Solar Panel Questions

[timmy67]

We just got back from our first 2 week vacation with our 1984, 25' Sovereign. And except for a problem with our fridge, (it did get repaired) everything went fairly smooth. An issue we ran into was, in British Columbia Provincial Parks there are no power sites. We did our best to conserve power but one problem we ran into was we couldn't use our toaster unless we used the outlets in the washroom. What a PITA that was. My wife and I talked about trying to use solar panels to keep things charged up for future trips so we don't have to rely on campgrounds with power. My problem is, is that I don't know where to start as far as research goes. There are some good looking deals going on right now around home with companies trying to clear out solar panels. Canadian Tire, Costco, etc but I don't want to go out and buy something and find out that I've made a bad purchase. Eventually we would like to add a pair of fantastic fans to the mix but other than that everything in the trailer is stock. I'm hoping someone can point me the right direction. Thanks for reading and thanks to all in advance.

Tim

[purman]

I've Been thinking about it for a while too.. There are plenty of thread on here is you search... I like the idea of a portable moveable solar unit... you will need a minim of a 30 watt system to recharge your batteries in a day... Anything less is a trickle charge and will not recharge the system.. 60 + watts and you can run stuff of it.... But I don't want to put in on the roof as i like camping in the woods sometimes... I have seen a suitcase style that was 30 watts on ebay, but I don't know about it so i didn't get it...

Still looking too...

[Airstream25]

I hear what you say about liking to camp in the woods, however even if you park right next to a single tree, you should have sun on our Airstream about half of the day.

I like the convenience of bolting the panel to the roof. There is absolutely no ongoing set up and take down. The risk of theft is also greatly reduced.
I like a big panel because it will restore the batteries faster. This is important if your campsite gets sun only part of the day.

The picture is of a 120 watt rated panel but don't expect to get that unless you are camping on the equator.

There are many threads to search on Airforums about where to buy, how to install, etc.

[davidz71]

Check out Welcome to AM Solar - Your RV Solar Specialists since 1987 as well as search for AM Solar SunRunner 100/H22B Install in this thread: http://www.airforums.com/forums/f448...all-32749.html.

I took a few pictures of the two 100 watt panels I installed as well as the wire run from the panels to the combiner box and then down the refrigerator vent. Pictures then show the cable run through a cabinet, under a shelf and then underneath and behind the couch where I mounted the H22B boost controller. Cable then ran to the battery box. I later added an additional AM Solar 65 watt panel (no longer available) and have had the system for 15 months with not a single problem. Their system is easy to install and top notch.

[TBRich]

Solar panels are great...we have a factory installed one...though we haven't relied much on it, we plan to do more with it...once we hone ou r dry camping skills. There is an art to living off solar...largely having to do with power conservatin and controlling how much you draw on your batteries so that they can recharge adequately to keep you going.

One thing you should realize is that you will need a good inverter to power up appliances from your batteries that require a lot of wattage to work (toasters, hair driers, etc...anything that heats or isbased on electrical resistnace). Our inverter (also factory) will convert 12v from the batteries to 110v for appliances requiring up to 600 watts. If you want/need to run a microwave or AC, you will need either shore power or a 3000w generator (or two 2000s). Poke around in the subforums hdealig with solar and such...there's a lot of great information there...

[lewster]

Originally Posted by purman

I've Been thinking about it for a while too.. There are plenty of thread on here is you search... I like the idea of a portable moveable solar unit... you will need a minim of a 30 watt system to recharge your batteries in a day... Anything less is a trickle charge and will not recharge the system.. 60 + watts and you can run stuff of it.... But I don't want to put in on the roof as i like camping in the woods sometimes... I have seen a suitcase style that was 30 watts on ebay, but I don't know about it so i didn't get it...

Still looking too...

