Solar

Discussion in 'General Community Discussions' started by pianotuna, May 2, 2009.

  1. pianotuna

    pianotuna
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    Hi All,

    This is day 2 for my new solar system.

    It consists of:

    4 unisolar us 64 panels (total 256 watts)
    1 blue sky 3024i charge controller
    1 2500 watt cobra inverter

    The RV was prewired for solar with a #10 wire (too small imho).

    The panels are wired in two banks of two in series using #12 wire that is twinned (i.e. four wires for each panel--two for the negative and two for the positve) to the combiner box at the fridge hood.

    The #10 goes from the fridge hood to the charge controller.

    I used #8 wire from the charge controller to the battery

    The wires are twinned to the inverter using #4 (because that was the maximum size the inverter terminals would accept)

    The inverter output is sent via a #10 wire to a plug in the shore cord box. When I disconnect from shore power I simply plug the shore power cord into that outlet. Before I turn on the inverter I manually trip the breaker that operates the stock converter for the RV.

    It was interesting to note that the stock converter only brings the batteries to 13.8 volts.

    On day one I was trundling down the road and had my 1120 watt water heater on (by accident not design). I gathered about 84 amp hours (nominally 1000 watts) from the solar panels.

    On day two I gathered in 84.9 amp hours (1032 watts) and ran a vacuum cleaner, the water heater, a small electric heater, some lights, ran the microwave (for one minute) drilled 68 holes and drove 68 screws.

    Charging from the solar panels started at 6:15 am and was 0.2 amps. It rose to a peak of 17.2 amps. The morning was cloudy so at noon I was gathering only 6.5 amps. The afternoon turned sunny and I had solid readings of 13 amps from 1 p.m. to 4 p.m.

    Battery voltage started out in the morning at "float" levels (14.8 volts) and at 8 p.m. the voltage was 12.3.

    The batteries are what came with my RV. They consist of two 105 amp hour 12 volt batteries--and another one that doesn't' match and may be of lower capacity. I intend to change them in the future--but I want to see just how much energy I can draw from them first before getting replacements.

    The only item I've not tried to run in the RV yet is the air conditioner. I may give that a shot later this week--particularly if I manage to figure out how to trigger an "equalization" charge.

    I'm not at all sure the inverter will handle the load--and in any event I do not intend to run the AC from the inverter.

    All in all, I'm extremely happy with the new system--it certainly will be of great use to me as I frequently boondock--and I try as much as possible to avoid propane use.
     
  2. DXSMac

    DXSMac
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    Wow! I don't understand all of it, but I'm sure it's high tech!

    JJ
     
  3. abbygolden

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    QUOTE(DXSMac @ May 3 2009, 12:02 AM) [snapback]16215[/snapback]

    Wow! I don't understand all of it, but I'm sure it's high tech!

    JJ




    Me either! Solar is an interesting topic about which I know almost nothing. I do know that if I used it at my house, the payback period would be long after my death!
     
  4. Florida Native

    Florida Native
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    Don't you need lunar for night time use???
     
  5. Denali

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    Congratulations on your new technology. Your data on how much power you harvested from the sun is interesting.

    When we boondock in the desert, we can get right around 100 amp hours a day from our panels. That satisfies about half of our energy-guzzling needs. We installed the solar system simply to cut down on the number of hours per day that we need to run the genset, and it has worked well for that. I don't know whether it will ever pay for itself in diesel savings, but the extra 2-3 hours a day of quiet is worth it to us.

    You won't be able to run your air conditioner from your inverter/batteries. The compressor on your air conditioner draws something like 75-100 amps for an instant when it kicks on. This is called the "locked rotor" load in the manual for your air conditioner. Those are AC amps, so the load is 750-1,000 DC amps. If you try it, you may either smoke the inverter or trip an auto protection device (like a fuse) in the inverter. Or, the air conditioner start capacitor may take that load so your inverter never sees it. In any case, after an air conditioner starts, it will probably draw 10-13 amps AC, about like a large microwave. That's 100-130 amps DC.

    With your 210 amp hours (plus the mystery battery) of house batteries, you would deplete them to the 50% level in about 15 minutes. I suspect that it isn't good for batteries to put that kind of sustained load on them, but I'm no expert.

    Our coach, like most others its size, has a whole-house inverter wired into it. It's a 2,500 watt, like yours. The motor home manufacturers never wire the air conditioners into the inverter system on these things. The only one I know that does is a Prevost conversion, which has two 4,000 watt inverters and many more batteries than you and I have.

