Checking My Numbers

[wildbillpdx]

Extreme Nubee...

I have 21 older Sanyo HIP-200BA3 solar panels just removed from my roof (long story). I want to use them with an EG4 6000EX (I have a deep well and water pump, limited money and this is just an experiment for now.) I've done some calculations and want to be sure I won't kill either component if I use them together.

Specs for the panels are 200watts, 68.7 VOC, 15amps. I plan to use 7 wired in series to power the 6000EX. Specs on that are 7500watts max PV input, 500 VOC max input, 27amps input. My calculations (if correct) show the 7 panels will produce 481voc, 15amps and 7214 watts, which appear to be fine for the 6000EX.

Do my calculations look correct?

Just noticed that the 15amps is the recommended fuse rating...would Maximum Power Current (Ipm) at 3.59amps be the correct number to use to calculate watts?

Thanks.

 

[Madco]

Something is wrong. 7 200w panels will produce 1400W, not 7214W. Looks like your're using the Voc and Isc ratings of the panels to calculate power. The panels will not operate at either.

The 481V input is too close to the 500V maximum. It will likely exceed that if you live in an area where it gets cold.

 

[Madco]

Pulled the data on your panels. The max power specs are 55.8V and 3.59A, so the 7 panels will indeed generate 1400W under STC. But, the Voc will be around 511V if the panels are at 32F.

Six panels in series will be safe (assuming the temp doesn't fall below 32 in your part of Oregon).

 

[Madco]

BTW, the 15A current you stated appears to be the maximum recommended fuse size. The Isc is 3.83A.

 

[wildbillpdx]

Pulled the data on your panels. The max power specs are 55.8V and 3.59A, so the 7 panels will indeed generate 1400W under STC. But, the Voc will be around 511V if the panels are at 32F.

Six panels in series will be safe (assuming the temp doesn't fall below 32 in your part of Oregon).

Thanks for the input. I noticed the fuse figure and posted an update. Would I be able to run two string...series then combined in parallel to increase the wattage or just run the one in series? Temperatures in the winter do fall below 32...sometimes on rare occasions down to single digits. I'm near Portland.

 

[wildbillpdx]

The max power specs are 55.8V

How does that compare to the VOC for the panels which is 68.7v? Trying to understand the 500voc limit on the 6000ex.

 

[Madco]

Yea, you could do 2 or 3 parallel strings of 6 panels in series.

2 parallel stings of 6 in series would give you 2400W with 335V and 7.2A input to the inverter.

3 parallel strings of 6 in series would be 3600W with 335V and 10.8A into the inverter.

In either case, the panels have a voltage temperature coefficient of .172%/C, so if you go down to 0F, the open circuit voltage applied to the inverter will be just under 429V.

With 7 panels in series, your open circuit voltage would have been 502V at 0F.

The comparison of Vmp and Voc is kinda an apples to oranges comparison. The panels are current sources so they will drive their terminal voltages up in an attempt to source current. But if the circuit is open (the same thing as if its early in the morning and the MPPT charge controller is not yet accepting power) there is a limit to how high the voltage can go. This is the Voc rating. The Vmp rating is the voltage at which the panels will deliver maximum power. The Imp rating is the current at maximum power.

The maximum PV input on the inverter is its maximum allowable applied voltage. You have to stay below that while considering that the panels produce higher voltage when cold.

 

[Madco]

I hate Celcius! I foobarred the Voc calc at 0F. Should be 439V for any 6 series string and 512V for any 7 series string!

 

[wildbillpdx]

I hate Celcius! I foobarred the Voc calc at 0F. Should be 439V for any 6 series string and 512V for any 7 series string!

Thanks for all your help. I have a very rudimentary understanding of things electrical, even less when it comes to solar. We have the 21 panels because it was better financially to replace our grid-tied solar array rather than removing it and reinstalling for a new roof. The array is 17 years old and the new system will be 9.6kW rather than 4.2kW. Cost for the new system was roughly double what we were being quoted to remove and reinstall. Just can't stand to waste the old panels since they should still be usable for something.

 

[Madco]

Happy to help out! Good luck with the project. Feel free to PM me if you have more questions.

 

[wildbillpdx]

Okay, a continuation with a new question. Based on all the input, I'm trying to decide whether 4 strings (5s4p) might not be a better choice. Per my calculations I get the following: 279v 14.36a 4000 watts vs 3 strings (6s3p) at 335v 10.77a and 3606 watts. The 4 strings are well within the limits of the inverter (500 VOC, 27a, 7500 watts). Just wondering if watts would be more important than volts. With 4 strings I get about 400 watts of additional potential. I've got 21 panels, which means I'd have one spare.

 

[Tomthumb62]

Sanyo HIP-200BA3 solar panels

Specs for the panels are 200watts, 68.7 VOC, 15amps

I looked up these panels, the Voc is 68.7, but the amps Isc is 3.83. The max FUSE rating is 15A.

Six wired in series at -10F (does it get colder than that ever in recorded history in Portland?), will give you 447V, so you're good there with a max 500VDC input on your MPPT. Seven in series puts you over at 520V, which would fry your MPPT.

 

[Madco]

That will be fine, sorry I didn't consider that earlier!

The watts/volts question is more or less moot by the time you move to several hundred volts. Power is conserved so the only consideration is reducing the current by increasing voltage and hence being able to use smaller wire.

Again, sorry my earlier analysis would have effectively cost you 400W!

 

[wildbillpdx]

That will be fine, sorry I didn't consider that earlier!

The watts/volts question is more or less moot by the time you move to several hundred volts. Power is conserved so the only consideration is reducing the current by increasing voltage and hence being able to use smaller wire.

Again, sorry my earlier analysis would have effectively cost you 400W!

You weren't costing me anything. I'm just trying to make the most of the used panels coming down from my roof tomorrow. I figure why waste a usable resource. Besides, with the new 9.6kW system and these old ones, I should be getting about 13.6kW give or take. Still getting my head wrapped around the serial/parallel combinations. Wasn't thinking clearly about it except I was trying to use all 21 panels in three strings.