This is almost the same scenario that Solar Guppy helped me with.

One thing I don't understand though, if it is absolutely CRITICAL to keep these batteries happy, couldn't you just put an Automatic Generator Starter on the XW6048 so when the batteries reach a certain voltage the generator would start? I see that a generator is already available, but currently has to be manually started. I don't know too if that would allow for the smaller 200ah battery bank to continue as is even when more solar capacity is added.

I thought too that you could actually reduce the charging rate if you wanted to somewhere in the XW's or SCC's menu. So even with 6kw of solar PV, you could possibly still get by with the smaller 200ah battery bank? I guess this would waste PV capacity, but it may only be for small periods of time.

I have been using load sharing, but I have the grid support voltage set at 52V. The XW6048 charger is OFF. I just recharge from the sun, and it has been sunny every day for weeks. Of course, if my night time use draws down a few kwhours and it is cloudy in the morning it takes a while for the battery to recharge, but so what. I inquired about a firmware upgrade from Xantrex and got this advice which included setting the grid support voltage at 62VDC. Is there something in the new firmware that really would make going to such a high grid support voltage acceptable?

"Firmware release notes attached. You should be able to utilize Enhanced Grid Operation with 1.3BN12. Try setting Grid Support Voltage to 62VDC and it should do a better job of keeping the battery full. We have instructions for upgrading, but you would need the XW Config Tool (865-1155). You can call Tech Support and we can set you up with a loaner (866-519-1470). The settings should be retained."

If money is not a problem, I will add another battery array and connected in parallel with the existing array for a total of 48 vdc and 400ah...

Be very careful when paralleling a new bank with an old one. Batteries should be identical, preferably from the same lot. Differences in internal resistance, will quickly (1-2 months) reduce the better performing bank, to the same performance/quality of the lowest performing bank.

Guys, thanks for the suggestions. I have given up on the idea of off grid for the common sense reason that there is no point in using all the energy to produce, distribute and recycle batteries when I can share my excess with others on the grid and get at least a reasonable credit of about 70% of full retail. I continue to work with the utility company to get to true net metering or some other way for solar investors to get more incentives. I appreciate all the advise and support! FYI, my net net zero home has produced about 1600 kwh more than used since moving in 15 months ago. So far, so good!