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 20, 2019 22:30:15 GMT
I've been running and slowly upgrading my solar for about 5 years. I live off-grid in my yurt, and for my work I move 4 to 5 times a year, and operate all my home and workshop off my system. I have the Rover 40 charging two Odyssey 2250 batteries, rated at 125ah each(used, actual capacity unknown). I have 4 Renogy 100p panels, and an oddball 145w panel, which will obviously be running at about 100 watts, due to all panels having to be equal. Also, due to the odd panel, I have them all running in series. I recently purchased a 2000w Renogy inverter to operate some of my more powerful shop tools. Now, if I am running my one horse buffer motor, I'm sucking around 80 amps, from an array that is producing (theoretically) around 44 amps. Which is just inside the rover's limits, I think. My question is: Have I maxed out how many panels I can connect to this controller in a 12v bank? Here are the specs of the panels I want to use: Electrical Data at STC Maximum Power (Pmax) Wp305 Voltage at Maximum Power (Vmpp) 36.5 V Current at Maximum Power (Impp) 8.36 A Open Circuit Voltage (Voc) 45.6 V Short Circuit Current (Isc) 8.92 A. If I wire two panels in series (72v) and (8.92 amps), they should output almost 3000 watts (thru mppt conversion) when the sun is shining, right? If my math is totally wrong, and the Renogy Rover 40 cannot handle these hv panels, and if I still want to switch to these high voltage panels, (currently available lightly used on Craigslist Houston) enough to generate 2000 watts or even 1500 watts, how big will my controller need to be? Thanks everyone for your help. I think I'm getting the hang of this math, but I would like to hear input on this, and making the switch to hv panels has me questioning again.
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Post by tattoo on Nov 20, 2019 23:07:13 GMT
You can go to 8 panels with your CC....... That's how many I had before I upgraded to my current 60a CC.............
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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 5:08:11 GMT
So, with 8 panels you would go 2 parallel strings to make twice the voltage, thus allowing 1040 watts? Which is 800 plus 25% safety? And that output will charge a 12v bank? I guess I am having a hard time with the terminology in the user's manual that indicates "max input voltage" of 1040w@24v because I thought that meant that the entire system had to be running on 24v.
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Post by bupkis on Nov 21, 2019 12:48:58 GMT
If I wire two panels in series (72v) and (8.92 amps), they should output almost 3000 watts (thru mppt conversion) when the sun is shining, right? can you explain your 3000 watt number? The string above is 72v x 8.9 = 650 watts, mppt conversion does not increase watts. 650 watts of charging a 12v system is ~50A (13vX50A). Rover 40 Max Solar Input Voltage: 100VDC, so your 72v is ok there. While 650 watts might exceed the rover's input limit, it is OK to over power the controller somewhat. Any battery output of the rated 40A will be clipped and not used if the sun and angle is perfect and panels exceed 520 watts. (650 watts of panels may never exceed 520w !) If you want 2000w of battery charging (12v system) then 2000 watts / 13v = 150A controller or multiple smaller ones! I hope you can get by without using the inverter and large load! Edit: the rover 40 is rated 40A output. That is where the 520 watt max input @ 12v comes from. for a 24v battery that becomes 40A x 26v= 1040watts. Your current 5 panels is SERIES should output (5x17v) 85v @ ~5A.
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raydas
Solar Devotee
Posts: 166
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Post by raydas on Nov 21, 2019 13:15:54 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.
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Post by tattoo on Nov 21, 2019 13:33:28 GMT
So, with 8 panels you would go 2 parallel strings to make twice the voltage, thus allowing 1040 watts? Which is 800 plus 25% safety? And that output will charge a 12v bank? Yes sir you are correct. It worked great but I wanted to add 4 more panels and that was to much for the 40w CC............
It's a VERY simple setup and it works very well, even if your in a shaded area like I am..........
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Post by bupkis on Nov 21, 2019 13:52:20 GMT
So, with 8 panels you would go 2 parallel strings to make twice the voltage, thus allowing 1040 watts? Which is 800 plus 25% safety? And that output will charge a 12v bank? I guess I am having a hard time with the terminology in the user's manual that indicates "max input voltage" of 1040w@24v because I thought that meant that the entire system had to be running on 24v. No, adding strings does not double the voltage. Yes the 1040 watt is for 24v batteries.
