Landracing Forum
Tech Information => Technical Discussion => Topic started by: donpearsall on June 29, 2011, 11:16:45 PM
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I have been thinking about putting LED light fixtures in my trailer for interior lighting. LEDs are pretty low wattage and the prices are coming down. I could power them with a 12v car battery that is charged by a solar panel on the roof of the trailer, and then also charged when hooked to the truck. Of course the solar panel has to be weather proof. And it would not be 100% efficient since it would not always be oriented to the sun.
Has anyone done this? Any tips?
Thanks
Don
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Make sure the solar panel has a diode to prevent discharging the battery. It won't take a big battery to power the lighting.
I used to store my trailers with a portable solar panel. I just made up a receiver connector and plugged in the trailer to the panel hanging on the fence.
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Are you just looking for enough light to keep from tripping over stuff, or enough light to do work by?
Those small touch lights that they sell for use in closets are LED lights running off of 2 to 4 AA batteries. They will run literally for a week continuously on one set of batteries. Walmart has some cheap led lights with about 10-20 LED's intended for camping that run on 4 AA batteries that provide enough light to do work that does not demand really bright light.
If you bought a few of those cheap LED touch lights and wired them in series to a 12V gel cell they would run for several weeks continuously on one charge. You can buy a small 5 watt solar panel from Harbor Freight for about $60 that would work to charge the gel cell.
For close work that requires really good lighting like final engine assembly and inspecting spark plugs etc. you would need several of the LED fixtures to have a bright work light environment. The one problem with the bright white LED lights is that they are not a true broad spectrum light source so it is difficult to judge colors with them. I use them for general emergency lighting, and a single 3 LED lantern from Walmart intended for camping will provide enough general illumination for moving about safely but not quite enough to work by.
I would suggest you pick up a couple of the LED touch lights and one of those large LED lights for camping and see if they provide enough light for your needs, and how you like the character of the light.
You can also buy small florescent tube fixtures designed to run on battery power that in my opinion give a better (true white) light than the bright LED's. I personally find the bright white LED's a little bit harsh in the character of the light they produce. I have 2 of the small florescent fixtures that run on AA batteries that I use for working on computers, they make them in 6" long and 12" long designs which work great to see what you are working on inside a computer case. They could also be wired to run off of a 12V power supply by rigging up the proper supply voltage or wiring them in series so the total voltage required for the set is 12V.
Once your eyes get dark adapted it does not take much light to do general work so the best way to judge how many fixtures you need is to actually test a couple of those cheap touch lights inside the trailer at night. In the day time out on the salt the exterior is so bright that most any light will seem dim by comparison, so you might actually need more lighting during the day time on the salt than at night because your eyes will be accommodated to the outside light levels.
The one advantage of the small touch lights is you can put them exactly where you need the light, rather than try to illuminate the whole trailer interior to suitable light levels.
Painting the walls and roof of the trailer interior white will help a lot!!
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Have you done much searching for the solar panel and associated equipment (regulator, diode stuff, and so on)? I have -- and found it isn't a cheap way to get electricity. I was looking for a 12VDC system - to run some 12-volt equipment in the trailer. Not lighting -- radios and other low-current stuff. But I figured about 60 watts would be needed from the solar charging system. Assuming about output 50-60 percent of maximum capacity (averaged over a 12-hour day, just because I had to choose some basis) -- I'd get about 30-35 watt/hours x 12 hours = about 400 watt-hours in a day.
The equipment that I want to power will draw abut 100 watts total, so I'd use all of the solar power and more than that amount again from the battery's reserves each day. A few days of this -- and I'd have to run the generator for a day or so (@ 8 amps DC output) to top off the battery again.
And now - why 60 watts from the solar system? Because that's a common output size in the world of solar arrays. Even though common - it isn't cheap. I found that it'd be on the order of $400 for the basic stuff - not including the battery or the mounting equipment on the roof or the wiring. I can run the generator for one heck of a lot less than that each day. I'd lose the silence of the solar - I'd gain the much higher output to serve my needs.
This, I know, doesn't answer your question with regards to a light source. But it does give you an idea of the costs involved for a different watt-hour requirement. LEDs might be able to live with 35 watt/hours from the solar device -- but you'd need a big bunch of them to give you lots of light. I don't think that fluorescent lamps will give you enough light on this power budget - so you might need to spin up the generator now and then to get the battery back to where it needs to be.
I really wanted to run the trailer on solar -- but it isn't going to be cost-effective at this time.
