diy solar

diy solar

Beginner solar setup

acalicolife

New Member
Joined
Jan 4, 2023
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5
Location
Idaho
I’d like some help to make sure what I’m planning is going to provide for my needs. I have a bp horse trailer that I’ve converted the tack room into living quarters. I currently have a 12v marine battery inside with a small inverter attached. I’d like to be able to power a small refrigerator. I’m looking at the Thunderbolt 100w folding solar panel kit to keep the battery charged. I believe it comes with everything I need but not positive. Ie charge regulator etc. Will this panel keep my battery charged with a refrig connected? Do I need to add a second battery? Please help. I’ve done some research but it’s all rather confusing.
 
There is not enough information to answer the question.

Is the fridge AC or DC (or both)?
What are the power needs of the refrigerator (Wh/Day)
What other loads are on the battery?
 
What is the power consumption of the fridge?

If it's a residential-type mini-fridge, it should have a yellow energy star sticker indicating annual kWh/year use. Divide by 365 to get daily.

We have a small dorm-style mini-fridge that uses about .4-.5kWh/day. You do not have sufficient battery or solar to reliably power it.
 
Blurb time!

Well, I'll start the default answer to these questions and we can work from there. Here's you To-Do list:

1: Power audit! This will give you some important information on how big your inverter needs to be as well as how much battery capacity you'll need. There is a link in the FAQ section (I think, or someone here will post it shortly) so fill in the blanks and see what it comes up with. You'll probably need some sort of Kill-A-Watt to get accurate measurements. Are you going to be running a 12v system? 24v system? 48v system? What are the specs on your solar panels? VoC? Vmp? Being as this is a new build, throw together a wish list of what you want and estimate on the high side.

1a: Where do you live? Speccing out a system for Scotland is a LOT different numbers than Arizona due to the amount of light you actually get. Someone here can post the link to the PVwatts.com or JCR Solar Uber-Sun-Hours calculator sites to help figure out how much you'll have to work with. That will be a box in the Power Audit form.

2: Parts list: You don't need a make & model list, just a parts list to start from for reference. You'll need an inverter, a MPPT charge controller, fuses, shunt, buck converter, batteries, wire, etc. Once you have a basic list it can be fine tuned to make & models after that. If you're looking at the All-In-Ones check for correct voltage outputs (120v or 240v Split Phase for North America, 220v Single Phase for European type areas) and make sure it has enough capacity for a little bit of growth and fudge factor.

3: Budget!: Steak is great but doesn't mean anything if your wallet says hamburger. :) Figure out what you're able to spend now vs what you'll have to cheap out on now and upgrade later.

4: Tape measure! Figure out where you're going to stick all the stuff you'll need. A dozen 3000AH batteries sounds great until you're sleeping on the floor because there's no room left for a bed. Is there a compartment that can house all this stuff? Will the server rack batteries fit? Are you going to have to make space? Physics can be pretty unforgiving.

5: Pencil out what you think you need and throw it at us so we can tell you what you've missed (because we ALL miss stuff the first go-round :) ) and help figure out which parts and pieces you're going to want to get.

Well that's the thing about solar systems, there is no 1-Size-Fits-All answer. Your system will need to be designed to fit YOUR needs. When you design and built the system, it's not going to be the perfect system for me, or Will or 12vInstall or anyone else, but it Will be the right system for You and that's the goal.

As for where to get started, let me throw my standard blurb in here to help point you in the right direction. There's going to be a lot of math and research involved, but that's going to be a LOT cheaper than just buying parts off of someone's list and finding out that it doesn't do what you need.

Don't panic on the Power Audit, you'll actually be doing that a few times. When you do the first pass put in ALL the Things that you might want. AirCon? Sure. Jacuzzi? Why not. MargaritaMaster-9000? Go for it.

The second pass will be the "I Absolutely Need This To Survive" list that isn't going to have much on there.

The third pass will be the "This is what is realistic" audit that you'll use to design the rest of the system.

The Power Audit is going to tell you 3 primary things: 1: How big does your inverter need to be to power your loads? 2: How much battery bank do you need to last $N number of days with krappy weather? and 3: How much solar panel will I need to install to refill those batteries in a 4 hour day (the average usable sun hours rule-of-thumb).

