The "Meg" Build

[Boondock Saint]

Thx for the update. I reached out to Daygreen and they're ghosting doing anything. My only option would be just buy the 13.5v unit and sell the other 100A one as open box unused.

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[Lt.Dan]

Thx for the update. I reached out to Daygreen and they're ghosting doing anything. My only option would be just buy the 13.5v unit and sell the other 100A one as open box unused.

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Just wish we found out sooner, and wish that Daygreen was a little better on communication!

 

[Hedges]

I'm going to leave this cap installed though. It still gets the job done and the leveling system works. Maybe in the future I will get the pump rewound to accept 48v if its feasible.

Is the pump starting into full pressure? Could a hydraulic accumulator be installed, something that could accept a couple cubic inches of flow before building pressure?

Or is there some operating mode that would be low pressure to start, like "retract" briefly, followed by "extend"?

 

[Lt.Dan]

Is the pump starting into full pressure? Could a hydraulic accumulator be installed, something that could accept a couple cubic inches of flow before building pressure?

Or is there some operating mode that would be low pressure to start, like "retract" briefly, followed by "extend"?

Yes the pump is starting immediately into full pressure, and quite frankly is very rough and "Shakes" the whole trailer.

The accumulator idea is fantastic. I'll have to see what I can get for that.

A softer start would be nice. I've noticed whenever it "deadheads" I have to retract before I can extend again, and that always makes it work correctly.

 

[Hedges]

My first thought was a spring or gas loaded pressurized accumulator.
But how about a hydraulic cylinder with small return spring. Orifice to bleed pressure. It should give zero backpressure until it bottoms.
Alternatively, an unloader valve from pump output to input. That might require check valve on output so jacks don't drain through it.

 

[Boondock Saint]

Do we have a bead on the current draw on these? Max or sustained?

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[Lt.Dan]

Everything is going smoothly right now. Outside temps have dropped below 100*, so the entire system is working flawlessly. I haven't switched back to grid power in over a week now, and I wake up every morning to the battery around 30-50% still. I have 16 more cells on order to make a 2P16S battery now, and am going to individually charge/capacity test every cell I have to group high/low batteries as best I can. the compression fixture/mounting system will be pretty cool when I'm all said and done as well.

What I do find a little disappointing is how the LV6548's have a max 8000 watt PV Input, but I can't get better than 4500 "actual" watts due to PV configuration of the panels I have. Currently I'm running a 2x 6s2p, which makes 150v VMP and 13-14a IMP on each string. I can't step up to a 7s because VOC gets to 263v, 13v over the VOC limit, and stepping up to a 3p makes it clip at 18a, which again, wastes PV production.

I wish I could series connect the optimum number of my panels (22 panels making ~550v VMP) with fewer wire runs, then have some sort of step down converter at the LV6548 to step down to an optimal voltage range (200-230v). This would yield 550v VMP X 7a IMP = 3850 actual usable watts PER PV INPUT. Is this possible?

Sorry if I seem a little scrambled. I can see it all in my head, but have troubles putting it to words lol.

 

[cinergi]

Everything is going smoothly right now. Outside temps have dropped below 100*, so the entire system is working flawlessly. I haven't switched back to grid power in over a week now, and I wake up every morning to the battery around 30-50% still. I have 16 more cells on order to make a 2P16S battery now, and am going to individually charge/capacity test every cell I have to group high/low batteries as best I can. the compression fixture/mounting system will be pretty cool when I'm all said and done as well.

What I do find a little disappointing is how the LV6548's have a max 8000 watt PV Input, but I can't get better than 4500 "actual" watts due to PV configuration of the panels I have. Currently I'm running a 2x 6s2p, which makes 150v VMP and 13-14a IMP on each string. I can't step up to a 7s because VOC gets to 263v, 13v over the VOC limit, and stepping up to a 3p makes it clip at 18a, which again, wastes PV production.

I wish I could series connect the optimum number of my panels (22 panels making ~550v VMP) with fewer wire runs, then have some sort of step down converter at the LV6548 to step down to an optimal voltage range (200-230v). This would yield 550v VMP X 7a IMP = 3850 actual usable watts PER PV INPUT. Is this possible?

Sorry if I seem a little scrambled. I can see it all in my head, but have troubles putting it to words lol.

If you were to use a converter (if such a thing existed and was compatible), you might as well just directly connect an SCC capable of handling that voltage, no?

 

[Hedges]

Or something like SolarEdge optimizers.
They allow more panels in series than Voc would suggest, but drop the voltage delivered. Probably only works with their proprietary communication.

 

[Lt.Dan]

If you were to use a converter (if such a thing existed and was compatible), you might as well just directly connect an SCC capable of handling that voltage, no?

I did have that exact thought, plus you would be dealing with efficiency loses stepping voltage down that far. Know any SCC that can handle 827 VOC? Lol, they can't be cheap!

Or something like SolarEdge optimizers.
They allow more panels in series than Voc would suggest, but drop the voltage delivered. Probably only works with their proprietary communication.

Thank you for the research lol, I will look into it!

 

[Lt.Dan]

Hmm. Looking around, I seem to have stumbled upon a possible solution.