    I use the equalization function built in to our inverter about twice a year. If you do that, remember that the equalization cycle raises the voltage going to the batteries to over 15.0 VDC. Purportedly, that can damage some DC equipment, like the circuit board in your fridge, fluorescent fixtures, thermostats, etc. When I run the equalization cycle, I disconnect DC power to the coach. You also need to remove the caps from the batteries while equalizing because it does boil them.

    Keep us posted!
     
  6. pianotuna

    pianotuna
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    Hi Dave,

    I agree on the Air conditioner--I have no plans to attempt to run it on the inverter. I suppose I could trip the breaker to it as well as the one to the converter--but I think that is needless. I do have a generator for that purpose, which is a "hand me down" from my previous RV.

    I had a 14.9 volt reading with the temperature at 10C--so I know the temperature compensation is working! It is in an inverse relationship--as temperature rises voltage drops by 10 millivolts per 1 degree Celsius. The 3024i is preset to 14.4 at 20 C--but from what I'm observing it takes it to 14.8 (@20C) then allows voltage to sag back to 14.4. I'll likely know more later today.

    I've already found that even trees bare of leaves have a large effect on the output.

    Today (day 3) is a "non use" day other than a quick trip across town. Voltage started out at 12.3 this morning at 9:00 a.m. Charge rate was only 1.6 amps (bare trees). It is now 11:30, voltage has risen to 13.3 and amps are at 13.4 I'm expecting that I'll finally get all three batteries completely charged by late this afternoon--and if not today--then tomorrow it will happen. The short drive will likely not skew my results as the house batteries will most probably be above the set point for the alternator charging system.

    I did read the manual and found out I can "force" an equalization--but it requires disconnecting the batteries from the 3024i. I'm too lazy to do so--so I guess I will let nature "take its course" and wait for the thirty day automatic equalization to take place. The 3024i limits equalization to 15.5 volts, but I may take your "tip" and use the coach disconnect switch when my unit is in storage.

    The "old" batteries did have a desulphator added to the charging circuit. I'm not sure if that was done on the shore power side or the engine alternator side. I'm luck enough to have a solenoid type isolator--so I should get lots of "opportunistic" charging when I drive--letting the solar panels "top off" the system so that when I stop the batteries will be near or at 100% capacity.

    If I'm standing still I think I'll have 1000 watts (100 amps) a day to charge and power the RV--with a reserve of 1500 watts (without dropping below 50% charge state) from the batteries.
     
  7. Florida Native

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    Lots of people boondocking in the desert use a swamp cooler instead of air conditioning and they can drop the ambient temp 10 to 15 degrees depending the humidity. They require extra water usage and a fan and small pump. We saw them a lot on houses in the West and I have read about them being used on RV’s in the desert.
     
  8. pianotuna

    pianotuna
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    Hi Abbygolden,

    Pay back depends on where you live. In Ontario, for example, the government legislation requires the electrical power grid to buy power from solar at 44 cents per kilowatt hour. My system may generate 1 kilowatt per day and cost for parts was $1900.00. Pay back in eleven years.

    Today on the RV I broke my promise to not use power. I wanted to blow out the water lines in preparation for putting the unit back in storage. So rather than drag a cord from the house out to the RV, I decided to use the new 115 volt outlet I had installed in the waste water valve hatch. It worked like a charm! It saved me time, and aggravation. That, for me, is priceless.

    On the other side of the coin, if I were boondocking and needed to run my generator I'd have about 1/2 hour "free" from the sun. Pay back would be about $1.50 per day, or three years. In actual fact, I think that with the system I have I'll but rarely start the generator at all, so pay back will be much faster than that.

    The end result is that I skewed my results for today LOL! So the panels will not get the batteries up to full power (almost though--they got to 14.2 volts). I did get my 1000 watts again today.

    A side bit of information is that I found out the charging voltage from my solenoid based isolator is 14.2 volts.

    QUOTE(abbygolden @ May 3 2009, 08:03 AM) [snapback]16218[/snapback]

    Me either! Solar is an interesting topic about which I know almost nothing. I do know that if I used it at my house, the payback period would be long after my death!
     
  9. DXSMac

    DXSMac
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    I think.... over on "another" RV forum, someone talked about swamp coolers, and said they are horrible in humid areas, as they create moldy conditions. I forgot where I read it, I think it was on "another" RV forum.

    JJ

    QUOTE(Lindsay Richards @ May 3 2009, 12:28 PM) [snapback]16232[/snapback]

    Lots of people boondocking in the desert use a swamp cooler instead of air conditioning and they can drop the ambient temp 10 to 15 degrees depending the humidity. They require extra water usage and a fan and small pump. We saw them a lot on houses in the West and I have read about them being used on RV’s in the desert.
     