Jason,

A 30 watt panel, assuming 100% output (which won't happen unless you have the sun directly overhead all day) will give you a huge 2.5 amps of charge to your batteries. This is a trickle charge. 60 watts will yield a maximum 5.0 amps but in reality, will be more like 3 amps......still a trickle charge.

Assuming you have a 100 amp hour battery (typical group 24 size) and that it is an AGM (for charge efficiency purposes)....and that you draw down said battery to 12.2 volts (50%)...then you have to have 20 hours of direct sunlight to re-charge your battery at the 2.5 amp charging rate.

Math: Ohm's law....P(watts) = I(voltage) X E(amps)
amp/hours = E(amps) X T(time in hours)

We at AM Solar recommend at least a 100 watt panel for every 100 amp/hours of battery capacity and also recommend one of our MPPT (multi-point power tracking) charge controllers, which will almost double the available amps for charging.

Also, be careful of what inverter you pick, as many have a significant draw on the batteries with NO LOAD on them. Also, there is a lot of crap currently on the solar market, as every shyster sees green (read $$$$$$) in the solar business now. Cheapo will not last, nor will it give you the results that you seek!!!!

I am using a 4 panel, 400 watt AM Solar array thru the HPV30-DR controller charging a pair of Lifeline Super golf cart GPL-6CT 300 amp/hour batteries. These power a Magnum 2000 watt sine wave inverter, which has virtually no draw when no AC load is present.

On a bright sunny day (here in northern OR), I have been getting a max. of 23.8 volts from the array, which translates into 18.9 charging amps. So far....so good. It will be interesting to see how the charge rates change when I get back to south FL and the higher sun angle. I will be adding another pair of 300 amp/hour Lifelines in the Fall.

Another benefit of the AM Solar mounting brackets is that they allow you to tilt the panels so they are at a higher angle to the sun as it's azimuth changes with the seasons.

Let me know if you have any other solar questions.

[TBRich]

Lew...you da sola' man!

[joecolao]

Hello, I have gone as long as 5 1/2 months without hooking up to electric. We disconnected our converter long ago. Running our vacuum, microwave, wifes hair blower, computer, sat. dish, 2 lcd tv dvd vhs and more.

There are basically 2 types of solar modules amorphus and silica crystal.

2 very different characteristics - crystal are in a glazed frame, twice the efficiency of amorphus. Thats the good news. The bad news is that should you shade as little as 10% of a module you reduce output by about a whopping 95%. So if you camp in the woods, you won't be happy with thier performance. They lose output if as they heatup over 70 f.
Amorphous modules are more durable and not as effected by heat and are flexible.
Check out gosolar.com for more information.
Go solar for sure, no gas, no funnel, no noise, less weight, superior charging characteristics. And Much More.
Good luck

[lewster]

Originally Posted by lewster

Jason,



Math: Ohm's law....P(watts) = I(voltage) X E(amps)
amp/hours = E(amps) X T(time in hours)


Let me know if you have any other solar questions.

In a mildly dyslexic moment (or short term memory failure) the above equation should read: P(watts) = I (amps) X E (volts)

amp/hours = I (amps) X T(time in hours)

Sorry for the confusion!!!!!!!!!!!!

Luckily, it didn't make a difference in the calculations.....

[lewster]

Originally Posted by joecolao

Hello, I have gone as long as 5 1/2 months without hooking up to electric. We disconnected our converter long ago. Running our vacuum, microwave, wifes hair blower, computer, sat. dish, 2 lcd tv dvd vhs and more.

There are basically 2 types of solar modules amorphus and silica crystal.

