Solar charger, power and panels


Capt. Mike

Moderator
Well said; lot's of hang-ups and a several hundred dollar solution to a 50 cent problem (fuel to run the engine enough to recharge the batteries once a day).
 

xckayak

New member
For the electrically ignorant, what is a "40-60 watt cell"? Is it a smaller battery? If so, would you hook it up to be recharged by the VW charging system? Would it require more relays than what is already in a Vanagon Westy?

xckayak
 

icarus

Moderator
What I was refering to was a 40-60 watt solar panel. A 40 watt solar cell would under ideal circumstances put out 40watts of power (About 3 amps @ 12 volts) Enought to keep a battery charged over time, and run the radio, reading lights at night etc.. A 60 watt panel is about 2'x3'. Not realy a very practical alternative unless you stay in remote sites for long periods of time and don't want to start the car.

Icarus
 

bethulah

New member
Just another point of view.
I have a complete music studio in my van which in the winter, I drive to the jungles in Central America and write music, off the grid, for weeks at a time. I needed a full-on power system to feed computers, synths, and all the compensitory tools for not learning music at an earlier age. I was not so concerned with the weight issue of the panal on top of the van, anyone living in a snowy climate knows that any wet snow weighs 10 perhaps 15 times more than a 50 pound solar panel. I was though concerned with the air dynamics on top of the van. Logic would suggest the flat face of the van would blast the air high enough off the forward section of the roof as to creat a near vacume. Not having a wind tunnel handy my sweety drove the van down a flat country road at all speeds between 0 and 60 mph while I checked things out on the roof. The presumption is valid. Only toward the rear on the roof do you get turbulance. In fact the wind will force the panal into the van roof as it does surf boards and all such things. I mounted the front of the panal close to the front of the pop to assure it would be in the vacume. Made it heavier to lift, but safe. I have had the panel on my van for almost four years now with no trouble whatsoever. I have driven deep into Central America three times, across a thousand 'topes' (mexican speed bumps, enough to break my rear spring once) with absolutely no problems. No leaking, no loosening, nothing. So . .for your info.

Regarding the holes and devaluation of the van on resale that Captian Mike mentions, I would have to agree. I did though find a clean roof at a junk yard for $140.

Also if you will be running high tech equiptment get a full sign wave inverter. Don't get cheap here, you'll be cranky about it right away.
 

T4Man

New member
I have just bought in Sept a 1996 Westy California exclusive with a high top. Recently to my suprise and I think the dealers I found there was a solar panel on the top of the roof to the rear of the air vent.
Can anyone tll me or guess what the panel charges and also how can I check if it is working.
Thanks
 

Capt. Mike

Moderator
I've been through the Eurovan wiring part of the Bentley up through '99 and can't find any reference to any sort of solar charger or option. It must be an aftermarket installation. My mother's 2003 Jetta TDI came with a solar battery charger (portable to stick to the windshield or back glass.) It only produces 3.2 watts, hardly enough for more than keeping the battery up. It plugs into the cigarette lighter, but one can be permanently wired to the battery with no ill effects.

What you might do is park it out in a bright sunny day and measure the output if it is not imprinted on the panel itself. That will give you some idea of what the previous owner might have put it in for. Most that small are only good for keeping a charge on the battery or perhaps a converter for something small like a computer. You might have something already installed to keep your auxiliary batteries topped off. Or it might be wired to a 2nd cigarette lighter or power plug. Look for connections. Per above, do the math -- see what it can accomplish.
 

icarus

Moderator
Solar panels output are rated in watts. Disconnecting a panel from a load such as a battery being charged (in full sun) will give you the open circuit voltage, Usualy 16-18vdc. To deterim the capacity of the panel you have to measure the AMPERAGE output under full sun.

