Solar charger, power and panels


Dave in KC

New member
Anyone care to offer suggestions as to how best to route wires into my Westy? I have one fairly heavy two conductor cable (8 awg) for my wind turbine, and two smaller conductors that I need to bring in from my solar panel. The wind turbine mounts on a mast affixed to the left rear corner of the van, while the solar panel will be mounted on the fiberglass pop top toward the rear. Thanks in advance for the advice.

Dave in KC http://members.fortunecity.com/davebaker1
 
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Dave in KC

New member
Well, the panel is mounted. I sure wouldn't have wanted to put anything heavier than the 50 watt unit up there! Still have to see how it behaves on the road. I'm routing the cable down through the driver's side air duct at the top rear of the coach. That gives me a clean shot into the engine compartment where I can go under the body to the cable chase in the battery compartment.

Dave in KC
 

imported_JohnB

New member
Dave,

What was the total cost of each of the installations (solar and wind turbine) ?

Also, if you compare each of them which is the best bet for offering a good charging system for the Westy?

We often camp at Assateague Island where there is usually no shortage of wind, but not too sure about other places where we tend to be surrounded by trees.

John
 

Dave in KC

New member
John,

The Siemens 50 watt RV solar kit came in at $419, including shipping. The cost of the 400 watt wind turbine was around $470. HOWEVER -- The Siemens kit provided everything I needed to get up and running and practically installed itself. The wind turbine, on the other hand, required that I build a control panel with a "kill" switch and circuit breaker. (It doesn't require a volt meter or ammeter, but I built those in anyway to monitor conditions in my charging circuit.) I also put some change (around $50) into the hardware for mounting the turbine. The Siemens kit includes a charge regulator with a built-in voltmeter/ammeter and battery condition light. It is SLICK; however, in terms of cost per watt, the wind turbine wins hands down. The solar kit is much more practical, though. I'll be testing both of them in the field next week and will report on performance on my web site.

Dave in KC
 

Capt. Mike

Moderator
Solar panel for battery

Ken Junior Member # 1014 posted 06-27-2001 01:44 PM

Has anyone installed a solar panel for a second battery in their Westfalia. In our Toyoto camper we used to have the solar panel charged up the second battery..I was wondering if anyone had tried this.......thanks Ken
 
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Capt. Mike

Moderator
daravenh Junior Member # 657 posted 06-28-2001 11:15 PM
The pop-top is not designed for the additional weight of an A/C unit and should not be put on one under any circumstances. (See posts under ACCESSORIES about roof racks!) Besides the fact that the entire pop top is basically attached to the roof with a few sheet metal screws in the two sheet metal hinges, imagine the air resistance of something sticking up, all pulling on one door-latch type clasp in the front. Price a replacement roof and canvas if you think it's worth it.

Regarding your comment as that an A/C unit should not be used on the pop-top -- I have just purchased a solar panel and was intending to have it secured to the pop-top. You have got me worried now! Is this advisable?

With thanks ...
 
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Capt. Mike

Moderator
There is a lot of difference between the 84-110 lb. of an A/C and the 5-40 lb. of a solar panel. But the principles remain the same.

Any holes through the fiberglass top leave a risk of them contributing to cracks & leaks. It will have a significant effect on resale value as a new purchaser will not appreciate having holes in the roof and the visible damage underneath.

Although a small unit like the battery chargers up through about 15w units are probably within the load abilities of the roof itself, the precaution of not having any wind lift or effect while underway remains. I'd be sure the mounting has no lift, perhaps even negative pressure (slight slope to front).
 
W

willy

Guest
I would like to place a Siemens 50, 75, or 100 Watt RV Solar Panel in the luggage rack on the front of my '80 Westfalia. I don't want to secure it there, I'd like to bring it inside when I travel and only put it out when I am camping. Are there problems with this arrangement?
 

