Final tire kicking for my new system

[SolarSteve]

OK. I thought you said that at lowest possible temperature you were overvoltage.

I might have. There was an earlier discussion that was more vague about temperatures and I thought more-or-less freezing was a concern for overvoltage. That is a possibility in October, especially with the factors J.P.M. mentioned being worked in. Then I found the MidNite Solar calculator which helped me get more specific about where the danger point really is. I was surprised to learn that point is roughly 10F with J.P.M.'s factors all at play, more like 5F or even less with those other factors not in play. Since it never gets down to 10F when I've got this up and running I'm fine.

Once the sun is up the panels get much warmer.

Yup, unless a front moves through during the night. A couple of times a year it's colder at mid day than the prior night. It is definitely odd to see the sun come up and the temperature drop, but it does happen.

I have to say this whole process has been extremely interesting and educational for me. I've lived offgrid for about 10 years now, but I didn't design my home system. These conversations here have resulted in a system that appears to be sound and balanced, which is a far cry from my first design. I'm very thankful to have people helping kick the tires because a number of them fell off

Steve

[jflorey2]

I might have. There was an earlier discussion that was more vague about temperatures and I thought more-or-less freezing was a concern for overvoltage. That is a possibility in October, especially with the factors J.P.M. mentioned being worked in. Then I found the MidNite Solar calculator which helped me get more specific about where the danger point really is. I was surprised to learn that point is roughly 10F with J.P.M.'s factors all at play, more like 5F or even less with those other factors not in play. Since it never gets down to 10F when I've got this up and running I'm fine.

OK, then no problem. As long as the temperature in your area never gets below that, you're covered.

Yup, unless a front moves through during the night. A couple of times a year it's colder at mid day than the prior night. It is definitely odd to see the sun come up and the temperature drop, but it does happen.

Right - but as long as it never, ever gets below the temperature you have calculated as resulting in a >150V OCV you're good. That's the critical issue here.

[SolarSteve]

Got the system up and running this weekend as per the last design. Seems to work very well with plenty of power going into the batteries even on a very cloudy day and the refrigerator running. Only problem so far is my refrigerator has electronics to automatically switch from 12v to 24v mode based on input voltage. Works fine in 12v, but when I hook it up to the 24v circuit only the light works (which indicates the circuit is live). I'll contact the manufacturer tomorrow and see what's up with that. Always something, eh?

Thanks for all the help. And Mike, you might be tickled to know that I used that cutoff switch three times already! Your nudge towards it is very much appreciated.

Steve