2 very different characteristics - crystal are in a glazed frame, twice the efficiency of amorphus. Thats the good news. The bad news is that should you shade as little as 10% of a module you reduce output by about a whopping 95%. So if you camp in the woods, you won't be happy with thier performance. They lose output if as they heatup over 70 f.
Amorphous modules are more durable and not as effected by heat and are flexible.
Check out gosolar.com for more information.
Go solar for sure, no gas, no funnel, no noise, less weight, superior charging characteristics. And Much More.
Good luck

Joe,

Thanks for pointing out the difference, but the new poly-crystalline cells that we use at AM Solar are not affected by the heat like the older panels were. They also respond better in the shade without such a high drop-out of voltage...................YMMV

[davidz71]

Originally Posted by lewster

Joe,

Thanks for pointing out the difference, but the new poly-crystalline cells that we use at AM Solar are not affected by the heat like the older panels were. They also respond better in the shade without such a high drop-out of voltage...................YMMV

Lew,
I've seen the statement about the drastic effect shade has on panels but have been surprised that this has not been the case with my AM Solar system. Now I know why.

[lewster]

.............just in case you're wondering

The panels that we use at AM Solar are custom manufactured to our specs by BP Solar (as in British Petroleum)....one of the biggest players in the game.

All of the electronics like the charge controllers are made by Heliotrope, Inc, which is a wholly owned subsidiary of AM Solar with manufacturing facilities in Springfield and Eugene, OR...............NOT CHINA!!!!!!!!!

[dufferin]

I myself start to look at solar. I am interested in flexible solar panels if they are any good.

Any thought on that?

[lewster]

Originally Posted by dufferin

I myself start to look at solar. I am interested in flexible solar panels if they are any good.

Any thought on that?

They will work....but have very low output and efficiency.

[RoadKingMoe]

There are some here who have gone into solar having no clue how much power they use, or how little they can get by with. You don't have to be one of those. With a multimeter that has a 10 amp or higher DC measuring capability, you can get an idea.

To get started, unplug from shorepower, turn everything off in the trailer (don't forget the antenna amplifier) and disconnect the cables from the battery negative posts. Put the black meter lead on one battery's negative terminal and the positive (red) meter lead on the cable that went to that terminal.

Don't be surprised if you see current being drawn. This is the sum of your phantom loads, the LP, smoke, and CO detectors, the radio remembering its settings, and any control circuit boards in appliances. This is your base load in amps and you can multiply it times 24 hours to get daily base amp-hours. Amperage (aka amps) is an instantaneous measure of current, amp-hours is the current used over time.

Now turn on one thing at a time, note the meter reading, and subtract the base load to get the amperage that thing draws. Multiply that times the number of hours per 24 hour period you think you will use that thing. Go through the trailer making an electrical use inventory. If you have Fantastic Vents, check them on each speed.

Don't forget to do this with the refrigerator and the water heater. Although they run on gas, they have circuit boards and ignitors, and possibly an electric gas valve. These cycle on and off and you need to measure their draw in each condition. You'll have to estimate how long each will be on vs off over 24 hours to calculate the total use for the day. Personally, I turn our water heater off until about 1/2 hour before it's needed.

I do NOT recommend doing this measurement with an inverter or the furnace fan on. Even if they aren't rated as high as the multimeter's maximum DC current, they have a start-up surge that may exceed a 10 amp DC meter's rating. For the furnace, you can use the manufacturer's rating.

For the inverter, you can use the wattage rating of the 120VAC appliance it will power, divided by 10 (that accounts for less than 100% efficiency) to estimate the instantaneous amperage the inverter will draw from the batteries. Note that the power drawn by an "X" cooking power microwave can be 1.5 times "X". Look at the data plate.

A total instantaneous amperage draw in excess of the sum of your batteries' 20 hour rate requires special handling. For example, a 100 amp-hour 12 volt battery will last from full charge to a defined full discharge 20 hours at the 100/20 = 5 amp rate (or two in parallel, this is a 10 amp rate).

