The Alternative Energy Thread - Generators, Solar, UPS, Wind

[mani9999]

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[nowshad1]

As far as i remember, maximum Voc which your inverter accepts is 500Volts DC. If you read the specs from your inverter, the VOC voltage of your system comes out to be 46.6 * 6=279.6 Volts, read again, that not does falls even close to MPPT tracker range. You need to least add four more solar panels in series with the current system.

Further tilt angle for Winters is around 50 degrees pointing towards south and during summers is roughly 20 degrees. All year angle is 33 degrees if your mounts does not have a flexibility to change the angles.

further you can use 6mm DC wires, that should not have a joint inside, use proper MC4 connectors as that could also be a reason for a limited current.

distance is not mostly an issue with high Voltage systems.

Thanks for the reply, This is a bit confusing as per specification MPP range @operating is 120 - 450 VDC while on screen mostly it is above 200 V and I assume that voltage is within MPPT range. Please correct me

[genius_787]

Dear Talha,

I appreciate your effort in educating the audience. I have a similar question regarding VMII. I am going to purchase Tesla Axpert VM2 3KW version but currently I have only 4 panels of 150W each. Now the minimum MPPT range of Tesla VM2 is 120 volts as mentioned in the specification. I want to know if I can run my 4x 150W panels without adding any more panels as I can not purchase more panels at the moment due to finance constraints.

What I presume is that it should run these 4 panels which will combine to form approx 80 volts, although in PWM mode, as MPPT requires minimum 120 volts.

[mani9999]

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[genius_787]

Yes. Its 150W, 18.8Vmp panel. And If i connect all four of them in series, it makes approx 80V.

That's what I want to know if that VM2 can cater below 120V of voltage and provide some output with these panels or I have to buy atleast two additional panels to increase the Voc to above 120?

[talhawaleed]

check your private message, i have replied you, you issues is mostly related to your battery settings on your inverter.

you will have to change the charging rate, cut off Voltage and floating Voltages on your system and all this would be done through the LCD screen on your inverter

1. Set the cut off voltage to 28 Volts if its a 24 Volts battery bank system and correspondingly to 56 Volts if its a 48 Volts battery bank system.

2. Set the maximum charging rate by solar to 15 amperes

3. set the floating voltage to 27 volts if its a 24 volts battery bank system and to 54 Volts if its a 48 Volts battery bank system.

plus electrolyte poured in batteries should always be prepared with de-ionized water.

[talhawaleed]

No it wont work, Maximum VOC voltage acceptable on this inverter is 500 V DC and MPPT range is from 120 Volts to 450 Volts, 150 Watt solar panels have a VOC voltage of 21 Volts maximum and you have 4 of them.

21 * 4: 84 Volts.

system is designed such as it wont even detect the solar panels. i would advice you not to use 150 Watt solar panels on this inverter. buy least 250 watt solar panels as it has a VOC of 37 Volts and you will have to connect 12 or 13 solar panels in series to make it work properly. Charge controller on this inverter is of 4000Watt.

so if you will connect 12 then calculation goes like this 12 * 37 = 444 Volts DC VOC or this makes a 3000 watt system

or alternately if you will connect 13 in series 13 * 37 =481 Volts DC VOC and this makes a 3250 watt system.

Alternately if you connect 8 solar panels of 250 watt in series

              8 * 250 =2000 Watt with 37 * 8 = 296 Volts DC VOC

and make two strings and connect both of them in parallel with you inverter to make it a 4000 Watt system.

with 150 Watt solar panels, you will have to buy many more 150 wall solar panels to make it work or make it any worthwhile system.

[nowshad1]

Mr. Talha
Would you spare some time and address my query;
Inverter VM II specification indicates
MPP range @operating is 120 - 450 VDC and Voc is 500V

As inverter LCD shows input Voltage more than 200, I believe it is within MPPT range.
This needs your clarification please.

[talhawaleed]

No, VOC of solar panels should be above 440 Volts and less the 500Volts as other wise system would not operate.

like for a single solar panel of 250 watts, if voc is 37 volts but then once solar panel is connected then voltage drops to maximum 30 Volts.

total VOC of solar panels should always be below 500Volts DC like if you have 13 solar panels of 250 Volts with VOC 37 volts each then calculation would go like this

                   total VOC: 37 * 13= 481

once connected then maximum MPPT voltage would be

                       : 30 Volts * 13: 390 Volts

this range is what matters.

during early hours, this voltage will rise from 100 Volts DC to 390 Volts DC till full sunlight, once voltage will cross 120 Volts then system would wake up but wont be generating enough electricity till the time it goes above 300 Volts DC.

system would operate effectively once mppt voltage will go above 300 Volts, this is how entire thing has been designed or least will remain between range of 400 Volts DC to 300 Volts DC.

                      :

[pwuser152119181238]

Dear Talha sb
I'm planing to install solar panels at my home, the search of which has brought me to your thread.
I have APC smart ups (980w) with 24v battery bank and I want to install as many panels which could generate around 980w when sun is available. Load which would be run during the day includes lighting and fans (6 fans and 6 tube lights)
I plan to get an on grid inverter in future, that's why I prefer to use pwm controller which could be disposed off latter without wasting too much money. Please guide me what wattage panels what amp charge controller should I buy. I would keep panels and get more when I install an on grid inverter of higher capacity.
I shall wait for your response
Regards

[pwuser152119181238]

Response from respected members, especially Talha bhai is requested.
Even if I go for mppt controller, for 980 watts, what should be specs (amp and VOC rating) of controller.

