Strings and volts for a 250Voc Growatt 6k split phase

[khisanthax]

As I'm in the market to replace my single phase inverter I found this growatt model. If I understand correctly, I currently have 8 panels at 20.2voc and this can handle 250voc but I plan to go to 24 panels, which I think I would have to in order to take advantage of the full wattage it can provide. That being side my current 8 panels would be 161.6v and 12 would be 242.4 which would be just inside the limit and I would have to be careful of temperature fluctuations that would change the voltage. So, if I wanted 24 panels it would have to be 2 strings that are in parallel so that the voltage wouldn't go beyond the 250voc. They must not have linked the right manual, or I'm reading it wrong because the manual still states 150voc?

Now, if I added more panels later I really need to make sure that voltage per panel doesn't go beyond 20.2 because it's getting very close to that cutoff line of 250voc, right? My current panels are 195w, but I saw a 250w panel with 22v, that would be a problem, wouldn't it?

 

[sunshine_eggo]

80 * 58V = 4640W max, i.e., no matter how much you put on it, you'll never get more than this.

Datasheet says 250V, manual says 150V.

250V is an absolute limit, i.e., you need to allow for cold temperature effects on voltage; lower temps = higher voltage.

You likely want to keep your Voc under 210V. You should be good down to about -25°C. Confirm your record low temperature is not below this value.

 

[Mattb4]

Check your panel's Voc. 20.2v seems a bit low. I have some 195w panels from Eco-worthy and they state 21.6Voc 12 of them would blow past your AIO's max Voc.

 

[khisanthax]

Check your panel's Voc. 20.2v seems a bit low. I have some 195w panels from Eco-worthy and they state 21.6Voc 12 of them would blow past your AIO's max Voc.

I was wrong and you're right, they're actually the eco-worthy but the manual states 22.8

 

[khisanthax]

80 * 58V = 4640W max, i.e., no matter how much you put on it, you'll never get more than this.

Datasheet says 250V, manual says 150V.

250V is an absolute limit, i.e., you need to allow for cold temperature effects on voltage; lower temps = higher voltage.

You likely want to keep your Voc under 210V. You should be good down to about -25°C. Confirm your record low temperature is not below this value.

I was looking at a slightly different model where the manual said 150v and this model seemed to have the same manual, but I should confirm that before I make any decisions. I don't get -25c at least not normally.

I'm sorry, but where did you get the 80 from? Was I correct that in order to achieve the most I would use 2 strings of 12 or is what you're saying that I couldn't get 2 strings of 12 because I wouldn't be able to get near the 250voc? Is that why some prefer 500voc aio?

edit: 80 is the amps. Got it.

 

[sunshine_eggo]

I was looking at a slightly different model where the manual said 150v and this model seemed to have the same manual, but I should confirm that before I make any decisions. I don't get -25c at least not normally.

I'm sorry, but where did you get the 80 from? Was I correct that in order to achieve the most I would use 2 strings of 12 or is what you're saying that I couldn't get 2 strings of 12 because I wouldn't be able to get near the 250voc? Is that why some prefer 500voc aio?

edit: 80 is the amps. Got it.

IMHO, 12S is WAY too close to 250Voc. 10S is where I would land with 21-22Voc panels.

10S w/22.8 means 228V.

If you ever hit freezing, you'll pop the MPPT.

Looks like 9S.

 

[Zwy]

As I'm in the market to replace my single phase inverter I found this growatt model. If I understand correctly, I currently have 8 panels at 20.2voc and this can handle 250voc but I plan to go to 24 panels, which I think I would have to in order to take advantage of the full wattage it can provide. That being side my current 8 panels would be 161.6v and 12 would be 242.4 which would be just inside the limit and I would have to be careful of temperature fluctuations that would change the voltage. So, if I wanted 24 panels it would have to be 2 strings that are in parallel so that the voltage wouldn't go beyond the 250voc. They must not have linked the right manual, or I'm reading it wrong because the manual still states 150voc?

Now, if I added more panels later I really need to make sure that voltage per panel doesn't go beyond 20.2 because it's getting very close to that cutoff line of 250voc, right? My current panels are 195w, but I saw a 250w panel with 22v, that would be a problem, wouldn't it?