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I keep one of those small solar chargers on my trailer year round while it's stored to keep the battery up. At the salt I use the 12v supply for the CB and regular radio. I've never had a problem at the end of the week using the winch or lights.......Good Luck
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Thanks for the replies and ideas everyone. I see that Harbor Freight has a 45 watt solar panel kit on sale now for $169. That is more than I need but the price is right. Will that work for you Jon?
Don
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JD, do I understand that you run the CB and broadcast radio off the battery (that's kept full by a solar panel) all week? Is the solar thing charging the battery? Does quality of the CB and radio degrade as the battery gets low on charge -- or are things still fine (as you say)?
I expect to have quite a bit more load -- CB, two broadcast radios, laptop computer, and probably another few items -- totaling 8 - 10 amps of the 12VDC. I don't want the voltage to go down enough for the equipment to suffer from low voltage, but maybe a solar unit would be able to stave off the need for the little generator. But -- as I said, 60 solar panels cost in the hundreds of dollars. I can buy lots of gas for the generator - but will have some noise. Worth the trade-off?
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Now I see your note, Don. 45 watts would be a help -- and I'll look at H F's catalog and see what I find. Thanks.
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Don, would you please send me the page from Harbor Freight showing the $169.99 price? My 'puter comes up with $179.99.
http://www.harborfreight.com/45-watt-solar-panel-kit-90599.html
Hey, ten bucks is enough money to - to - to buy at least a hamburger and Coke.
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With photovoltaic panels they generally assume that you get full rated power (full sun conditions) from approximate 10:00 am to 2:00 pm and degraded output for a couple hours earlier and later in the day. (assuming you are not tracking the sun with the panels but place them in a fixed location looking due south. That works out to being able to expect near full rated power for 6 hours a day under cloudless conditions.
The power out is directly proportional to the illumination levels on the panels, so in some special cases you can actually get more than rated power. For example I had a solar panel test bed I set up years ago to figure out how much power I could get from cheap surplus panels available at the time from Gateway Electronics, and I closely monitored charging current through out the day and found that when the panel was in full sun but a large cloud was near the sun, but not obstructing it, the scattered light from the cloud added to the illumination of the panel enough to noticeably increase charging current. On most panels power out drops sharply if any part of the panel face is shaded, so you want to keep shadows off the panel face.
Out on the salt flats you have an infinite reflector in the form of the salt which if they are getting a lot of scattered light from the salt, during mid day they should exceed rated power out.
The normal recommendation is to angle the panels at the local latitude - 15 degrees. For Bonneville that would be about 40-15=25 degrees above the horizon for the optical axis of the panel. If you moved the panels east - west 2 x during the day you could extend that full sun period another hour or so.
I have used one of the 5 watt harbor freight panels on the car battery to keep from running it down while using my lap top intermittently and occasional use of the CB and car radio. I don't have any test numbers for actual power out.
The other thing to consider is the duty cycle of your power use. It might be cheaper over all to use a larger battery pack on a small solar panel so you had more reserve capacity. On my ham gear at home I have 2 deep cycle 12 v batteries on a trickle charger and if I lose AC power they will run the radios on receive with occasional transmissions for about 24 hours. In most situations you will have long periods of partial sun where you are not using any power early in the day and late in the day for the panel to recover the battery charge.
You will need to audit all your power demands to figure out how much actual watt hours you need per day and size both the solar panel and the battery pack accordingly.
Larry
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Our new Costco store here in Tucson is selling two types of solar panels-- a polycrystalline 220 watt panel and a smaller thin film panel. The 45 watt Harbor Freight solar panel is a thin film type.
Thin film solar panels are cheaper but have much shorter lifetimes than a polycrystalline or monocrystalline panel. The latter two types are typically at least 80% after 25 years while thin film panels start to lose efficiency after about 5 years.
Check out Amazon.com; they also sell solar panels of various sizes.
Regards, Neil Tucson, AZ
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Thanks for the lifetime estimates, Neil. In my case I assume it wouldn't be an issue -- because I don't expect to use the panels more than 5 - 6 weeks/year. I've got a deep-cycle battery in the trailer - and the battery stays charged enough all winter long that I can use the 12V lights in there -- with no trickle charger or anything. If I do elect to go with a solar array I'll likely add another battery to the trailer, which'll give me twice the reserve power. That ought to eliminate worries about the voltage sagging as the day goes on and the sun goes away. I could cheat a bit by hooking up the trailer wiring plug to the pickup since that way I'd be drawing off the dual batteries in there. But -- I can stay hooked and drive to the line at the same time. :roll:
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Jon, the $169 price was from a flyer that I get mailed to me. Today was the last day of the sale. BUT on July 4, they have a 25% off everything sale.
