Solar System Advice - Fiberglass RV


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Old 04-09-2003, 10:07 AM   #1
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Solar System Advice

:cool
Bob and I want to get a solar system for our 16' Scamp. We have air conditioning and use some AC appliances, but only when plugged in to shore power. The 12V solar system will be used to run lights, water pump, small .16Amp stove exhaust fan, .5Amp radio, and probably a roof vent exhaust fan (yet to be installed). We are seriously considering a SP75 (4.4A) Siemens panel and plan to mount it remotely on an A-frame.
Now the questions ...
:conf Any opinions or suggestions on solar controllers in the $70-$125 range? We would like a dial or digital readout, and a controller that could accomdate at least one more panel in the future. Prostar 15 and ACS Mark 15 have been recommended.
:conf We have a Centurion 3000 converter in the trailer, what is the wiring sequence to combine shore power and solar power? ie, connecting the battery, converter, and controller.
:conf When our group 24 deep cell stock battery gives up, we would like to replace it with 2 6V golf cart batteries and mount them on the tongue with the dual propane tanks. Anyone else have such a setup?
Any suggestions would be greatly appreciated.
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Old 04-09-2003, 11:12 AM   #2
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Solar

SP75 panel should be great. The one in the photo is an SR50
<img src=http://www.fiberglassrv.com/board/uploads/3e9444afcc310Casita solar panel up.jpg/>


Controllers, I dunno, mine's an el cheapo.
<img src=http://www.fiberglassrv.com/board/uploads/3e94455e9d2ceCasita solar regulator.jpg/>

Wiring: It's suggested the controller is mounted near the battery. Temperature compensated controller is a nice feature.

Wiring doesn't have anything to do with the converter. Ya come off the solar regulator with 2 wires to the battery. Put a fuse in the positive line, run the other direct to the negative terminal. (I also installed an on/off switch for both the solar panel and each battery).

The way I think of it is that: It's still the battery that supplies the power to your devices, the solar panel just tries to keep replentishing what's used from the battery.

Removing the existing battery and installing two T-6s on the tongue will have quite an effect on the trailers weight balance. If you already have two propane tanks, I'd think long and hard about this. I've added one 24 battery on the tongue of a 16. Use a 29 in the trailer compartment. Switch em to use 'either/or'
<img src=http://www.fiberglassrv.com/board/uploads/3e9445a3e5aaeCasita Battery on hitch.JPG/>

One Casita owner has installed two T-6s inside, under a bench. Thats the only conversion using two 6v batteries I've heard of.
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Old 04-09-2003, 12:12 PM   #3
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Thanks, Don

Thanks, Don. The photos are especially helpful.
Concerning the battery, the Scamp already has the group 24 battery on the tongue, we would be adding about 70 lbs by changing to golf cart batteries. Our tongue weight has been running around 230 with propane full, so it is a concern. On the other hand, moving both batteries under the rear seat would be an even larger distribution change and we would need to cut a door for access/ventilation to the outside. I dunno ... but we will consider it.
Sure would be nice to have the capacity of the golf carts.
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Old 04-09-2003, 01:01 PM   #4
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Golf Cart Batteries

I would give the use of Golf Cart batteries a lot of thought before I used them. I have a Golf Cart that is 5 years old. The batteries put off a lot of gas and acid out of the vents when charging. The area around the mounting is corroded and the floor under has deposits that fall off. I tried to keep them and the area around them clean with baking soda(which is a neutralizer for the acid) with very little help. The acid has eat through the clamps that hold them down. And the floor where the cart sits is pitted.

If you must use them, I wouldn't consider installing them inside at all. Outside they would have to be in a vented plastic box that could be cleaned each month.

I would rather use gel-cells of some type for higher amperage systems. Because with a lead acid battery this rule applies-- The higher the amperage the more gas and acid vapor when charging. The gas is highly explosive and the acid is corrosive. When I worked for the telephone company the batteries were in a well ventilated isolated area. There was no smoking, open flames, or power tools allowed in the area.

Good Luck
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Old 04-10-2003, 12:53 PM   #5
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Ron, I would suspect that you are overcharging your batteries, esp if you are using an on-board charger and it's not equipped with a very recent smart-charging circuit board. What you described is pretty typical of overcharging a flooded lead-acid battery, regardless of whether it is two 6V or one 12V. Typical charging voltage, applied to a charged battery, will result in gassing and bubbling...

You might want to do some research on gel-cell charging if you are considering a change.

Diane, you might consider AGM batteries as they can be mounted anywhere, even upside down, but they have two main drawbacks:

1. Expensive (very expensive if they fail early); and,

2. MUST be charged properly and not with a conventional flooded lead-acid charger, much less an RV converter like those typically found in our Eggs.

Pete and Rats
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Old 04-10-2003, 10:31 PM   #6
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Diane,

If you add a 75 watt PV array, you should not need the additional storage capacity of golf cart batteries unless you're real energy hogs.

