Long time listener, first time caller from Dateland, AZ

[sarossell]

Hello everyone!

I've been banging my head against the solar puzzle wall for the past eight years. I managed to successfully live off-grid in a box truck on the streets of San Diego on 1100 watts of mixed panel sizes connected incorrectly for only 900 watts max output (Well, I know that now). Still, I was able to run a microwave oven, refrigerator/freezer, Keurig coffee maker (with a massive 80 farad capacitor), XBox 360, 32" TV, lights, laptop and iDevices.

So, hey, I figured I could take on the deep desert, right? Well... I may have bitten off more than I can chew. We'll see what the 120° Summer heat does to me out here.

I decided to build a whole new power system. I got 30 used 270 watt panels and then as I was about to order a new solar charge controller, I learned something basic I should have learned 8 years ago; you can have all the panels in the world, but your 60 amp charger is going to give you about 800 watts max. That's it. (Yes, I'm aware of the early and late light concentration effect of having a larger array, but stick with me here.)

So I decided to look at the Growatt 3000TL LVM-ES. 4000 watts max in, 3000 watts out of the inverter, battery optional, scalable and expandable. All for just $712?! Crazy, right?

Then I read the specs and hit another wall in my understanding. It says it can handle from 150 to 250 VDC, but only 18 amps from the solar panels. Surely that's a typo, right? But page 44 of the manual says "Max. PV Input Current” 18 Amps. So, okay 4000 / 18 amps = 222 volts; within the stated maximum input voltage. But how the heck do I combine 270 watt panels with a 38.5 volt in-circuit voltage at 7.6 amps each? The best I can figure is six parallel groups of two panels in series reaching 231 volts at 15.2 amps for a total of 3,511 watts. I can’t parallel more than two panels. That would exceed the 18 amp limit.

If I flip it and go with two parallel groups of six panels in series, again I get 231 volts @ 15.2 amps for 3,511 watts of course. How do I get closer to the 4,000 watt maximum?

Is it possible that the Growatt can have panels connected within the voltage range but above the amp max of 18 amps, in my case, 22.8 amp, and be able to handle it? My 60 amp MorningStar charger does that. I can feed it 75 volts @ 16 amps for 1200 watts and it converts it to 60.5 amps max with a maximum equalization voltage (when reached) of 15.4 volts.

Please, somebody take pity on me. I'm a single man living in the AZ desert with a swamp cooler and it's already reaching 100° in April! I need air conditioning pronto!

?

 

[curiouscarbon]

hello and welcome to the forum

i might be missing something but won’t the device simply current limit if overpaneled? sorry i’m not that familiar with growatt exact hardware operation.

if you need a small air conditioning unit, i use a midea one and it’s a godsend on a hot day. https://www.amazon.com/Midea-Inverter-Conditioner-Flexibility-Installation/dp/B08677DCKN/ 8,000BTU/hr

it’s extremely energy thrifty and uses less than 800W almost always

with some solar chargers it’s safe to connect more solar than it needs, but some it’s not, maybe someone more familiar with growatt could help

 

[sarossell]

"...current limit...?" That's my guess, but I'm not sure. The manual makes no mention of over current protection.

I do like the Medea A/C you linked. Crazy "U" design. I'm currently using a very efficient 10,000 BTU Frigidaire that uses 916 watts at full capacity and am strongly considering this 12,000 BTU split-system with a SEER rating of 19: https://www.amazon.com/gp/product/B07RPDSKXK/ref=ox_sc_saved_title_5?smid=A111YL3NSD4TNL&psc=1

I'm anxiously awaiting Mr. Prowse's review of the Growatt he promised coming soon on his YouTube channel: https://www.youtube.com/c/WillProwse/videos?view=0&sort=dd&flow=grid

 

[sarossell]

Sorry @curiouscarbon, I got all caught up in my problem, I forgot to be neighborly. Thank you for welcoming me to the forum and responding so quickly to my message. Very kind of you. ?

 

[Supervstech]

Welcome!

 

[sarossell]

Thanks, @Supervstech !

