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Bi Facial output

gray webber

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I am a newbie to this so I can easily be bashed but I wanted to share what I found out today.
I had ordered 4- 445 watt panels for AltE. Bi Facial because I am in a cold snowy area at about 47 degrees latitude.
I hooked up two panels today at my shop to my midnight solar classic 150 and a 24 volt 300 ah bank of lithium to do a test run.
The panels where tilted up against a garage door. It was cloudy and at first about 1 hour before solar noon I had started at about 500 watts.
The sun peaked out for about an hour and I checked at solar noon to see 1205 watts coming in and 44.2 amps out to batteries????? Now I am worried that my charge controller may not handle them???? I have 4 to hook up on site. It is cold today about 8F. Hope they do good but do not over power my controller/??? Anyone have experience to share on this type of situation?
Thanks!!!!!
 
Run the Midnite sizing tool on the Alte site. It says you are perfectly matched in a 2S2P configuration. You are at 70% loading, and even only 94% if you allow the 30% over production you saw with the Bi-facial panels. People over panel all the time, just don't exceed the max voltage (the tool will calculate it for you).
 
So what you are saying is the panels will exceed the charge controller power inputs?
Thought it was close but Adam at AltE felt the Midnight would handle them. He did not think the panel outputs would be that good?
I’ll have to get with him on an answer?????
Others with experience please share.
Thanks!
 
I’ll do that !
I sure hope it’s ok as it would be a mess to reboot design or parts now.
Thanks for your insight!!
Off to the Alt sight.
 
You can't even use 4 in parallel because the voltage would be too high.
4 in parallel would be the individual panel voltage. What is the Voc of each panel?

You can't use 2s 2p either.
Why is this? Presumably Voc would be ~100V (50Voc per panel?) and Isc around (445W / 50V = 8.9A per panel) 2x = 17.8A. The Classic 150 can easily handle this.
 
Alt sight says ok up to 2700 watts. I had 1206 on 2 panels today which is 4% over the high end of rating on bi facial outputs?
Taking 2700 /4= 675 watts or 1.16 x max. Today I saw 1.03 x max of 580 from spec sheet. If I can feel confident not to get 13% more then the Midnight Classic should handle it?????
Did I miss anything?
 
4 in parallel would be the individual panel voltage. What is the Voc of each panel?


Why is this? Presumably Voc would be ~100V (50Voc per panel?) and Isc around (445W / 50V = 8.9A per panel) 2x = 17.8A. The Classic 150 can easily handle this.
Voc is 48.9. Running amps is 11.54 or 15.0 BF max. 580 watts. I already got 602 watts from them. Rated at 445 standard.
It’s the added bi facial power that causes questions.
 
Your Classic 150 will be just fine. Enjoy your system.

What questions?
Would be great if it handles thing!
Questions: will these panels exceed rating by enough to cause issues due to very cold temps we get?????
It was -12f at the camp site today.
 
will these panels exceed rating by enough to cause issues due to very cold temps we get?????
So you're talking exceeding the max input voltage. The Voc x2 is 100V and your SCC will handle 150V (correct me if i am wrong).

If you know the exact thermal coefficient of your panels, please specify, it may be listed on the back of the panels. Typical is around .35% voltage change per degree C below 25C (77F). I cannot imagine it getting that cold anywhere on this planet to increase the Voc by that much.

Lets try 100 deg C temp drop (-75C) (-103F):

49Voc x 100deg x .0035 = 17V change. So that puts a 2S array at about 132V, at -103F.
 
So you're talking exceeding the max input voltage. The Voc x2 is 100V and your SCC will handle 150V (correct me if i am wrong).

If you know the exact thermal coefficient of your panels, please specify, it may be listed on the back of the panels. Typical is around .35% voltage change per degree C below 25C (77F). I cannot imagine it getting that cold anywhere on this planet to increase the Voc by that much.

Lets try 100 deg C temp drop (-75C) (-103F):

49Voc x 100deg x .0035 = 17V change. So that puts a 2S array at about 132V, at -103F.
Voltage is not the issue? 2in series would top out at 97.8volts- Voc. Stat sheet says .26 % per degree C. Classic can handle 150 v.
they already reached 603 watts each. If watts alone are the issue then the classic can handle 2700 max or 675 watts per panel.
Just so close.
 