To get an you and idea of capacity, a 12"x12" panel is about 10 watts. In our remote cabins our big panel arrays are 24"x36" and they put out about 60 watts in full sun, properly oriented. Under IDEAL conditions a single panel will put out under 5 amps. You can easily see, (as Capt. Mike says) if you do the math, a 5 amp charge over a long day is a lot of watt hours of charge capacity. But contrast the 5 amps with the 90 or more the alternator puts out. Running a big stereo with amp and ipod can draw as much as 10 amps, so you can see that solar panels are an expensive add on for little practical gain. I agree that if you stay in one place for long periods of time they are great idea for certain applications, but for most of us they don't make much sense except to keep the battery up.

On another soap box however, the idea of installing them on our houses to reduce the demand on the grid is a great idea, and getting cost effective, even with the minimul tax credits available. We live several months a year in a remote site, with 63 watts of panel, 400lbs of batteries and have all the electricity we need to run needed lighting, satelite internet system, voip phone and laptop charging. (No tv helps) It is remarkable how little you can get away with using effeciant compact flouresents and not wasting. Enough soap box, sorry Mike,

Icarus
 

Cobmojo

New member
I contacted gowesty about them selling a solar panel and they just sent me this - oct. 18 2006

"It's in the works! We have installed several kits here, and are working on installation instructions. The kit should be on the site by the end of the year. The 50W system will include a high quality "no glass" RV panel with aluminum frame, charge controller & mounting feet/hardware and wiring. It is going to retail for about $495."
 

rturenne

New member
Can I safely charge an auxiliary battery using the alternator and a solar panel at the same time?
I use an auxiliary battery in my Westy (1985 Canadian Westfalia). It is used to power the radio, interior lights, sink pump, and other 12–volt accessories such as fans, laptop computer, etc, but NOT the fridge which is on the main battery. It gets recharged by the alternator when the vehicle is running. I have just installed a 15-watt solar panel on the roof to provide charging when the vehicle is stationary for several days. I also installed a battery charge controller between the solar panel and the battery to prevent overcharging from the panel.
When the vehicle is running, the battery would be getting a charge from both the solar panel and the alternator. Can I safely do this or do I have to disconnect the solar panel every time I turn on the engine?
The instructions for the controller state that "when the battery reaches 14.2 volts, controller will cut out voltage thereby ensuring no overcharging." The voltage regulator in the alternator exists to prevent the alternator from overcharging. It would therefore appear that there are safeguards from each of these charging sources to protect the battery. However, the solar panel instructions state: "please make sure that this panel is not in use while you are using the vehicle." But why not? Am I missing something? The solar panel specifications also states: "this solar panel has a built-in blocking diode that protects the battery from reverse discharge."
All that leaves me somewhat perplexed. I want to avoid having to unplug the panel every time I start the vehicle. But can I safely do so?
Thank you for your help.
Roger Turenne rogerturenne@shaw.ca[/email]
 
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icarus

Moderator
Having built several solar systems I have a bit of experiance. In a genaric sense, there should be no reason to have to disconnect the controler/panel when you charge the battery from an outside source, be it alternator or battery charger. Most charge controlers are designed to be wired in along with another charging device. Having said that, the admonision not to use the panel with vehicle connected is somewhat mysterious. I would contact the panel/controler manufacturer for more information.


Icarus
 

jerepowers

New member
Solar chargers don't have to be expensive. On eBay several people sell genuine VW solar chargers for as little as $30 delivered. These are 4 amp models. They are quite small and easy to store. Most come with suction cups to stick to a window on the inside. They then just plug into a cigarette lighter socket.

Just type in "VW solar charger" into the standard search box on eBay. I had 27 come up on July 10, 2007.

My biggest problem with a solar charger is that you have to be in the sun. I go out of my way to move the Westy OUT of the sun because I would rather have a cool night's sleep than an hour more of music, light or whatever.
 

itlives

New member
Those little ones are only good for trickle charging the battery. That's ok for your start-up, but usually the reserve battery uses more energy for longer periods of time.
I take enough wire attached to the panel to follow the sun around with my 55W panel. I camp in Arkansas where I like to park in the shade. While it is a pain to keep moving the panels , I have never run out of power in the battery(s).
 

