Off-grid solar power

[omicron1792]

Will they have cold weather charge and discharge issues like KSJoe mentioned with the other ones?

I do know they struggle more in cold. Would need to heat them. Forgot about that. All batteries do worse in the cold though.

And, on fuse, I guess it depends on maximum amp rating for inverter, so would need to just be 10 or so amps below that. I run a 4000/8000 inverter with large amp rating, so I have a large amp breaker there. Don’t remember but like 150amp maybe.

You can see my water pump on the right. It will spike the amp/watts when it turns on. Again, ask me how I know!

 

[ksJoe]

What's the advantage of breakers over fuses?

You can just flip back on if it trips, so its easy.

But the cheaper DC breakers can be polarity sensitive, meaning you cannot run the current through them in the "wrong" direction. Even if its not over current, just having the current flow the wrong way through a polarized DC breaker is enough for it to burst into flames if you try to turn it off. Here's a video showing one catch on fire due to nothing more than reverse polarity on a DC breaker when its turned off.

So if your'e using DC breakers, make sure they are wired in the correct polarity, or make sure they are not polarity sensitive. If a cheap imported DC breaker claims to not be polarized, I wouldn't necessarily trust their word on it.

If you want to keep it very simple and safe, go with fuses and accept that you'll have to replace them rather than have the convenience of resetting a breaker.

Also on the solar panels, if there are no more than 2 parallel strings of them, there is no need for over current protection on the panels. The panels are fine with their short circuit current, so if they're all in series, there is no over current protection needed. If its two strings in parallel,the two strings do not need protection because the most current they could see is 1x the short circuit current. If there's 3 or more strings in parallel, over current protection is required, because shorts in a single string could see 2x the short circuit current of the panels. What's worse - (depending on where the short is) that current can be in the reverse direction. Which means if you have 3 or more parallel strings of panels, there is no safe way to use a polarized DC breaker to protect to panels. Although a polarized DC breaker may be fine and protect you in most circumstances, if the short is in the wrong place, the breaker itself can cause a fire.

So on the panels (when 3 or more parallel strings) I'd suggest fuses for protection, and breakers for convenience elsewhere.

My charge controller is rated 500v on the PV input. One string of 12 panels in series would slightly exceed that, so I have two parallel strings of 6. My max voltage will be 250v, and I have no fuses or breakers on the solar panels because no panel can see more than 1x its rated short circuit current, and the wire is fine at the full current. Which is a long way of saying, in my configuration, the panels are not capable of producing enough current trip a properly sized fuse/breaker. So I just have a big DC rated switch.

BTW, diysolarforum.com is a great resource for figuring this stuff out.

 

[bigboreblr]

Your cooking was gas there KS Joe. The inverter controllers can put out some heat when the batteries are fully charged and the sun still is cranking. Give them some air gap on the back. Maybe avoid mounting on wood, or gap it good if you do.

I would of made a roof for that solar rack. So you have a place to relax outside while it's raining. Get something to wash the panel up twice a year or so.

Overkill is better than underkill. Your system makes the one I have at camp a toy. Just (1) group 24v battery, 12x12 panel, and a few DC lights when you don't want to run the generator.

What are you doing for refrigeration? With that amount of solar cells, you could put A/C in a small room easily.

 

[buckdeer1]

How do you deal with the heat in buildings

 

[ksJoe]

What are you doing for refrigeration?

I forgot to mention that. We're looking at a small dorm refrigerator. Either a large 1 door (with the tiny freezer area), or small 2 door. We'll also get a small microwave. For frozen food we'll probably just have a few hot pockets or something like that. But I'm thinking I might want more freezer space to store some ziplock bags of water. That way I can have ice blocks on site for hunting.

How do you deal with the heat in buildings

Nothing yet. I'd welcome suggestions though. I've thought about putting a roof vent, maybe with a fan. The building isn't insulated, so I don't think there's any point in getting a split unit.

 

[SD51555]

What are you doing for refrigeration? With that amount of solar cells, you could put A/C in a small room easily.

I have an 18 cubic foot propane fridge and freezer. They get a mint for them new, but they are nice to have if off-grid. Mine uses 8 gallons propane/month and I run it from April - November.

A guy could maybe look for a used one out of a camper. I knew a guy that was going to throw away a 10' fridge/freezer because he couldn't find anyone to buy it. I bet the used value of that unit was over $1200.

 

[buckdeer1]

I have friend that has a insulated building with vents and he says when it's 100 degrees outside it's 100 inside unless doors are open

 

[ksJoe]

I got it connected today. I made it semi-portable. The aluminum rack is not secured to anything and the PV input and AC output are both twist lock plugs. So I can disconnect it and set in the truck as a portable power supply if needed.

I was a little concerned because the batteries were in sleep mode when they arrived, as if they had been shorted and the BMS shut them down. Maybe they put them in that mode to ship them? It delayed me a bit because I didn't have a 50vdc +/- power supply, so I had to wait on one to arrive. Once the batteries saw an appropriate charge voltage, the BMSes woke up and said they had around 50% charge (which is what the vendor says they're shipped with).

Once I powered it up (around noon), it charged at 2650 - 2700 watts and had the battieries fully charged by 2 pm. I wasn't sure how much to expect out the solar panels. They're labeled for 3660 watts (305 * 12), but they should be angled more, especially for the winter sun angle. I hoped to see more than that, but that should be plenty of power.