You can always add a separate charge controller for extra panels and have a higher VOC for larger series strings. I've been running this one: https://signaturesolar.com/eg4-solar-charge-controller-mppt-500voc-100a-mppt100-48hv/

Be aware this is a low frequency inverter and standby idle draw is considerably higher than a high frequency inverter. Do not push VOC to the limits, cooler temps will cause the string VOC to be higher. Midnite has a calculator where you can see what series string voltage will be at your area's coldest temperature. https://www.midnitesolar.com/sizingTool/

 

[khisanthax]

You can always add a separate charge controller for extra panels and have a higher VOC for larger series strings. I've been running this one: https://signaturesolar.com/eg4-solar-charge-controller-mppt-500voc-100a-mppt100-48hv/

Be aware this is a low frequency inverter and standby idle draw is considerably higher than a high frequency inverter. Do not push VOC to the limits, cooler temps will cause the string VOC to be higher. Midnite has a calculator where you can see what series string voltage will be at your area's coldest temperature. https://www.midnitesolar.com/sizingTool/

Do you connect that to the all in one or not use an all in one?

There was a sungoldpower model that had 500voc, would that be worth the extra price?

I get that the limit would be 9/10 on a string but I can still have two strings right?

 

[khisanthax]

IMHO, 12S is WAY too close to 250Voc. 10S is where I would land with 21-22Voc panels.

10S w/22.8 means 228V.

If you ever hit freezing, you'll pop the MPPT.

Looks like 9S.

Also, to clarify you mentioned 4640w, is that per hour or estimated per day? I get confused when referencing watts in an hour versus watts in a day (4-5 hrs of daylight as an estimation)

 

[sunshine_eggo]

Also, to clarify you mentioned 4640w, is that per hour or estimated per day?

Power is power. It's a rate of energy consumption. It's the peak output of the array at noon. Less before and less after.

I get confused when referencing watts in an hour versus watts in a day (4-5 hrs of daylight as an estimation)

I hope you're getting more than 4-5 hours of daylight. Hopefully, you're referencing the typical 4-5 hours of insolation per day, i.e., the equivalent of 4-5 hours of PEAK output over the course of the entire day from sunrise to sunset.

You multiply your peak array power by your insolation hours to get kWh.

4.64kW * 4.5h = 20.9kWh

 

[khisanthax]

Power is power. It's a rate of energy consumption. It's the peak output of the array at noon. Less before and less after.



I hope you're getting more than 4-5 hours of daylight. Hopefully, you're referencing the typical 4-5 hours of insolation per day, i.e., the equivalent of 4-5 hours of PEAK output over the course of the entire day from sunrise to sunset.

You multiply your peak array power by your insolation hours to get kWh.

4.64kW * 4.5h = 20.9kWh

Yes, that's what I was referencing, I just didn't know what that was when sellers and manufacturers were using that metric or how they were using it. The 80A is the max charging amperage for the battery. So, would I get a different max output if the solar panels were powering the load directly? Or powering the load and charging the battery? The 20.9kWh is the max that I could potentially charge the battery in a day of sunlight?

If this unit, on the datasheet, has a 5000w max for the PV array and 250voc, does that mean that the max amperage would be 20A and that would be the most I could use for 2 strings?

 

[Zwy]

Do you connect that to the all in one or not use an all in one?

Not using the MPPT's on the all in ones.

There was a sungoldpower model that had 500voc, would that be worth the extra price?

Yes if under $400 difference. You also would have 6Kw for max array size.

I get that the limit would be 9/10 on a string but I can still have two strings right?

VOC at 22.8V times 18 would be 410V. I don't see a 200W panel available from Eco Worthy so can't input the specs into the Midnite Calculator I mentioned in my prior post. You will have to enter in that data. You might be able to run 18 panels in one string using the Sunpower if VOC at the coldest temp remains under 450V.

Charge controllers will simply clip input when amps are above it's rated amps but VOC is a hard limit and should not be exceeded.

One more word of advice, the Ecoworthy 195W panel is listed at $150 to $200 per panel. That is a range of $0.75 to $1.00 per watt. At Signature Solar website, you see panels like this Canadian Solar at $0.49/watt. That means you could buy a 4400W array size of 11 panels in one string for $2165. The same size array of Ecoworthy 195W panels at $175 each would be $3850. I checked the Canadian Solar panel thru the Midnite Calculator and 11 panels at -25F will stay under 500VOC.

 

[Zwy]

Yes, that's what I was referencing, I just didn't know what that was when sellers and manufacturers were using that metric or how they were using it. The 80A is the max charging amperage for the battery. So, would I get a different max output if the solar panels were powering the load directly? Or powering the load and charging the battery?

A load on a SCC is a load no matter whether it is being used to for powering loads thru an inverter or charging the battery. It really doesn't have an effect. Some inverters like the 18Kpv from Lux/Signature Solar have a slightly higher output rating for powering loads from both battery and PV. This is mainly due to cabling requirements, once you hit a certain point the battery cables would need to be quite large plus the battery bank would need to be much larger.

The 20.9kWh is the max that I could potentially charge the battery in a day of sunlight?

