Newbie solar system voltage question and sizing

IMHO, you could get away with using 8 panels on the single controller. Although the 8 are STC rated for ~2.2kw, realistically they'll usually produce less with warm panels. For example, maybe 1.7kw / 28v charging = ~60a or a bit more at your altitude. Within reason, having "excess" pv makes sense, as you're able to charge better on light overcast days. Most controllers can limit output (within reason), so moderate overpanelling isn't such a bad idea.

That said, with ~5kwh/day load, 48v likely makes more sense long term. On the short term, if you have any large wattage loads (eg pumps), a 24v system will need heavier wire to handle surges, and battery voltage sag may be worse. Longer term, you may find the 5kwh load wants more pv to both charge batteries and support loads. At 48v you would have expansion room with the one controller, but at 24v, not really. Running a controller at close to full current also means more heat and a likely shorter lifespan. It may also need altitude derating.

If you did add a controller at 24v, you wouldn't run 4 batteries on each. You would have two strings (4x6v batteries x 2 strings in parallel), with 2 controllers in parallel charging the 2 parallel battery strings. You wouldn't normally want controllers charging battery strings separately. Each controller would have it's own pv array though, and this has advantages in some applications (eg different array orientations).

Going to 48v initially would also give you some flexibility with storage. If you find a single string at 48v isn't enough, you could add a second (although you would want to do this while the first string is newish). At 24v, adding more strings beyond 2 could be problematic.

If the inverter is new in the box, I would probably sell it and go to 48v initially. At 5kwh/day, there's a decent chance I'd want more pv, more storage, or both, and adding either/both would be easier at 48v. If the inverter is used already, I might install it in a 24v system and see how it goes for a bit.

learaviator said:

... It appears judging by Outbacks sizing tool on their website that at 24 volts I can only run 7 panels because of the wattage rating of the controller, or add another charge controller and run 4 batteries on each. ...

Just to be clear: If you do have run with two charge controllers, you would put both on the entire battery bank. What you would split is between two sets of panels, one feeding each charge controller.