I am interested in AC-coupling the XW6048 with 44 - M215 Enphase micro inverters using 245W pv panels. I have read the frequency shift for the XW6048 occurs in -0.4Hz/s increments. That seems too large and would likely cause too many (all) of the M215 inverters to drop off line at one time. Causing all of the inverters to cycle on - off at the same time.

Has anyone performed any testing in this area?
Is it possible to adjust the -0.4Hz/s to a smaller value? Perhaps -0.1Hz/s or -0.05Hz/s?

The goal is to have the grid tied M215 inverters (producing about 40amps) feed through the XW6048 until there is a loss of power. Then the XW6048 would go off grid, produce 240VAC/60Hz, the M215s would sync up with the XW6048, battery voltage would go up, XW6048 would quickly reduce frequency causing the M215s to sequentially drop off due to out of spec power.

Or should I look at another solution? A data center UPS...

I sent out some emails. Hopefully someone will be able to point me in the right direction.

While I'm waiting please double check some math for me.

The forums suggest 100 amp/hr for each kW of inverter capacity.
-XW6048 is 6kW at 48VDC
-So I should have 6x100 amp/hr at 48VDC=28800W/hrs of capacity
-About $10K worth of batteries, equipment & delivery

1. Am I doing my math correctly? That seems like a very large battery setup.
2. Is a battery system this size needed for an AC-coupled system?
3. Should I abandon all hope of trying to make the idea work?

AC coupling is intended for supplementing loads on the output of the XW-6048 ( or sunny island for that matter ), not to sell energy to the grid through the XW inverter.

If the GT inverters have excess energy, then they would feed that battery's, not sell to the grid.

Separately, if you want to sell energy from an XW-6048, you need as a minimum, 100ah per kw, so yes 600ah @ 48volt bank is required, lower than this and you will damage the battery's from excess AC ripple. ( this would use charge controllers )

I have a cross-over breaker, that in the event of a grid loss, I can switch the GT inverters from the main panel to the XW-6048 so I can supplement loads and charge the battery's of the XW-6048, its not automatic

From reading the xw_hybrid_ic_install_guide_gbr(975-0384-01-02_rev-c) I was thinking the Automatic Transfer Relay could carry 56 (or 60?) amps when AC1 & AC2 are connected. Which should allow the pv panels to feed through to the grid. Does it not work? Or is it not supported? As I understand it, AC-coupling was not supported at first, but it still worked.

So it would be better to set up a bus transfer to switch the panels from GT to feeding only the XW6048 as per ac-coupling-app-note(976-0240-01-01_rev-a). In that case can I get by with a smaller battery? What would you suggest as a reasonable size?

Do you know of any adjustments that can be made to the XW6048 to change the frequency shift? i.e. changing the -0.4Hz/s to different values. Would it be worth asking Xantrex?

Thank you