THIS GUY could be used at each panel to regulate it to a 24v output, no matter the temp difference as it has a wide 30-60v input. They are only ~$15+shipping, and this would fix any issues with exceeding VOC, and would let me do a 10S2P setup, with 20 panels. It would regulate the entire string to 240v (just below the 250v limit), and output a theoretical max wattage of 3840 (very close to the 4000 watt max per PV Input on the LV6548), whereas realistically the panels would probably max out at 3600 watts, and then Daygreen claims a 95% efficiency, bringing that down to 3420 watts. Now, this does technically output LESS power than what I am currently getting from the panels strictly because of the efficiency losses of the converter, but it allows me to fit almost 2x the amount of panels per PV input, which reduces cost on extra equipment, and unnecessary PV wire. They are waterproof and can be mounted underneath the panel and I guess instead of the term "Microinverter" its a "micro-converter" lol.

Win-win-lose? Maybe some testing should be involved? Or will the LV6548 MPPT Tracker freak out because it can't "pull down" the voltage coming from the regulators?

 

[Lt.Dan]

Actually I realize the Trina panels normally operate in the 25-27V range, which is too low for the one posted above. But Daygreen does make this Buck/Boost with a 9-40v input, and 24v output. Perfect.

 

[Hedges]

Those modules would seek to deliver constant voltage output at variable current.
Your SCC adjusts its current draw seeking maximum power. Best you can hope for is it pulls all current it can until buck/boost module output voltage drops. But won't necessarily function well together. SCC and buck/boost are tuned for different applications. Also, switcher feeding switcher doesn't necessarily behave well.

A circuit to short out last panel in a string if voltage approaches max might be a possibility. But everything is a design/verification problem. Selecting panels/SCC with compatible parameters is best way to go.

 

[Lt.Dan]

Those modules would seek to deliver constant voltage output at variable current.
Your SCC adjusts its current draw seeking maximum power. Best you can hope for is it pulls all current it can until buck/boost module output voltage drops. But won't necessarily function well together. SCC and buck/boost are tuned for different applications. Also, switcher feeding switcher doesn't necessarily behave well.

A circuit to short out last panel in a string if voltage approaches max might be a possibility. But everything is a design/verification problem. Selecting panels/SCC with compatible parameters is best way to go.

Damn, I had a feeling. Oh well, back to the drawing board, maybe i'll change panels in the future if the opportunity presents itself.

 

[Hedges]

What I do find a little disappointing is how the LV6548's have a max 8000 watt PV Input, but I can't get better than 4500 "actual" watts due to PV configuration of the panels I have. Currently I'm running a 2x 6s2p, which makes 150v VMP and 13-14a IMP on each string. I can't step up to a 7s because VOC gets to 263v, 13v over the VOC limit, and stepping up to a 3p makes it clip at 18a, which again, wastes PV production.

3p clips at 18A - if only a small fraction of the time that's not a big deal. Off angle or less than clear day and it is under the clipping limit.
Clipping only occurs at max production, which hopefully is more Wh/day than you need (except maybe for A/C)

If some of those parallel strings are of a different angle, that will reduce current but extend hours of production. "Passive tracking".

 

[Lt.Dan]

3p clips at 18A - if only a small fraction of the time that's not a big deal. Off angle or less than clear day and it is under the clipping limit.
Clipping only occurs at max production, which hopefully is more Wh/day than you need (except maybe for A/C)

If some of those parallel strings are of a different angle, that will reduce current but extend hours of production. "Passive tracking".

This is a snapshot from when I had it in a 6S3P config. It clips at 17.5a for about 4 hours a day. Setting opposing directions would be good, but I dont really have the real estate on the ground for that. Im in the process right now of putting my 24x panels on top of the Shipping Container, which will force them all directly south unfortunately. But I have to get them off the ground and this enables me to tilt them all as well.

 

[cinergi]

So it really all boils down to -- how much money are you willing to spend?

 

[Lt.Dan]

Well I finally got around to making my Adjustable ground mount. I initially wanted to put it on top of the shipping container, but I dont want to put and holes in it, or risk the wind taking the array down and into the neighbors yard. I mounted it on the ground next to the side to impede wind from moving it around. I also got some concrete blocks at Lowes that had some 2x6 blocks of wood nailed to them, so I could screw my array down to the blocks and have some extra weight/ballast. It came out pretty good i think, and I can very finely tune the angle I want them to sit at.

Leveled the ground a little first with the tractor.



The old array mount, very crude and quite frankly, a little embarassing lol. You can see the new array in the background.



Dirty solar panels. Need a little scrub down.



From the underside, before wiring etc.



Now I just need to do the 2nd array to get all the panels off the ground and out of the dirt. But damn it was a lot of work putting it together! I am already seeing very good results with a better tilt angle, and the panels arent shaded in the morning. Before the panels didnt really come on until 9:30, but now they come on at 8am and make much more power, much sooner.

 

[Hedges]

I think it should be anchored securely against wind. Ground screws, stakes, or something.

 

[Lt.Dan]

Well they're sitting on top of 3 feet of sand, so im hoping the shipping container would block enough wind to just rely on the shear weight of the fixture.