I always figure 5 hours of good sun because of winter. 5 hours x 4000W array would be roughly 20Kwh in a day. Anything over that is a bonus and I find loads for excess. My array is 8400W, I've pulled as much as 57Kwh off it on a good sunny day in spring with clear skies and battery SOC was down after a few cloudy days. I actually could have pulled more with more loads.

If this unit, on the datasheet, has a 5000w max for the PV array and 250voc, does that mean that the max amperage would be 20A and that would be the most I could use for 2 strings?

As long as you stay under VOC, the unit will just pull up to the max amps it is rated for from PV if the array is overpaneled for inverter size. If it is rated at 20A on the SCC input, then it will pull up to 20A. It caps the pull at 20A. Always remember amps create heat , voltage doesn't. Higher the voltage, the less current (amps) = less energy wasted as heat and electrical components last longer with less heat.

 

[sunshine_eggo]

Yes, that's what I was referencing, I just didn't know what that was when sellers and manufacturers were using that metric or how they were using it. The 80A is the max charging amperage for the battery. So, would I get a different max output if the solar panels were powering the load directly? Or powering the load and charging the battery? The 20.9kWh is the max that I could potentially charge the battery in a day of sunlight?

Without additional specifications, it means the MPPT can output no more than 80A. Some units can use more than their rated charge current for loads, but I don't see that indicated here.

If this unit, on the datasheet, has a 5000w max for the PV array and 250voc, does that mean that the max amperage would be 20A and that would be the most I could use for 2 strings?

Most units with an explicit PV input current limit list it in the specifications. This one does not. I would presume it can handle significantly more than 20A PV input current limit.

Again, the 5000W is not attainable due to the fact that the unit can't put out more than 80A @ battery voltage. Unless you're charging to 5000/80A = 62.5V, you'll never get 5000W out of it.

 

[khisanthax]

One more word of advice, the Ecoworthy 195W panel is listed at $150 to $200 per panel. That is a range of $0.75 to $1.00 per watt. At Signature Solar website, you see panels like this Canadian Solar at $0.49/watt. That means you could buy a 4400W array size of 11 panels in one string for $2165. The same size array of Ecoworthy 195W panels at $175 each would be $3850. I checked the Canadian Solar panel thru the Midnite Calculator and 11 panels at -25F will stay under 500VOC.

I saw some ebay sellers that had significantly reduced prices for 200w panels but your point is well taken: that I can get a better price for solar panels that can have a voc that works within the range of the inverter.

Being that I already have 8 panels, I would have to do the math to find out the additional number of Canadian solar panels I would need. I assume I can mix and match as long as the numbers add up?

 

[Zwy]

I saw some ebay sellers that had significantly reduced prices for 200w panels but your point is well taken: that I can get a better price for solar panels that can have a voc that works within the range of the inverter.

Being that I already have 8 panels, I would have to do the math to find out the additional number of Canadian solar panels I would need. I assume I can mix and match as long as the numbers add up?

I'd put those 8 panels on a different SCC.

I wouldn't buy panels off ebay either. Check out Watts247 too, Ian has been selling pallets of panels. The idea is to match up panels to the MPPT to maximize yield.

 

[Farm Boy]

As I'm in the market to replace my single phase inverter I found this growatt model. If I understand correctly, I currently have 8 panels at 20.2voc and this can handle 250voc but I plan to go to 24 panels, which I think I would have to in order to take advantage of the full wattage it can provide. That being side my current 8 panels would be 161.6v and 12 would be 242.4 which would be just inside the limit and I would have to be careful of temperature fluctuations that would change the voltage. So, if I wanted 24 panels it would have to be 2 strings that are in parallel so that the voltage wouldn't go beyond the 250voc. They must not have linked the right manual, or I'm reading it wrong because the manual still states 150voc?

Now, if I added more panels later I really need to make sure that voltage per panel doesn't go beyond 20.2 because it's getting very close to that cutoff line of 250voc, right? My current panels are 195w, but I saw a 250w panel with 22v, that would be a problem, wouldn't

 

[khisanthax]

I'd put those 8 panels on a different SCC.

I wouldn't buy panels off ebay either. Check out Watts247 too, Ian has been selling pallets of panels. The idea is to match up panels to the MPPT to maximize yield.

So either stick with the echo worthy or plan a new set of panels to match the voc.

 

[khisanthax]

I've been looking at four models of inverters and their manuals but only one states that the PV array can handle 27A, the others don't. At least not that I can see. Is there a way to determine how many strings you can use on one inverter?

 

[Zwy]

So either stick with the echo worthy

Over pay for the size. Those 8 panels could be on a cheap MPPT charge controller.

or plan a new set of panels to match the voc.

I certainly would look into sourcing panels that are cheaper per watt.