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Old 11-28-2005, 05:22 PM   #1
tonymessana
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Question Generator and Solar Panel

First thanks everyone for the information on this forum it has been very helpful to us new TM owners. Couple of questions. First we have a 70W solar panel and two 6 Volt batteries. Being out twice camping we seem to been not charging very much. We are going up about 50% from morning till evening from where we started even when using minimal lights and radio. We are thinking that we may have a ground somewhere. Any thoughts on if we are on the right trail and if so where to begin on checking.

If this does not work out we are thinking of getting a small generator to assist in this effort.

We have a 2005 2619 and love it so far except for this power issue. Any help would be greatly appreciated.

Tony
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Old 11-28-2005, 08:34 PM   #2
Paul_Heuvelhorst
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Tony,
You haven't given enough information. However, let me try to explain as best I can from the information you have given. I assume when you refer to 2-6 volt batteries, you are referring to deep-cycle batteries wired in series to produce 12 volt output. With this assumption, the following results will vary with the specs of the batteries:

70 watt solar, at max. output will charge the batteries at the rate of 5.8 amps per hour. So, given 12 hours of daylight, the solar panel should be putting approx. 70 amps/per day into your batteries. If your batteries are each rated at 225 amp/hr, you have 450 amp/hrs available, but you are only charging them at the rate of 70 amps per day.

Check the rating of your batteries, and if they are rated at less than 225 amp/hr the charge ratio is better, but still not enough to fully charge them. At the rate your solar panel is charging (at max. output) it would take approx. six and one-half days with NO LOAD to recharge the batteries fully. Please understand, if the daylight is subdued, your solar panel will not operate at its maximum capacity, so the charging rate would be less. Does that make sense?

If your batteries are fully charged (by your tow vehicle) when you arrive at camp, and you use no more than 5.8 amps per hour, then your batteries will not run down. However, if the fan for your heater comes on, it is using more than 5.8 amps per hour.

The solution to your dilemma is to (1) get more solar panels to improve the charging capacity, and/or (2) buy a generator to charge the batteries. Two more solar panels would produce about 17 amp/hr charge, which may meet your needs. You mention you use minimal lights and radio, but it would appear you are draining the batteries faster than that. How many lights do you have on at one time, for example? Each lamp draws at least 1.5 amps, or more.

I hope this helps you chose the right solution to give you the camping enjoyment you desire.
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Old 11-28-2005, 09:00 PM   #3
tonymessana
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Paul,

Your explaination was very helpful. We are using two 6 volts to produce 12 volts. This trip we did use the heater fan one night (temps approaching 40 degrees) a few times to keep things warm. At most we did use a couple of lights at one time but some other thing may be adding to our situation. It sound like a small generator to replenish the batteries in addition to the solar panel is the answer. I am a little miffed with the dealer who said that the solar panel would be able to replenish the batteries in one day. That is not necessarily the case. Will keep tweaking our use of the batteries but your comments are very helpful. We are thinking of a Kipor generator which sounds similar to a Honda/Yamaha but wanted to get other thoughts.

Thanks

Tony
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Old 11-28-2005, 09:04 PM   #4
RockyMtnRay
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Default Amp hours of capacity don't double with 6 V batteries in series

Quote:
Originally Posted by Paul_Heuvelhorst

70 watt solar, at max. output will charge the batteries at the rate of 5.8 amps per hour. So, given 12 hours of daylight, the solar panel should be putting approx. 70 amps/per day into your batteries. If your batteries are each rated at 225 amp/hr, you have 450 amp/hrs available, but you are only charging them at the rate of 70 amps per day.

Check the rating of your batteries, and if they are rated at less than 225 amp/hr the charge ratio is better, but still not enough to fully charge them. At the rate your solar panel is charging (at max. output) it would take approx. six and one-half days with NO LOAD to recharge the batteries fully. Please understand, if the daylight is subdued, your solar panel will not operate at its maximum capacity, so the charging rate would be less. Does that make sense?
Paul,

While I totally agree with most of your analysis, there is one rather large error in your math. Specifically, when batteries are connected in series (as is done with a pair of 6 volt T-105s) , the total amp hours of the pair won't exceed the total amp-hours of the lowest capacity battery since all the current has to flow through both...and when the lowest capacity battery is exhausted, the total voltage drops very rapidly. Therefore Tony's max capacity is 225 amp-hours and his time to recharge fully depleted batteries with a 70 watt panel is around 3 days of full sunshine.

