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The Nitty Gritty
This section is geared toward those installers and homeowners who are thoroughly familiar with the previous
section. In this section, we’ll use a few acronyms and technical terms the reader is assumed to know and
understand. If you’re still learning about solar plus storage and/or the SkyBox, make sure you’ve read the
previous section. If you’re an installer, it wouldn’t hurt for you to have installed a few basic SkyBox systems
before continuing through this Handbook.
More Power Please
What if 5 kW just doesn’t cut it for your site? With proper planning, two SkyBoxes can be linked to work
together to provide up to 10 kW of power. We call this stacking. Two SkyBoxes can be stacked. If you find
you need more power than this, contact OutBack Sales (
) before proceeding.
In this configuration, one SkyBox acts as the ‘leader’ and one as the ‘follower’. The master is in charge of the
system’s overall behavior when operating off-grid (power outage, the
Maximum independence
profile, etc.).
Each SkyBox acts independently when operating on-grid. The
SkyBox Stacking Application Note
describes
more details.
What About This Inverter I Already Have?
(AC Coupling)
While AC coupling is not the most preferred use for the SkyBox, or any battery-based inverter, it is possible to
link your old grid-dependent inverter with the SkyBox.
So, what happens when these two devices work together? In normal day-to-day operations, not much
changes. Your old inverter continues to produce solar power from the existing array and send it to the grid,
albeit now the power is routed through the SkyBox. The SkyBox also produces power from its own solar array
(if installed).
The biggest change comes when the utility goes down. Previously with just a grid-dependent inverter, if the
power went out, so did the grid-dependent inverter. Even though the sun could still be shining, no power was
being produced because there was no safe place to send it. Now, when the utility goes down, the SkyBox
fakes the grid-dependent inverter into thinking the utility is still operational. The grid-dependent inverter
continues on its way, making power from the solar panels and sending it through to “the grid”, which is really
the SkyBox. The SkyBox takes this power and sends it either to the protected loads, uses it to charge the
battery connected to the SkyBox, or both.
The ability to AC couple with grid-dependent inverters is inherent in the SkyBox firmware (with version 1.4.15
and later). More details along with a wiring diagram can be found in the
SkyBox AC Coupling Planning Guide
).
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