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Hi, I'm Lance from the Ozark Hills of Southwest Missouri, where we average 4.73 hours of solar insolation a day...
I'm going to slowly build a home and live on-site in a mobile for the next several years, and can't/don't want to hook to the grid just yet. Right now I have a 2000w generator & two(2) GLC115 230ah 6v in service @12v. I don't yet have appliances other than LED TV, Blu-Ray, & laptop; and plan to use a propane stove, propane hot water, and wood heat. Refrigeration is undecided but probably a converted chest-type freezer. I'm going to have to start small on the solar system and upgrade along the way, so my goal is to get as much solar electricity as I can for my money. Rather than build to a certain watts/day goal, my thought is that I can add more creature comforts as the electricity to run them become available. I also think it's probably more economical to just fire up the generator during periods of lots of electrical use, like power tools, etc, rather than buying a large enough solar system to run them.
Because it's a bad idea to mix new and old batteries and I already have 2 in service at 12v, I'm going to stick with 12v until these need replaced and then upgrade to 24v. If I understand correctly, it's best to charge batteries at 10-13% current, so my 230ah batt should be charged with 23-30a, which means I need 331-432w to charge these batteries with enough current to keep them mixed and not require charging off the generator (23ax14.4v=331w, 30ax14.4v=432w). I'm not entirely clear if this means I need a 30a charge controller to avoid sending too many amps to the battery, or if it means I need at least a 40a charge controller to handle the watts required before losses and have some overhead for usage while charging? If the 40a, do I need to limit amperage to the battery somehow, or will the battery simply not pull more than 30a?
The best values in charge controllers seems to be at the 40a point, costing only $20 more than 30a controllers and hundreds less than 60a controllers (looking at EPever/EPsolar, which seems to be a decent brand of genuine mppt at a value price). Now I want to get the most out of every piece of equipment I buy, but this is a balance between maximum output and long life. The EPever Tracer4210 is rated 520w@12v, 1040w@24v and claims to be able to handle 300% more PV than that, but will clip production to no more than the rated watts. This means it can handle over-dimensioning, but only charges the battery at mpp if the panels are producing less than 520w. If the panels actually produce more than that, the excess is clipped to maintain the rated watts. And because STC rarely if ever occur in the real world, this means I need more than the rated watts of pv to full utilize the capabilities of the controller. But how much more? I see 75% thrown around as a downrating for real world conditions, so perhaps 690w STC generates about an actual 520w? If so, that would be the max pv to avoid any clipping, but when designing for maximum value it seems like some clipping would be desireable. But how can I determine how much? Perhaps I can maximize my power produced per dollar spent by going with 800 or 900w (rated STC) of panels into this controller? Anybody know where I can find more info on over-dimensioning calculations?
Sanity check. If I produce an actual 520w with about 4hrs solar insolation/day, that is 2080wh/day actual production. That might work for most days, but seems likely I will need more with refrigeration. So my longer term plan would be to double this by eventually going 24v on the same controller and doubling the number of panels, if my actual usage on the 12v system indicates I need to. Thoughts?
I'm going to slowly build a home and live on-site in a mobile for the next several years, and can't/don't want to hook to the grid just yet. Right now I have a 2000w generator & two(2) GLC115 230ah 6v in service @12v. I don't yet have appliances other than LED TV, Blu-Ray, & laptop; and plan to use a propane stove, propane hot water, and wood heat. Refrigeration is undecided but probably a converted chest-type freezer. I'm going to have to start small on the solar system and upgrade along the way, so my goal is to get as much solar electricity as I can for my money. Rather than build to a certain watts/day goal, my thought is that I can add more creature comforts as the electricity to run them become available. I also think it's probably more economical to just fire up the generator during periods of lots of electrical use, like power tools, etc, rather than buying a large enough solar system to run them.
Because it's a bad idea to mix new and old batteries and I already have 2 in service at 12v, I'm going to stick with 12v until these need replaced and then upgrade to 24v. If I understand correctly, it's best to charge batteries at 10-13% current, so my 230ah batt should be charged with 23-30a, which means I need 331-432w to charge these batteries with enough current to keep them mixed and not require charging off the generator (23ax14.4v=331w, 30ax14.4v=432w). I'm not entirely clear if this means I need a 30a charge controller to avoid sending too many amps to the battery, or if it means I need at least a 40a charge controller to handle the watts required before losses and have some overhead for usage while charging? If the 40a, do I need to limit amperage to the battery somehow, or will the battery simply not pull more than 30a?
The best values in charge controllers seems to be at the 40a point, costing only $20 more than 30a controllers and hundreds less than 60a controllers (looking at EPever/EPsolar, which seems to be a decent brand of genuine mppt at a value price). Now I want to get the most out of every piece of equipment I buy, but this is a balance between maximum output and long life. The EPever Tracer4210 is rated 520w@12v, 1040w@24v and claims to be able to handle 300% more PV than that, but will clip production to no more than the rated watts. This means it can handle over-dimensioning, but only charges the battery at mpp if the panels are producing less than 520w. If the panels actually produce more than that, the excess is clipped to maintain the rated watts. And because STC rarely if ever occur in the real world, this means I need more than the rated watts of pv to full utilize the capabilities of the controller. But how much more? I see 75% thrown around as a downrating for real world conditions, so perhaps 690w STC generates about an actual 520w? If so, that would be the max pv to avoid any clipping, but when designing for maximum value it seems like some clipping would be desireable. But how can I determine how much? Perhaps I can maximize my power produced per dollar spent by going with 800 or 900w (rated STC) of panels into this controller? Anybody know where I can find more info on over-dimensioning calculations?
Sanity check. If I produce an actual 520w with about 4hrs solar insolation/day, that is 2080wh/day actual production. That might work for most days, but seems likely I will need more with refrigeration. So my longer term plan would be to double this by eventually going 24v on the same controller and doubling the number of panels, if my actual usage on the 12v system indicates I need to. Thoughts?
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