I've had a 75 watt fixed panel on my Casita for four years now and have never run low on power. Our limiting factor when boondocking is the black water tank (17 gallons). That lasts the two of us about six days, then we have to find a dump station.

I mounted the PV controller in the battery compartment because it is temperature compensated. It should be at the same ambient temperature as the battery.

When my original group 24 battery died (because of a converter failure) I replaced it with an Activated Glass Mat (AGM) battery of 85 AH. It is completely sealed and perfectly safe indoors or out. You don't even have to look at it. They're expensive as was mentioned; mine cost US$160. It was well worth it for me.

Some of today's AGM batteries have charge curves identical to flooded lead-acid batteries. Mine is like that. If you get one of those, your converter will charge them without a problem.

I second Ron and Bernice's cautions about lead-acid batteries inside. Overcharging them causes gassing as Pete said, but the bouncing and vibration on rough roads can cause spillage. sulphuric acid is a nasty thing to have in your trailer.

Try your PV array first with your stock battery, I think you'll find that provides enough power for your usage. If not, add another array.

I just noticed you're in Vermont. You might want to start with a 100 watt array. My experience is mostly in the southwest US where sunshine is abundant and not filtered by so much atmosphere. :o
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Old 04-11-2003, 01:33 AM   #7
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Battery Charging

Pet,

I think you misread my post. The golf cart batteries are in my Golf Cart.

Anytime you are charging a lead acid battery it puts off gas and acid vapor. Even if it isn't over charged. You don't notice it so much in a vehicle because of the large amount of air flow through the engine compartment. But in a stationary location like a Golf Cart or a trailer you don't have that large air flow. And that is why you will see more damage in that environment. My Golf Cart has a computer controlled charger that senses the condition of the (6-8volt) batteries and then applies the correct charge. When finished it shuts completely off. It doesn't recharge unless it hasn't been used in 14 days.
This is my second cart with same condition. Everyone I know at the golf club have the same problem.

Lead Acid batteries are just nasty. AGM type are probably a good choice.
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Old 04-11-2003, 09:30 AM   #8
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Thanks for the good responses about batteries. I am now considering a gel-type replacement for my group 24, but only when the current one gives up the ghost. My battery is mounted outside on the trailer tongue, not inside like on the Casita. The controller will be inside about 5 linear ft away, to the right of the entrance door. This location is not ideal for temperature compensation, but the controller can't be mounted outside either.

Concerning the controllers -- I'm planning to order a Specialty Concepts Mark 15. It uses pulse width modulation and has manually adjustable Voltage setpoints. The user manual is available at http://www.specialtyconcepts.com/1-20_frame.html Does anyone know of problems using the Mark 15 with a gel or AGM battery? I don't want to spend more than around $100, but want a versatile controller for at least 10Amps.

I anticipate that most of our boondocking will be done in the Southeast and Southwest between December and April. We've had solar hot water at our house in Vermont for about 20 years. This winter the panels gave us a lot of backup because it was cold and sunny, but many years the clouds and snow really cut down on the output.

Thanks again for all your help.
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Old 05-09-2003, 10:13 PM   #9
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Hi All
I just bought two golf cart batteries(6Volt)I am going to install this Sunday.My next step will be a 75 watt solar panel.I checked out prices the last few days and found all solar panels in my area, 50 watts and over come with a controller.
:wave
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Old 05-10-2003, 08:49 AM   #10
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Panels - Where to buy?

Chester,

We bought the Siemens (Shell) SP75 single crystalline silicon panel and controller from Solarpath Energy Systems in Florida ... over the phone and delivered in 3 days. Phone number is 1-800-222-0017, Ben was quite helpful and was willing to answer all my questions. At the time the panel was on sale for about $100 less than I found it anywhere else, and he offered the controller for slightly less too. We'll be able to get the entire system mounted and hooked up for less then $450.
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Old 05-10-2003, 02:27 PM   #11
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Hi Dianne
Thanks for feed back.I have been doing a lot of research on this subject.Reason being is that this whole exercize of fixing and setting up my Boler has to do me well into retirement.No extra cash for new Fiberglass Unit.
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Old 05-13-2003, 11:03 PM   #12
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Hi All,

I have been using two Seimans 50 watt panels for the last couple of years and have had quite satisfying results both during the summer and during the winter. These panels seem to be a good match with a costco group 24 deep cycle battery. I have never had a problem with being out of charge. (so far, keeping my fingers crossed on those cloudy winter weekend trips)

The 100 watt panel is normally used only on trips of a weekend or longer. I also have a small home brew solar panel (approx 4 watts) that is connected to the system to trickle charge the battary while the Burro is parked. This does two things:

1. keeps the battery happy and stops it from self discharging(prolongs the battery life)
2. keeps the small quiescent current drain (approx 300 uA) from depleating the battery over long times of inactivity.

I am considering installing a 24 volt switcing power supply to the charge controller through a current limiter. The purpose of this is to provide charge current (approx 4 to 5 amps) when connected to shore power. Has anyone else done this kind of experiment?
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