Ski Skoolie Solar Upgrade; 2x Power & Wattage

[ADDvanced]

Hey dudes, just sharing a quick video where I threw an extra panel I had on the ski skoolie, and doubled the battery power. I am now running mixed panels, AND a mixed battery bank (the company that made my current lithiums does not exist anymore so I can't run matched). I also give a shoutout to this forum in the video, because you guys are all awesome.

 

[sunshine_eggo]

Running "matched" is primarily driven by battery suppliers. Back in the lead acid days, it could make a difference.

Inherent lower battery resistance and proper wiring makes it mostly a non-issue with LFP.

That panel combination is past the ragged edge of best practices. You generally want your parallel strings within 10% to avoid potential short circuit through the lower voltage string. I see you used Vmp, which is good, but you have two 12V panels in series and then in parallel with a 60 cell panel - about 36Voc. When your Vmp of one string is higher than the Voc of another string, you run the risk of the lower voltage string acting as a short for the higher voltage string. Since you're seeing improved power over the 200W, that's not happening, and you should be thankfully surprised the Renogy can handle it.

Thanks for the forum props. You gave some decent advice. Looks like you've actually learned this shit!

Good luck getting "this turd" insulated... I feel yer pain. A shipping container has an R-value of about 0.002.

Hope your dad's good.

 

[sunshine_eggo]

There's a scenario you didn't consider that's actually better.

Your config at 29.8V * 12.68A = 377W.

PARALLEL the 100W for 20.4V @ 9.8A

Then series them with the 230W, 29.8 * 7.78A.

This will yield (29.8+20.4V) * 7.78 = 390W

So rather than cutting down the voltage of the 100W panels, you're cutting down their current by a little less. Zero risk of issues with the significant string voltage disparity in the 2S 100W in parallel with the 230W config.

Furthermore, your actual yield may be higher when you consider panel orientation. Since your 230W panel is more optimally tilted compared to your flat 100W panels, your 100W panels are likely not being throttled since they're outputting less anyway.

 

[42OhmsPA]

You're Arctic Cat quit video is excellent. .

 

[ADDvanced]

There's a scenario you didn't consider that's actually better.

Your config at 29.8V * 12.68A = 377W.

PARALLEL the 100W for 20.4V @ 9.8A

Then series them with the 230W, 29.8 * 7.78A.

This will yield (29.8+20.4V) * 7.78 = 390W

So rather than cutting down the voltage of the 100W panels, you're cutting down their current by a little less. Zero risk of issues with the significant string voltage disparity in the 2S 100W in parallel with the 230W config.

Furthermore, your actual yield may be higher when you consider panel orientation. Since your 230W panel is more optimally tilted compared to your flat 100W panels, your 100W panels are likely not being throttled since they're outputting less anyway.

DAMMIT! I'll update that next time I get out there, which should hopefully be in a few short weeks.

Thanks for all the help! Always more to learn.

 

[ADDvanced]

There's a scenario you didn't consider that's actually better.

Your config at 29.8V * 12.68A = 377W.

PARALLEL the 100W for 20.4V @ 9.8A

Then series them with the 230W, 29.8 * 7.78A.

This will yield (29.8+20.4V) * 7.78 = 390W

So rather than cutting down the voltage of the 100W panels, you're cutting down their current by a little less. Zero risk of issues with the significant string voltage disparity in the 2S 100W in parallel with the 230W config.

Furthermore, your actual yield may be higher when you consider panel orientation. Since your 230W panel is more optimally tilted compared to your flat 100W panels, your 100W panels are likely not being throttled since they're outputting less anyway.

Got back here yesterday; wouldn't putting the big panel in series with the two smaller panels limit the big panel? Like, if the smaller 100W panels in parallel aren't doing much, but the big panel is, wouldn't it be throttled by the partially shaded 100W panels?

 

[sunshine_eggo]

It depends on how much shading you have. At max output, the big panel, 7.78A, would limit the parallel 100W panels, 9.4A.

 

[ADDvanced]

Well like if the one that's flat and not tilted gets dirty and doesn't put out much, will it nerf the big panel's production?

 

[sunshine_eggo]

Well like if the one that's flat and not tilted gets dirty and doesn't put out much, will it nerf the big panel's production?

7.78A panel
2P panels @ 9.8A total

The lower current of the above two will limit the other. The 2P "panel" will not limit the 7.78A panel until it the 2P producing 79% rated, and that assumes the 7.78A panel can output 100%.