Sizing an array for MPP Solar LV2424

[Alan-HH]

Hello,

I have just purchased a LV 5048 MPP and i have 16S CALB 100AH cells with a Daly 100A BT and 6 Canadian solar panels 320MS the VOC is 44.0 and the VMP is 36.2 how would you config the panels if the LV5048 shows this (will got me started on this COVID project)
and does any one know what would be the best setting for the BMS and also the LV5048 Thank you

 

[dirtybobby423]

Hello,

I have just purchased a LV 5048 MPP and i have 16S CALB 100AH cells with a Daly 100A BT and 6 Canadian solar panels 320MS the VOC is 44.0 and the VMP is 36.2 how would you config the panels if the LV5048 shows this (will got me started on this COVID project)
and does any one know what would be the best setting for the BMS and also the LV5048 Thank you

2s3p Would be my thought

 

[Alan-HH]

2s3p Would be my thought

Yes this is what i was running it at today would 3s be to much ???? every one says that 3s X 44.0V = 132V

 

[gnubie]

Do your low temperature voltage rise calculations using the Voc derate factor for your panels. Assuming 0.3% derate / degree C and a buffer of 13V, approx -8C is required to hit 145V. If you can't make icecubes outdoors, you should be safe with 3s. Some panels will give you a mV / degree C drop instead of a percentage but I'm sure you can work that out too.

13V / 132V * 0.003 = 32.8 reduction in temperature from STC, STC is 25C. 25 - 32.8 = ~-8C.

Assuming my maths is right that's it. I'm sure someone will correct it if it's wrong

 

[dirtybobby423]

Yes this is what i was running it at today would 3s be to much ???? every one says that 3s X 44.0V = 132V

I think 3s would be pushing it especially if cold, and if the mpp doesn't charge from 115V+ then not sure what your gaining.

 

[Mac6792]

Yes this is what i was running it at today would 3s be to much ???? every one says that 3s X 44.0V = 132V

I have similar specs as yours but with 8 panels. (VOC of about 38) I chose 2s4P. I'm in New England so that gives me lots of buffer on variable temps as well as better shade production with 4 strings. In actual use, what I'm seeing at the inverter is a VOC with no sun of about 71-75 volts and 40-70 while producing power. Full sun I see in the mid sixties. I could probably get away with a third panel in series given what I'm seeing but I have yet to go through winter with this setup to see how high the voltage goes so I'm fine with my decision

 

[Alan-HH]

Do your low temperature voltage rise calculations using the Voc derate factor for your panels. Assuming 0.3% derate / degree C and a buffer of 13V, approx -8C is required to hit 145V. If you can't make icecubes outdoors, you should be safe with 3s. Some panels will give you a mV / degree C drop instead of a percentage but I'm sure you can work that out too.

13V / 132V * 0.003 = 32.8 reduction in temperature from STC, STC is 25C. 25 - 32.8 = ~-8C.

Assuming my maths is right that's it. I'm sure someone will correct it if it's wrong

Hello I live in Phoenix Arizona, 85383

 

[erik.calco]

I have similar specs as yours but with 8 panels. (VOC of about 38) I chose 2s4P. I'm in New England so that gives me lots of buffer on variable temps as well as better shade production with 4 strings. In actual use, what I'm seeing at the inverter is a VOC with no sun of about 71-75 volts and 40-70 while producing power. Full sun I see in the mid sixties. I could probably get away with a third panel in series given what I'm seeing but I have yet to go through winter with this setup to see how high the voltage goes so I'm fine with my decision

Same here. Will be interesting to see what we see on really cold days.

 

[Alan-HH]

Hello Gentlemen I have a few picture of the test system with BMS and the LV5048 Remember its a test system and I'm a newbie

 

[Alan-HH]

Part 2

 

[gnubie]

I think 3s would be pushing it especially if cold, and if the mpp doesn't charge from 115V+ then not sure what your gaining.