Capt. Mike

Moderator
Willy & Dave in KC: I'm not a big fan of drilling holes in the body but you might want to consider a permanent pigtail. Whether installed through a waterproof grommet in the body, or some arrangement that comes out the bottom near a bumper or from under the pop-top, if you wire internally to a weather resistant plug and have a matching socket on the solar panel, you should be able to connect & disconnect easily. I have weather resistant pigtails for block heaters on 3 vehicles (including the Westy) and haven't had a problem. Once connects behind the bumper; a 2nd behind the license plate and the third just sticks out near the grill. The latter gets the full impact of driving in rain, snow & freezing weather with no more protection than it's cap, but has worked like a charm for over 100,000 miles.

See the above posts about size & weight, since you'll be putting it up on the roof and back down every night.
 
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A. Cooper

New member
I'd like to purchase a solar cell to help replenish my auxiliary battery while parked, and would like help in determining my power requirements.

My auxiliary battery is used only for running the fridge (Dometic RM128) in my 1983 Vanagon Westy. I'm not powering a big sound system, laptop computers, planet-tracking telescopes, or margarita blenders -- just the fridge. I realize a practical-size, compact solar panel probably won't provide enough power to run the fridge perpetually; I just want to extend the duty cycle of the auxiliary battery. Is it an accurate assumption that if the unassisted battery would typically run the fridge, say 3 hours, then a solar panel which provides even HALF the fridge's consumption rate would extend that time to 6 hours?

Obviously, if I knew I'd be away from the van for that long I'd simply switch the fridge to LP. But if an unexpected delay comes up, the extra battery life would be helpful. And a typical day of start-and-stop sightseeing can add up to several hours of battery drain which may not be recharged by the short drives in-between.

One affordable solar unit I've seen lists its power output as 1.8 Watts, and 125mA per hour at 15 Volts. Another claims 5 Watts and 350mA per hour at 15 Volts.

How is the fridge's power consumption measured: Watts, or Amps per hour? And how does one translate this into power output of a solar panel?

How would these solar panel examples perform for my intended purpose? And since these are trickle chargers, intended for battery maintenance, would their 15-volt output damage the fridge circuits?
 

Capt. Mike

Moderator
Down in the FRIDGE forum there's a topic on DC fridge consumption. Dometic is remiss in publishing any tech data, even in their own OE installation & operations manual. That posts quotes RV Mobile as saying 3-6A depending on model and Norcold's equivilent fridge as 3.1A.
Another post says their efficient ceramic units draw 50 watts = 4.1A. (So figure 4 because the math is easier!)

That still doesn't look good from the math point of view. At 4A, the 72Ah OEM battery should go 18 hours. HA!!! How about 6 if you're lucky. So you see a 5W/.35A solar won't go very far.

Now that I've rained on your parade, the good side is that the solar will charge 100% of the time in sun but the fridge only runs part time. That would depend very much on your use and ambient temperature but I'd suspect 25-33% cycle time (after it's completely precooled). That would be an interesting experiment -- putting an ammeter on the circuit to see how often and how many amps it really draws. Next time I'm doing my monthly maintenance run -- which takes 2 months to get to -- run I'll try that! Remind me -- half-hiemers has set in.
 

A. Cooper

New member
Lemme get this straight: if the fridge draws, say, 4 Amps, then a solar cell which produces 350mAh (.35 Amps) will provide less than one-tenth the total power requirement? Yikes, that ain't much at all ...

But your point is well taken regarding the intermittent nature of the fridge. So even a compact solar cell should offer some long-term power assistance while the fridge is operating on 12VDC, and definitely during those times when one is parked and running on LP or 120VAC.

Assuming the sun is shining ...
 
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flyingms

New member
You hit the nail on the head. The time element is the key. If you store your PV energy (over time) in a battery you can use the energy (at full voltage) for short durations. The figure AH (Ampere Hours) is basically a capacity. A device that draws 1 Amp will run for 4 hours on a 4 AH battery. As Mike illuded, that is not always the case. Other battery factors like internal resistance, temperature, age ... work against the
published capacity of a battery.

