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Post by tattoo on Nov 21, 2019 18:42:25 GMT
And the higher up the less pollution so more direct sun light..........
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Post by bupkis on Nov 21, 2019 19:35:57 GMT
yurtdweller as you may know panels are ~15% effecient. But that is included in the numbers on the back or spec, set temp, set light, set air density .... There are weather conditions, locations, cloud effect, etc... where a 100w panel makes more than 100w.
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yurtdweller
Solar Newcomer
I am a modern-day nomad. I live in an off-grid yurt for up to 9 months each year.
Posts: 21
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Post by yurtdweller on Nov 21, 2019 19:50:13 GMT
Believe me, I am familiar with a wide array of different locations and conditions. My CO campsite gets tons of power, in mid summer. My Maryland campsite, at very low alt, about 50ft, in autumn, gets almost 30% less sunlight, and 100 foot trees mean fewer sun hours. Midwinter, as now, I'm in East Texas, and it's cloudy about 30% of the time, sometimes I'm only generating 3 amps for ten days in a row. A few months ago I was in Minnesota, and insolation was moderate, but I was not running my workshop, and I was fine. This February, I get to find out how much sun Phoenix gets. But hauling 8 100 watt panels around? I'd rather haul two high voltage panels. I don't carry a rack, so I need set them on the ground, and we're talking about a lot of real estate in sometimes very crowded camping conditions. I guess I'll keep buying 100s until that won't do the job anymore, then upgrade to a bigger cc and switch to 24 volts. 12v is just so convenient :/ Thanks for all the advice, folks. I'll get the hang of this eventually, but I had no electrical training coming into this, and there is a slight gap between what I know and what the user's manual provides. I will admit that I am having a hard time grasping watts. I get amps and volts, but watts are still confusing me. They seem almost unnecessary. And as to using my 2k inverter, I'm running about 1200 watts for about an hour, then I take a break for about an hour, and my bank recharges to full, then I go again. I'm not currently running the full 2k continuously. I think adding another 300 watts of panels will give me about 70% duty cycle, on sunny days.
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Post by bupkis on Nov 21, 2019 20:06:09 GMT
Watts is what to deal in (power). volts or amps mean nothing unless you have the other!
add time and we get watt-hr, so 1 watt for 1 hr is 1 watt-hr. for 30 mins it is 0.5wh
1000w microwave is 1000w/120v = ~8.5A. Now take that 1000 watts @ 12v and it is ~85A.
and the inverter loss, wire loss etc and you are near 100A @ 12v or 1200 watts!
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yurtdweller
Solar Newcomer
I am a modern-day nomad. I live in an off-grid yurt for up to 9 months each year.
Posts: 21
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Post by yurtdweller on Nov 21, 2019 20:20:25 GMT
can you explain your 3000 watt number? The string above is 72v x 8.9 = 650 watts, mppt conversion does not increase watts.(OK. I misunderstood this concept, YD) Bupkis: This is how I'm calculating the hv panels. Please correct any errors. 72 v divided by my highest charging rate, which is 14.6 for my batteries, works out to 4.93. I multiply my amperage 8.9, by this number and I get 43 amps output? Yes? So, this output is technically too high for the Rover 40? I'm not sure how many amps I'd need to keep up with my inverter pushing 1200 watts. My batteries can each accept a recommended 50 amps inrush, which I think means that two batteries could accept 100 amps inrush? Sorry. I feel I may be presenting too many questions on each response, and will break them into smaller bites going forward. Again, I appreciate the informative responses. Sometimes I get things like "say goodbye to your batteries" With no explanations. This conversation has been very informative. I really appreciate it. |
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Post by bupkis on Nov 22, 2019 2:26:54 GMT
you don't divide 72 by 14.6. Watts = V * A, A=W/V, V=W/A
Let's take the 650 watts and divide by 14.6 (650 w / 14.6 v) = 44.5A, ie 650 watts is 44.5A @ 14.6v.
You will never make that much and there is ~10% ineff with the Rover. Also the controller clips excess if there ever is any.
The inverter will get power from the batt and solar (sunny). 1000w tool will need 78A from solar and (13v) battery.
I don't have any issue with large loads for short periods of time if the batts are rated for that. The general rule of thumb for long life is to charge FULLY ASAP after use and not to drain them below 50% of somewhere around 12v. (Flooded/AGM lead acid). Lithium can handle low discharge levels.
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Post by Guest on Nov 22, 2019 18:52:55 GMT
For clarity, if you have 2 x 100W, 12V, ~5.46A panels in parallel = 100W, 12V, ~10A. The amps double in parallel. In series, 2 x 100W, 12V, ~5.46 = 200W, 24V, ~5.46A, the volts and watts double. I think a spreadsheet for doing these calculations would be a plus. With two panels, it is quite easy to get the results, in your head. If you have, lets 5 panels, and maybe you have a mix, like some are parallel and some are serial, then it gets very complicated. If you have two 100 watt panels in series, operating at optimum current and voltage, realistically, you will get about 160 to 170 watts.
If you have two 100 watt panels in parallel, operating at optimum current and voltage, realistically, you will get about 160 to 170 watts.
When two solar panels are wired in parallel the current doubles and the voltage stays the same as one panel. The wattage doesn't change.
When two solar panels are wired in series the voltage doubles and the current stays the same as one panel. The wattage doesn't change.
The panels in series produce a higher voltage and less current so the wires from the panels to the charge controller can be thinner compared with the same panels wired in parallel.
Wire size is determined by the amount of current. So, if the voltage doubles and the current stays the same, the wire size doesn't need to
be increased even though there is twice the power of a single solar panel.