 

[Supervstech]

The big reason you are having issues getting all the solar watts in is your choice in battery voltage.
12v just REALLY hurts panel possibilities.
The GW3000 inverter is a 24V inverter.
That means your existing 60 amp controller can output around 1600W.
12v is easy, but hard in so many ways.

 

[sarossell]

@Supervstech : My apologies if I was not clear. The 3000TL is a 48 volt all-in-one and can even be run without a battery at all. I've run both 12 and 24 systems in the past with mixed results. Most recently, I ran a 24 volt with two parallel Orion DC-DC converters for 24 to 12 volt conversion to the 12 volt inverter. It was nice being able to dial in the converter voltage to a steady 14.3 volts to mitigate volage drop on big loads, like the Keurig coffee maker, but the posts on the Orions are so small and so close together, you can't use large enough gauge wires to handle the current. Poor design.

 

[Supervstech]

At 48V, the max current that inverter will ever see is 63A, so, #4 is as big as the wire needs to be. How big are the terminals? What wire size can you fit?

 

[sarossell]

#6 was the best fit on the terminals, but couldn't handle the prolonged current flow at 1800 watts. The eyelets on the #4 were too big to fit next to each other without shorting out. I was able to find some #2 with slim but thick eyelets that were still too wide, but I was able to stagger them ion the terminals and then separate them with tape. If the terminals were further apart, it would probably work just fine. I just don't think the designers were expecting someone to use them to make a ridiculously instant cup of coffee.

 

[Hedges]

Your 30 x 270W panels would make about 8100W peak only if all aimed the same direction. If you aim some at the morning sun and some at afternoon, with a 90 degree angle between them, they'll make a peak of about 0.7 times as much current/power or 5600W. That could fit your charge controller and battery charge rate better, and charges for more hours.

Battery prices can get ridiculous, but if night time consumption is lower, and your system limits charge rate to what batteries can accept, you can have a small battery but a big PV array to generate AC and power the A/C.

My PV array is almost big enough to charge my battery bank at 1.0C, but the system is configured for 0.2C charge rate. I do this with AC coupling, but any of the all-in-ones might do the same within some limits. They probably don't allow additional charge controllers while keeping that behavior.

I understand Victron components can work with a battery shunt so charge controllers deliver enough for target battery charge current plus what inverter is consuming. Or you can do AC coupling like me. But I don't think I can help you match the $712 price you're looking at!

 

[sarossell]

Wow @Hedges !

That's great info and I understood about half of it. I'll need time to absorb. But thank you so much! Clever use of panel angles for early day and late afternoon activity while also limiting daytime total input. I hadn't considered that option.

Sadly, here in the deep desert of Arizona, once it hits 100° at night, it doesn't fall below that for about 3 or 4 months! So, night time power requirements are horrendous. Also, I'm on a fixed income, and not much at that, so batteries are a premium for me. In spite of that, I do have eight years worth of equipment keeping me afloat (three different sized panels and two charge controllers. I know, right? It's a mess of parallel and series connections to try to mitigate losses).

My plan is to use the Growatt 3000LT all-in-ones during the daylight hours for full-on air conditioning with a night time fail over to the swamp cooler on my old 2300 watt array on the two charge controllers and 600 amp hour 12 volt bank.

Potentially, I can achieve 0.2C charge on my 600 amp hour 12 volt bank using the two charge controllers in parallel from the backup hodge-podge 2300 watt array. So the idea is to have two Growatt all-in-ones pushing 6000 watts total output during the day for direct air conditioning with the rest for charging my hodhe-podge 2300 watt setup and then failing over during night to the 2300 watt system with minimal battery on the Growatts just to connect them at 48 volts. I might have to try using a 48 volt AIMS charger to charade as a 48 volt battery between the two Growatts. Insane. More likely, I'll just separate the two Growatts and use the 3000 watts from each to do what I need to get through the day with one and charge the hodge-podge mess for night with the other.

As for AC coupling, I haven't the slightest clue how to go about that. As I understand it, the Growatt does this between grid and solar or generator. I may be able to achieve this between the Growatt solar and the hodge-podge.

Admittedly, the stress of trying to figure this out while also dealing with a squatter on my property has driven to me to have a few more drinks this evening than is prudent, so perhaps none of this makes any sense. My apologies.