[pwuser152119181238]

@talhawaleed Sir your response please

[talhawaleed]

go for a mppt charge controller with VOC above 100 VoltsDC and of minimum 1000 watts so that you may comfortably attach 4 of 250 watt solar panels and two of them in series.

i would recommend Tracer4210AN of 1040W, can be attached with 24 Volts battery bank and has a VOC voltage of 100 Volts.

i think, you can easily attach four of 300Watt solar panels with two in series, make an array and connect two arrays in series.

here is the link

https://www.aliexpress.com/item/32973117264.html?spm=a2g0o.productlist.0.0.1683133fvw8STE&algo_pvid=22956d58-8224-4441-aa54-c96ba723f20b&algo_expid=22956d58-8224-4441-aa54-c96ba723f20b-0&btsid=0be3743b15831834998707681e884c&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_

[pwuser152119181238]

Brother it's too expensive, costing around 20000. Moreover, due to corona virus epidemic, I doubt I would be able to get it shipped. Please suggest me specifications of pwm charger. I won't keep this system for more than a year. I plan to install 3kva system.
Also, Pakistan made mppt charge controller are available in market (absun and one by ayan electronic). A link to one of them is

Are they really mppt? Should I buy them instead of pwm?
Regards

[talhawaleed]

mppt are much better, you can buy from the link you have provided. it also supports 24 Volts battery bank and has a VOC voltage of 90 Volts so you can easily connect two 250W solar panels in series.

[pwuser152119181238]

Dear sir. Thanks for your response.
I have a question. You have installed axpert3kw plus with 1500w solar capacity. My question is, with 1500 PV input, how does the inverter run 3kw load? Does it take the differential from wapda? Or it entirely shifts to wapda once your load exceeds the max of solar input. I actually meant to say, if the inverter has the capacity to mix two energies (wapda+solar) in real time? I know that this inverter can mix PV+battery, but don't know if the battery voltage drops below a certain limit at which the load is run by wapda+solar.
PS: I'm attaching a screenshot of an inverter, which claims to harvest 3kw from sun. Can it really harvest this much? If so, how many and how would, I install 250w panels with it?

[talhawaleed]

A lot depends upon as how you set things on Solar inverter,

Suppose, you are generating 1100Watts from Solar and your Load is 1500 Watt, Depending upon the settings you have kept on inverter

1) it will take 1100 Watt from solar, while borrow 400 watt from Wapda keeping your batteries topped up or will continue to charge your batteries as per settings you have kept.

2) Depending upon different settings, it will take 1100Watt from solar while it takes rest from batteries till the time voltage on battery terminal does not drops to a specified limit. if it reaches the specified limit then it will again start to charge the batteries while borrowing rest from WAPDA.

3) with your load still 1500watts, wapda is not available or you are experiencing load shedding, it will borrow rest from batteries till the time your WAPDA returns. then it will borrow rest from wapda and will again start to charge the batteries.

VOC voltage of this mppt inverter is less, higher the VOC voltage the inverter accepts better the system is usually. With higher VOC voltage, line losses are less in form of current in wires and you can get away with things pretty easily with standard 4mm or 6mm flexible wires. otherwise the rule of thumb is, that you have to run pair of wires from every string to the inverter and that increases the cost of wiring's if you dont want to compromise on solar output.

[pwuser152119181238]

Thanks for your reply. As I'm not aware of electrical things, so don't know if the advertised capacity (solar=3kw) can be harvested by the inverter (growat). I'm saying this because, an inverter with similar specifications by Inverex and sold as aerox-3.2, can harvest a max of 1800w. I don't know how they claim to harvest 3kw from sun, after having similar specs as that of aerox-3.2.
Inverter with high VOC are quite expensive. For instance, Tesla is selling 3kw inverter with VOC of 450+, it costs 55k. While the inverter by growat, having less VOC is being sold at 35k. I don't need 3kw from sun. I just want to run lights, one fridge and fans with sun during day time, and if sun sends less energy, I don't mind if differential load is run by wapda or batteries.
I have to make a decision between aerox-3.2 and growat. If growat can harvest 3kw from sun, I would go with it. Aerox-3.2 costs 48k. If you can guide please. I'm attaching specs of both inverters.

[talhawaleed]

See, if you read the above article, you will realize that once solar radiation is 1000w/m2 and if your solar panels is at correct angle with respect to sun, only then you will get 250watts from your 250 watt solar panels.

Solar radiation from sun varies through out the day at any given point on Earth, so from your 1500Watt solar panels, if installed correctly, you can get roughly 1100 to 1200 watts maximum at peak time. but if you want to harvest maximum then you need solar tracker and mounts should have an ability to track the sun in both the axis.

Apart, further losses accounts in transmission, these losses are substantial to make a very good impact on system's output. Once VOC is high then these losses are minimal that's why inverters with highter VOC voltages are expensive and at the end of the day, its every penny worth buying an inverter which can accept higher VOC.

[pwuser152119181238]

Yep, I read your article again. Having double wire from panels to inverter, and that too DC wire, would make the investment even higher. So, I would go with an inverter with VOC 450V. Tesla vm2 is my first choice. If you know another inverter, in 3kw, please share its name etc.
PS: how to know correct angle and other parameters relevant to position of panels? Compass would tell the position with respect to North, South etc. How would I fix the angle with respect to sun?