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Author: Subject: Let's talk solar panel on an RV
Hook
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[*] posted on 12-16-2007 at 08:25 AM


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Originally posted by jorgie
It's still early....yawn....Trojan L50.....60db means deeper hole to baffle the noise, a bit ply to deflect it.....my 104 watt solar keeps the 2x12 marine batts in good shape but at 92 amp/hrs/wk each they are too light for some useage but have kept the batts at 12.79 volts for over a year . If I could lift a L50 I would buy 2 .....196 lbs each...ouch.


Trojans....Spartans.........an easy mistake to make, if you know your Greek history and it's early. :lol:

My draw would be about 92 ah/DAY, running the freezer!

I am going to experiment with bringing a plastic doghouse, modified for more ventilation and maybe some Sonex on the inside walls and ceiling. I can carry this with the genny inside on a Hitchhaul up front or in back. That's where I carry the genny anyway. One of those plastic DH with the removeable roof.




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[*] posted on 12-16-2007 at 08:37 AM


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Originally posted by grover
There must be a good reason for all this screwing around to avoid using propane.

:?::?::?::?:


Have you priced the propane freezers of a portable size? There's your good reason. The cost is approaching the solar setup......but at least the solar gives you other benefits. Plus, you can put an electric one just about anywhere in a rig.




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[*] posted on 12-16-2007 at 10:49 AM


To get a true feel of what you need, you first have to calculate what your total daily load is. This calculation has to include a "Demand Factor" (DF), that takes into consideration how many hours a day that the load unit will be on or running.

For example, a small refrigerator/freezer is given a 75% DF by the National Electrical Code 2008 (NEC8). That is, the compressor is only running 75% of the time. Also, small refrigerator/freezers are rated at about 300W but you're better off using nameplate data if available.

This DF has to be applied to all your loads that are not considered "Continuous".

For convenience, a lot of the battery and solar websites offer on-line worksheets to do the calcs for you. One of these is Oasis Montana

Suggestion, If you're doing your own calcs, do everything in Watts, then convert the final results to A/H. Watts are not affected by the voltage, If your calculating the loads for AC equipment that will be powered by an inverter, the Watts are the same at 12V as they are at 120V. You do have to factor in the efficiency of the inverther though.

You should also calculate the recharge time/rate so you know how long it'll take to restore your batteries. If your solar system can't recharge the battery bank in 8 hours AND supply the daytime loads, then you're going to end up running the generator every day anyway. Which kinds of defeats the whole solar idea, doesn't it.

As a retired electrical/electronics systems designer, I'm here to tell you that this field can get very complex very fast if you let it. And it's easy to overlook something.:o

But for a simple truck camper, you should be able to handle it. Just do a little research on the web and make use of the tools that are offered. Just google "Calculate Battery Loads" and you'll be surprised at the stuff you find.




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[*] posted on 12-16-2007 at 11:09 AM


I thought maybe it was clear that I have made an energy audit (your DF) in my post that started with "reality setting in". 93 ah/day is what I might conceivably draw, running the freezer. Less than half that w/o running the freezer.

With a 120 watt panel (the largest I can accommodate on the roof), probably the best I can realize is about 30-40 ah/day of charging. Less than half of my needs and I would still be drawing that load the following day so there would be no replenishment.

The genny is really a must with the freezer.

I need to rethink how valuable that freezer actually is. It's best use is in freezing fillets for returning "home"; whether that be in Mexico or the US. But, realistically, I dont start accumulating fillets until the last day or two before I return. And the whole time I am returning, I am charging the battery and running the freezer off the alternator.

Maybe I need a bigger RV. :yes:




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[*] posted on 12-16-2007 at 11:16 AM


Hook - I'm with you on the uncertainty for a need for a freezer to take fish 'home'. For me, the drive home is two 10 hour shifts which mean that the fish were caught the day before I leave - what's the point? The only use would be to freeze the fish on the way home and let your vehicle recharge the battery. Anyway - you have a built in excuse to go fishing if she-who-must-be-obeyed wants fish for dinner.;D
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[*] posted on 12-16-2007 at 11:25 AM


Hook
Like others have noted I think your a little light with one panel. If you do go ahead with the do it your self plan. M.E.C.S. Solar had a complete RV kit with great step by step instructions,when I did our camper a couple of years ago. A word of caution,if you put additional batteries anywhere but in a seperate battery box,make sure you enclose and vent them to the outside. The fumes are corrosive and can be explosive.Good luck.
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[*] posted on 12-16-2007 at 02:24 PM


Roger, I do already have the standard, built-in Dometic in the camper. It's just got such a small freezer. Really only accommodates a single, 1 gallon ziplock with ice cubes, a quart of ice cream and a fillet or two IF they are not too big.

