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diy solar

Bootstrapping sanity check & Introduction

KevinC_63559

New Member
Joined
Jan 26, 2024
Messages
150
Location
NE Missouri, USA
Hi all. I've been tracking solar power since my dad brought home a few cells in my teenage years. I'm 65 now, so awhile... I love seeing things like the newer Hybrid inverters which seem to be pulling a lot of "wouldn't it be nice if..." things together (peak shaving, off-prime charging, etc.). I live on a 121 acre farm, described by one visitor as "Officially the backside of nowhere!" (actually in NE Missouri, USA - but its 15 miles to the nearest gas station). We recently experienced the longest power outage since we bought the place in 2008 - over 37 hours. Compliments of gas generators, we didn't lose any food storage, but it was tough getting out for gas to run those. Had to share that generator between my house and my office/workshop (about 500 feet away). The incident has pushed me into finally "doing something" with solar. Oh, handy enough around basic power electronics that I built my own 2000 amp data center and wired it back to the pair of transformers the electric company dropped on pads for me (yeah, (10) 200amp panels all maxed with 20amp 240V breakers - that was not a typo).

So here is the plan - I would appreciate feedback. A main goal is to be able to bootstrap up a full system without having any significant parts left over at the end.

1) Try and spend roughly $300/month and build up a basic system that might be usable for something, like charging cell phones (minimum) and running a freezer or refrigerator a few hours a day (goal). To that end, I've bought my first LiFePO4 12V 100amp battery, a small 4amp charger (which will double for charging some 12V9A gell cells), and a 500W (1000W surge) full sine wave inverter. Charged up the battery, played with the bluetooth BMS via my iPhone, and hooked up a 12V USB charger (also purchased). Meet month 1st budget and have a few things to play with.

2) Found DIY Solar for U and this forum. Figured it was better to ask first and buy later. Love the diysolarforu (?DSFU?) Sol Boost Buck 20amp MPPT charger - the only MPPT charger I found so far that is USA made and sourced, and that features great FCC Class B stats. Figure if they are focused on making a unit that comes in 19db below FCC requirements, they likely have the big things down pat.

3) Sketching out in my head a potential sequence of events:

Month 1: Buy one of the above charge controllers.
Month 2: Buy a bundle of 10 solar panels (for best price - but blowing the budget this month, but that is what tax returns are for).
Month 3: Mount (1) pane generating 12V @ 350W (STC) to max input into the charge controller. Likely do this on a temporary wooden fixed frame.
Month 4: Buy an eco-worthy tracker to get more hours out of the array, removing the temporary wooden fixed frame.
Month 4b - rig a 12V system to power the eco-tracker, perhaps (1) extra panel on the eco-worth feeding a basic 12V battery system.
Month 5: Another battery - another 3 panels on the tracker, convert to 24Vx700W
Month 6: Another battery for a standalone 12V for the long term supply to the tracker.
Month 7: Check on the specs of the latest Sol Buck Boost - hoping for 24V/48V variant. Depending on results, things get a bit fuzzy, but:
Either another charge controller for the standalone 12V battery, or a new 24V/48V one repurposing the original for the standalone system
Month 8: Another tracker, using up 4 more panels (1 spare at this point - maybe parallel that one into the 12V standalone system)
Month 9-13: Learn LEARN Learn. Maybe expand batteries monthly. See where Hybrid inverters are.
Month 14: <maybe> Convert to hybrid inverter using tax refund.

There are a bunch of questions associated with the above, and I suspect more to follow:

A) Understand battery pricing better. My current 12V100A LiFePO4 was sourced from Amazon, and sold for $180 shipped. Came with a Bluetooth BMS and sounded decent, but what do I know?!? Obviously Chinese with the brand-of-the-month being "Fiunie" which I've never heard of before. Cheap, maybe usable for the 12V standalone system later, if not will be considered an educational expense. When I web surf most solar battery sites, I typically see 12V100A in the $800-$900 range and don't understand the 4X price. DSFU sells what I suspect is the best BMS system for $80, so the difference between my $180 unit and a $800 unit can't be the quality of the BMS. Should I instead me buying (4) packs of individual cells from https://ezealco.com/ and adding a DSFU BMS? Total cost would be around $245 - a small premium over the $180 I spent. Of course doing that would lead me to a System's Data Master for $240, but that is a one-time charge, so maybe a month 9-13 thing.

B) The DSFU charge controller advertised a max STC 12V350W input, or 24V700W input. Using the Sunwatts reference site, that's going to be tricky. I remember when panels were 100W each, but apparently modern ones start at 360W. Is that 10W difference really going to break things, or is it within the margin of error, especially since its STC not PTC or NOCT?

C) What can the Eco-worthy tracker actually handle in panels? They sell 100W and 190W ones, but modern ones are a lot cheaper per watt (like almost half).

D) If I eventually end up with a hybrid inverter, what would I use my DSFU controllers for? One for the 12V standalone system, that's cool. Most (if not all), of the hybrid inverters have their own MPPT charge controllers, with loser, if any, FCC Class B ratings. I dabble in listen-only HAM radio, so interference is a concern.

E) Confused about matching solar panel max voltage to the specification for the DSFU charge controller. The text on the charge controller page indicates a maximum working voltage of 54V. A typical solar panel per Sunwatts shows a max open circuit voltage of 49.8V, and (connected?) max voltage of 33.9V. Not a problem for a 12V system but would be way out of range if two panels were run in series to make a nominal 24V system. Amperage is a tad high too, at 10.8 amps X 2 for a 2x2 array yielding a max of 21.6 amps of input into a 20 amp controller. Really REALLY don't want to burn up controllers.

