Adding pv to an inverter with only one mppt input?

[jimmyge2001]

I'm looking at an eg4 6000. It has one mppt input. So I understand I'll do a parallel/series scheme to supply pv power to it. If, later on, I want to add more pv, and I can't get exact panels, how do I add a series circuit of other voltage and amperage panels since it wouldn't work to parallel them onto the original setup?
I'm wondering if it's OK to add an external mppt to charge the batteries, in parallel with the 6000 inverter. Or some other scheme.
Thanks for setting me straight.

 

[jimmyge2001]

I guess I'm wondering if an inverter with only one mppt is a drawback. I see some with 2 or 3 mppt inputs.

 

[timselectric]

You can add extra SCC's without issues.
Just don't exceed the maximum charge rating for your batteries.

 

[Hedges]

You can add PV strings in parallel if similar Vmp.
If more than two, should have fuses or breakers.

Avoid exceeding max short-circuit current rating of inverter/scc, but it can be OK.
Of course, some brands may not handle continuous max power as well as others. More heat means shorter life.
If curves available for efficiency vs. voltage, maybe select Vmp to minimize power dissipation.

 

[Hedges]

I guess I'm wondering if an inverter with only one mppt is a drawback. I see some with 2 or 3 mppt inputs.

Multiple orientations of PV strings on one MPPT only have about 2% performance penalty vs. separate MPPT.
Slightly different PV strings could be similar, look at V x I at Vmp of each vs. pulled to a voltage in between.

Inverters with one MPPT tend to handle more current, vs. multiple MPPT each around 10A max or so. Larger PV panels only one string per input without clipping, so multiple PV strings of different orientations don't fit well. Single MPPT of higher current it is easier to over-panel without clipping for more hours production.

Assuming all similar voltage, which means that one does not get large percentage of PV panels shaded. Just one panel out of 10 shaded is OK, but if half the panels on one string are shaded, there is more loss. Either that shaded string stops producing anything, or the unshaded strings are reduced in voltage to match it. (bypass diodes let current past the shaded panels.)

With shade on a large part of one string, that's where separate MPPT would be needed to let each string deliver maximum power available.

Considering the cost of another SCC, if you wanted more PV you might add another EG4 instead.
But considering idle consumption, you might prefer lower power loss of a dedicated SCC.
Only if you can't simply overpanel.