Oh yeah, and one Frosty Paw that always seems to have to come.

My Norcold electric is for more freezing capacity. About 45 quarts more.




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[*] posted on 12-17-2007 at 07:57 AM


PJ, the other option, which I have used a lot of times, is to max out the refrigerator for the trip home. I set it as high as possible and I have turned the whole refrigerator in to a freezer. Not very good for keeping lettuce but most of the other things do quite well and the fish definately gets beyond crystal stage and while it may not be at minus zero, it is definately cold enough to make the 5 day trip back to Colorado. Coke and beer on the bottom shelf would stay slightly above freezing as long as they did not spend the night in the fridge.
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[*] posted on 12-17-2007 at 09:52 AM


What year is your fridge, Jim?

Mine is the original from 93 and it's acting like I need to do a flue cleaning as well as service the burner and jet. Havent done that since I've owned it for 3-4 years.

I've never been able to get it as cold as you are talking while on the road. In camp, yes. I've always suspected it's due to wind affecting the flame. I have the aftermarket door for the outside enclosure. But the best I can usually hope for is about 40-45 degrees below ambient temps.

Tell me about your battery system. Have you figure out an easy way to go with 2 6v batts or are you using a single in the compartment?




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[*] posted on 12-17-2007 at 09:58 AM


Quote:
Originally posted by Pescador
PJ, the other option, which I have used a lot of times, is to max out the refrigerator for the trip home. I set it as high as possible and I have turned the whole refrigerator in to a freezer. Not very good for keeping lettuce but most of the other things do quite well and the fish definately gets beyond crystal stage and while it may not be at minus zero, it is definately cold enough to make the 5 day trip back to Colorado. Coke and beer on the bottom shelf would stay slightly above freezing as long as they did not spend the night in the fridge.

Sometimes you just have to say "Damn I knew that" when someone jogs you pea brain...Refers work from top to bottom...Just partition off a section up top with cardboard with two holes in center back and you have a new freezer compartment. the things below the cardboard will not freeze.




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[*] posted on 12-17-2007 at 05:23 PM


Quote:
Originally posted by Al G
Quote:
Originally posted by Pescador
PJ, the other option, which I have used a lot of times, is to max out the refrigerator for the trip home. I set it as high as possible and I have turned the whole refrigerator in to a freezer. Not very good for keeping lettuce but most of the other things do quite well and the fish definately gets beyond crystal stage and while it may not be at minus zero, it is definately cold enough to make the 5 day trip back to Colorado. Coke and beer on the bottom shelf would stay slightly above freezing as long as they did not spend the night in the fridge.

Sometimes you just have to say "Damn I knew that" when someone jogs you pea brain...Refers work from top to bottom...Just partition off a section up top with cardboard with two holes in center back and you have a new freezer compartment. the things below the cardboard will not freeze.


You know, that is REALLY not a bad idea to try. I could maybe remove the freezer door, temporarily, to let the cold travel farther downward. This might be practical for the drive home when you're down to almost nothing anyway.

I love trailer trash type solutions!!!




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[*] posted on 12-18-2007 at 03:38 PM


Hook, I have only used the single 12 volt battery from inception. The refrig is a 2000 which is the year of the camper. If you are going to go through the system, make sure you check water column pressure as most of the older regulators do not put out what they should. There was a post some time ago that referred people to a web site that had a ton of information about the system. I clean the flue once a year with a steel brush, clean the propane orfice with alcohol and then blow it out with compressed air(it is a semiprecious stone so be very careful with it), and check my water column pressure about every year or two. I had to add baffles to my outerdoor to keep the unit from blowing out when I was traveling and I take the baffles out when I am stationary. It is a Dometic unit, which I consider superior to Norcold and the other stuff that is produced out there. We now use it for a back up refrigerator to keep beer in and even in hot weather we are able to stay just above freezing. When I turn it up I can definately get it below 32 degrees and keep it there and Al's suggestion of a piece of cardboard to enlarge the freezer area is a good one.
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[*] posted on 12-18-2007 at 03:43 PM


Pesca, I had to replace the regulator that goes between the two tanks this year. That is the regulator you're talking about? There isnt one inside the fridge compartment, is there?



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