Capt. Mike

Moderator
Install solar panel wiring?

Transferred to consolidate same topic.

surfcasa"]surfcasa Junior Member

I'm getting ready to install a 23w solar panel in my 89 Vanagon and am trying to get info as to where I should plug the incoming electrical from the panel. I've been advised and also advised against plugging it into the fridge relay. Anybody w/ suggestions or advise on where to find a wiring schematic and where I should bring it in?
 
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Capt. Mike

Moderator
Insufficient information. What are you trying to accomplish? Just to power the fridge? If so, have you done the math? 23W will not power the Vanagon fridge on DC. Do you have an auxiliary battery? Are you trying to recharge it or the main? Please go back and use the edit button on your original post and update. (I will then delete this response.) The VW wiring diagram to help decide where you want to hook-up the solar input is in your Bentley. The wiring diagram for an auxiliary battery with charger from the 120v AC shore power is shown in the Tech Drawings.
 
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cocodc2

New member
What voltage solar charger would be sufficient?

What voltage, or more significant power rating, solar panel charger would be sufficient to maintain the main, and only, battery for a week of parked camping with minimal incandescent light use, moderate (1-4 hr) stock radio use, and fridge's exhaust fan in 100 degree plus temps as the only draws from the battery? Will be using LP for fridge cool.
If using previously mentioned "start up engine when getting low on charge" method is used, what amount of idle time is sufficient to charge the battery fully?

cocodc2
82 Vanagon Westfalia
 

Capt. Mike

Moderator
Do the math for me.

:( I can't say it often enough, "Do . . . the . . . math!"

To refresh: W = A x V. An AHr is one Amp for one Hour. A typical battery is rated at 72 AHr.

You say "minimal incandescent use"; which is what? The door dome light (per owner's manual) is 10W = .83A. The cabin is 3 x 10W (2.5A). Between set-up and the usual ins & outs, the front doors will end up open an hour a day and the cabin light ~3 hours, more if you're a nightowl. That would be 10A x 7 days ≈ 70Ahr.

Fridge fan -- don't know Dometic's but the typical replacement (from Internet fridge vendor parts catalog) is .4A. In 100°F days, it will run how long? Go time yours on a hot day -- see how much it cycles per hour and do the math! Let's guess at 50% ≈ 35Ahr for the week.

Stock radio? Which is what? AM/FM?; Amplified speakers or not?; Or w/ Cassette, which add a HUGE load with the motors? A quick Internet search gave us 8W for the typical car radio & 35W for a CD player. Bare bones -- not street thumpers. I don't know if VW ever published any specs but YOU can measure your radios consumption with a the typical multimeter. Only you know what your use will be but let's guess you keep it down (Power consumption is directly proportional to volume) and don't use the casette. 8W = .67A x 4hr x 7d ≈ 20Ahr.

So far we're at 125Ahr or 18Ahr per day. Without the clock, glove box light, or plugging anything into the cigar lighter. You need 18Ahr of recharge from your solar every day. That's ~225W-hr per day. Divide by hours you can guarantee full-power sun and you have capacity needed. Whoops, what if it's cloudy, or raining, or you're in the shade of big trees much of the day? Camping World's 15W "Sunforce battery charger" solar panel is 42½" x 16" and is advertised at 15W/1A for $198. Their biggest folding portable is 12W/.8A; it takes 3 hrs. to charge a cell phone. Their 80W kit ($700) puts out 80W/4.67A -- sounds like plenty on 4 hours direct sun per day. But at 47¼" x 21", where & how are you going to mount and protect it.