Wire size is determined by the amount of current flowing through it. The wire insulation is important if you increase the voltage.
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yurtdweller
Solar Newcomer
I am a modern-day nomad. I live in an off-grid yurt for up to 9 months each year.
Posts: 21
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Post by yurtdweller on Nov 22, 2019 20:11:10 GMT
you don't divide 72 by 14.6. Watts = V * A, A=W/V, V=W/A Let's take the 650 watts and divide by 14.6 (650 w / 14.6 v) = 44.5A, ie 650 watts is 44.5A @ 14.6v. You will never make that much and there is ~10% ineff with the Rover. Also the controller clips excess if there ever is any. The inverter will get power from the batt and solar (sunny). 1000w tool will need 78A from solar and (13v) battery. I don't have any issue with large loads for short periods of time if the batts are rated for that. The general rule of thumb for long life is to charge FULLY ASAP after use and not to drain them below 50% of somewhere around 12v. (Flooded/AGM lead acid). Lithium can handle low discharge levels. First, the math. It seems we both did the math differently, but wound up with a very similar number. My 43a VS your 44.5a. Second, it is good that I have found through this conversation that over-amperage will not damage anything, merely result in waste. And third, these Odyssey batteries are beasts. Although I never do it, they are capable of outputting 2250 amps for starting jobs(momentary), and will offer 400 cycles at 80% dod. Again, I got these after they were removed from a commercial vessel at a mandated one-usage-year, so I cannot really know their full capacity, and I have never done a true capacity test, although I once had to pull 90ah out of them during bad weather. Over about ten days, they never reached full charge, but I was drawing very little out of them. Maybe 10ah per day. I ceased using them when the voltage appeared to be nearing 12v(34%soc), but after total disconnect and rest of 5 days, the voltage was actually still around 12.4(66%soc)iirc. Lastly, it looks like this cc will be insufficient to support enough panels to ever fully power my new inverter, so I will likely be getting some hv panels and a much bigger cc. I suspected I would be getting an new cc before too long. I want to power a diversion load water heater, so I may be looking for a cc with that built in, or I may try to make my bmv-700 bms with relay perform that job. I suspect I will also be making a switch to a higher voltage bank within a year. Every time I think my system will be big enough to hold me for a few years, I find newer and bigger demands:/ |
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Post by tattoo on Nov 23, 2019 13:09:04 GMT
Lastly, it looks like this cc will be insufficient to support enough panels to ever fully power my new inverter, so I will likely be getting some hv panels and a much bigger cc. I suspected I would be getting an new cc before too long. Yep that's how I ended up with a little bit larger system.......I found out real quick how little you can do with a smaller solar system...... And I also figured out real quick how much power is wasted with a larger than you really need inverter........ That's why I went from a 2000w to a 500w for my everyday uses...... |
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raydas
Solar Devotee
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Post by raydas on Nov 23, 2019 13:31:02 GMT
Are you using some kind of switching device between the 2000W and the 500W. Or are you just using the 500W, exclusively.
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yurtdweller
Solar Newcomer
I am a modern-day nomad. I live in an off-grid yurt for up to 9 months each year.
Posts: 21
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Post by yurtdweller on Nov 23, 2019 15:29:46 GMT
Lastly, it looks like this cc will be insufficient to support enough panels to ever fully power my new inverter, so I will likely be getting some hv panels and a much bigger cc. I suspected I would be getting an new cc before too long. Yep that's how I ended up with a little bit larger system.......I found out real quick how little you can do with a smaller solar system...... And I also figured out real quick how much power is wasted with a larger than you really need inverter........ That's why I went from a 2000w to a 500w for my everyday uses...... Yes. I nearly sold my old 650 aims psw, but when I saw the sheer size (footprint) of the 2k, I decided to hold on to it. I now have both connected to my bank, though the my new renogy 2k only uses .8a resting, which is really only about twice what the 650 uses, so I usually use the big one. The little one will go into my van build. Putting a coach battery in my van. |
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Post by tattoo on Nov 23, 2019 16:47:47 GMT
Yes. I nearly sold my old 650 aims psw, but when I saw the sheer size (footprint) of the 2k, I decided to hold on to it. I now have both connected to my bank, though the my new renogy 2k only uses .8a resting, which is really only about twice what the 650 uses, so I usually use the big one. The little one will go into my van build. Putting a coach battery in my van. You should just up grade your CC to a larger one and use the smaller CC in your van...........
I used my 40w CC in my shop for a power back up when I went to a larger CC since I needed more panels........
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yurtdweller
Solar Newcomer
I am a modern-day nomad. I live in an off-grid yurt for up to 9 months each year.
Posts: 21
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Post by yurtdweller on Nov 25, 2019 16:30:49 GMT
Yes. I nearly sold my old 650 aims psw, but when I saw the sheer size (footprint) of the 2k, I decided to hold on to it. I now have both connected to my bank, though the my new renogy 2k only uses .8a resting, which is really only about twice what the 650 uses, so I usually use the big one. The little one will go into my van build. Putting a coach battery in my van. You should just up grade your CC to a larger one and use the smaller CC in your van...........
I used my 40w CC in my shop for a power back up when I went to a larger CC since I needed more panels........
I will probably do this. I am looking at a screaming deal on some used 250w 30v panels right now @ $60 each, if I buy 10. So much less expensive per amp than the 100p. Especially if I can sell off a few for a profit. If I do that, I will probably throw my current system in my van. I have an art shop at a seasonal venue, and I'd like to throw a system in it, as well. It has hard line power, but customers love it when I tell them my art is solar-made:) |
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