Only if he had a pair of 225 Amp-hour 12 Volt batteries connected in parallel, would he would have 450 amp-hours total.

Quote:
Please understand, if the daylight is subdued, your solar panel will not operate at its maximum capacity, so the charging rate would be less. Does that make sense?
This, I suspect, is the chief problem. Although I have a 2 panels totalling 170 watts on my TM's roof (a 120 and a 50), I've found that unless the entirety of a given panel is in full sunshine, the output drops off to nearly nothing (maybe 1 amp). Even a single branch of a pine tree that shades as little as 10% of a panel is usually enough to almost totally kill output from that panel. Similarly, even thin overcast, much less a full fledged cumulus cloud, will cut output by 50% or more.

Accordingly I count on only having 3 to 5 hours of full, unshaded, unclouded sunshine a day...and I camp in a very sunny state. And I also try to choose campsites that have little to no morning or even mid day shade. The trailer sometimes gets a tad warm but at least I can usually get half a day of full, unobstructed sunshine this way.

The natural tendancy of most folks is to choose a shady campsite and many campgrounds have very shaded campsites. These campsites are virtually useless from a solar generation point of view.
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I use my TM as a base camp for hiking, kayaking, mountain biking, and climbing Colorado's 14ers


The Trailer: 2002 TM Model 2720SL ( Mods: Solar Panels (170 Watts), Dual T-105 Batteries, Electric Tongue Jack, Side AC, Programmable Thermostat, Doran TP Monitor System)

The Tow Vehicle: 2003 Toyota Tundra V8 SR5 4X4 w/Tow Package (Towing & Performance Mods: JBA Headers, Gibson Muffler, 4.30 gears, Michelin LTX M/S Tires, Prodigy Brake Controller, Transmission Temperature Gauge)


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Old 11-29-2005, 08:18 AM   #5
tonymessana
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Paul and Ray, I did check and they are two 225 6 volt in series. I found the same situation with the panel and direct sunlight. I camped this last time on top of a 4000 foot hilltop. The sunlight was never directly at the solar panel but a little bit to the top of it since it is angled slightly down towards the door of the TM. Mid-day it peaked at the input of the panel and then trickled downward as the day passed. Now the decision is to add another panel or to go the generator route. Any suggestions on a generator?

Thanks
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Old 11-29-2005, 09:02 AM   #6
BobRederick
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Tony

Go to the honda web site and drool over them.
http://www.hondapowerequipment.com/g...U2000i#EU2000i


1000 watt great for weight and charging

2000 watt runs lots of things like charging, microwave, and A/C under some circumstances.

3000 watt runs A/C under most circumstances but weighs about 145#. It features a remote start option.

I just brought home a 2000. If needed, I can parallel 2 of them for 4000 watts some day and cost is about the same as the 3000 watt model.
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Old 11-29-2005, 06:54 PM   #7
PopBeavers
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I have a 2005 2720. I do not have solar.

If it is just my wife and I we can go for 4 days without charging the batteries (2 group 24 12 volt batteries). I have used the furnace twice, in April and again in November. The rest of the year the furnace is not needed in California. I believe that the 2005 models have more florescent lights than the older models do.

I have the Honda 2000 generator. If our kids are with us I take the generator and toss a pint of gasoline in the tank every day or two and let it run until it dies.

The generator was just under a thousand dollars. A pint of gas costs about 30 cents.

So I have essentially a setup that has a fixed up front cost of 1,000.00 plus 30 cents per day.

A solar system has a daily cost of zero, but I am not sure what the up front cost of a solar system would be that could fully recharge my batteries when parked in the shade. Probably more than the cost of the generator.