Once you know what you Want and what you Need and what your budget can Afford there will be somewhere in that Venn diagram where those three things meet.

After that, THEN you can start looking at parts.

Yes, it's a long drawn out process, but it's worth it in the end. Not every house has the exact same floorplan, not every vehicle is the same make & model, and not every solar system is designed the same.
 
There is a link in the FAQ section (I think, or someone here will post it shortly)
 
Thank you everyone for your replies, especially Rednecktek! I’ll follow your directions and get back with you. I don’t need much power but as you said better to plan for future needs. Thanks again. At least now I know where to start.
 
Let's look at your needs and fit in what other responders have already mentioned. SSE already mentions that a little frig might consume ~0.5kWh per day. Let's also assume that you might want to have a bit of lighting, and maybe an hour or two of TV in the evening. We can guestimate that maybe you need at least 1kWh of power per day (1000Wh). Or you can go with RNT's recommendation and do the full audit.

I assume you want to lay your panels flat on the roof of the trailer? De-rate the output of the panels to 60% to compensate for a less than optimal sun angle. Let's also say that this is mostly for summer use and you have 4 sunhours available in summer. You want to keep it 12V because the trailer is pulled down the road. The math looks something like this....

(1000Wh needed/4 sunhours)/60% = 417W of solar panels: So the realistic solar needed is about 4X what you planned on.

Now, the battery. Let's assume you stick with lead-acid, which should not be drained routinely past 50%. The math for the battery looks like....

(1000Wh X 2X)/12V = 167Ah of battery capacity. Looks like a standard 100Ah Marine battery is not enough. Better to go with 6V golf-carts that you can wire in series for 12V. Costco is selling a 210Ah 6V golf-cart right now for 110$. Get two of those for 12V.

The 210Ah battery will need a bit more solar to keep it happy. It will like charging at 1/8th of C, which is 210Ah. The math looks like....

[ (210Ah/8) X 13Vcharging ]/60% = 569W of panels

So, get the bigger deep-cycle battery, and get 500-600W of solar panels. As a general rule of thumb, get 100W 12V panels only if your system is sized smaller than 200-300W. For something in the 500-600W range, you'll save money buying high-voltage grid-tie panels paired with an MPPT controller. The MPPT takes the raw high-voltage and transforms it down to battery charging voltage.

Look on Craigslist for grid-tie panels in the 250-300W range. I am driving over to a local seller next Monday to pick up some 240W Trina's for 78$ each. Shopping on Craigslist, you might find what you need for ~ 150-200$. Add 125$ for a MPPT controller like the Epever 4210AN, and you will be all set.

Keep in mind that this math is with My numbers. If you follow RNT's advice and do the full audit, you may get different numbers. Just plug your numbers where mine are. Values may change, but the math stays the same.
 
Thank you so much! I may have to go to a propane frig :(. I don’t use this but about 4 or 5 times a year for a week max. Was trying to get away from ice chests.
 
may have to go to a propane frig
I’d manipulate your usage time and do the 600W+ which could be made to run the fridge. A/C is limiting but you should be able to run the fridge and some lights. I do in Vermont with 800W 8 or 9 months of the year.
 
Thank you everyone! I had an Euhomy Car Refrigerator, model CF-45, given to me for Christmas. If I’m reading the attached specification right then the consumption is a max of 45W and the rated current is 2.5A. It has both a cigarette lighter DC plug and reg 110. I have a female cigarette light plug attached to my inside trailer battery for external use. The only other thing I might use the inverter attached to the battery for is charging my phone and an occasional light. Most of my lights have batteries or are solar charged. My heater & stove is propane. No AC and not planning on one. I’ll have to figure out rounding up the requirement for the car fridge.
 

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I've had a Truckfridge in my van for years, it's a 12v Danfoss compressor fridge, does a fantastic job. My original solar setup was 200w of panels and a 150ah lead / acid battery, it ran the fridge and lights just fine. I spent 2-3 months a year on the road living in the van, camping around the SW and Mexico, a fridge is a HUGE upgrade from an ice chest.
 
I’m pretty sure my battery is a 150, I’ll have to double check. Instead of a 100w panel, I’ll get a 200w. Did you have you panel mounted on the vans roof?
 
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