  10. pianotuna

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    Hi Lindsay,

    Lunar you say? Is this a further development of the "Lindsay pole"? Solar from a flashlight? (get on the roof and wave it furiously over the panels?) *grin*

    I've considered a swamp cooler--but they want huge prices for them. Zero-2-Cool made a portable unit for a while that used ice and/or water--I would have ordered one--but they discontinued them. I suppose I could hang a wet towel under the vent for my Fantastic Fan. and that might do a little cooling.

    I'm happy as a pig in **** about how well the new system is working. I almost don't want to put it into storage so I could keep on monitoring the results. I finished today at 13.3 volts (and rising). The high point of the day was 14.2 and then I "ruined" things by using the air compressor--and later a vacuum cleaner. It is 7 p.m. and charge rate is 0.9 of one amp. (Thanks to the MPPT Blue Sky 3024i and my choice of series installation for the panels).

    QUOTE(Lindsay Richards @ May 3 2009, 01:28 PM) [snapback]16232[/snapback]

    Lots of people boondocking in the desert use a swamp cooler instead of air conditioning and they can drop the ambient temp 10 to 15 degrees depending the humidity. They require extra water usage and a fan and small pump. We saw them a lot on houses in the West and I have read about them being used on RV’s in the desert.
     
  11. pianotuna

    pianotuna
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    Hi all,

    This is just another brief report on my system.

    It appears to be producing more than 1000 watts per day on sunny days. At high noon maximum output has been up to 17.1 amps. (or ~249 watts)

    I've been waiting for an overcast day--which finally appeared May 8, 2009. At high noon output was 8 amps (or ~115 watts), and at 4 p.m. it was still 3 amps (or ~40 watts). I'm quite favorably impressed with those numbers. Perhaps 500 watts on a totally overcast day.

    I'm happy as a pig in **** about these numbers. They are better than I had hoped.

    As it is going to -8 C (17.6 F) tonight, and as I don't care about the tired old house batteries in the RV and as I did not fully re winterize this time (I only blew out the lines--never dreamt it could get this cold), I've put a thermostatically controlled heater in the waste valves hatch set at 5 C (40 F).

    It will be a torture test for those 5 year old abused batteries--and it should protect the plumbing.
     
  12. DXSMac

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    Lordy! The worst I have camped in was MINUS 2 Farenheit, but that was only ONE night.

    JJ
     
  13. pianotuna

    pianotuna
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    Hi JJ,

    -2 F = -18 C

    It is the -8 C which fooled you I think. +17.6 F is not very cold at all compared to -2 F

    QUOTE(DXSMac @ May 8 2009, 09:04 PM) [snapback]16294[/snapback]

    Lordy! The worst I have camped in was MINUS 2 Farenheit, but that was only ONE night.

    JJ
     
  14. DXSMac

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    QUOTE(pianotuna @ May 8 2009, 08:57 PM) [snapback]16295[/snapback]

    Hi JJ,

    -2 F = -18 C

    It is the -8 C which fooled you I think. +17.6 F is not very cold at all compared to -2 F



    Yea.... after I posted that, I realized that -2 was colder than the temps you were quoting.

    DUH!

    JJ
     
  15. Denali

    Denali
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    QUOTE(pianotuna @ May 8 2009, 07:31 PM) [snapback]16293[/snapback]
    As it is going to -8 C (17.6 F) tonight, and as I don't care about the tired old house batteries in the RV and as I did not fully re winterize this time (I only blew out the lines--never dreamt it could get this cold), I've put a thermostatically controlled heater in the waste valves hatch set at 5 C (40 F).

    It will be a torture test for those 5 year old abused batteries--and it should protect the plumbing.

    Let us know how that works out. A 1500 watt heater would draw 125 amps DC, which should drain your batteries down in an hour or so.
     
  16. pianotuna

    pianotuna
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    Hi Denali,

    That's why I set the temperature on the heater for only 5 C. The heater is a car warmer type that draws 650 watts. It will be heating a tiny area. Too bad I didn't think to put a timer in the circuit so I could tell how long the heat will be on. I have 3 batteries--two 105 amp hour and one xxx amp hour, so I think safe run time would be about two hours in total. Of course if the batteries were allowed to be deep discharged run time would be closer to four hours. The inverter shuts down at 9.5 volts. That would be way below what I'd consider "prudent". But for these old "free" batteries that I intend to replace--this is a good experiment.

    I'll be going over at noon hour to check on it--a much brighter day today and 4.6 C outside--so the heater will not be running when I arrive.

    What I am seeing from solar on an overcast day would run the furnace for 4.6 hours per day without drawing from the batteries at all. If the forecast is correct for Tuesday night I may go to that option depending on what I find today--propane would be lots cheaper than replacing taps and plumbing lines.

