TheChamp
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Will 75V and 15A be adequate for your application?
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Adding solar to inverter-battery systems 101
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impracticaldogg
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I'm calling a few different people to quote on full hybrid solar vs this kind of supplementary solution. So I'll ask them. I thought installing an MPPT and solar panels with the battery backup would be a much cheaper route than going full hybrid.
My thoughts at the moment: A friend bought a 5.5kW Sunsynk Inverter for their house with three adults and two kids. A quick search turns up a price of R27 000. And it includes the functionality of an MPPT as well as handling 3 x the power if I read the specs correctly. So hybrid looks like a better option atm
Hi All,
Long time lurker in the inverter forums. Thanks to everyone and the hundreds of pages in threads, learnt alot, and eventually did my own setup. And in turn have educated others on buying building (sizing, requirements, runtime etc).
Very light setup, but as many have mentioned, some future proofing is always a good idea.
Question, this is the inverter (12v) I have with a lithium battery (Revov 200ah 2nd Life), works like a charm, sees to my needs and capacity is more than sufficient. Now I've always been considering adding a solar panel to the mix, as the inverter is capable (MPPT). But I have no clue how to match an appropriate size to it... or if I'm understanding the data correctly.
Do I just make sure that the solar panel Open circuit voltage )eg, 37V, is within the Operating Voltage of the inverter (15v - 80v)? So what happens if the panel voltage is less than the Inverter requirement like, 10v?
Make sure the Max power of the solar panel eg) 250w, is less than the Max Pv Array input power of the inverter (825w)?
Max power current of solar panel eg) 8A, is within the range given by the inverter Max Solar Charging current (55A total = 25A Utility max +30A solar max)
Now these other bit of data, what are they for:
What is the Max PV array Power to support on the inverter spec (660w), any relevance to matching a solar panel?
Solar Panel Maximum Power voltage is 18v, what is this value for?
Short-circuit current on the solar panel spec 10A? How I understand it is, if the panel goes above the 8A (max power current output) up to 10A, then it shorts? So a fuse on the panel wires rated for 10A would mitigate this?
Lastly, as we know wind and temperature affect solar, how do you size or rule of thumb to select the correct panel to prevent heavy fluctuations in Voltage and Current?
Thanks in advance, on the quest for knowledge.
Inverter Specs:
Solar panel example:
Long time lurker in the inverter forums. Thanks to everyone and the hundreds of pages in threads, learnt alot, and eventually did my own setup. And in turn have educated others on buying building (sizing, requirements, runtime etc).
Very light setup, but as many have mentioned, some future proofing is always a good idea.
Question, this is the inverter (12v) I have with a lithium battery (Revov 200ah 2nd Life), works like a charm, sees to my needs and capacity is more than sufficient. Now I've always been considering adding a solar panel to the mix, as the inverter is capable (MPPT). But I have no clue how to match an appropriate size to it... or if I'm understanding the data correctly.
Do I just make sure that the solar panel Open circuit voltage )eg, 37V, is within the Operating Voltage of the inverter (15v - 80v)? So what happens if the panel voltage is less than the Inverter requirement like, 10v?
Make sure the Max power of the solar panel eg) 250w, is less than the Max Pv Array input power of the inverter (825w)?
Max power current of solar panel eg) 8A, is within the range given by the inverter Max Solar Charging current (55A total = 25A Utility max +30A solar max)
Now these other bit of data, what are they for:
What is the Max PV array Power to support on the inverter spec (660w), any relevance to matching a solar panel?
Solar Panel Maximum Power voltage is 18v, what is this value for?
Short-circuit current on the solar panel spec 10A? How I understand it is, if the panel goes above the 8A (max power current output) up to 10A, then it shorts? So a fuse on the panel wires rated for 10A would mitigate this?
Lastly, as we know wind and temperature affect solar, how do you size or rule of thumb to select the correct panel to prevent heavy fluctuations in Voltage and Current?
Thanks in advance, on the quest for knowledge.
