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To: Tell It Right

Wow. And you use batteries. Interesting. And that allows you a better backup power source when the utility power is offline. Unlikely that you’d be able to provide decent power to the house directly from the panels. Even for a small load. Also, be careful with the batteries. They can be dangerous when the system runs away. Maybe a separate shack from the house? What battery chemistry do they use for this solution?

There is additional conversion loss — converting DC to AC. Have you considered using the DC directly from the battery subsystem? One less conversion loss step (less heat generated, etc). You’d probably still need a DC-DC converter to regulate down to 5V, etc. Then raw DC, etc.

Anyway, many of your household electronics may run directly off of DC. You’d have to figure out which. My guess is that you’d have a DC port (or ports) in your wall panels right next to the three prong IEC plug outlet. There may be a bit of voltage drop since DC doesn’t distribute as efficiently as AC. Depends on the nominal DC voltage I guess. But the distances and distribution IR losses might be low and manageable.

Does your inverter provide a “perfect” sine wave? Or a crude square wave?

IMO, I’d wait on the 100% EV since it still half baked on the power utility end. Not enough power being generated at the power plant. Unless you can charge your EV from your home solar panels. :)


49 posted on 03/02/2022 8:27:49 AM PST by dhs12345
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To: dhs12345
Actually, the solar system does almost completely run the house. Take yesterday to today. From 8:00 AM yesterday until 7:00 AM this morning I didn't pull any power from the grid. Why? Because my inverter can produce 9 kW continuous DC to AC power. So as long as I have enough solar coming in (10.2 kW with optimum conditions, currently 8.1 kW) and/or battery storage (30 kWh total, but since I drain them no more than 70% count it as 21 kWh usable storage) I don't pull from the grid except for the rare times I'm running so many heavy powered appliances to total over 9 kW (and even then only the power beyond 9 kW is pulled from the grid).

Yes, to batteries being dangerous, but that's mainly older model batteries from the "early" days of solar storage. My batteries are much safer for two reasons. Each battery has built in BMS (battery management software that, among other things, does internal checks to make sure it's not overheating, and only if things are in the good does it keep the circuit closed). The other thing is that I have a total of six 48V LifePo4 lithium batteries that store 5 kWh each. Basically, it's much safer to pull a load from many powerful batteries simultaneously than it is to pull the same load from only one or two small-powered batteries and hope it keeps up without burning itself up.

50 posted on 03/02/2022 9:14:47 AM PST by Tell It Right (1st Thessalonians 5:21 -- Put everything to the test, hold fast to that which is true.)
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To: dhs12345
Yes, there's a conversion loss from DC to AC. But my inverter is 96% efficient. It'd be infeasible to run DC lines from my inverter throughout the house to be able to plug our phones and tablet to regain that 4% lost, especially since my few DC powered items draw little power anyway. They do make DC powered appliances, but those are almost all small appliances for RV's. For a while, RV's were a major portion of the solar/battery market. Now that inverters are much more efficient I doubt DC appliances will be around much longer.

Yes, my inverter produces a "perfect" sine wave. But that's because I spent extra on the inverter for other reasons. I wanted an inverter powerful enough to give me 9 kW conversion from DC to AC, and also have powerful charge controllers. Basically, there was no use spending a lot on solar panels to give me up to 10 kW coming in unless I made sure that power could be put to somewhere useful. (One weak link in the system makes the overall throughput weak and horribly inefficient.)

As far as waiting for a 100% free charged EV goes, it's not about improvement in EV technology that I'd be waiting on. It'd be about upgrading my current solar system. The system I had put onto my house was meant to provide as much as my house usually needs and not much more -- why pay for more than I need? I overdid it a little and there are many days I have a little extra power that could be used to charge an EV. Especially if I use an optional feature of my inverter to power a separate circuit panel intermittently -- only if my home batteries are at a configured charge (say 80% or more). The idea being that if I have enough battery charge to make it through the night (probably) before the sun comes up the next day, then use any power above that for stuff I don't need all the time.

Imagine me coming home with an EV, which means it's time to plug it in to charge it like all other EV owners do every time they come home. And imagine I had two charging outlets to choose from: either a 240V/48A constant powered outlet to charge the F-150 Lightning for 19 miles for every hour it's charged, or a 240V/32A outlet that's powered only some of the time (giving 14 miles for every hour its charged). If I came home with a low "tank" in my EV or if I planned to do a lot of driving the next day, I'd plug it into the constant powered outlet knowing that most or all of that power would come from the grid. (If I need it charged I need it charged, no getting around it.) But if I come home with a lot "left in the tank" I'd plug it into the intermittently powered outlet. I may get a charge for a while until my home solar batteries drop to 80% charged (because of power demand from charging the EV plus demand from the house) and at that point it'll automatically shut off without me having to monitor it and go out to the garage to unplug the EV. The same with it automatically start charging the next day if I leave it charged after the sun comes out and my home batteries are charged enough. Then there's also the DC to AC conversion max of 9 kW (the intermittent charging of 240V/32A is 7.7 kW, so for it to be powered not only do I need a high home battery charge but also not be consuming more than 1.3 kW with the rest of the house).

52 posted on 03/02/2022 9:34:59 AM PST by Tell It Right (1st Thessalonians 5:21 -- Put everything to the test, hold fast to that which is true.)
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