2019, 11:26:15 PM »
I don't think that installing a pair of golf cart batteries would be too difficult on a popup.  Two 100 watt solar panels and you wouldn't have to worry much about running out of juice for the OEM heater.

Another thing you can do is just use the battery you have and recharge it with a small generator.  That would probably be the most cost effective option for you.  If money is tight, I carry a 800 watt 2 stroke Harbor Freight generator that cost me $89.  I run a 25 foot extension cord away from my camper and its noise is tolerable.  It is my backup if the sun doesn't shine for 3-4 days in a row and I need to top off my batteries. 

Gary RV_Wizard

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Re: solar panel charging batteries
« Reply #10 on: May 01, 2019, 09:33:28 AM »
Quote
I don't think that installing a pair of golf cart batteries would be too difficult on a popup.
It would have been a major task on either of the two PUPs I owned, back in the day.  Battery space is sometimes both enclosed and quite small, e.g. room for a single Group 24 battery. The ones with a battery box out on the tongue are probably expandable without a lot of effort, but those with a small compartment for a battery can be a real pain.
« Last Edit: May 01, 2019, 09:36:04 AM by Gary RV_Wizard »
Gary
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Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

2floating

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Re: solar panel charging batteries
« Reply #11 on: July 10, 2019, 10:00:58 PM »
Here is one thing to consider. Your solar energy comes in big lumps midday, your use is probably spread over time at a much lower level. SO it would be most efficient to place the batteries near where the panels need to be, so the peak power level can be carried efficiently to them. Your long run then may be at a lower, longer interval power level. Could even be a 120VAC or 240VAC the inverter you remotely turn on, minimum current.
Experience is what you get when you don't get what you want

GotSmart

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Re: solar panel charging batteries
« Reply #12 on: July 11, 2019, 06:41:00 AM »
As someone with solar knowledge, that answer is not right. 240 volts from a single 100w panel?

We are talking heating at night.

Heating with solar is not efficient. You will kill your batteries quickly.

Mark_K5LXP

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Re: solar panel charging batteries
« Reply #13 on: July 12, 2019, 06:20:10 AM »

Not implicitly stated but it's assumed it's a forced air propane furnace with a 12V fan motor.

Mark B.
Albuquerque, NM
 

Gary RV_Wizard

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Re: solar panel charging batteries
« Reply #14 on: July 12, 2019, 07:53:24 AM »
I think the 120v/240v reference was to an inverter using the stored power from the solar panel.
Gary
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Gary Brinck
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