You are correct that the PV array is only capable of supplying about 1/10 th of the refrigerator's
load. But, considering time, you can get about 6 minutes of run time for each hour (60 minutes)
of solar charging.

You may not need a whole lot more..
 

A. Cooper

New member
So if Capt. Mike's estimate is close, that the fridge probably runs only 30% of that hour -- or 18 minutes -- and the solar panel provides 6 of those minutes, then the auxiliary battery need only provide the remaining 12 minutes of power. So the net result is that the solar cell is providing fully 1/3rd of the total power requirements, right? Geez, that ain't so bad...

As you and Mike point out, there are a lot of variables in weather conditions, battery strength, etc., but a 30% extension of the auxiliary battery is pretty good.

Lemme know how your experiment goes Captain, the results could be very informative.

Thanks for all the help, guys!
 

flyingms

New member
Exactly, PV arrays are spec'd at certain conditions. Usually the term "1 Sun" is used. That means on a nice crisp clear day at 12 noon, your array if placed on the ground (read perpendicular to the sun) would give you the 350 mA of current. Of course, clouds or haze will scatter (diffuse) the sunlight and result in a lower output. There are days which scattered or partly cloudy conditions prevail (usually around a cold front or a day or two later). The tall puffy white cumulus clouds are good at reflecting sunlight onto your array and achieve more than one sun of output. On the other hand, when your array is in shadow, output drops. Nothing is ever straight forward. Don't forget moon light. On a crisp clear full moon night (read cold front) you will see actual PV current flow. Even more if you are parked under one of those high output sodium vapor street lamps
 

pherrman

New member
CATCH-22! One other thing to consider, although you would want to be parked in the sun to achieve high solar charging output, at the same time, you're heating up the bus interior (ALOT) and thus making the fridge work that much harder. I suspect in the end you'd be better off saving the money and parking in the shade.
 

Capt. Mike

Moderator
Well said! No matter how many times I've said it, "Do the math," nobody listens -- they think solar is free. If they would do the electrical math, the BTU math and the dollar crunching, most would give it up -- no free lunch. If solar was cheap & easy, it would be a factory option. Even now I only see it for available on new cars for trickle charging batteries. To get into the big amps for fridge, etc., you are talking some huge solar panels. Not to mention weight, space, engine load.
 

uktim

New member
hello to all from the uk
i have read this discussion with interest, and looked at dave kc's web site.
i would like to add 2 thoughts to the discussion.
1. i have used my 1980 westy for a window cleaning business for a few months and now have found a crappy ford fiesta to use, but in those few months we carried large and heavy ladders on a roof rack attatched to the fibeglass elevating roof and no harm came to it. i doubt very much if the solar panel was anywhere near the 50-60kg that the ladders were, or if they caused the same wind resistance, so i would have no worries there
2. capt mike says do the maths..and i couldn't agree more, however what price a cold can of beer over a hot one when you're at the perfect beach/mountain range/whatever?

tim
 

icarus

Moderator
I can see the value of a solar panel for keeping the battery(s) up for interior lights when you don't travel on a daily basis, but not for running the fridge (amps, amps, amps) Why do people have such a big hang up lighting the fridge on l/p? If you have been running the fridge while underway, In 30 seconds after stopping it is fired and running on l/p.

I don't even have a second battery installed. I don't generaly stay in one place for more than a day or two. I have found with flouresent kitchen light, and the 5 watt dimmable reading lights (see lighting posts) I ahve never had a problem with the one battery.

I prefer not to have the weight, plus the second battery box under the seat, carries most all the tools, (In small rubbermaid fridge boxes), the bentley, as well as other manuals and assorted small parts. If I spent multiple days in one spot on a regular basis I would consider a 40-60 watt cell, perhaps instead of a second battery. If all you are running are the lights for a couple of hours, a bit of water pump, a cell can put back enough almost every day what you are likely to take out. In a normal night I have never drawn the one battery down below 12.3 volts in one day of camping

Icarus
 

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