Small system to power small freezer

[Sonnyboy]

Overloading your controller with too many amps though could be an issue. Your system is 12V? Even with 85% de-rating, that's (1600W/13Vcharging) X 85% = 105A. What you can do is what I mentioned in post #19, having each string pointed in a different direction. Maybe one facing East, one facing South, and one facing West. I'd put the 100W string in the middle, facing South. Then current flow will be a bit more balanced over the course of the day, but you'll be getting the most amps in the early morning and late afternoon.

Thanks Michael. The specs of my Epever SCC state 520w max for solar input at 12v and 1040w on a 24v system. I only have a single pitch roof to mount on but the trees make it so I only get direct Sun on the whole roof for about four hours max.

 

[Leeds]

Before you add solar panels to your system have you considered making your current setup run more efficiently?

Your design appears to keep the inverter on all the time. Spend the $15 on an inkbird style 12vdc digital thermostat and wire it's cooling relay output it in series with the go signal in your inverter.

This $15 should just about cut your battery drain in half.

 

[Sonnyboy]

Before you add solar panels to your system have you considered making your current setup run more efficiently?

Your design appears to keep the inverter on all the time. Spend the $15 on an inkbird style 12vdc digital thermostat and wire it's cooling relay output it in series with the go signal in your inverter.

This $15 should just about cut your battery drain in half.

Whoa, really? Thanks, I wasn’t aware of that. I will check that out.

 

[Sonnyboy]

Before you add solar panels to your system have you considered making your current setup run more efficiently?

Your design appears to keep the inverter on all the time. Spend the $15 on an inkbird style 12vdc digital thermostat and wire it's cooling relay output it in series with the go signal in your inverter.

This $15 should just about cut your battery drain in half.

Would you mind being more specific with your wiring suggestion? I am going to try this.

 

[Leeds]

Would you mind being more specific with your wiring suggestion? I am going to try this.

Sure thing. This is what I'm describing:

 

[Leeds]

To be clear- you'll now be in charge of the temp in the freezer.
Before you take over that control (before wiring the relay in the back of the stat to the inverter switch) I would suggest that you power up the thermostat and watch what it does for a few days.
If you drape the temp sensor in the freezer the internal temp will be displayed. Note how high and how low the temperature goes when you have the freezer set at your preferred temp.
Then set the inkbird to come on a degree or two higher than the freezer comes on and set it to go off a degree or two higher than the freezer goes off. Then cut into the circuit and you're done.

 

[MichaelK]

Thanks Michael. The specs of my Epever SCC state 520w max for solar input at 12v and 1040w on a 24v system.

Keep in mind that these are the "pen and paper" design specifications. The real-world is somewhat different. You need to remember that the panel specifications are determined in a special test chamber held at a specific temperature (25C) with an artificial light source producing exactly 1000W/square meter.

In the real-world though, panels will rarely, if ever produce their rated output. That's because the sun at the earth's surface is not exactly 1000W/square meter, and the panels are hotter than 25C. From empirical testing, I've routinely used 85% as a "de-rating" for the label specifications. If you go through any of my other posts where I do solar production calculations, you will see that 85% value popping up over and over.

So, what will give you an honest 40A while charging at 13V, the math is..... (40A X 13V)/85% = 612W. Call that two 300W panels.

 

[Sonnyboy]

Someone should invent a box that turns on additional panels in overcast conditions and deactivates them when the sun is shining again.

 

[pollenface]

Someone should invent a box that turns on additional panels in overcast conditions and deactivates them when the sun is shining again.

someone has already done that here, I read it about 6 months ago

 

[efficientPV]

Why disconnect them? Find a use for the power. I use diverters to heat water and all energy is used every day.

 

[Sonnyboy]

Why disconnect them? Find a use for the power. I use diverters to heat water and all energy is used every day.

It’s a matter of planning really. At the moment, the solar and power is located away from any other possible use cases. But in the future that might change, so until then, if I add more panels with my current setup, it’d be great to be able to easily(automatically) engage them when needed and disengage them when they would throw too much wattage to my controller.

What if I wired them to a manual cut off switch and activated them manually when the days were overcast?

 

[Sonnyboy]

Keep in mind that these are the "pen and paper" design specifications. The real-world is somewhat different. You need to remember that the panel specifications are determined in a special test chamber held at a specific temperature (25C) with an artificial light source producing exactly 1000W/square meter.

In the real-world though, panels will rarely, if ever produce their rated output. That's because the sun at the earth's surface is not exactly 1000W/square meter, and the panels are hotter than 25C. From empirical testing, I've routinely used 85% as a "de-rating" for the label specifications. If you go through any of my other posts where I do solar production calculations, you will see that 85% value popping up over and over.