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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 16:07:35 GMT
If I wire two panels in series (72v) and (8.92 amps), they should output almost 3000 watts (thru mppt conversion) when the sun is shining, right? 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) 650 watts of charging a 12v system is ~50A (13vX50A). Rover 40 Max Solar Input Voltage: 100VDC, so your 72v is ok there. While 650 watts might exceed the rover's input limit, it is OK to over power the controller somewhat. Any battery output of the rated 40A will be clipped and not used if the sun and angle is perfect and panels exceed 520 watts. (650 watts of panels may never exceed 520w !) If you want 2000w of battery charging (12v system) then 2000 watts / 13v = 150A controller or multiple smaller ones!(I thought it was a bad idea to use multiple controllers on one system?YD) I hope you can get by without using the inverter and large load! Edit: the rover 40 is rated 40A output.(I guess I never really understood what "Battery Load Current" meant" YD) That is where the 520 watt max input @ 12v comes from. for a 24v battery that becomes 40A x 26v= 1040watts. Your current 5 panels is SERIES should output (5x17v) 85v @ ~5A.
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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 16:14:33 GMT
So, with 8 panels you would go 2 parallel strings to make twice the voltage, thus allowing 1040 watts? Which is 800 plus 25% safety? And that output will charge a 12v bank? Yes sir you are correct. It worked great but I wanted to add 4 more panels and that was to much for the 40w CC............
It's a VERY simple setup and it works very well, even if your in a shaded area like I am..........
. Sorry to beat this question into the ground, but I am getting two different answers, here. Can I run my pv at 24v into a 12v bank? I am not prepared to go to a 24 bank, at this time, having just purchased the 12v inverter. Unless I find someone who wants to buy my brand new inverter. One comment said I could run 8 panels to charge 12v, one said I cannot.
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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 16:24:35 GMT
I just want to mention one thing about sticking with the safety margin. I spend each summer at very high altitudes, in Colorado. I camp at 7000 feet, and one day, while running my system on my old pwm, without temperature comp, my system actually output MORE power than it was rated for. If I recall, I was producing about 220 watts from 2 100 watt panels. I believe that event, when temps were near 90, pumped too many amps into a battery that was over temp, and damaged my lifeline battery. I understand this may have been due to 'cloud lensing' and I don't plan to take such chances again, even though I now have temp controls.
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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 16:28:52 GMT
Also, I did misspeak. My panels are currently in parallel, not in series. I always get that wrong :/ and my Rover reports as much as 22 amps, on occasion. Obviously I cannot series 5 panels.
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Post by bupkis on Nov 21, 2019 16:50:49 GMT
no one said you could not use 8x100w properly configured. each sting of 4 in series would yield ~65v (mppt or 80 Voc) and 5+A for a total of 65v & 10+A (note, adding an identical string does not double voltage).
yurtdweller Yes, you can use hv big panels either in series or parallel with the Rover and 12v battery.
The input limit based on Voc is 100v > 2 x 45.6v in series or run them in parallel.
The mppt controller clips excess power, I would have no issue using ~700w with the Rover 40, it would rarely exceed 40A battery charging. It might on those pretty days, clear blue sky, panel angle perfect.
Folks with poor angled panels and poor light do not make nearly the panels rated power.
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Post by tattoo on Nov 21, 2019 17:47:17 GMT
. Sorry to beat this question into the ground, but I am getting two different answers, here. Can I run my pv at 24v into a 12v bank? Don't worry about it, Your not beating it in the ground, You will be just fine running it with a 12v system..... That's what I have and it runs great.........
NO panel is 100% efficient no matter the angle or light......... That's a myth.............
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Post by tattoo on Nov 21, 2019 17:51:32 GMT
Also, I did misspeak. My panels are currently in parallel, not in series. I kinda figured that............ It use to always confuse me also...........
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Post by bupkis on Nov 21, 2019 18:22:50 GMT
I just want to mention one thing about sticking with the safety margin. I spend each summer at very high altitudes, in Colorado. I camp at 7000 feet, and one day, while running my system on my old pwm, without temperature comp, my system actually output MORE power than it was rated for. If I recall, I was producing about 220 watts from 2 100 watt panels. I believe that event, when temps were near 90, pumped too many amps into a battery that was over temp, and damaged my lifeline battery. I understand this may have been due to 'cloud lensing' and I don't plan to take such chances again, even though I now have temp controls. Yep, panels in ideal (COLD) conditions and direct good sun make more that they are rated for. This did not harm your battery as the controller is there to prevent overcharing, that is its job. With PMW it is less likely to happen cuz the panel operated at batt voltage and not the higher MPPT (current the same). Also high altitude with less air the sun is stronger than the test/rated conditions. The colder the panel, the more the light = more power.
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