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Post by machinehed on Mar 15, 2017 15:17:29 GMT -8
Hey all ,
Would a Renogy MPPT40CC controller be compatible with 2 SolGate SG210P grid tie panels ?
Max. solar input on the controller is 100VDC.
Panel open circuit voltage is 36.8 per. panel.
Controller max. PV input is 500W/12v and 1000W/24v
New to this stuff so any help is appreciated.
Thanks to all.
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Post by tattoo on Mar 15, 2017 15:50:22 GMT -8
I'm also new to this but you learn fast.. You should be just fine with that set up...
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Post by spiderbob on Mar 15, 2017 17:55:30 GMT -8
Those are known as grid-tie solar panels or high-voltage solar panels. When used in a grid interconnected system, panels are connected in series to achieve voltages of 600VDC and 1000VDC. The high DC voltage is then converted to AC voltage compatible with the utility grid. If this is what you are doing you might want to look at the Commander series of chargers. You will end up going to that or larger if you add more of the same panels.
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Post by rabird on Mar 16, 2017 5:15:55 GMT -8
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Post by spiderbob on Mar 16, 2017 6:05:36 GMT -8
Machinehed, we need to know what your intention is with the panels, are you grid tieing or are you just a stand alone?
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Post by machinehed on Mar 17, 2017 14:48:46 GMT -8
Hey Spiderbob , Thanks for the reply . Wife found a good deal on the 2 panels but she did not understand the dif. between grid tie and other etc. She grabbed them and now im trying to incorporate them . The system is stand alone for a small cottage in the middle of nowhere with boat access only. Im being asked all these questions as im a tech. but need some help here. What do you think ?
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Post by rabird on Mar 17, 2017 16:29:04 GMT -8
What makes a grid tie panel a grid tie panel? Connecting it to the grid.
You can use the panels you have and a charge controller to connect them to batteries to charge.
Since they are '24v' panels you need a MPPT controller to utilize their full power, they will charge a 12v batt bank.
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Post by spiderbob on Mar 17, 2017 19:30:18 GMT -8
An off-grid system requires a storage system for the electricity that you produce so that it will be available for times when there is no source of electricity. This storage system is one of the main features that distinguish an off-grid system from a grid-tied system. The other is a backup generator for long periods of cloud or calm, and a final difference is the grid tied is not set up in parallel, they are banks of series, which in turn use a different controller, remember you are not charging batteries in a grid tie. So back to basics, yes, those panels will work just fine and you can look at the MPPT or a PWM it is debateable as to what is better. I use a 60a PWM.
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Post by spiderbob on Mar 17, 2017 19:39:26 GMT -8
Befor I'm asked the difference between MPPT and PWM:
The "good" for PWM: It is simpler and lower cost technology. Under some common circumstances–it can actually deliver more amps to the battery. That could be when:
(1)days are moderate or warm, with few clouds.
(2) batteries are charging at over 13 volts, (in a 12 battery system) which they almost always are when actually CHARGING.
(3) Panel voltage is properly matched to the battery voltage, for example "12V" panels are being used with a 12V system.
PWM is actually more "power efficient" than MPPT–which means less total power loss in the controller itself. So heat sinks in the design can be smaller (and less expensive). Missing in most analysis of MPPT is that there is always a conversion loss with MPPT, which tends to be higher the greater the voltage difference between battery and panels. That's why PWM can actually beat MPPT under circumstances described above.
Some places that analyze MPPT assume that panels with 30V open circuit voltage are being used in a 12V system. Any good MPPT system will easily provide better performance in that case. They also may assume batteries are charging at 12 or even 11 volts, which is unrealistic. Lead acid batteries are typically below 13 volts only when discharging, or perhaps charging with very little charging current–meaning the actual potential gain in amps is not great.
The benefit for MPPT becomes apparent if you use panels not voltage matched for the battery. If they are not, MPPT will utilize more of the potential energy of the panels. For example, if you use 24 volt panels to charge a 12 volt battery system you must use MPPT, otherwise you would be using your panels very inefficiently. If you are trying to use PWM in that case, you are misusing the PWM technology.
Another potential benefit with MPPT is that if distance between panels and batteries is far, smaller wire can be utilized by running panels at higher voltage to the batteries. Running at twice the voltage reduces wire size to 1/4, which for a long run can be a significant saving in copper wire.
If temperatures are low enough, the slightly less power efficiency of MPPT will be compensated by the higher panel voltages, which will result in a little more battery current. But in actual measurements were made using a commonly sold MPPT solar controller, this would occur at temperatures less than 55 F degrees (in full sun, when charging at more than 13 volts), where there is a slight advantage to MPPT in my location (Boulder Creek, near the California coast). As temperature drops below that (in full sun) MPPT will get some advantage, such as could occur at high elevations in Colorado in the winter. Potentially this would be maximum about a 2.5% improvement in amps output for every 10 degrees F lower in temperature (or 4.6% per 10 degrees C colder. I'm using data from Kyocera KD-140 panels.)