Don
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Thanks for the 4th of July tip, Don. I'll look forward to it - shipping costs and all. By the way, this is being sent AFTER I sent an email back to you a few minutes ago.
Have a safe and happy Fourth of July, buddy.
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Here's a goog online solar source I have used.http://store.sundancesolar.com/
Also, be sure to run a charge line from your tow vehicle.
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Slim. The little $20 solar charger seems to do the job. I normally have the CB on for listening for times; rarely if ever broadcast. The "car" radio also mounted on the door is on all day too even if we are up at the line. Our pit seems to have guys just sitting and listening. I have a volt meter in the trailer and I check it daily it's stays right at 12 VDC. We do the same for the Oct meet also and never had a problem using the electric tongue jack or winch to pull in the car when leaving. I do use a conventional battery charge for a day before leaving but the battery has the solar on it while stored during the year..JD
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I expect to be running a computer (laptop) and a gaggle of electronic devices as well as the two radios. My battery is kept full via the charging system in the pickup - but the truck isn't hooked up much once we're on the salt. And it's out there that I'm anticipating a 100-watt or so continuous load for 10-12 hours/day. Lots is going on - so I need to make sure I've got the energy available. I don't want any surprises.
Thanks for the help.
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Updates on this thread. I bought the 3 panel 45 watt solar kit from Harbor Freight. It comes with a solar controller that provides battery charging, 12V outputs and even a USB charger receptacle. It seems to work well, even up here in cloudy Seattle. I am going to replace the existing trailer breakaway battery with a deep cycle marine battery, then rewire the trailer for 12 volt LED lighting and have an inverter from the battery for 120v AC. The truck 12v aux power line will now go to a charger for the new battery, and the panels will also charge the battery when the trailer is not connected.
I think I have the wiring all worked out.
One question; do I need a battery isolator to keep the trailer electrical usage from discharging the truck battery? I know I can just pull the plug off the truck and that solves it, but am just wondering it it is needed for safety sake?
Thanks
Don
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Don, my HF 45-watt solar kit arrived the other day. Thanks for the shopping tip. Anyway -- I haven't got it out of the box yet - so - - any hints on ways to put it together? Things that you discovered after you were done with the assembly?
I plan to wire the trailer with 12VDC outlets here and there, all feeding off the deep cycle battery that is charged by both the truck wiring connector and the solar. They not be hooked up at the same time so I won't worry about discharging the truck's batteries. I haven't decided on whether to put a 12VDC-110VAC inverter in the trailer, but probably will - since running the generator when I need AC will be extra noise in the pits -- and I sure wouldn't like it if I were the only one making such noise. :roll: :roll:
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Jon, I was going to mount the panels on the top of the trailer by using channel aluminum. I will screw the channel to the roof ribs then set the panels in it along with some rubber weather stripping so they don't rattle. Then route the panel wires inside the trailer to the controller. The marine battery will be in the same place the existing little battery was and I will route some heavy battery cable on the bottom of the frame to a spot near the door. The inverter and the controller will be mounted on the wall by the door for easy access. That way I can easily plug in extension cords to the inverter and run them outside or inside.
I still don't know if I need that isolator or not. Probably not.
Don
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One note regarding solar power. The state of Colorado had a solar power communications van (one of the first in the country) back in the 1980's we had about a kilowatt of power from the panels in full sun light. One of our techs learned the hard way, the panels produce power even in moderate light levels, and like a 12v battery should be consided "always hot"! He blew the tip off a screw driver that got in the wrong place while working on the van when "everything was shut off". He was on the hot side of the power relay to the panels.
Also remember that solar panels do not like to be partially shaded. Some include diodes to prevent reverse current flow in a partially shaded cell others don't (not sure regarding the HF panels) Try to avoid placing the panels where a hard shadow falls across the panel.
http://www.reuk.co.uk/Diodes-and-Solar-Panels.htm
You at least want a diode in the panel to battery circuit to avoid dark current issues and a fuse about 2x the max amperage you expect from the panels in full sun in case you short the panel leads some where. A dead short across a full sun solar panel or the battery it is charging could be a fire hazard without fuse protection. Since you effectively have two possible current sources to a short, I would place a fuse near the solar panel and near the battery.
I would also add the voltage isolator to protect you on those occasions you forget to unplug the system.
Larry
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Thanks, Larry -- the more tips I get - the more likely I'll be happy with the system.