So, what will give you an honest 40A while charging at 13V, the math is..... (40A X 13V)/85% = 612W. Call that two 300W panels.

So if I add say 600 or 1200 additional watts of panels to my system on overcast days will that fry my controller? When you say you are overpaneled, are you over your limit for what your controller can handle but because of placement it works? I would like to not have to upgrade to 24v at this time.

 

[SamDeleted]

but my amp capacity is reduced this way to 100Ah

Yes but you've got the same amount of watts, two batteries wired either way around , they still have the same capacity

Two 100ah 12v batteries in parallel:

12v X 200ah = 2400w



Two 100ah 12v batteries in series (to make 24v):

24v X 100ah = 2400w

 

[SamDeleted]

I run a whole house, dishwasher, hot water, laundry, etc, besides refrigeration on a single car battery

I'd have to see it to believe it!

How does that work then, do you only use appliances when the panels are making ?

 

[12VoltInstalls]

located away from any other possible use cases

Not being mean and nothing personal but “use case” is too many letters to say “use” or “purpose.” Just say what you mean and leave the pseudo jargon buzz phrases to die and rot away. There’s nothing clinically advantageous to be gained by using extra words.

do you only use appliances when the panels are making

That seems the only logical possibility. The battery is just an in-the-moment capacitor with a long discharge characteristic.

When you say you are overpaneled, are you over your limit for what your controller can handle but because of placement it works? I would like to not have to upgrade to 24v at this time

If your demand is under 2200W or so and you already have adequate panel wattage on sunny days, adding panels to perhaps have enough harvest on cloudy days does not require moving to 24V. You just will have a lot of wattage unused. It’s the ‘cost of doing business’ in northern latitudes. While I don’t want to confuse a tank of gas as a metaphor for a battery, I’m going to use it as a metaphor for extra panel wattage. It’s like having a full gas tank versus putting $2 of gas in every time you drive 10 miles. The full tank of gas (having extra panels for cloudy-day solar) doesn’t waste the remainder of the tank of gas but it is available the next time you need to drive 60 or 100 miles. There is no real ‘waste’ with solar. They will still last 20 years whether you daily use 100% of panel capacity or 20% of panel capacity.

 

[SamDeleted]

That seems the only logical possibility.

Live long & prosper

 

[pollenface]

What if I wired them to a manual cut off switch and activated them manually when the days were overcast?

You could or you could just leave the system over-paneled permanently (while staying within a safe VOC range)

Better yet, get another SCC and split your array between them.

 

[pollenface]

I have 3,000W of panels on a 500W controller.

Out of curiosity, which SCC do you have?

 

[Sonnyboy]

Out of curiosity, which SCC do you have?

I have the Epever 40amp one

 

[MichaelK]

So if I add say 600 or 1200 additional watts of panels to my system on overcast days will that fry my controller? When you say you are overpaneled, are you over your limit for what your controller can handle but because of placement it works? I would like to not have to upgrade to 24v at this time.

I have Midnight controllers, and I know they will automatically clip off the peaks once the set limit is reached. For 48V, my set limit is 65A. I see my controller doing that around noon or so. It's not to much clipped off because of the panel orientation.

Whether or not the budget model of the budget brand does exactly the same, I can't say for sure. What it's "supposed to do" and what it "actually can do" could be two different things. I"m assuming you don't want to find out by trying to run 80A through it.

 

[Sonnyboy]

I have Midnight controllers, and I know they will automatically clip off the peaks once the set limit is reached. For 48V, my set limit is 65A. I see my controller doing that around noon or so. It's not to much clipped off because of the panel orientation.

Whether or not the budget model of the budget brand does exactly the same, I can't say for sure. What it's "supposed to do" and what it "actually can do" could be two different things. I"m assuming you don't want to find out by trying to run 80A through it.

yeah but if I wire them the way you suggest I am just over wattage not over the controller 40amps

I’ll check out the Midnight controllers

 

[pollenface]

I have the Epever 40amp one

I was actually asking @efficientPV

 

[efficientPV]

Out of curiosity, which SCC do you have?

I have a makeskyblue.

 

[Sonnyboy]

Sure thing. This is what I'm describing:

View attachment 123255

I don’t have two simple wires going to my rocker switch. I have it all on small boards with a white multithread cable going to it. Do you have any idea which is which?

 

[Leeds]

I have to admit that I'm not understanding where the rocker switch is seeing only the back view.

But if the issue is that the rocker switch is a thruhole part then there would be no easy wire to snip. Instead it would be a solder job where I'd solder a wire into each of the rocker through hole posts.

The difference would be that in the initial concept (snipped wire) the rocker switch would need to be on for the system to work and it would disconnect the output if you turned it off.

If you solder in parallel with the switch then the rocker switch would need to be off for the system to work and it would force on the output if you turned it on.