Your alternator is 65A @ 3000 RPM, unless it's been upgraded to the 90A unit that began with the '83 models. Even at idle, it should put out ~20A. Idling one hour seems like it should do it? However, recharge depends completely on your battery & condition. Go get a Specific Gravity tester -- one that actually gives the numbers. And test it! Recharge the battery to full. Read the SG. Draw the battery down to 12V by leaving the lights on a while (which will also activate the red warning light on the LED panel), measure SG. Then see how long at idle it takes to recharge back up to that original full SG.

I've got nothing against solar panels. I think they can supplement battery life. Actually have one myself, a little 'battery maintainer'. But they are not some magic cure-all! Considering their cost, why aren't you looking at an auxiliary battery, discussed in detail elsewhere on the site? Why haven't you changed to a flourescent cabin light? It puts out the same light at 8W (.67A) as the 3x10W factory. And why not take a Walkman if you've got to have noise in the woods. That way you won't be irritating the neighboring campers either.

Every one of these are at best, S.W.A.G. -- with less info than you have or can readily obtain. Do some actual testing & measuring under your circumstances. Then I repeat :rolleyes:, "Do the math!"
 
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icarus

Moderator
PV solar

I wrote this out before and the ether has eaten it. Perhaps it will show up somewhere else.

So lets try this again! As the good Captain sez,,,"Do the math!" Let us start with a some basic assumptions and a bit of a primer about solar panels. In addition to doing the math on the load side, you have to do the math on the PV side. Solar panel output is rated under what we call Standard Test Conditions, or STC. This is so that one panel can be compared to another. In addition to the voltage and the amperage of a panel, it has to be compared with similar sun and similar temps. Contrary to intuition, PV panel efficiency drops off considerably as the PANEL temp rises. My panels put out way more than their ratings at -40, but way less at +80f. The average panel is rated at ~80% at STC In addition there are battery charging losses that are not insignificant. The rule of thumb is that for every amp/hour (ah) you take out of a battery, it takes ~1.25 ahs just to stay even. (the perkett effect?) Solar panels are constant voltage (relatively) devices. They operate at a fairly constant voltage, with the amperage (current) changing according to sunlight conditions. As such there is another considerable loss to calculate between the PV panels STC output voltage, ~17vdc for a 12 vdc (nominal) panel. The voltage above the battery voltage is lost. Add in charge controller losses, wiring losses etc, and you end up with a REAL panel output projection.

So lets take all this, and use real numbers. Lets say for the sake of this conversation you have a 100 watt, panel. In general we consider anything above 50% to be doing well, that would be 50 watts of output. Let's see how we get to that number. 100watt panel @ 80% efficiency=80 watts, charging efficiency 80 watts@ 80%=64 watts, controller, wiring losses, say 5%= ~60 watts. Still not to bad. (The numbers are technically different if you do the math in a different order, and in fact the charging ef should come last, it will make the numbers worse, but I'm tired of writing). Now consider this, if you have a 60 watt, 17vdc panel, would put out ~3.5 amps right? But wait, it is not putting out 3.5 amps into 17 vdc, but rather 12.? -14.5 vdc. So at 12.6 vdc (full charged battery at that same 3.5 amps would only be ~44 watts!!!!. This is because the panel cannot compensate for te battery voltage that is lower than the STC panel voltage. There are expensive MPPT controllers that can help this, but you can never eliminate it, and they are expensive for such a small installation. (BEWARE BZ PRODUCTS!!!)

So now you are left with a 100 watt panel that really only puts out 44 watts. Getting pretty shaky. Let's see what we can do with these 44 watts,,,,oh wait, we have to factor in what happens if we have less than perfect solar conditions. A clear, cold day might produce the 80% STC rating. Now factor in warm weather, haze, normal stuff AND most importantly on a mobil mount, and that my drop off to nothing. Lets be generous and say 80%, so now our panel is down to ~35watts. One important thing to note is that even the simple shading of part of a panel by a branch for example, can drop the panel output to near zero. This is because most panels are wired in a series, or series/parallel array. Any shading on any individual cell will serve to block the entire series!

