Building my own Solar Panels - Let's see if I can do it!

[Sipester]

Originally Posted by geordi

I
800 watts per hour at 120 volts is 19,200 watts per day - 19 kWh!
At 120 volts, that is drawing a continuous 6 amps, or roughly around 73 amps (with losses) out of a 12V battery system. Continuously. To power this off of an inverter like a Magnasyne 2812, you would need significant battery capacity. My array is 8 GC2 flooded batteries, for a total of 880 amp-hours of capacity, of which 440 is usable if I want to keep them above 50% state of charge for their protection. Lithium doesn't have that limitation, but at a MINIMUM you would need 1800 amp-hours of 12V batteries for just ONE DAY of running that perfect-scenario AC.

Costco just ended a sale on 12v lithium batteries, I don't know what the regular price is, but the sale was $700 for a 100-amp battery. Here's where the road ends. For JUST ONE DAY of all-battery-power on lithium - with NO CONSIDERATION of space or weight or wires or anything else, JUST buying the batteries... $126,000.

I think you want to check your math. Those Costco batteries have 105 amps, so that is 1,260 watt hours. For a total capacity of 19,200 watts, that would be 16 batteries. 16 batteries times * $699 = $11,184. You are only off by a little over 1,000%.

[okcnewbie]

Just to be a naysayer;

It's going to be a long, long time before someone comes up with an economical solar solution to being in really hot places that require cooling.
The cost of panels has come down and it's not very economical IMO to build from scratch.
However, most hobbies just end up costing us money so go for it. I know I've had lots of hobbies...…. I'm still waiting for any of them to "save" me money.
Good luck pard!

[C5c5]

Originally Posted by jcussen

Would not run any type of lithium setup without a BMS which should protect you against a cell failure.

Absolutely, a BMS system is a must.
Is there one that you know of that would zero in on the exact cell if it failed so one could replace it? From my understanding, I'm not sure if there is.

[C5c5]

Originally Posted by okcnewbie

Just to be a naysayer;

Nothing wrong with folks pointing out reality. Naysayers keep dreamers in check or at least attempt to. [emoji106]

It's going to be a long, long time before someone comes up with an economical solar solution to being in really hot places that require cooling.
The cost of panels has come down and it's not very economical IMO to build from scratch.
However, most hobbies just end up costing us money so go for it. I know I've had lots of hobbies...…. I'm still waiting for any of them to "save" me money.
Good luck pard!

Totally agreed. Solar is NOT the most efficient or cost effective method to harvest power. Not by a long shot.

It is however a practical hobby that will be useful for full-timing.

It definitly is not a $$ saver.

For me, solar is an emotional investment. The trade-off is money & efficiency.

[jcussen]

Originally Posted by C5c5

Absolutely, a BMS system is a must.
Is there one that you know of that would zero in on the exact cell if it failed so one could replace it? From my understanding, I'm not sure if there is.

Not sure about a bms for a single battery, my setup is 14 4 volt battery packs in series, and my bms reads voltage and temps and balances each one of those packs. Thinking that if you have a bunch of the little batteries making up one cell, and one battery in parallel goes bad, don't know if the bms could see it.
I have bluetooth bms's, so I can see each cell voltage on my phone, so if one of my packs go over or under voltage, bms will disconnect that pack, and I can see it.
Tesla has some way of handling it, maybe because they are in parallel, it just ignores the bad battery unless it causes problems.
Good question for Will.

[nvs4602]

Originally Posted by C5c5

Do you get a lot of Sanyo brand 18650's when you order them? I am seeing that while they work, they are not as good as the Samsung, Panasonic, Sony, or others.

I'm currently using lg 2600 mAH batteries. If you look up tesla power wall you will see each 18650 battery is individually fused, so if one goes bad it's fuse will blow this removing it from the pack.
I'm sure you already know this but a lot of people don't. Is that 18650 batteries are not capable of more than 3600mAH. There are a lot of fake batteries being sold that claim to be more then 3600mah.
Battery hookup is selling a new product line of cell level fusing. That you spot weld on the cells.
https://batteryhookup.com/collection...el-nickel-fuse
But they sell out as fast as they can get it in.

[C5c5]

Originally Posted by nvs4602

I'm currently using lg 2600 mAH batteries. If you look up tesla power wall you will see each 18650 battery is individually fused, so if one goes bad it's fuse will blow this removing it from the pack.

How do you personally locate bad batteries in your powerwall? Do you routinely measure them?

I'm sure you already know this but a lot of people don't. Is that 18650 batteries are not capable of more than 3600mAH. There are a lot of fake batteries being sold that claim to be more then 3600mah.

I did know that. It is good to spread the word!

Battery hookup is selling a new product line of cell level fusing. That you spot weld on the cells.

https://batteryhookup.com/collection...el-nickel-fuse

But they sell out as fast as they can get it in.

I trust them as a company and have shopped there.
The latest video I watched on assembling a powerwall showed how to spot weld. Very nice!

BTW, my order came in today! Christmas in March!!



I had helpers to assist in opening the package and inspection of the batteries.Attachment 279120


Hoops decided it was playtime after he put in a long minute of inspecting.Attachment 279117Attachment 279119



They are in packs of 4. Ordered 50 of the packs. Now its time to get the Dremel out!

