The upgradable system problem

sunshine_eggo

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This is such a relief, its the ideal setup then because the AIO inverters come with large inverters but small Sccs, for example 24V. 3k inverter with 60A Scc, you are restricted to about 1500W of Solar array, but with such an array is difficult to use the 3000w potential of the inverter.

Not really. 60A is actually a pretty hearty MPPT, and some come with 80A.

You may be falling into the trap that leads you to think, "If my inverter can provide 3000W, I need 3000W of solar." That's rarely the case UNLESS you have an atypical application that utilizes the inverter power to near max all the time - few do. Most systems with 3000W inverters and 3000W solar will have WAY more solar than they need.
 

Begginer7

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Not really. 60A is actually a pretty hearty MPPT, and some come with 80A.

You may be falling into the trap that leads you to think, "If my inverter can provide 3000W, I need 3000W of solar." That's rarely the case UNLESS you have an atypical application that utilizes the inverter power to near max all the time - few do. Most systems with 3000W inverters and 3000W solar will have WAY more solar than they need.
You are right my wording was off, actually the issue I see is not that the Scc is small but that the inverter power is too big, I cannot think of a combination that uses both to max. capacity, the Scc most probably yes but in winter with an array of 60A×24V=1440Wx3sh=4320Wh I cannot see how you will put to use a 3k inverter,even in summer with 1440Wx9sh=12960Wh is hard for me to figure a "normal" usage. Having said that the price difference (Mpp Solar) between the 1k and the 3k inverters is 200eur, at the same idle consumption probably it makes sense to get the 3k.
 

Begginer7

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So Beginner7, it's pretty cool how you can hang out here and learn about "almost everything under the SUN". Don't you agree?
Oh yes, I got a quote from probably the largest installer around here and they put on the quote Mppt but on the specs a PWM, without Wills videos and the help of the people in this forum I would not have even known the difference.
 

sunshine_eggo

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You are right my wording was off, actually the issue I see is not that the Scc is small but that the inverter power is too big, I cannot think of a combination that uses both to max. capacity, the Scc most probably yes but in winter with an array of 60A×24V=1440Wx3sh=4320Wh I cannot see how you will put to use a 3k inverter,even in summer with 1440Wx9sh=12960Wh is hard for me to figure a "normal" usage. Having said that the price difference (Mpp Solar) between the 1k and the 3k inverters is 200eur, at the same idle consumption probably it makes sense to get the 3k.

By saying what I said, but in reverse, you've just fallen into the trap backwards. There is no implied parity between inverter power and array power.

Again, it's rare that an inverter is used at its maximum power for a substantial portion of any 24 hour period. Sure, there are special cases that may apply, but there is still no implicit parity between the power of an inverter and the power of an attached array. As an example, I have 10kW of inverter, but I currently only have a 3kW array.

on 2/13:

17.56kWh consumed/produced (731W continuous averaged)
Peak inverter power used: 3,215W
Peak PV output: 2,829W

There are 3 main rules in system sizing:
  1. Inverter is sized for your maximum continuous loads.
  2. Array is sized for your daily consumption + surplus charging and your solar conditions.
  3. Battery is sized for the duration between charges.
Note how none equate inverter power to array power. It is very possible that the above could yield inverter and PV power the same, but that's only if your daily use and solar conditions happen to work out the same.

You don't need 3000W of PV to run a 3000W inverter. That's what the batteries are for. If you exceed the PV, the inverter will just start drawing the batteries down by the current needed to supplement the PV. On that same day I mention above, this is what my battery voltage and current looked like:

1646712553610.png

The red areas are where my loads exceeded my PV, and the inverter was drawing from the battery to make up the difference. The green area is where I had gobs of PV surplus that charged the battery to full, so at the end of the day, I started the evening with full batteries. Nighttime usage is typically 100-200W average, so I had plenty to get through the night.
 

12VoltInstalls

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Not really. 60A is actually a pretty hearty MPPT, and some come with 80A.

You may be falling into the trap that leads you to think, "If my inverter can provide 3000W, I need 3000W of solar."
I get your point very well but I also interpreted the poster to be sorta wanting to use solar power at a potential rate higher than the solar input without leaning on the batteries.
Like I try to run the shop vac, a buffer, an electric blower etc early in the day rather than later simply so the batteries don’t have to absorb the use that is beyond its typical daily use charging capacity that lets me be fully charged for overnight.

So there sometimes is situations where the overnight use battery recharge capacity isn’t the primary use but daylight output is priority for them. Like AIrcon use or office folks that want to run a 1200W heater most of the day.
 
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