So now we have our 35 watt (net) panel up and running what can we do with it 35watts divided by 12.6 volts equal 2.77 amps, under all the conditions set forth above. Give an average of 4 hours of sun a day (remember, if the panels are not at right (and correct!) angles to the sun, their out put will drop substantially, so if you are not going to re-aim your panel every 15 minutes you should count on 4 hours). 4 hours times 2.77 amps equals a whopping 11 amp/hours of charging, or put another way, enough to run a good cd player radio for ~10 hours! Put another way, it is about the equivillent of running the 90 amp car alternator for ~ 6 minutes!

So, long story short,,, Do the math.

If you take the the OP's ~20 watt panel, you could run the radio for about 3 hours.

Icarus

PS I'm still lurking about, even though I am not as active as I was in the olden days!

PPS. Just so that I don't give the mis-impression that solar energy is a loser. Quite the contrary. I am whole hog into and Pro-solar, but in this context it pays to "do the math" A modern grid-tie PV system of 2kw or better can under good site conditions yield efficiencies of 80-90%. The rub comes in when you start adding batteries. The cost of the batteries roughly doubles the cost of a stand alone system. ( a grid tie system needs no batteries, AND through MPPT (Maximum Power Point Tracking) inverter technology can convert to grid voltages/phases with efficiencies better than 95%). The scale of the loses is way less as the system size increases.

Point of fact, grid tie systems can be ALMOST competitive with grid power under ideal circumstances. (not the least of which is the political climate for energy policy). When you see the price of grid power double in the coming few years (as it has with most energy!) then it will become competitive in most areas of the country. If you are interested in reading more, I invite you to visit http://www.wind-sun.com/ForumVB/index.php. This is a forum for users and those that are interested in building systems and learning, a forum that I am fairly active in.

Just for another comparison. I live ~ 6 months of the year on a small island in Northern Canada. We live completely off grid. Our solar system is tiny by most standards. 200 watts of panel, 500 amp hours worth of batteries. We use about 30 ah/day,,,360 watt hours! That for all lighting, water pumping, radio, satellite internet,,,no TV though! Just shows you can live well with little energy use!

T

T
 
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Capt. Mike

Moderator
Solar Panels

JohnB
user_offline.gif
Administrator

I would love an option of a solar panel roof. On my '81 westy I am going to install two 120W panels to charge he three auxiliary batteries I have and it is important that the panels must have some power to them, something around 200W or more. JUst having a solar panel on your car seems so awesome. In this digital age electricity is a must and you must also have more than one battery or maybe even two or three. additionally, built in inverts would be a must.
 
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icarus

Moderator
Inverters

Beware of inexpensive 120vac inverters. Most inexpensive inverters use modified sine wave technology, as opposed to the true sine wave form we get from our line voltage.

The problem with MSW inverters is they are not very efficient, AND, the wave form can damage a number of things, including, but not limited to battery chargers for computers and power tools, some electronics etc. It can be a very expensive lesson. True sine wave inverters are significantly more expensive than MSW units. This is a link to some information on various types of inverts:http://store.solar-electric.com/inverters.html

Icarus
 

mbecherer

New member
Inexpensive 60 Watt Panels

This is all fantastic information. I have really learned alot, especially relative to "doing the math". A big thanks to Capt. Mike and Icarus for the detail.

I am looking for a solar panel to charge an auxillary 44ah battery on my Westy. Having "done the math" I understand that I can't go hog wild with electircal usage, but I want something that will give a little extra "oomph" during longer campouts next summer.

I stumbled across this the other night. It seems like it is priced significantly less than other panels with similar output, and assuming that you get what you pay for, can anyone tell me why this is so cheap? Is there something about the materials or technology used that makes it inferior?

http://www.cabelas.com/cabelas/en/te...set=ISO-8859-1
Thanks,
Matt
 
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