Depending on how your PV array is wired, it can be generating 1000+ volts, but, not much amperage behind it. Say, 10 amps or so, under perfect conditions. My box takes the high voltage DC, reduces it by a wide margin, boosts the amperage by a wide margin (relatively speaking) and feeds that to the inverter on the battery bank terminals.
If the incoming voltage should drop below a pre set threshold where my box cannot provide 48 volts DC to the inverter, my box will provide it nothing instead. Not less, but, nothing. As far as the inverter is concerned, it becomes a 'dead' battery. There are a couple of components inside the box to give the inverter a 'dummy load' for charging purposes, so that the inverter isn't harmed and my box isn't either. But, that's actually being wasted, since it's not storing the current like a real battery would.
My box is simply taking advantage of a series wired PV array for high voltage DC to generate amperage equ to a small battery bank, roughly
100amps or so. I can increase it's amperage output by changing out some of the components. But, nothings for free, in order to run the changed out components, It'll require additional voltage.If the PV array is parallel and/or a series/parallel combination, addtional changes would be necessary in order for my box to work properly without smoking itself, damaging the PV array and/or the inverter it's tied into.
This is why I said it's VERY specific to the inverter and the PV array configuration it *was* able to provide power to. As the client is using an actual battery bank now, my device has been disconnected and is sitting on a shelf or something waiting for myself and/or boss persons to come get it. As, it's no longer a necessary item.
Essentially what happened was the following:
If the grid goes down, an interlock seperates the inverter AC output from the grid, so that a line man or other personal won't be lit up when they are working on the grid. And, prior to the battery bank installation, my box would take over as long as the PV array is up and running and temporarily continue providing power to the inverter by 'pretending' to be a small battery bank. Now, if it's very cloudy and/or nighttime and the grid goes down, my box isn't able to do anything for the inverter, so, no power is being sent back onto the grid, anyway, and, no power is being provided for the house, either.
At this point, a 30 second delay without grid power or inverter power being detected will cause his generator to start up. The way it was wired, though, if the generator is running, the interlocks will kick in and isolate both the generator as well as the inverter from the incoming mains (the grid); so there's NO chance someone working on the grid will get anything nasty there way and the inverter won't be damaged by power spiking as the generator begins providing power. IE: if the generator is running, the inverter has no access to the 'grid' or the power being supplied by the generator, either. It's isolated from both and doing nothing useful for the client at this point, even if it were able to do something useful. As it's electrically disconnected from the mains that feed the house at that point. And, well, if the generator is running, it's because the inverter and/or grid for whatever reason, couldn't provide power in the first place.
I hope that clears things up.
It depends on what you need/want to use it for...