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Old 04-04-2011, 02:45 PM   #1
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Solar battery charger

Don't know if this is the right spot, but couple years ago bought a 15 watt solar panel and control from Harbor Freight. First day of use, fully charged the battery on my Terry 5th wheel (one 12 volt battery and not much power drain from trailer).

Second day battery crapped out (9years old).

Third day the control for the panel crapped out. Got a new one from H. F.

This year finally got to use it for 5 days on Padre Island. With two 12 volt batteries, electric jacks, electric awning, and slide, seemed like it kept up but never reached the full charge state. Wayne
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Old 04-04-2011, 05:37 PM   #2
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Originally Posted by wayne anthony View Post
Don't know if this is the right spot, but couple years ago bought a 15 watt solar panel and control from Harbor Freight. First day of use, fully charged the battery on my Terry 5th wheel (one 12 volt battery and not much power drain from trailer).

Second day battery crapped out (9years old).

Third day the control for the panel crapped out. Got a new one from H. F.

This year finally got to use it for 5 days on Padre Island. With two 12 volt batteries, electric jacks, electric awning, and slide, seemed like it kept up but never reached the full charge state. Wayne
You are kidding right? 15 watts?

Dude your batteries did it ALL.
15 watts?

At FULL SUN that's a bit over 1 amp! Your propane detector draws that!

Minimum solar panel size for two 12 volt batteries is 180 watts. Even then you will need to run your generator with a good 20-40 amp battery charger for several hours every few days or so to keep them topped off.

A few more trips like that 5 day trip like Padre Island and you will be buying another pair of batteries I am thinking.
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Old 04-04-2011, 05:53 PM   #3
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Some of us can get by a couple of day without t. v.s and our electrical junk.
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Old 04-04-2011, 05:56 PM   #4
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Originally Posted by wayne anthony View Post
Some of us can get by a couple of day without t. v.s and our electrical junk.
GOT ME!

Still that panel is a trickle charger designed to keep a fully charged battery from freezing due to internal resistance discharging the battery that is not hooked up to anything.
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Old 04-04-2011, 06:21 PM   #5
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Herk,

A couple of weeks ago I bought a 45 watt solar charger set from Harbor Freight, my intentions are just to keep the batteries charged for normal daily use, which mostly consists of the lights and water pump, very seldom do I use the heater and never in the summer. I do realize there is some uncontrolable electrical burn such as the fridge control panel, propane monitor alarms etc.

I do not have any high volume electrical needs such as televisions, radios, fans or other appliances.

Do you think I am behind the 8 ball with this? I usually camp 4-6 days at a time, rare that it ever exceeds that.
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Old 04-04-2011, 06:49 PM   #6
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Do you think I am behind the 8 ball with this? I usually camp 4-6 days at a time, rare that it ever exceeds that.
Well, I guess that depends on what "behind the 8 ball" means to you.

45 watts is a bit over 3 amps at full sun.

"Full Sun" is when the sun angle is exactly 90 degrees to the surface of the panel. Unless you have a motor drive on your panel system; this happens exactly once a day IF you have the azimuth set correctly for your latitude.

If you just flop it down, you will get less than rated output.

Now, back to the 8 ball.

Say you average 2 amps all day. Say 12 hours of sunlight. That will put 24 amps into your battery a day. If all you pull from the battery is 24 amps you will use "none" of the battery capacity that day. Net zero.

If you use more, say 50 amps per day. You will have reduced the battery capacity by 26 amps per day; not 50. This will effectively double your battery life.

Now 50 amps may seem like a lot, but ONE 12 volt incandescent light fixture uses about 3 amps (~1.5 amps per bulb). The water pump running uses about 13 amps. My motor driven slide draws 18 amps when running them in or out. Running both at the same time...
Well I don't want to say but it sure looks cool.
Can you say "Transformers."

I know you don't run the slides every day or the awning up and down either but you get the drift. Some is better than none.

To go "off the grid" without a generator you are going to need to create more power than you use. A minimalist would need a 200 watt panel and a fair sized (500 amp-hour) battery bank.
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Old 04-04-2011, 07:07 PM   #7
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Thanks Herk
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Old 04-07-2011, 07:41 PM   #8
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Just got this sale in an email. They are reputable and I and another friend have done business in the past.

Solar Cell, Solar Panel, Solar PV, Solar Products, Charge Controllers, Solar Trackers

Great deal on a 180 watt panel 24 volt 10 charging amp panel!
Make sure you get the correct controller to drop the output to 12 volts.
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Old 04-17-2011, 08:21 PM   #9
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At 5-15 W, I am assuming that this size/type of system would be suited for maintaining the charge on a battery that is sitting around idle, in storage....

Has anyone used one of these systems for just charge maintenance??

