Enphase IQ8-planning a system

Bluedog225

Texas
Joined
Nov 18, 2019
Messages
482
Good morning,

I appreciate all the good information available here. I‘ve been waiting for the IQ8 to begin detailed planning and purchasing equipment. It looks like the IQ8 lineup is at long last going to be available next year. I’d like to get down to actually drawing out a system with specific components and prices.

I will be off grid. No looking back. My array will cover 600 square feet of flat roof. At whatever wattage/price makes sense at the time of purchase. I’m very flexible and my energy needs will be adequately covered even with lower wattage panels. In the neighborhood of 12kw. There may be a ground array later more oriented towards late afternoon sun.

I’ll probably purchase a non-Enphase LiFePo battery bank due to budget (e.g. Fortress) or something similar.

Does anyone have an understanding of the variety of IQ8 options? I started trying to dig into the specs of each model and it occurred to me that there might be a something published that explained the differences.

IQ8, IQ8+, IQ8M, IQ8A, IQ8H, IQ8—208V

Also, I’m a little confused by the type of panel the IQ8 states that it is “optimized” for. That is, “high-powered 60-cell/120 half-cell and 72-cell and 144 half-cell modules.” What does that mean in terms of actual panels. Anything 60/120 or 72/144? Or some minimum wattage or voltage?

My thought was to start with the panels and IQ8 so I can pin down my amps, volts, and watts. This will inform my choice of charger/inverter.

Any input appreciated.
 

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svetz

Works in theory! Practice? That's something else
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I’ll probably purchase a non-Enphase LiFePo battery bank due to budget (e.g. Fortress) or something similar.
Make sure it's compatible, the IQ8s need to know to throttle back when the battery is full. See Incrementally Adding AC Batteries.

...Also, I’m a little confused by the type of panel the IQ8 states that it is “optimized” for. That is, “high-powered 60-cell/120 half-cell and 72-cell and 144 half-cell modules.” What does that mean in terms of actual panels. Anything 60/120 or 72/144? Or some minimum wattage or voltage?...
If you look at the datasheet I think the two important characteristics are matching voltage and watt ranges. For example, from this we know the IQ8PLUS-72-2-US can handle 235 – 440 watts from 30 / 58 volts. So, it would be a bad match for a 62V 400W panel.
 

Bluedog225

Texas
Joined
Nov 18, 2019
Messages
482
Dang. Thanks for the link. Using a different battery was definitely part of the plan.
 

Bluedog225

Texas
Joined
Nov 18, 2019
Messages
482
I’m hung up on a couple of issues.

1. buy/build batteries-leaning towards buy.
2. Which inverter/charger system
3. How worried I need to be about communications.

I’m hoping to see a few system layouts that incorporate the IQ8 with other components so I can learn/evaluate.

Once I can pin down the equipment, I’m ready to roll. Hoping for getting it installed prior to the summer heat.
 
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Hedges

I See Electromagnetic Fields!
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Mar 28, 2020
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9,134
Entirely off-grid.
IQ8 AC coupled micro-inverter.

Any particular reason for AC coupling and for microinverter when off-grid?
I like AC coupling, but do it with string inverter.
The key to an off-grid system is the battery inverter.

Something about IQ8 and off-grid or battery systems, but I think battery inverter is still a separate box.
And working with a generator probably looks like a grid-backup system with relay to disconnect.


What would the whole setup cost you? How may kW?
If using IQ8, what is its wattage? If less than PV panel, it'll sometimes clip, so you get less out of your 600 square foot area.
 

Bluedog225

Texas
Joined
Nov 18, 2019
Messages
482
My deal is, I want to minimize high voltage DC. I’ve put a ton of time and money and blood and sweat into my cabin. I’m just more comfortable with AC safety systems.

I’ve got two options. I can set up a traditional DIY station in my shipping container with panels, DIY batteries, a string inverter and run 120 or 240 to the cabin. That whole setup seems riskier but it’s just the shipping container. Not the end of the world if something goes wrong.

Or I can put the panels on the cabin roof. Which would be absolutely brilliant for security and additional shading in the 110F texas sun. With IQ8s and run a traditional AC system. Probably with rack batteries.

I had this notion that I could use the IQ8s for AC, have a cheaper than enphase battery inverter, and have cheaper than enphase batteries.

The utility wants roughly $25,000 to run electric to my place. And an 30’ cleared easement which would suck.

I’m hung up a little on whether I can use the IQ8s, some suitable battery inverter, and 48V rack batteries and make all this work. The communications requirements are unclear to me as are the micro-grid requirements of the IQ8s. They may be related.

I am under the impression that going 100% Enphase is going to be much more expensive.

I’ve learned a lot over the last 6 months or so hanging out here but still have a ways to go.

Edit-and thanks for the link!

4A91C0CF-3E8F-49DE-9A98-962922A059B5.jpeg
 
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Hedges

I See Electromagnetic Fields!
Joined
Mar 28, 2020
Messages
9,134
The high voltage DC of a string inverter could present some risks.

Shock hazard? Never touch it. Open switch to interrupt current, unplug MC cables or remove touch-safe fuses before working on wiring.

Arc, which could start fire. A 3000W, 480 Voc series string could draw a large arc and ignite something. Arc-fault is typical in GT PV inverters. That opens the circuit at inverter. Multiple faults in string could still sustain arc. Rapid Shutdown, which isolates circuit between each PV panel, would likely provide additional protection. So long as inverter stops sending keep-alive signal. With RSD, cost advantage over microinverter is gone.

So yes, that could have some risks.
Low voltage DC would be higher current, also fire risks.
So I can see how micro inverter might be better for fire safety.

The following shows AC coupled system with GT PV inverter, and grid-forming battery inverter.
Not shown is a relay to disconnect loads but keep AC going to GT PV inverters when battery is low, needed to recharge.

Alternative is DC coupled. An SCC with about 100V from each string of PV panels (and fuses or breakers per string). That would be like any traditional off-grid system.

Consider what motor loads you may have. They require sufficient surge from battery inverter.

This inverter (Sunny Island) works with FLA, AGM, or various lithium batteries having compatible BMS. Commercial ones are expensive, but REC is one BMS available for DIY batteries. Sunny Island isn't cheap, but there are liquidation sales on eBay, and Midnight sells a bundle with pre-wired panels (DC SCC optional). Compared to Enphase, may well be less expensive.

 

Hedges

I See Electromagnetic Fields!
Joined
Mar 28, 2020
Messages
9,134
Some microinverters support frequency-watts (can AC couple to a grid-forming battery inverter that does frequency shift.) Don't need to wait for IQ8 for that, some but not all earlier models work.

You can then use a different brand battery inverter, with whatever batteries it supports. I suggest Sunny Island, but there are several other brands. You may be able to get new old stock microinverters and battery inverters at a discount.
 
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