Don, I intend to make the panels into a roof mount that's easy to lean up to the correct angle (Wendover's at 40.85 degrees N - figure from there on what's the correct angle), but also lie flat on the roof for driving down the highway - with the panels themselves stored inside the trailer in case of hailstorm or low-flying trees.
The big battery is in the nose of the trailer and will stay there. I'll put a couple of 12VDC outlets along one wall and no more than 10-12 feet from the battery. I expect the operating position for the audio console will be there - and we don't really need the 12VDC elsewhere in the trailer. I'm now vacillating on the need for an inverter - but'll probably put in a 400-watt or maybe smaller. If we need good amounts of 110VAC it's easy enough to fire up the little generator - and it's pretty quiet, too.
I wonder, though - when I have the DC system wired up and need to charge the battery (with the solar disconnected, of course) how 'bout if I power up the DC to AC inverter, running of the 12VDC system, and plug a regular battery charger into the AC outlet and hook the DC leads to the battery. . . :? :?
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I wonder, though - when I have the DC system wired up and need to charge the battery (with the solar disconnected, of course) how 'bout if I power up the DC to AC inverter, running of the 12VDC system, and plug a regular battery charger into the AC outlet and hook the DC leads to the battery. . .
It would work, you would just have conversion losses on each step, so it would be less efficient (power in vs power stored in the battery) than a single conversion, like going directly from the solar panels to the battery. In most cases convenience would probably trump needs to save that 2%-5% loss in efficiency caused by each conversion step, but if you were in an emergency situation where you had to make use of every single amp hour of charge a direct hookup would be slightly more efficient.
That brings up another option. They make power regulators that will take in 8-15 volts and output a rock solid 12-13.8 volt output. They are most often marketed for high power stereo sound systems but their use can allow you to charge a battery from a voltage source that is lower in voltage than that needed to charge the battery. It must how ever be able to deliver the higher amperage necessary to produce the necessary power.
For example you want to charge a car battery at 13.8 volts and 10 amps, but your voltage source is only able to produce 11.8 volts but can deliver 20 amps at that voltage.
Your charging current at the battery would require 13.8x10=138 watts, if the conversion loss of the voltage stabilizer is 5%, it would need 145 watts in, which at 11.8 volts would be about 12.3 amps.
Some racers also use voltage stabilizers to ensure their ignitions are always supplied with full 13.8 - 16 volts necessary to deliver a strong spark, and the same for fuel pumps whose flow rates drop off radically as battery voltage drops.
Similar to these ( I have not used these just an example of the type device I am describing) -- http://www.powerstream.com/dc2.htm
(low power designs)
http://www.xscyz.com/index.php?main_page=product_info&products_id=239
http://www.revolution-robotics.com/micro_power_module_24w-12vsu
Here is a solar battery charging regulator I stumbled across while searching.
http://www.energymatters.com.au/morningstar-sunsaver-12volt-10amp-dc-solar-controller-p-395.html
http://www.apolloenergy.com.au/
Larry
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"I wonder, though - when I have the DC system wired up and need to charge the battery (with the solar disconnected, of course) how 'bout if I power up the DC to AC inverter, running of the 12VDC system, and plug a regular battery charger into the AC outlet and hook the DC leads to the battery. . . "
OK, Jon-- I got it! :-D
Regards, Neil Tucson, AZ
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Slim. The little $20 solar charger seems to do the job. I normally have the CB on for listening for times; rarely if ever broadcast. The "car" radio also mounted on the door is on all day too even if we are up at the line. Our pit seems to have guys just sitting and listening. I have a volt meter in the trailer and I check it daily it's stays right at 12 VDC. We do the same for the Oct meet also and never had a problem using the electric tongue jack or winch to pull in the car when leaving. I do use a conventional battery charge for a day before leaving but the battery has the solar on it while stored during the year..JD
SOlar powered trailer lighting is pretty worth.. I have been using it for a while and got nice outcomes.
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Slim. The little $20 solar kits (http://www.shinesolar.net) seems to do the job. I normally have the CB on for listening for times; rarely if ever broadcast. The "car" radio also mounted on the door is on all day too even if we are up at the line. Our pit seems to have guys just sitting and listening. I have a volt meter in the trailer and I check it daily it's stays right at 12 VDC. We do the same for the Oct meet also and never had a problem using the electric tongue jack or winch to pull in the car when leaving. I do use a conventional battery charge for a day before leaving but the battery has the solar on it while stored during the year..JD
SOlar powered trailer lighting is pretty worth.. I have been using it for a while and got nice outcomes.