I think the generator is cheaper. The solar panels are greener. I have pretty much given up on the idea of solar panels.

If the price of gas gets so high that I can no longer afford to run the generator then I certainly will not be able to afford gas for the TV.

The Honda 2000 is very quiet. I also will purchase a second one if I ever need to run the a/c. However, I have been able to run the a/c on a single Honda 2000. I'm just not sure it is good for the generator or the a/c, but it will start and run from the generator power when everything else is off.
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Old 11-29-2005, 09:42 PM   #8
Paul_Heuvelhorst
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Quote:
Originally Posted by RockyMtnRay
Paul,

While I totally agree with most of your analysis, there is one rather large error in your math. Specifically, when batteries are connected in series (as is done with a pair of 6 volt T-105s) , the total amp hours of the pair won't exceed the total amp-hours of the lowest capacity battery since all the current has to flow through both...and when the lowest capacity battery is exhausted, the total voltage drops very rapidly.
Ray is absolutely correct... my error was trying to correlate Tony's use of 2-6 volt batteries while we used 2-12 volt batteries on our TM as well as our present trailer. 2-12 volt batteries give more amp/hrs than 2-6 volt connected in series. My mistake.

Being frugal with the battery useage (2-12's in parallel), we were able to get 6 days on our TM while on the No. CA coast, but we ran out of propane for cooking (our first trip). Didn't have the right tools to disconnect the propane tanks for refilling, so headed home a day early.

Tony, there are several good ideas offered here... you just need to consider your own style of camping and go with the solution that fits your needs. Just remember, if you want to use your A/C, you'll need the generator (2-3,000 watt). Solar will not help you with the A/C.
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Old 11-30-2005, 09:47 AM   #9
Bill
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Wow! Lotta good information in this thread! Let me add a couple details.

First, Wayne wrote
Quote:
... the up front cost of a solar system that could fully recharge my batteries when parked in the shade.
NO solar panel will generate power when it is shaded. As RMR noted, output drops near zero if even a small part of a panel is shaded. There are physics reasons for this, and I will correspond offline with anyone who cares - but the bottom line is that you need full direct sun on the entire panel to get the rated power out of it. This is one reason (in fact, the only reason I can think of) to make your panels portable rather than bolting them to the roof of the trailer. With portable panels on the end of a cord, you can move them into the sun, even if the TM is in the shade. RMR camps mostly in high altitude areas where there is little-to-no shade, so bolt-down panels work well for him. I often camp in wooded areas with some (or a lot of) shade, so portable panels work for me.

And Paul wrote
Quote:
So, given 12 hours of daylight, the solar panel should be putting approx ....
Sad to say, this is way too optimistic. Solar panels don't generate power from simple daylight. They require bright sunlight shining directly on the panel, at not too much of an angle. In most areas of the country, you get about 4 hours of solar-panel-usable sunlight each day, assuming you don't have a complicated steering mechanism to make the panels track the sun's movement. In some really sunny southern areas (like southern California), the average can be as high as 6 hours per day in summer. In northern areas, it drops to as little as 2 hours on a sunny day in winter. Again, RMR noted this when he said he experiences 3-5 hours of good sun in sunny high-altitude Colorado. That's about right.

The Dept of Energy's National Renewable Energy Lab (NREL) has collected an enormous amount of data regarding solar energy. You can find a lot of it at http://www.nrel.gov/solar/ .

All of this has to be factored in when you size a solar system. Solar is great! But it is not magic.

Bill
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Old 11-30-2005, 11:46 AM   #10
Senorsedona
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Default Solar

I have a 75 watt solar panel mounted on the rear shell. A single 12 volt battery. My wife and I can go at least 3 days with out worrying, I carry a Honda 900 with me. When needed I help the panel with it. I try not to use the generator, even the Honda makes more noise then I want. We have gone 8 days, again no problems. I do have a Mr Heater to keep us warm. This is a major battery saver and does a super job. We have dry camped in Oregon, Colorado, California, Arizona and Washington.

Let's all have fun

Jack
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