    My new RV is far less "cold tolerant" than my old one. I'm especially afraid of freezing the china toilet. I will be adding heater rods before the fall (finding them is the problem, I did take them from the old RV--but where in the heck did I put them).

    The "overhead" for running the inverter is about 1 amp. It is a cobra 2500 modified sine wave--chosen because of space limitations. It "lives" behind the driver's seat which allows a cable run to the batteries of less than four feet.

    When I went over today (May 9) to see what had happened overnight at 11:00 a.m. the solar panels had already gotten the batteries back to the "float" stage--they were still charging at 5.8 amps. I'm again, very pleased with how well the heater was powered.

    I will be letting the batteries "recover" until Tuesday when our next cold front is due to arrive. I wish I could have access on Sunday to check out the results.

    On Tuesday I'll probably put a 100 light bulb in the waste tank area, and move the heater with thermostat to the water closet. I may put a timer on the light bulb--and I may put a timer in parallel with the heater so I'll have data about consumption to share.

    QUOTE(Denali @ May 9 2009, 09:31 AM) [snapback]16298[/snapback]

    Let us know how that works out. A 1500 watt heater would draw 125 amps DC, which should drain your batteries down in an hour or so.
     
  17. pianotuna

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    Hi all,

    I changed some things today as it is supposed to go well below freezing tonight.

    At 10 AM, I put a total of 34 watts of heat rods into the waste tank valve area--and did not put it on a thermostat.

    I moved the thermostat and the 650 watt heater into the bathroom, plugged in my Kill-o-watt meter and plugged the thermostat into it--and set the kill-o-watt to record the total number of watts that are going to be drawn.

    At 3:00 PM I went back and checked the system. The solar panels were putting out 5 amps (75 watts, from what I can infer) in a totally overcast situation and the batteries were at "float" charge level. So there was enough solar to run the 34 watts in the waste compartment, to do a 1 amp "overhead" from the inverter and keep the batteries essentially fully charged.

    I deliberately triggered the heater by plugging it directly into the wall, and the output from the panels jumped up to 6.9 amps! This also caused the inverter fan to cycle *on* which surprised me a bit as the inside of the RV was only at 7 C.

    It looks as if I get about 105 watts at 3 PM on an overcast day with an outside temperature of 2 C. That is pretty much in line with my guess of about 500 watts per day.

    The Kill-o-watt meter also informed me that voltage was 114. My old "elcheapo" 800 watt inverter used to do 127 volts which I was a little uncomfortable about.

    I'll be doing this three days in a row as the next two nights are forecast for below freezing too!

    I'm deathly afraid of the China toilet bowl splitting.
     
  18. pianotuna

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    Report after running for 24 hours!

    At ten AM today for the last twenty four hours I drew 1678 watts from the system. Voltage was sitting at 12.2 and charging was at 5 amps under an overcast sky.

    At 3 PM yesterday the batteries were float charging at 15 volts. The panels were providing enough energy to run the 34 watts of heat in the valves area--and provide the overhead on the inverter as well.

    Running the valve area heaters 24 hours non stop used 816 watts, or 2775 BTU's

    The heater in the bathroom used 550 watts overnight, or 1870 BTU's. It is set at 5 C.

    The overhead for the inverter itself is at least 312 watts.

    At noon today the batteries were at 12.7 volts and in darker skies than at ten AM were charging at 4 amps.

    At 3 PM the batteries were at 13.1 volts and there was a bit more sun so they were charging at 7 amps. 7 amps represents a C42 charging rate for my system so the 13.1 would indicate 85% of full charge—with another 3 hours for charging to continue, though probably only the next two hours will be significant.

    Changes for today:

    At ten AM, I unplugged one 9 watt heater bar and added a thermostat to the valves area. This unit is also set at 5 C. This should considerably reduce the number of watts used--but equally I will not have a way to measure that. I suppose I could put the kill-o-watt meter just after the inverter--but I did not have a cord to do that with me.
     
  19. DXSMac

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    That's all Greek to me, but if I remember, you are in 30 degree F temperatures (less than 0 Celsius) right now? Hopefully those solar panels are keeping you toasty at night!

    JJ
     
  20. pianotuna

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    Hi JJ.

    It would require some use of propane--but there would be enough energy to keep the furnace running for 4.7 hours per day--without "touching" the reserve energy in the batteries.

    The RV is actually in storage at the moment so I've been driving over to "check it out".

    As it has been overcast and is going below freezing each night this is a real "torture test" of the system.

    QUOTE(DXSMac @ May 14 2009, 11:46 PM) [snapback]16407[/snapback]

    That's all Greek to me, but if I remember, you are in 30 degree F temperatures (less than 0 Celsius) right now? Hopefully those solar panels are keeping you toasty at night!

    JJ
     

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