Solar Powered Trailer Lighting?

[jimmy six]

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

[Seldom Seen Slim]

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. 

[donpearsall]

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

[Seldom Seen Slim]

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. 

[donpearsall]

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

[hotrod]

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

[Seldom Seen Slim]

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. . .

[hotrod]

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

[manta22]

"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! 

Regards, Neil  Tucson, AZ