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Old 02-15-2003, 10:08 PM   #1
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Generator or Solar?

I like to camp in National Forests, National Parks, State Parks and such... as far away from KOA's as possible (I find many RV parks crowded and "trashy" - but that's another subject). I could use advice on solar vs generator power for 2-5 day stays.

I'd like the quiet of solar, but I do not want to mount panels on my roof. I don't want to drill holes. Also, we are usually in the woods and don't get much sun. Perhaps a portable solar panel that I could set up in the sun near the trailer? Anyone try this? Would a small panel, say 2 feet by 3 feet, be able to produce enough juice to charge the battery for typical use of water pump, a few lights for a few hours each night, and perhaps a laptop computer playing DVD's for the kids for a couple hours?

The alternative is a generator - how long does a Honda EU2000i take to recharge a half-spent group 27 battery?
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Old 02-16-2003, 06:45 AM   #2
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A generator might be your best bet. A solar panel is very expensive, if not bolted down eventually it will walk. As the sun moves through the trees you will have to keep moving the panel. I used a 350 watt generator in much the same sitution for quite a few years. That was pre personal computer days, it ran a small tv and vcr, would charge the battery enough so we could make it day to day. For long weekends I didn't even carry extra gas.

John
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Old 02-16-2003, 07:31 AM   #3
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Dan,

This thread may give you some insight into adding larger batteries to your Safari.

Also I believe that Forum member "Jace" added these batteries to his Safari and gets 3-5 days without charging and he has a family of 4.

John

http://www.airforums.com/forum...=&threadid=482
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Old 02-16-2003, 11:38 AM   #4
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Looks like I now have 4 options... assume we use 50 a/h per day:

1. A second battery: about 100 a/h, weight 60 lbs, size 13 X 7 X 10", could be mounted on the A-frame, about $100.

The 2 batteries will be dead in 4 days, but really shouldn't be drawn down more than 50% - so 2 days. Not enough!

2. Honda EU2000i: 1600 watts, weight 50 lbs, size 20 X 11 X 17", could this be mounted on A-frame under some type of cover?, about $860.

Would need to run generator for 5-6 hours/day to recharge the battery (8 a/h charge rate X 6 hours = 48 a/h), although the generator could also be used at peak usge times to reduce battery drawdown. The generator could also be used for backup power at home.

3. Solara SM225M solar panel w/regulator and install kit: (per forum user "Bubbla") 56 watts, size 75x61x0,2mm, a flexible panel that can be glued onto the roof (no holes!), $729

Assume 75% efficiency (?) this might produce 56 w X .75 X 8 hrs / 12 volts = 28 a/h per day, a net loss of 22 a/h per day, would last 2.3 days before drawing battery down 50% Not enough, would need two panels, too expensive!

4. "Home Made" portable solar lashup, example: Kyocera KC80, 80 watts, size 38 X 26 X 2", weight 21 lbs $343, plus $63 for controller, plus some wire. I could wire it to a standard trailer plug. Then just plug it in, lean it against a tree pointing towrds the sun,and lock it to the tree!

Again, assuming 75% efficiency, this might produce 80 w X .75 X 8 hrs / 12 volts = 40 a/h, a net loss of 10 a/h per day, would last 5 days before drawing down the battery 50%. This meets my requirements!

Option #2 and #4 would both work. Both would need to be locked to a tree or the trailer to prevent theft. $860 for a generator, or $400 for "portable" solar panel? Perhaps both someday.

Advice?
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Old 02-16-2003, 01:57 PM   #5
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We plan around an extended three day weekend, i.e. take Friday off with a 3 day weekend. With a half day of driving on each end, that's 72 hours of camping, and 3 nights of use.

Assuming you can't pump all the water out of the 50 gallon tank, that gives you 16 gallons per day of water over 3 days, or 12 gallons per day over 4 days.

A pound of propane has 21,560 btus, so two 30 lb bottles would give over 323,400 btus/day over 4 days (propane on during driving but the tow vehicle alternator powering the gas solenoids).

I haven't measured it yet, but the refrigerator circuit board, and the LP detector, probably take 250mA each or about 12AH/day.

The refrigerator's gas solenoid should draw about 1A when the flame is on, so if that's 60% of the time, that's another 16AH/day.

Make sure you turn off the 12V door frame heater that keeps condensation down during high humidity conditions. See the frig owners manual for that.

The hot water heater's gas solenoid should also draw about 1A when the flame is on, so running it 2 hours/day that's about 2AH/day.

The water pump draws 6A, so 16 gallons at 1.6 gallons/minute is 10 minutes of pump time, or 1/6th of an hour for 1AH/day.

So you're up to 31AH/day before lights, etc.

Add one 2.3A double-tube flourescent light for 4 hours and you're up to 41AH/day.

Run the 2.1A double-tube flourescent light in the bathroom, the 1.5A shower light, and the 2A bath vent fan for a bit over 1/2 hour and you add another 3AH for 44AH/day.

Run the 1.5A stove vent hood light and its 2A fan for a half hour during cooking, and you're just over 45AH day... with no radio, TV or other "luxuries."

If you put a pair of 225AH T-105s in one of those Blue Sea battery boxes on the tongue, and start with 100% battery charge, you could get 3 days camping at 45AH/day, taking the batteries down to 40% charge, or 4 days camping taking them down to 20% charge. This is in mild weather.

But what if it's warm out and you run the Fantastic Vent on medium (2.1A) for 12 hours (25AH) and low (1.8A) for 12 hours (22AH), you've doubled your daily usage.