But this does NOT mean it will last 100 amp-hours/25 amps = 4 hours at a 25 amp discharge. At that rate, which is the one used to establish the Reserve Capacity rating, the battery will only last roughly 180 minutes or 3 hours. One way of looking at this is that a battery that's rated 100 amp-hours at a 5 amp draw is only a 75 amp-hour battery at a 25 amp draw. Another way of looking at it is that a 25 amp draw is like a 1.33 x 25 = 33 amp draw when it comes to calculating use out of 100 amp-hours. This is due to something called the Peukert Effect. I won't go into the calculations, but will say that the higher the draw, the worse this effect is.

Two paralleled 12 volt batteries, each supplying 25 amps, is about what it takes to power a little 500 watt inverter supplying its rated 120VAC output. A 2000 watt inverter can draw as much current as an automobile starter and many know how quickly that can drain a battery.

I am not a fan of inverters, but there are some things that need them. Such things are laptop computers and LCD TVs for which there are no 12VDC adapters, satellite receivers, etc. Fortunately, these are low draw items. On the high draw side, I'll include vacuum cleaners. I've never found a 12 volt vacuum that works worth a darn. Just minimize the time you use a 120VAC model on an inverter, or better yet on hard-surface floors, use a dust mop or broom.

The worst thing one can use battery power for is making heat. If you do the math, the effective amperage drawn for a coffeemaker or toaster is mighty high when the Peukert Effect is considered. Fortunately, a pop-up toaster isn't on very long, but I prefer to use a camping toaster over a gas burner.

I'd rather you use an inverter to power an electric coffeemaker than power up a generator right next to me early in the morning. If you're smart, you'll shut the inverter off as soon as the coffee is done and pour it into an air pot thermos. But if you're smarter, you'll boil water for coffee on the stove and pour it into a Melitta or Dripolator, or use the Coleman drip coffeemaker on the gas stove.

When taking inventory of electrical use, you can see how much these high draw of inverter-fed applications increase your expensive solar requirement. You may also be surprised at how much long-duration, low draw things use over a day. Over 24 hours, Fantastic Vents can use much if not all of a large panel's daily output.

Once you've done your inventory, consider the rule of thumb that a horizontally mounted solar panel typically provides 1/4 of its wattage rating as amp-hours per sunny day in the summer. To account for cloudy or rainy days, you may want some reserve capacity, or you may just choose to carry a small generator to augment your solar setup.

By doing these measurements, you can make an informed choice about how much capacity you want AND how much value conserving electricity has for you.

[joecolao]

Originally Posted by dufferin

I myself start to look at solar. I am interested in flexible solar panels if they are any good.

Any thought on that?

Hello,
I have used the Unisolar Flexible Solar Modules. They are 15" wide and about 9 feet long and are rated at 68 watts. They are much more tolorant of shading, self stick, very durable, light weight and they can conform to the radius of an airstream. I first mounted them on an airstram about 8 years ago. I used a flat piece of aluminum threshold bedded in silicone and rivited to hold down the leading edge. I am very happy with them. I can't provide you with any photos but you can go to gosolar.com and see them mounted. Good luck.

[joecolao]

Don't know you, never read your posts. Never read such a detailed and accurate description and recommendaton about how to get into solar. Great Job!

[LI Pets]

Originally Posted by joecolao

Hello,
I have used the Unisolar Flexible Solar Modules. They are 15" wide and about 9 feet long and are rated at 68 watts. They are much more tolorant of shading, self stick, very durable, light weight and they can conform to the radius of an airstream. I first mounted them on an airstram about 8 years ago. I used a flat piece of aluminum threshold bedded in silicone and rivited to hold down the leading edge. I am very happy with them. I can't provide you with any photos but you can go to gosolar.com and see them mounted. Good luck.

How much does GoSolar.com sell those for do you know?

[ArtStream]

Great 1,500th post RoadKingMoe!

[davidz71]

Originally Posted by joecolao

Don't know you, never read your posts. Never read such a detailed and accurate description and recommendaton about how to get into solar. Great Job!

joecolao,
Those of us who have been on the forum for years realize that RoadKingMoe is pretty sharp on his electrical/generator /solar info.