Would appreciate and welcome all comments and clarifications!

Kevin
 
I can speak to what the Eco Worthy tracker will handle. I think they will handle no more than what Eco Worthy shows on their web site when it comes to weight. Having said this, I had purchased four 560 watt bifacial panels and one mount then realized there was no way the four panels were going to fit on one mount not to mention the weight of those four panels (70 pounds each) was probably WAY too much for the mount. So… I bought another Eco Worthy mount and mounted two panels on each mount. They measure 108” (if I remember correctly) and the way Eco Worthy shows their panels mounted it will hold six. That is a little less wind load than two of my 560 watt panels so keep that in mind- don’t exceed 70 square feet - that mount may not be strong enough for high winds even with it’s automatic wind protection feature. Overall, for the money I think they are a great mount - just know their limitations. Once you have the timing parameters set for “return to neutral” position in the case of high winds or night parking, they just plain work. I added a 30 watt 12 volt panel (Amazon) with charge controller on the bottom of one mount which charges a battery powering both mount drives. My plan is to make my own on a much beefier scale to haul six and perhaps even eight of those big panels Using the Eco Worthy mount as a reference. Good luck and have fun!17AC716E-3145-4CAE-9625-B3129B7F3D41.jpeg0DA39967-AD57-4C97-A692-C87B09AD2BC0.jpeg
 
I can speak to what the Eco Worthy tracker will handle. I think they will handle no more than what Eco Worthy shows on their web site when it comes to weight. Having said this, I had purchased four 560 watt bifacial panels and one mount then realized there was no way the four panels were going to fit on one mount not to mention the weight of those four panels (70 pounds each) was probably WAY too much for the mount. So… I bought another Eco Worthy mount and mounted two panels on each mount. They measure 108” (if I remember correctly) and the way Eco Worthy shows their panels mounted it will hold six. That is a little less wind load than two of my 560 watt panels so keep that in mind- don’t exceed 70 square feet - that mount may not be strong enough for high winds even with it’s automatic wind protection feature. Overall, for the money I think they are a great mount - just know their limitations. Once you have the timing parameters set for “return to neutral” position in the case of high winds or night parking, they just plain work. I added a 30 watt 12 volt panel (Amazon) with charge controller on the bottom of one mount which charges a battery powering both mount drives. My plan is to make my own on a much beefier scale to haul six and perhaps even eight of those big panels Using the Eco Worthy mount as a reference. Good luck and have fun!View attachment 191741View attachment 191742

Thanks. The 360W units I'm looing at are 19.6 sq ft, so 78.6 sq ft total, about 36% more than their units with their (6) 195W panels. Weight would be a bit worse at 44lbs each, so 176lbs for (4), 43% more than their configuration. I've written them to see if (4) of what I have in mind would remain in spec.

FWIW we are a bit "breezy" here, with 10-15 mph days normally, 25 mph days routinely, and gust upwards of 45mph once-in-awhile. So wind load capability is of some concern to me for anything that isn't a fixed mount.

I didn't see specs on power usage per day and/or max amp draw for sizing the 12V system for the drive motors. Would you happen to have those specs?
 
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I have a 7 amp hour 12 volt SLA battery powering both mounts and charging from a 30 watt panel. I mounted it inside the larger of my two boxes (14.8”x10.8”x6.1”) along with its charge controller, breaker, PV cell breakers and terminal strips for the cells. No problems even in some -15 F weather for about 5 days straight. Was a little concerned that each mount might require it’s own battery, but my set up seems to be doing fine so far. These mounts are down to $440 each and there’s a coupon for another $20 off (BRACKET20) S\so if you need to buy a second one it sure beats what they used to charge……….
 
Forgot to add: I used 15 amp breakers on each controller.
Where are you in NE MO? I’m on US 36 east of I-35 a few miles. You’d be more than welcome to take a look at my system especially the mounts before you buy them.
 
So here is the plan - I would appreciate feedback. A main goal is to be able to bootstrap up a full system without having any significant parts left over at the end.

This requires you to completely spec out the system including an energy audit to determine your needs, your available insolation, etc.

1) These are my needs based on measurements and/or analysis.
2) This is how much sun I have available in my location.
3) This is the design of the complete system to meet those needs.
4) This is how I'm going to acquire it over time.
5) This is how I'll deploy it in stages.

When you piecemeal a system, you must design it in its entirety at the outset. Otherwise, you'll almost certainly waste money.


2) Found DIY Solar for U and this forum. Figured it was better to ask first and buy later. Love the diysolarforu (?DSFU?) Sol Boost Buck 20amp MPPT charger - the only MPPT charger I found so far that is USA made and sourced, and that features great FCC Class B stats. Figure if they are focused on making a unit that comes in 19db below FCC requirements, they likely have the big things down pat.

IMHO, if you're going to make this product a foundation of your system, you're shooting yourself in the foot and forcing yourself into very restrictive and expensive piece of hardware. I have a hard time paying more for 1/3 to 1/2 the function of quality MPPT controllers with far greater features.

$250 for 280W of max charging @ 12V or 560W of max charging @ 24V is just nuts, and it doesn't allow for high series Voc.


45A and good for 12, 24, or 48V systems.


1706509011406.png

It's also very over-paneling tolerant. The 50A PV input current limit means you could easily put up to 4000W (estimated based on the Voc and Isc limits above) on that controller safely even while only running at 12V.
 
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