Feeding two Enphase IQ7 from one DC input source - Results

WebPower

Inquiring minds want to know: Can you share an input between 2 Enphase IQ7 microinverters?

Yes, it appears you can. Using a DC power supply as the input, the microinverters I'm testing this with have a similar turn on voltage of about 22.2vdc. The interesting thing to note, is they appear to pull maximum current (5.8A in this case) and clamp the input voltage down around 16.8v. This is what I see with my wind turbine circuit using only one IQ7. It could be a by-product of the power supply as it indicates its in the constant current (CC) mode. Where as if you only feed one IQ7, it allows the voltage to rise to whatever value the power supply will provide, blinking the constant voltage (CV) mode with the CC light on steady. I believe this means that the MPPT of the IQ7 is active and adjusting as the power supply puts out more power. But with two IQ7s in parallel, the power supply doesn't have enough reserve capacity to allow the MPPT algorithm of each IQ7 to search for the sweet spot.

That's my take on it. I'm sure someone out there has more than my rudimentary knowledge of the IQ7's and/or MPPT algorithms to make sense of it.

But now that I know that it works, I have 600W of solar on my RV that I'd like to maximize back into the grid when it's parked in the driveway. Right now at peak solar, the IQ7 max's out at it's rated power which is only about 290W. So I've got more in possible generation waiting to be pumped back into the grid.

So stay tuned for more testing and some plots from the IQ7s.

And yes, I started a new thread instead of putting this in my wind turbine thread as this can apply to multiple uses to hopefully larger amounts of power into the grid. Mainly if you have something that generates more power than just one Enphase microinverter is rated for.

Pat

WebPower

So even though the IQ's will work in parallel, there is a reduction in the power production of at least 30%. This isn't a problem if you are trying to feed a larger producing item such as a wind turbine where there aren't what I see as very good options for feeding back into the grid. So its a trade-off.

Here is a typical comparison between panels. Top right corner is the test panel that will be feeding 2 IQ7s.

Here is yesterdays production feeding two IQ7s in parallel. A sunny day with clouds. And I have shading issues with trees. Results for a cloudless day should still show the difference, just won't have the current and voltage swings that my plots have.

You see it has considerably less production for that panel adding the two production values.

In the morning you can see you're already off to a bad start when sharing a panel. Instead of about 8Wh, you get 5Wh.

Plots of voltage and current from the Envoy for each IQ7: Voltages are equal scale, current is not, but plots provide a good idea of what you will typically see. One IQ becomes the leader. The large producer is an IQ7A. The other is an IQ7. The bench test was with two IQ7s and indicated similar results. The panel is a Canadian Solar Bifacial.

Reference day for a typical day with clouds for IQ7 #x0889:

WebPower

To continue this thought process with more detail, I have 900W of solar on top of my RV. When it's sitting in the driveway I shift the solar from the RV house batteries to feeding back into the grid with IQ7s. The panels are separated as 300W + 600 W due to the input voltage limits of a couple of renogy MPPTs. One is a Rover, which can take higher DC from the solar panels. The other is a 50A DC-DC Charger that is rated at 24VDC max solar input. The solar panels are generic ones with Vmp of about 17.5v. The 300A is easy as it feeds right into the IQ7 via a switch and its 200W+100W in series. The IQ7 is fine with that 35+VDC input. But the 600W is three 200W panels in parallel. This is where this topic is rooted. At Vmp in the 17, unloaded they get up to around 22VDC which may or may not turn on the IQ7. Mostly not. So what I've done is take a boost power supply and set it to 30V to ensure the IQ7 turns on. It's working pretty reliably and the next step is to add a second IQ7 to fully utilize the 600W available. I'll be adding a second boost power supply to see what happens. It's a different model as I'll show below in the photos. The first one has a nice display so you can see what's going on. The second one is a simple 4 wire boost supply off Amazon. I'm using two different ones to see if there are any issues for one versus the other. Single supply power production curve from Enphase is shown below. May 31 and June 1 were nice cloudless sunny days. You see I still have lots of reserve power to pull from the panels. Only a peak of 175 for the one IQ7. This was later in the day with the sun lower hence the 50W production value.

WebPower

So I've been running the setup for a while now. It turns out there is a bad panel in the string. So now I'm at 400W (2x200) in parallel. Using the two boost power supplies in parallel, both set for on voltage of about 23vdc or so. One tends to be the master and uses more of the power. Here's some production for a couple of different days. It's RV300 and RV600 on the screen shots below. The RV600 is the one now at 400W. Not optimum as you can see, but from what I mentioned before I have to have them in parallel due to the input voltage limit on the Renogy controller in the RV. But hey, something is better than nothing with it sitting in the driveway. Definitely de-rates the panel setup.

You can also see that the wind turbine IQ7 is under producing. it's 200W of solar on the tracker. It's de-rated due to the wind bias circuit design. I'm working on getting the MPPT wind controller working. Trying to get the programming on the chip. Using a raspberry pi to program it and having a bit of fun trying to get it to talk to the microcontroller chip. Once I get it on It should be reasonably soon that I get the controller hooked up and running for some tests. That info will be added to the wind turbine IQ7 thread on this forum.

Pat