If so, what are pros and cons??
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Old 06-19-2011, 10:23 AM   #10
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All I am looking for is a small solar charger to keep the deep cycles from dropping off over the cold winter. I don't believe in taking batteries out in fact I think cold is better than warm for them as long as there is a trickle of current going into them..any recommendations
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Old 06-19-2011, 03:20 PM   #11
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I don't believe in taking batteries out in fact I think cold is better than warm for them as long as there is a trickle of current going into them..any recommendations
I, for one, would be curious to know what led you to this belief?

As to a good trickle charger the Battery Tender series of chargers do a great job. Of course you would need 120 VAC to run them. 10 watt Solar chargers don't do a good job and are a total waste of money.

The 10 watts is in full sun with the ray incidence being 90 degrees. Unless you constantly adjust the angle for time passage (solar drive motor) and Latitude, you will not get anywhere near rated output.

10 watts (FULL output) at 12 volts is less than 100 milliamps. Not enough to keep up with internal resistance loss let alone temperature degraded capacity loss.

Best practice for cold climates is to remove the battery to a warm place and put a battery minder on it.
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Old 06-19-2011, 03:57 PM   #12
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I have just purchased a 2011 Sabre Silhoette 25 foot fith wheel and am looking at installing a solar system. My last unit had been prewired for solar conection...is this also the case with the Sabre? I have taken a quick look at the fridge vent and there dosent seem to be anything in this area.
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Old 06-19-2011, 04:16 PM   #13
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http://www.forestriverforums.com/for...ems-12500.html

One of many threads on this forum. There are also dedicated web sites for solar power and off grid RVing like:

Solar Cell, Solar Panel, Renewable Energy, Wind Energy, Charge Controller, Solar Trackers

Solar Blvd has an EXCELLENT FAQ and Blog regarding solar systems.
I, and one of my friends, have done business with them in the past. I bought an inverter from them and my friend bought one of their 275 watt panels and a charge converter for it. They were fast and provided excellent tech support after the sale.

No, I do not have a financial interest in Solar Blvd. (but maybe I should look into it!)
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Old 06-19-2011, 09:00 PM   #14
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Sorry to say Herk, I disagree with you. Batteries sitting dormant (not being used) will sulfate quicker than one sitting in freezing temps. I have had deep cycles in all my rv's and never have I taken a battery out over winter and we get cold winters. I did however disconnect the negative terminal on the batts. Deep cycle's fair well in sub zero temps as long as you have them full charged before you park the rig.
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Old 06-19-2011, 10:07 PM   #15
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All kinds to make a world, they say.
I just play an "expert" on the internet in any case.
You were just the first to have offered that point of view.
Always looking to learn. Do you have a source for that?
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Old 06-21-2011, 10:26 AM   #16
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Lou,

Stop being a solar snob!

There are people out there that would prefer not to pay upwards of $500+ for a solar kit for their RV. I for one don't see the cost benefit of a good sized solar system on my RV. My wife and I go camping 4-8 times a summer and although I have been tempted, I just can't bring myself to spend the money for something that would not be used a great deal. I don't generally run electronics when we camp and if I do, I'll kick on the generator for a short time.

As it happens, my RV came with a 15W solar panel. Not sure why the previous owner installed a small panel (oh, he installed it "in" the rubber roof) but it is there and I intend to put it to use.

The truth is, I envy your system (yes, I have solar envy) but to each his own.
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Old 06-21-2011, 11:02 AM   #17
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Costco had a Coleman 55W Solar Back-Up Kit for around $219, was wondering if anyone had any experience with it. Walmart.com: Coleman 55W Solar Back-Up Kit: Tools (Walmart site, but same unit, for less)

We just don't dry camp enough to justify a full blown solar system, or probably even a generator.
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Old 06-21-2011, 11:28 AM   #18
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The truth is, I envy your system (yes, I have solar envy) but to each his own.
Sorry, no hab solar system on my rig. Hab BIG HONKIN generator.

A 15 watt panel is a trickle charger (and I do mean trickle). I doubt it would provide enough current to keep your battery warm in the winter.

Your envy (and mine) is misplaced. Still waiting for prices to come down further (they will). You can easily get a 200 watt system (smallest I would consider) for under 300 bucks including the controller.
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Old 06-21-2011, 11:36 AM   #19
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Generally you can figure about half of the rated wattage from solar panels. And that is on a sunny day. Any clouds and you won't even come close.

A lead-acid battery will lose charge just sitting idle. And this is what the small 15 to 30 watt solar panels are meant to prevent.

As for a system to move the panels throughout the day...It is generally cheaper and easier to just use more panels and keep them fixed.

If you want to use serious solar power system, make sure the charge controller has MPPT (maximum power point tracking). This will give you much more charge into the batteries than a non-MPPT charger.

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Old 06-21-2011, 11:50 AM   #20
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Excellent tutorial:
Solar Tutorial
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