Voltage is not the issue?
Not even close.

If watts alone are the issue then the classic can handle 2700 max or 675 watts per panel.
This is called over paneling and its common to maximize what an SCC will produce. The key word is "handle", meaning the most it can/will use.

Max Current Out 96 Amps​


96A x 28V charge voltage = 2688W depending on your chosen charge voltage.

They must be using a charge voltage of:
2700W / 96A = 28.125V
 
Not even close.


This is called over paneling and its common to maximize what an SCC will produce. The key word is "handle", meaning the most it can/will use.

Max Current Out 96 Amps​


96A x 28V charge voltage = 2688W depending on your chosen charge voltage.

They must be using a charge voltage of:
2700W / 96A = 28.125V
For 24 volts it’s rated at 94 a. I have bulk set at 28.4 volts.
Over panel? Maybe. Adam at AltE said it will work and said not to expect the claimed outputs for Bi-facials. I said ok:). Then today I get much more from the panel then it’s rated. Yikes! Got me asking others what’s up. Just trying to get settled on what if any issues exist.
 
The Midnite Classic is smart enough to limit the output amps to what it can handle without danger. There is a "hard cap" of around 92 amps or less depending on the exact model, but the user can lower that by software settings, and in addition the controller itself will limit current if the temps get too high.

My setup is "severely overpaneled" by most poeple's definition, I have a 45 kWh lithium battery system fed by two Midnite 150's. I have close to 5KW feeding each Midnite 150, or about twice what it can handle at 24 volts. I manually set the maximum output current to. 85 amps on each one, which keeps the temps down in a comfortable zone and is plenty to do the job. When we get sun they saturate for about 3 hours to fully recharge the batteries, no issues. On the vast majority of days when it's cloudy here they generate maybe 20 percent output, that's the reason for the overpaneling, as here in western Oregon it's cloudy a lot more than it's sunny.

With a good charge controller overpaneling isn't an issue.
 
The Midnite Classic is smart enough to limit the output amps to what it can handle without danger. There is a "hard cap" of around 92 amps or less depending on the exact model, but the user can lower that by software settings, and in addition the controller itself will limit current if the temps get too high.

My setup is "severely overpaneled" by most poeple's definition, I have a 45 kWh lithium battery system fed by two Midnite 150's. I have close to 5KW feeding each Midnite 150, or about twice what it can handle at 24 volts. I manually set the maximum output current to. 85 amps on each one, which keeps the temps down in a comfortable zone and is plenty to do the job. When we get sun they saturate for about 3 hours to fully recharge the batteries, no issues. On the vast majority of days when it's cloudy here they generate maybe 20 percent output, that's the reason for the overpaneling, as here in western Oregon it's cloudy a lot more than it's sunny.

With a good charge controller overpaneling isn't an issue.
Great info! Thanks, this relaxes me about things. Great to know it will limit amps to not burn up. It will be seldom that it runs hot but without safe guards one time would be enough. While reading the manual some of this comes out but in language that does not hit home. Your verbiage is very good!
Thanks again and now I can sleep!
 
4 in parallel would be the individual panel voltage. What is the Voc of each panel?


Why is this? Presumably Voc would be ~100V (50Voc per panel?) and Isc around (445W / 50V = 8.9A per panel) 2x = 17.8A. The Classic 150 can easily handle this.
Yes, I was puzzled by that too. The panels are 48.9 VOC and amps of 14.2 but i was seeing 14.6 in real live. so I was planning on 2s and 2p for the feed into the collector box.
I did run the number into the Alt E store midnight solar tool and even with the 602watts I experienced the other day it said it would handle it but I am close. I may have to dial up my charge voltage but with lithium, I was trying to stay a bit lower so to not force charge too much? Im set at 28.4 now. Also, I will have to change the charge controllers max output somehow or change my breaker as I have an 80 amp now. Looks like 90 would be safer to use and not lose input by mistake during a nice solar day.
 
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