Inverter Specs:
Solar panel example:
leon.davibe
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ok @Zem_936
first question 10v one , the mppt has a range in which it finds the optimum output of the panel, you would have to check your devices manual ie though it falls outside mppt range they have a minimum volts where they can still charge the batter ie mine is a 48v system but the manual says it can still charge as long as the voltage is over 32 but the mppt only starts operating at a higher voltage (ie finding the spot you get more bang for buck mostly morning afternoon and bad weather that this helps the real benefit of mppt is not dragging the panel down to battery voltage )
and avoid the 100v like the plague, high voltages kill charge controllers
have had many tell me 80% rule of thumb ie so max 80v of mppt is perfect
the max 660w is just the max panel size the unit can effectively use
ie 660/12= 55A charge current, if you go over mid day you won't get any more than 55A , but may gain in the morning and late afternoon when the sun angle isn't ideal ie coming onto peak charging current sooner and stay there longer ie my dad has 1000w on a 600w controller no problems
edit: though since this one specifies the 825w explicitly i would heed that
the current of the solar panel doesn't need to fit in the charging amps
the mppt will change the voltage and thus the amps,
so lets say you have 660w solar power at 50v that is thus 13.2A, the mppt then converts that to 12v so now the 660/12= 55A charging current at battery voltage, you just need to stick within the voltage range and naturally if going over the 660w ie 800w you are paying for panel power you don't always get so it is just inefficient buying but can make a difference in bad weather ,morning and afternoon but wasted at noon with 660w cap
the 18v power max volts is the voltage at which the panel produces it's maximum power at,for people with a pwm controller it's way more important to select a panel closer to battery voltage ie to not lose to much output, just how a pwm controller works, with an mppt it doesn't matter as the mppt converts to 12v the voltage on the panels is important in string compilation to stay away from max voc, so if you go to high a voltage ie 50v voc you can' put 2 in series(too close to voc max), you need 2 to hit 660/825w so would need a panel 40-42v voc too not be too close to voc max with 2in series
If going high voltage ie 50v voc you need to put panels in parralel
the panel will never produce more amps than it's max amps on the sticker the 10A fuse rating is the max amps that can flow over the panel before it can become a fire risk, this is the size fuse you have to use to keep parallel strings separate ie if you have 2 panels in series and have that parallel with 2 more in series , you want a 10 amp fuse on each string so that if a panel goes faulty and has a short that the other strings power can't be combined to it and exceed the panels rated current carrying capacity , your charge controller is the path of least resistance so the power will flow there and fuses won't burn , but when a panel has a fault that dead short becomes the path of least resistance the power will flow too
the 80% of voc rule of thumb is what cover you in cold weather/cloudy sun pops out and increases panel voltage situations , can post a link to a site that gives the math if you want to go the exact calculation, then you would most likely come closer to the 90% of the max voc, but extra headroom is nicer for perfect storm events
first question 10v one , the mppt has a range in which it finds the optimum output of the panel, you would have to check your devices manual ie though it falls outside mppt range they have a minimum volts where they can still charge the batter ie mine is a 48v system but the manual says it can still charge as long as the voltage is over 32 but the mppt only starts operating at a higher voltage (ie finding the spot you get more bang for buck mostly morning afternoon and bad weather that this helps the real benefit of mppt is not dragging the panel down to battery voltage )
and avoid the 100v like the plague, high voltages kill charge controllers
have had many tell me 80% rule of thumb ie so max 80v of mppt is perfect
the max 660w is just the max panel size the unit can effectively use
ie 660/12= 55A charge current, if you go over mid day you won't get any more than 55A , but may gain in the morning and late afternoon when the sun angle isn't ideal ie coming onto peak charging current sooner and stay there longer ie my dad has 1000w on a 600w controller no problems
edit: though since this one specifies the 825w explicitly i would heed that
the current of the solar panel doesn't need to fit in the charging amps
the mppt will change the voltage and thus the amps,
so lets say you have 660w solar power at 50v that is thus 13.2A, the mppt then converts that to 12v so now the 660/12= 55A charging current at battery voltage, you just need to stick within the voltage range and naturally if going over the 660w ie 800w you are paying for panel power you don't always get so it is just inefficient buying but can make a difference in bad weather ,morning and afternoon but wasted at noon with 660w cap
the 18v power max volts is the voltage at which the panel produces it's maximum power at,for people with a pwm controller it's way more important to select a panel closer to battery voltage ie to not lose to much output, just how a pwm controller works, with an mppt it doesn't matter as the mppt converts to 12v the voltage on the panels is important in string compilation to stay away from max voc, so if you go to high a voltage ie 50v voc you can' put 2 in series(too close to voc max), you need 2 to hit 660/825w so would need a panel 40-42v voc too not be too close to voc max with 2in series
If going high voltage ie 50v voc you need to put panels in parralel
the panel will never produce more amps than it's max amps on the sticker the 10A fuse rating is the max amps that can flow over the panel before it can become a fire risk, this is the size fuse you have to use to keep parallel strings separate ie if you have 2 panels in series and have that parallel with 2 more in series , you want a 10 amp fuse on each string so that if a panel goes faulty and has a short that the other strings power can't be combined to it and exceed the panels rated current carrying capacity , your charge controller is the path of least resistance so the power will flow there and fuses won't burn , but when a panel has a fault that dead short becomes the path of least resistance the power will flow too
the 80% of voc rule of thumb is what cover you in cold weather/cloudy sun pops out and increases panel voltage situations , can post a link to a site that gives the math if you want to go the exact calculation, then you would most likely come closer to the 90% of the max voc, but extra headroom is nicer for perfect storm events
Last edited:
leon.davibe
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See i missed something
The max charge amps from solar is 30A
So although the 660w solar will be able to supply is 55A @ 12v
The max that can get into the battery 30A (420w @ 14v ) the rest can flow to load
If no load you lose that extra production
this will just be at noon with perfect sun angle
Thanks for BOTH repiles!
Now this makes sense. Thank you for illuminating me.
Hope this helps other out there in deciphering these specs.
leon.davibe
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just sharing what i have read so naturally if you find something i am wrong on do correct me