There can be theoretically optimal situations where MPPT could give some advantage: that is when solar current is present, but the batteries are quite low in charge–but because loads are high and even greater than the solar current the batteries are still discharging despite the solar current. Under these conditions the voltage COULD be at 12.5 volts, or even lower. Again, using data from Kyocera panels, ("Normal Operating Conditions") there is a theoretical maximum gain over PWM of 20% current assuming NO MPPT conversion loss and no voltage drop in the wires to the panels, at 20C (68F). With PWM, the voltage drop in the wires in this case would not affect the charging current. Now if in addition you lower the temperature to below freezing at 28 degrees F (while sun is shining) you might actually get up to a THEORETICAL nearly 30% gain while the batteries are discharging.
The only REALLY BAD part of MPPT, is all the hype surrounding it–for example one manufacturer advertises "UP TO 30% OR MORE" power harvested from you panels. If you are using solar panels properly matched to the batteries, 30% ain't gonna happen unless it's EXTREMELY cold. And your batteries have to be abnormally low in charging voltage–which tends not to happen when it's cold (unless you assume the battery is still discharging while solar is happening). Virtually all the analyses seen touting MPPT on the Internet ignore the conversion loss, assume really cold temperatures, assume unreasonably low charging voltages, assume no voltage drop in the wires from panels to batteries, use STC conditions for the panels (that the marketing types prefer) rather than more realistic NOCT conditions, and in some cases assume panels not voltage matched to the batteries.
The other thing that is misleading about MPPT, is that some manufacturers make meters that show both the solar current and the battery current. In almost all cases for a well designed MPPT type the battery current will be greater. The engineers making these know better, but it is implied (by marketing types?) that if you were NOT using MPPT you would be charging your batteries with only the SOLAR current that you read on their meters. That's not true, because the PWM BATTERY current should always be higher than the MPPT SOLAR current. It is the nature of the MPPT that maximum power occurs when the current is lower than the maximum, so they must operate there to get the maximum power. So to properly compare the two you need to compare MPPT with an actual PWM controller in the same circumstances.
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Post by rabird on Mar 18, 2017 4:18:25 GMT -8
grid tie inverter for grid tie, the inverted 120vAC must match phase of the utility. charge controller for battery charging -panels will not know which you are using! 60 cell '24v' panel need MPPT to take advantage of the full power of the panel for 12v battery connect in either parallel or series to the limit of the input voltage/wattage of the controller If shading is likely, go with parallel and bigger wire. 2x210 watts is 400 watts to charge a battery bank. @ 15v that's ~25ah and at ave irradiation of 4kwh/m^2/day, that's 100ah/day irradiance calculator -location,time of yr, tilt. www.solarelectricityhandbook.com/solar-irradiance.htmlminimal battery bank 2x6v golfcar batteries ~ 220ah@12v. This is putting the cart up front of the horse, ie what might your daily usage be?
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Post by machinehed on Mar 19, 2017 14:11:11 GMT -8
So far load will be mini freezer , occasional water pumping to sink ,charging laptop , phone . Led lamps.
What do you advise re: series or parallel wiring for the 2 panels to controller and controller to 3 deep cycle batteries.
Panels are less than 20 feet from the controller .
Note: Just to be sure... I am understanding that the 2 SolGate SG210P panels are compatible with the Renogy MPPT40CC charge controller .? Im a little freaked as these panels are " gridtie " panels.
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Post by spiderbob on Mar 19, 2017 15:29:01 GMT -8
When you mentioned grid-tied I assumed you had no batteries and were making it compadable for a utility system use as back up power. The manufacture that made the so called Grid-tied panels, probably sells primarilly to the home buyer using solar as an extra source. For the most part they would take a heavier controller for that purpose. You can use the MPPT 40, but check with the guys when you decide to purchase it, call them. It's just a phone call to varify. Rather series or parallel, that depends on where you are. Does a panel get shaded (at all) by a tree or other item sometime thru the day? In a series wiring if one panel even gets 10% of just one panel shaded, the whole system will shut down until they both (or all) have full sun. In a parallel system, the shaded panel (even 10%) will shut down just one panel (the one that is shaded). There are tradeoffs, with parallel you use heavier cable than with series. Sounds like you have a good set of batteries . I use 4 - 6v golf cart batteries in series/parallel for 12v - mine are set up for an RV. One battery is 220AH so 4 wired as stated gives me 440AH
Also, keep in mind that it will take a few days to completely charge those batteries, don't expect it in just a few hours. Once you are completely charged up, then you should have a battery monitor (one that uses a shunt) to monitor your system. Do you have any other sytem to help with charging? Utlility power, generator, wind, anything? If you get several cloudy days, you will probably not get a good charge going while still using the items you mentioned.
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Post by rabird on Mar 19, 2017 15:34:37 GMT -8
so do these panels have existing wire coming out their junction box on the back? size? Vmp? Imp? Parallel is Vmp, 2*Imp. Series is 2*Vmp, Imp let's use 60vDC and 7A compared to 30vDC and 14a Try 10g! how much voltage drop do you intend to design to? www.calculator.net/voltage-drop-calculator.htmlplease let me know what makes a panel grid tie only? Grid Tie INVERTER for GRID TIE Charge controller for battery charging.
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Post by spiderbob on Mar 19, 2017 15:36:20 GMT -8
please let me know what makes a panel grid tie only? I've answered that twice already
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Post by rabird on Mar 19, 2017 15:38:42 GMT -8
Incorrectly X2
grid tie INVERTER, remember the grid is VAC
BTW, the commnder is not a grid tie inverter
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