Please check my solar math...

Panel Info:

VOC: 47.7 V
ISC: 5.75 A

3 in series: 143.1 v and 5.75 A
The above paralleled 3 times: 143.1 V 17.25 A
Total Wattage for 9 panels: 2468 W

This falls in line with specs for MPP PCM60X Solar Charge Controller, which is programmable (intend to use with DIY Powerwall)
48 V Battery System, Max Open Circuit Input V = 145 v, Max PV Input Power 3200W and Max Input Current of 50A.

(4 parallel strings brings total wattage to 3291.3W...is it worth pushing it or just keep the headroom...)

If you live in an area where it gets cold (freezing), that won't work. Cold panels can give a voltage spike when the sun hits them, and that will take out the charge controller.

I made this mistake on configuring panels with my Victron 150/100. They want it below 150/1.22 = 123V if cold is a factor. The only controllers that I know can handle over-volts is the Midnite solar classic. They go into a standby mode of sorts until voltage drops.

I've bit the bullet and bought a 250/100. The change from 2S would necessitate the purchase of another controller once my full array is deployed. The 250/100 will put me within 100W of the SCC power limit.

Anyway, you need 2S4P or get another panel for 2S5P.

I agree with @snoobler, you're too close to the Maximum PV Voltage specification, but there's nothing stopping you adding more parallel strings of 2S (string Voc = 95.4V), just be sure to spec you PV cable correctly (i.e. array Isc x 1.56) and, obviously, don't exceed Max PV Input specs.

Although I agree that max specs are not nominal, they are a good design basis. This way the system is designed to handle the max output open circuit.

Rich, you run the risk of blowing your SCC if you do 3S. Period. It's not about nominal operation, it's about cold morning panel when the sun hits it with NO CURRENT, because the charge controller isn't charging yet. POP! When it sees 155 to 160V.

I'm at 142 on a 150 limit. My victron EXPLICITLY states to use a 1.22 factor if cold panels are a possibility. I thought I knew better too, but missed that in the manual. I've ordered a 250/100 unit.

Rewire your panels unless it NEVER gets chilly where you are.

Listen to them, moderation is key to maximize system performance and longevity. I will also add with tongue in cheek that a great deal of the chinese sourced components and assemblies that are available to us while good, are more of a consumer grade and not an industrial grade quality, therefore, not pushing the maximum specification envelope is prudent.

offgriddle said:

Listen to them, moderation is key to maximize system performance and longevity. I will also add with tongue in cheek that a great deal of the chinese sourced components and assemblies that are available to us while good, are more of a consumer grade and not an industrial grade quality, therefore, not pushing the maximum specification envelope is prudent.

Click to expand...

Oh I agree. I likely would go 2s2p for a fudge factor. Just want to know that I am calculating the totals accurately.

So, based on my provided data:

2s4p...results in Max Voltage of 95.4V and 28.8A for 2747.5W. All well below spec of the MPP PCM60X Solar Charge Controller:

Max V = 150 V (150/95.4 = 1.57)
Max A = 50 A (50/28.8 = 1.73)
Max W = 3200 W (3200/2747.5 = 1.16)

Numbers look good.