[nvs4602]

IYou will need to test each battery prior to assembly I use liitokala testers. https://www.amazon.com/dp/B083K9WGFB..._vE.EEbTPQR9FC
This is a long process. If you can recharge the batteries before testing this saves time. I built a 5s3p battery pack to recharge mine in, so I can charge 10 batteries at a time. I could charge 15 but I found the current draw goes over 10 amps if i do. See picture 5s = 5 batteries in series. 3p = 3 batteries in parallel. Also leaving one charged battery in speeds up the charging process. It will also bring back batteries that may have fallen below 2.75volts, which a lot of chargers won't try to charge because it doesn't think it's a lithium ion battery because of the low voltage.

I recommend at least 2 testers, as it takes 8 to 9 hrs to run a test. About 5.5 hours to discharge and about 3.5 hours to recharge. That's why I charge all the batteries before I test. It saves tieing up the testers another 3.5 hours.

[nvs4602]

After you test the batteries write on each one what it's mAH value is. Then use this web site to build your packs.
https://secondlifestorage.com/repackr.php

Enter the value of each battery separated by a coma. After that you enter the battery pack size you are building. In your case a 7s 80p. This will sort the batteries into 7 packs of 80 cells by the mAH average value. This way each pack starts out with the same amp hour capacity.

I hope this is making sense

[C5c5]

Originally Posted by nvs4602

After you test the batteries write on each one what it's mAH value is. Then use this web site to build your packs.

https://secondlifestorage.com/repackr.php



Enter the value of each battery separated by a coma. After that you enter the battery pack size you are building. In your case a 7s 80p. This will sort the batteries into 7 packs of 80 cells by the mAH average value. This way each pack starts out with the same amp hour capacity.



I hope this is making sense

You are awesome! Yes, thank you for the info!

[nvs4602]

Originally Posted by C5c5

Goal: Build my own solar panels to install on my RV roof


Today my solar cells arrived!
Attachment 278783

They measure 4 X 5 inches apiece
Power per cell = 4.5 Watts
Total quantity is 100 pieces.

Subscribe to follow along as I build my first one!

Since this will be my next phase will you post a link to the cells you bought? And was there a reason you picked these cells? Thanks

[C5c5]

Originally Posted by nvs4602

Since this will be my next phase will you post a link to the cells you bought? And was there a reason you picked these cells? Thanks

I got these from Amazon.
https://www.amazon.com/Vikocell-156M...=vicoce&sr=8-2


I picked these from Vicocell in particular because compared to other similar cells, they had a good rating.

I chose poly cells based upon Will Prowse's advice that poly panels are just as good as mono panels and less expensive.

Other reputable websites sell used and/or broken cells for pennies on the dollar. I decided to go with new cells for my first DIY so that I have assurance of it working well if I do it correctly. Also it is less work because there wont be any sorting with trial & error.
I look at it this way: spend a little over $100 on solar cells, or spend just as much for a nice evening out with drinks. Since I'm naturally an introvert, I win with buying the cells! We really can't go out anyways right now with the virus panic.

Not counting the large expenditure of my time, and depending on what the costs are for the frame, epoxy, and construction materials, it evens out going the DIY route.

If this project is successful, I'll try out some deals with the used cells. If one is patient with sorting good from bad cells, it actually is way cheaper for large panel DIY.

[cwk]

Originally Posted by C5c5

2. Replace the floor insulation with at least 2" of polyisocyranurate rigid board or extruded polystyrene to give a minimum R-value of 16.

3. The ceiling is where I am still determining what to use. I want to sprayfoam the entire ceiling, but it is expensive (since I'm choosing fireproof or fire retardant) and it will require A LOT, so I'm wondering if I could combine the high R-value polyisocyanurate rigid boards or even extruded polystyrene with an additional layer or 2 of sprayfoam? I need to seek further guidance on that to determine what would be best.

I am still in the research phase for the insulation materials for my remodel. I found the following document at Owens-Corning. It is a technical document, but I think I am interpreting it correctly.

http://www.owenscorning.com/NetworkS...s-Poly-FAQ.pdf

It appears that Polyiso insulation has a slightly higher R-value at 75F ambient temperature than XPS (Extruded polystyrene). However, when the ambient temperature drops to 15F, the R-value of Polyiso drops from R5.6 to R2.0.

The R-value of XPS is R5.0 at 75F, and increases to R6.0 at 15F.

Since part of our future plans include spending winter holidays in cooler temps, this information was enlightening.


For me, it looks like XPS is the correct product.

Comments welcome!

[Ken Thompson]

Originally Posted by C5c5

Goal: Build my own solar panels to install on my RV roof


Today my solar cells arrived!
Attachment 278783

They measure 4 X 5 inches apiece
Power per cell = 4.5 Watts
Total quantity is 100 pieces.

Subscribe to follow along as I build my first one!

I don’t want to burst your bubble, but even if you bought the best of the best solar panels, they aren’t efficient. I’m sure there are numerous people who swear by a solar system, and will argue their greatness all day. Solar is somewhat like wind power, if they are so great, why does the government have to subsidize them to get people to use them? Maybe in the future, but so far, the investment you put up, never totally comes back. If you are doing this for a hobby, go for it, but if you are trying to save money, it’s not going to happen, but good luck!