diy solar

diy solar

Behold! My $1200 Tesla charger!

Great info. Thank you for the post! Sounds like I’m going to have to test each panel individually at some point. I got them for so cheap I’m pretty happy they work at all.

Here’s a breakdown:
2x four panels in series with those two connected in parallel. Interestingly each series of panels perform (or underperform) equally. While everything is connected (on this particular day) I’m getting 92/100 volts under no load, 6/8 amps per side and 65/80 volts under load. It’s consistent that my voltage goes down under load and the higher the amps, the lower the voltage. It’s worth mentioning that I have a 100’ run of 10 awg from the panels to the SCC. I measured the voltage drop under no load it was 1.5%.

I’m guessing I should measure the voltage drop under load. I haven’t don’t that yet.

I used 14 gauge connectors between the panels, 12” only. Could that be limiting my flow?

Still got some work to do
 
One string 92V 6A vs. other 100V 8A would be significant difference.
If that's what you mean, it was for similar reasons I measured individual panel performance. Mine were all connected together (12s2p) and after I got a clamp DC ammeter I measured significantly different current.
Your array we would call 4s2p

The wire won't cause particularly great loss, unless higher current or longer run.

"I measured the voltage drop under no load it was 1.5%."

??

I would expect no drop, 0.0%, under no load.
 
One string 92V 6A vs. other 100V 8A would be significant difference.
If that's what you mean, it was for similar reasons I measured individual panel performance. Mine were all connected together (12s2p) and after I got a clamp DC ammeter I measured significantly different current.
Your array we would call 4s2p

The wire won't cause particularly great loss, unless higher current or longer run.

"I measured the voltage drop under no load it was 1.5%."

??

I would expect no drop, 0.0%, under no load.
Oh sorry. I meant I was getting 92 volts voc out of the rated 100 volts. And 6 amps out of the rated 8 (per panel series) under load and 65 volts of the rated 80 under load. I actually peaked at 15 amps/16 today, but the voltage had dropped to 55.
So it seems I would have to test each panel under load to find if I have any individual underperformers. That’s where I seem to have the most discrepancies. You wouldn’t happen to have a bunch of space heaters I could borrow?

I’ll check my voltage drop for the 100’ run again. You’re right I shouldn’t have any issues based on some online calculators. I’m more suspicious of a bad panel. In my 4s2p (thank you for the nomenclature) would one bad panel being down the whole array?
 
I think I read most of this thread, hoe I am not repeating too much, there are some really smart people already on this thread.

At solar noon sun, I am hitting over 240 watts from my 300 watt panels, and that is the output of the Enphase inverters, but they are claimed to be 97% efficient. So I would think a panel that is getting decent sun with good tilt angle should be able to hit 80% of it's STC power rating, depending on where you live though. Haze in the sky can knock the output down a bit more. A few days ago, all 16 of my panels were well over the 80% (240 watt) mark, but today, it looked just as sunny, but I only hit 230 watts on the best panels, a few were down to 220 watts. The air was hotter and less wind, so the solar panels also got hotter in the sun.

If you want to do the VOC and ISC tests on your solar panels I would only do it one panel at a time. Not only is it a lot safer when you open the short, it will also let you see if you have a weak panel as you can compare them all separately. Ideally, you want the open voltage and the shorted current of all the panels to match and be at least 80% of the ratings on the panels. If you are running the panels in series, just one weak panel will drop the output of the entire string.

Have you looked up how many "sun hours" you should be getting at your location and with your panel tilt and heading angles? I saw you said "6 good hours of sun" but it does not really work like that. Sun hours is the total equivalent sun you get in the entire day of sun. Today, I was getting some power from my solar panels for 11.5 hours, to get that 5.4 sun hours of energy. The power starts very low at sunrise, climbs to the peak close to panel rating at solar noon, and then drops back down to zero again at sunset. I use this site to get a decent estimate of sun hours.


Go to the bottom left of the page and click on the arrow under "Solar Irradiance Tables". It will give you a rough idea of the sun hours you should be able to get on a clear day each month. Closer to winter, the numbers drop, and closer to summer the numbers are better, the table give the average for each month. I get 15% more at the end of March compared to the beginning of March as the days are getting longer. I was getting about 5.4 sun hours a day this past week, but I am in sunny SO Cal. If your 1,320 watts of solar panel were here, they should produce about 7.1 kwh a day, if they were turned 20 degrees west, and 20 degrees up from flat towards the equator. That is the position of my array, at 32 degrees north latitude.