And the same with cool weather. That 7.5A (25k btu) furnace running an average 1/3 duty cycle over 18 hours (45AH) also doubles your daily usage, not to mention uses 7 lbs of LP per day on top of the frig and hot water heater usage.

Under these conditions, or if you want more than 45AH/day, you're into charging. Don't plan on getting charge level any higher than 90% with several hours/day of generator, solar, or tow vehicle alternator. And the rule of thumb is that you need 10% more charge than dischage, so you'd have to put in 50AH to replace 45AH and 100AH to replace 90AH.

It isn't the Honda generator that's charging your batteries. It's the converter. If it's only 13.8V constant, it's going to require the generator running longer than if it were a 3 stage with 14.5V bulk charging. If the converter could put out 20A charge, it would take 2.5 hours to do 50AH. But if the converter only puts out 10A, it would take 5 hours. The Inteli-Power or TruCharge converters can give you this higher voltage. And the deeper the discharge, the faster the initial bulk charge.

Keep in mind that the generator running from say 6PM to 10PM is supplying the lights, vent fans, water pump, and several hours of Fantastic Vent or furnace use WHILE it's charging the batteries. Since this doesn't come out of the batteries, charging time is less. And there's plenty of current for "luxuries" like TV, DVD, not to mention charging notebook computer batteries, and even AC-powered ones like microwave oven and using the vacuum cleaner.

IMHO portable panels would be a pain. While tilting them to the appropriate angle for the latitude would let you use a little smaller ones than what you'd have to roof mount flat, especially considering you're up north, you'd really have to secure them well or their tilt could generate a lot of lift in higher winds... not to mention their theft vulnerability.

If you're going to try to get by with one battery, the generator run daily during heavy usage time is the no-brainer answer. If you want to go longer than 3-4 days, you have to address the water and propane issues.

I'd personally opt for the generator, but frankly I would get a two battery setup. I'd also get a Link 10 battery monitor. AFAIK, it's the ONLY one that lets you program in the Peukert effect for discharge.
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Old 02-16-2003, 02:19 PM   #6
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A really electrical-savvy guy in Arizona is getting about 40-60AH day out of TWO horizontally mounted KC120 panels using a Solar Boost controller, depending on time of year. IMHO, that's realistic for two of these panels... 25-30AH each per day.

There's no way you're gonna get 8 hours of productive sun in MN!

Keep in mind you aren't going to get anywhere near the 80W voltage out of them if the temperature is 68F, where panel temp will be at or above 45C. More like 16V. And if you tilt one, you might get a 4.5A average current over 5 hours average... count on maybe 22.5AH/day for each of these panels tilted to the appropriate angle. You'll need at least two of these panels.

You roll up your awning when winds are predicted... you darned well better have these panels well secured if you don't want them trashed. Forget the tree... it shades the panel too much around noon.

BTW, it really isn't battery murder to run them below 50%. Batteries run down to 20% have about 1/3 the life of those run down to 50% but if you only have room for two, then live with it. It's not that bad when you consider you're replacing half the batteries 3 times as often.
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Old 02-16-2003, 07:34 PM   #7
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Wow, after reading Maurice's "Battery Budget", I am really glad I have a vintage unit with "ancient" technology. As far as I know, my only "phantom" load is the clock in the AM/FM/CD player I just installed. After 2 weeks of setting with no AC to the trailer I still had 12.72 volts in the battery. No circuit boards in anything, and my fridge is a 120 v model. The water heater has no power to it, unless you run the electric element on AC power.
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Old 02-16-2003, 08:24 PM   #8
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Thanks for the information! I did not realize that the actual solar panel output would be such a small percentage of rated output.

The Honda's can put out 120VAC and charge the battery using 12VDC at the same time (separate windings). I was planning to charge the battery using the DC mode (I assumed that the trailer's converter would add a layer of inefficiency), reserving the AC mode for when using appliances that require it.

For my limited needs perhaps the EU1000iA2 would work - it has the same 8 amp 12V charge rating.

Some park campgrounds (see Yellowstone ) do not allow generator use between 8pm and 8am, limiting us to daytime battery charging only.

Our travel plans are for several 9 day trips, with 2-5 days between trailer moves (when the trailer battery will be recharged by the tow vechicle). Water is not a problem as it can be refilled every couple days. LP should not be a problem as our travels are in spring/summer/fall, and we can refill en-route.
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Old 02-16-2003, 10:37 PM   #9
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I've read some posts on other forums about charging from the DC output rather than the AC output through the converter. Here's what I've picked up. Any EU2000 owners are certainly welcome to speak up on this.

To charge off the 12V/8A windings the generator must be at full throttle, where when using the AC output, you can use the Eco-Throttle and charge at much lower engine speed.

The AC through a good converter charges faster than the DC charge.

With both using Eco-Throttle, and with say a 5-6A load, the EU2000 will be running slower and quieter than an EU1000.

A couple of other posters haven't been happy with the amount of charging from the tow vehicle once they got a meter that showed how much they were getting.

Although I plan on getting an EU2000, they've pretty much convinced me I need a meter. That way you can find out for sure how much each appliance draws, and how much charge you're getting. I'm looking at the Xantrex Link 10 from windsun.com.
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Old 02-17-2003, 10:24 AM   #10
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Maurice,
you are correct- the EU2000 will charge the batteries faster throuth the converter. The Eco-Throttle is a great feature. Under small load the generator is so quiet (59dB) you forget it is running. The only time it runs at full throttle is when my wife turns on her 1875W hair dryer!
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