Another sunny day complete.
The XW-Pro hit it's 56.7 volt absorb even earlier at 11:42 am this time. The DC solar kept going, hitting the 57.6 volt "BOOST" at about 3:15 PM. Wit was still able to make over 1,300 watts, but it curtailed back to just 500 watts as it went into CV mode. I am confident it would have been able to do 7 KWHs again, but with the power rollback, it only hit 6.6 KWHs when the sun set. The float mode was able to keep the battery up to 57.4 all the way out to 5:25 pm. And that was with the XW inverter pulling 10-15 amps off the battery bank. It is now almost midnight and the battery is still over 55 volts. It will certainly keep running to sunrise. Today started at 54.8 at midnight, and it only fell to 52.5 before the sun came up.
The big test is going to be Thurs. to Sat. They are predicting a bad winter storm. We might even get snow here in the valley at 1,100 foot altitude. And I won't be here to baby sit.
Going to the XW-Pro "Energy" page is a bit fun. So far this month, the batteries have only been charged with 157.8 KWHs, but they have discharged into the house 203.8 KWHs. That extra 48 KWHs of energy is from the DC system going directly into the batteries. The XW does not know about that power. Since we are 20 days into the month, you can see I use just about 10 KWHs a day overnight from the battery system. Yesterday, I pushed 7.9 KWH's from the Enphase system back to the grid, and I pulled nothing back from the grid, the entire graph is at or below the zero power line. But it exported pretty strong for 4 hours when the XW went into No Float early while the DC system pushed over 7 KWHs into the batteries, even though it curtailed. So this time of year, I am now easily making more than I need, as long as we have a sunny day.
As the days get longer, I will end up exporting more and curtailing more until the weather gets hot enough to fire up the A/C again. At 5 pm on a HOT!! day, It will be fun to see the DC system pushing power into the batteries while the XW and Enphase inverters are both working to power the A/C compressor. Last August 18th, I had to pull 15.64 KWHs from the grid to keep the house cool. On that day, the Enphase system made 26.4 KWHs. That works out to 5.52 sun hours. If the DC system holds to making 90% of that, the 2,000 wats of DC panel could make about 9.94 KWHs. By those numbers, I will still fall short by about 5.7 KWHs. I need a little over 1 KW more solar panel to fully cover running the AC on those hot days.
I may add 4 more 300ish watt panels. But their position will incur a bit of morning shading. What I would love to do is move 4 of my old 300 watt Sil-Fab panels from the top row of the upper roof down to the lower roof extending my existing array on the lower roof. That way they will all look identical as you can see them from the street. Then on the top row of the upper roof, I would replace those panels with newer 365 watt half cut panels where they get the best sun and no shading. And way up there, they are hard to see from the ground, so even if they look a little different, no one will notice. I don't think I will ever have to worry about too much export power, but to be on the safe side, I can wire the 4 moved 300 watt panels on a relay that the PLC can shut off if the export limit is getting close. As soon as some load turns on, it can re-activate them.
I talked about this idea in the past. If I break the AC side of Enphase microinverters, it will take 5 minutes before they can make any power again. So my idea was to wire a series resistor into the DC solar panel side and have the relay jump it out. If the 300 watt panel is making 8 amps at 30 volts (240 watts) But then I wire in a 10 ohm resistor, that 8 amps will drop the voltage by 8 to just 22 volts x 8 amps = 176 watts. A 20 ohm resistor would drop it to something like 112 watts. Dropping 4 panels like that will keep me out of exporting too much. The MPPT will just see it like a big shadow hit that panel. Jump out the resistor and the power jumps right back to full with no delay. If I go with 4 more iQ7A inverters and the newer panels maxes them out, That would be 1.45 x 4 amps = 5.8 amps extra. But then I also cut 4 of my 1 amps micros down to about half power .5 amps x 4 = 2 amps. And then 12 more amps from the rest of the micros all maxed out. That pushes my to 19.8 amps total. To stay "legal" I just have to be sure the house is using at least 3.8 amps at 240 volts = 912 watts. Between battery charging or the A/C compressor, I think I am good with that.