To make use of the panels you have, you do need a lot more battery. You solar panels should be able to make 130 amps hours or so in a 48 volts system. So with AGM you should have close to 300 amp hours to make them last. If you can really put 7 kwh into your car at a more realistic 4 miles per kwh, then you might get 28 miles of range per day. A bit less in winter, and maybe a little more in summer.
That you for the link, that’s some great info. I’m in Central Valley CA, so my numbers should be pretty close to yours. I’ll check my tilt. Currently my tilting system is an advanced setup of milk crates and cardboard boxes.

Yeah, I’m not going to try and short the whole array. I’ll just do one panel at a time. I should have some time next week to do it while the Tesla is in the shop.

Yep, too little of a battery bank for the panels (if I get the efficiency up), but batteries are expensive! I’m probably going to run these down then switch to LFP.

Thank you for your efficiency numbers. That gives me something to aim for.
 
I think I read most of this thread, hoe I am not repeating too much, there are some really smart people already on this thread.

At solar noon sun, I am hitting over 240 watts from my 300 watt panels, and that is the output of the Enphase inverters, but they are claimed to be 97% efficient. So I would think a panel that is getting decent sun with good tilt angle should be able to hit 80% of it's STC power rating, depending on where you live though. Haze in the sky can knock the output down a bit more. A few days ago, all 16 of my panels were well over the 80% (240 watt) mark, but today, it looked just as sunny, but I only hit 230 watts on the best panels, a few were down to 220 watts. The air was hotter and less wind, so the solar panels also got hotter in the sun.

If you want to do the VOC and ISC tests on your solar panels I would only do it one panel at a time. Not only is it a lot safer when you open the short, it will also let you see if you have a weak panel as you can compare them all separately. Ideally, you want the open voltage and the shorted current of all the panels to match and be at least 80% of the ratings on the panels. If you are running the panels in series, just one weak panel will drop the output of the entire string.

Have you looked up how many "sun hours" you should be getting at your location and with your panel tilt and heading angles? I saw you said "6 good hours of sun" but it does not really work like that. Sun hours is the total equivalent sun you get in the entire day of sun. Today, I was getting some power from my solar panels for 11.5 hours, to get that 5.4 sun hours of energy. The power starts very low at sunrise, climbs to the peak close to panel rating at solar noon, and then drops back down to zero again at sunset. I use this site to get a decent estimate of sun hours.


Go to the bottom left of the page and click on the arrow under "Solar Irradiance Tables". It will give you a rough idea of the sun hours you should be able to get on a clear day each month. Closer to winter, the numbers drop, and closer to summer the numbers are better, the table give the average for each month. I get 15% more at the end of March compared to the beginning of March as the days are getting longer. I was getting about 5.4 sun hours a day this past week, but I am in sunny SO Cal. If your 1,320 watts of solar panel were here, they should produce about 7.1 kwh a day, if they were turned 20 degrees west, and 20 degrees up from flat towards the equator. That is the position of my array, at 32 degrees north latitude.

To make use of the panels you have, you do need a lot more battery. You solar panels should be able to make 130 amps hours or so in a 48 volts system. So with AGM you should have close to 300 amp hours to make them last. If you can really put 7 kwh into your car at a more realistic 4 miles per kwh, then you might get 28 miles of range per day. A bit less in winter, and maybe a little more in summer.
“That is the position of my array, at 32 degrees north latitude”

Took your advice and looked up the best angle for my area. It gave me 30.5, so I built a stand accordingly. I’ll have to do the other four panels when I have more time. Let’s see if this makes a difference. Thanks again for the input!
 

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Problem is it is around 30 amps regardless of C. 30 amps for my setup is only .075C. Well below the max current. Maybe my SCC doesn’t know how many amp hours my setup is and keeps it at 30? Or maybe it’s rates at 60 amps, but never actually achieves it. I wish someone with the same SCC could compare numbers.
Your first impression- "The super cheap charge controller might be my limitation." was similar to mine. Not so much the price but the expectation...split the array and another cheap controller over just getting a more expensive one of the same amperage.
Or better still, if room allows, duplicate the Pv system.
 
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