The string Vmp is at about 108V with 3s that gives a leeway of 7V. If it's 0.3% derate (no idea here it could be 0.4%) that means the cells need to be at 5 degrees C to hit about 115V. That might be a problem very early in the day, but they'll soon heat up given his location.

 

[TJ King]

Would I add up the 21.3 Voc in series and ignore parallel, so that 4Sx3P would be 4x22V or 88V?
Yes. And you would have a good deal of headroom for cold morning spikes. As long as the VOC of the series string is lower than 145v, you are set.

But what is the total power output of your array in watts? This MPP unit can handle 2kw array, so be sure not to exceed that limit. It can max out at 83 amps, but its rated for 80 amps. I would keep it below 80.

Considering the size of array that you are building, you may consider using larger panels. 100w panels are pretty small for this application. Also, with larger panels, you can put them all in series and skip the branch connectors. Boost the voltage up to 80-120v VOC and keep the amps nice and low for that long wire run.

When you say "don't exceed 2k watt", what happens? I get the 145v drop dead limit, but I was under the impression if you step over 2k to let's say 2250w, the mpp2424 just receives 2k of the 2250 as long as you stay below the 145v and amp limits. Example 9 santan 250 panels in 3s3p at 37.6voc x 3=112.8v and 8.27a x 3=24.81a. Am I right that this lives in the limits, but just fails to exploit the last 250w of the 2250w?

 

[mrdavvv]

When you say "don't exceed 2k watt", what happens? I get the 145v drop dead limit, but I was under the impression if you step over 2k to let's say 2250w, the mpp2424 just receives 2k of the 2250 as long as you stay below the 145v and amp limits. Example 9 santan 250 panels in 3s3p at 37.6voc x 3=112.8v and 8.27a x 3=24.81a. Am I right that this lives in the limits, but just fails to exploit the last 250w of the 2250w?

In reality the inverter can exceed 2000W, ive seen mine hit 2200W, my array is 6x380W, so 2280W. Havent seen any problems. Also keep in mind that rarely the panels hit 100%, so you would be below 2000W most of the time.

As you know, you only need to avoid the Voc of the inverter, generally you can "overpanel" without problems", the MPPT of the inverter will limit itself if the current goes below limit.

 

[MountainMatt]

My used panels 8x275 = 2200. Seen 2kw a few times, no problems. Put breakers in.
Just built my Ironridge ground mount system, all finished today.Ground Mount

 

[openplanet]

Would I add up the 21.3 Voc in series and ignore parallel, so that 4Sx3P would be 4x22V or 88V?
Yes. And you would have a good deal of headroom for cold morning spikes. As long as the VOC of the series string is lower than 145v, you are set.

But what is the total power output of your array in watts? This MPP unit can handle 2kw array, so be sure not to exceed that limit. It can max out at 83 amps, but its rated for 80 amps. I would keep it below 80.

Considering the size of array that you are building, you may consider using larger panels. 100w panels are pretty small for this application. Also, with larger panels, you can put them all in series and skip the branch connectors. Boost the voltage up to 80-120v VOC and keep the amps nice and low for that long wire run.

Hello Will--I certainly believe you that the max input VOC for the LV2424 is 145v. But I've looked and looked in the manual and can't find where this is specified. As I'm consisering a series pair of 375 Watt panels each with a VOC of 47.2 Volts, I'd like to extra extra extra sure I'm not going over the max input voltage. Thank you very much.

 

[Will Prowse]

Hello Will--I certainly believe you that the max input VOC for the LV2424 is 145v. But I've looked and looked in the manual and can't find where this is specified. As I'm consisering a series pair of 375 Watt panels each with a VOC of 47.2 Volts, I'd like to extra extra extra sure I'm not going over the max input voltage. Thank you very much.

Check the sticker on the side of the unit.

 

[jasonhc73]

Page 8.

http://www.mppsolar.com/manual/PIP-LV%20110_120VAC/PIP-LV%203KVA%20manual-20210701.pdf