 

[Hedges]

???

For a large battery cycling every night, DIY LiFePO4 made from 280 Ah cells and a BMS seems to be the economical approach. I understand the cells are around $100 each, so 16 cells for a 48V battery would cost $1600, plus whatever BMS of suitable current handling costs. That gives you about 13 kWh. So maybe 1 kW average through the night.

AC coupling the way I did it is multiple Sunny Island (if just one then a 120/240V transformer is needed), and one or more Sunny Boy. Sunny Islands might be $2000 each, and older Sunny Boy $500 or $1000. If your Growatt does you you need, that seems to be cheaper. One question is how much power is need to start an air conditioner. My measurements so far have shown starting surge for a fraction of a second is 5 times nameplate rating. See what surge Growatt lists. If it is for 100 milliseconds, won't be long enough. Sunny Island provides 3 seconds of 11 kW, so enough to start a 2000W motor.

My system is oversized except for the AGM battery, and is grid-backup. When grid is down, battery supplies momentary power to start appliances, then PV inverters take over supplying all power. A/C, laundry, everything else runs from PV during the day. At night I shut off all except refrigerators, lights, computer, and so on.

 

[Hedges]

If only you could have an ice house, making ice all day long from PV, then blow air through it to cool your home at night.
H2O is so much cheaper than Li or Pb.

Of course, making ice in the heat of the day takes more energy than doing so in the less hot night. But PV panels are cheaper than batteries ...

 

[sarossell]

Sadly, LiFePO4 is WAY out of my budget for the moment.

Curiously, my efficient Frigidaire 10,000 BTU is doing just fine with my 3500 watt pure sine inverter on the 600 amp hour flooded lead acid bank. Sure, it dims the lights a bit when the compressor kicks in, but it stays the course.

I'll look into the Sunny Island/Boy options for sure. Any links would be greatly appreciated. Thank you.

Running laundry off PV must be intense. You must have an impressive array and power distribution system. Are you running 240 multi-phase?

 

[Hedges]

120/240V split phase.
Over 10kW of PV. 23 kW of battery inverter (just because could)
20 kWh AGM (14 kWh usable)

DIY LiFePO4 might be 40% the cost of my AGM. I think the only way you can go cheaper is used batteries or lower Wh capacity.

eBay is where I've found the deals on SMA products. What happened with Sunny Island is the DC solar bankruptcy, so $5000 inverters got sold sometimes well under $2000. Lately I've seen $2000 to $2500. Very nice systems, but if a $1600 battery is out of your budget I think a SMA system like this would be too.

 

[sarossell]

I have considered ice in a brine solution with a submerged evaporative coil circulation system, but I suspect the cost per pound of ice production is too low within my budget. This was the most affordable option for me to consider but it only puts out 100 pounds per day.

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[sarossell]

@Hedges : Yes, sadly, my income is practically non-existent at the moment. So I'm cursed with baby-sitting cheaper flooded lead acid from year to year. Poor health and bad choices in life... Still, you learn how to nurse lead very very well when it's all you've got. But I own an acre of the Mojave and have water, food and internet, so electricity and air conditioning is just my main challenge currently. I'm even playing with a vertical wind turbine design for dark hours since the wind out here is almost constant.

 

[Hedges]

Having land is good
I have some acreage in the hills, but living in a house closer to work.

Water is the key thing, everything else can be made.

I understand wind usually isn't very effective, but maybe in your case. Tall tower needed for less turbulent flow and higher speed.
I don't know if vertical is very good, or if horizontal would be most practical.

For ice maker, I would think DIY just like everything else. It obviously needs to be of a scale similar to A/C for a house. old home or car A/C components?

 

[sarossell]

My only experience with wind turbines so far has been an inexpensive horizontal Chinese 5-blade. It made a heck of a noise as the wind here spun it up significantly and then eventually ripped it off the roof. It lasted about a week and didn't generate enough electricity to even run a small fan. Pure crap. I don't hold much hope with a vertical design either, but it can be made to be more sturdy.

As for ice, I wouldn't know where to start if it was anything more than a simple adaptation of existing equipment.