More Solar for "Us"
Ok, I went off.the deep end? Bought 3 used 37watt uni-solar panels and a blue sky 2000e controller for the hefty price of $400, They were being listed as 75w panels, they are not The tested open...
Forum Discussion
Hi greenrvgreen,
Like Cool Hand Luke you have to "get your mind right".
If you full time, solar may need to favor a large wattage.
If you part time, 60 watts per 100 amp-hours of storage will be enough to let every trip start with 100% state of charge, and equalize the battery bank, too. With bank switching it is possible to do it with only 30 watts per 100 amp-hours (which is what I did).
MPPT makes the greatest sense when panel prices are high per watt, OR, when there is limited "real estate" on the roof. They may also be used to lower transmission losses by allowing panels to be wired in series. (there are pros and cons to that, as always). There are some low cost MPPT controllers coming online now, but there are few reviews about them.
If you full time with solar the battery bank may need to be fairly massive. Between 6 and 10 times daily use. The larger the solar wattage the smaller the battery bank size can be, so long as it is not smaller than 6 times daily use. Why six times? Well, some days it rains.
Why 1200 watts? Well Mr. Wizard has gotten about 25 amp-hours for two days in a row from 211 watts. So 1200 would offer about 150 amp-hours on a not great day (~1890 watt-hours). That's enough to run his fridge--and some of the other loads too. If the charge controller offered diversion loading it might well provide most of the hot water, on a better than poor day, too. (Blue Sky 3024 does 20 amps diversion loading once the battery bank is full).
That is why what Mr Wizard is doing is so valuable. He is posting *real* data about a *real* full time RV. That will allow a "real" size to be suggested for a battery bank--and from that the wattage of solar panels may be be determined. (Thanks, yet again).
By the way, I have a generator, but all my high electrical draw is done via an inverter and battery bank. I have not run the generator except to exercise it since Feb 2009. But I part time, and do have a medium size battery bank (875 amp-hours). When I do travel (about 1500 miles a month so far), my alternator does a significant amount of charging.
Like Cool Hand Luke you have to "get your mind right".
If you full time, solar may need to favor a large wattage.
If you part time, 60 watts per 100 amp-hours of storage will be enough to let every trip start with 100% state of charge, and equalize the battery bank, too. With bank switching it is possible to do it with only 30 watts per 100 amp-hours (which is what I did).
MPPT makes the greatest sense when panel prices are high per watt, OR, when there is limited "real estate" on the roof. They may also be used to lower transmission losses by allowing panels to be wired in series. (there are pros and cons to that, as always). There are some low cost MPPT controllers coming online now, but there are few reviews about them.
If you full time with solar the battery bank may need to be fairly massive. Between 6 and 10 times daily use. The larger the solar wattage the smaller the battery bank size can be, so long as it is not smaller than 6 times daily use. Why six times? Well, some days it rains.
Why 1200 watts? Well Mr. Wizard has gotten about 25 amp-hours for two days in a row from 211 watts. So 1200 would offer about 150 amp-hours on a not great day (~1890 watt-hours). That's enough to run his fridge--and some of the other loads too. If the charge controller offered diversion loading it might well provide most of the hot water, on a better than poor day, too. (Blue Sky 3024 does 20 amps diversion loading once the battery bank is full).
That is why what Mr Wizard is doing is so valuable. He is posting *real* data about a *real* full time RV. That will allow a "real" size to be suggested for a battery bank--and from that the wattage of solar panels may be be determined. (Thanks, yet again).
By the way, I have a generator, but all my high electrical draw is done via an inverter and battery bank. I have not run the generator except to exercise it since Feb 2009. But I part time, and do have a medium size battery bank (875 amp-hours). When I do travel (about 1500 miles a month so far), my alternator does a significant amount of charging.
greenrvgreen wrote:
--On a nominal 12V system, the MPPT charger makes only a small difference (~10%, as predicted by some and verified by Wiz). If I were to dip a toe in, buy a couple panels, I might not start with a $500 MPPT controller. (snip)
--Wiz's "typical day" mirrors mine. When I get up, I want a high power draw. IMO, only a generator can supply this. AFAICT, ten times the panels still isn't going to get you the power you want at six a.m. (snip)
--Is there an automatic method for diverting unused solar power to something useful? (snip)
--It doesn't seem like solar is going to make a difference until eleven a.m. By then I will have put in three hours of gennie time, just running things. So my batteries will be ready for a topoff, but nothing more. How does, say, 1200W or 2000W of solar come into play, when most of the heavy lifting has already been done by the gennie?
