On 7/29/20 11:49 AM, Lee Hart via EV wrote:
I think it depends on how they work. I have two MPPT trackers that still
work if they're fed with batteries; and one that doesn't.
With a battery input, the big one that works maximizes its output, as if
it's in full sun. Its input is current-limited to 8a; so that's what it
draws, regardless of the battery voltage.
The little one is the same, except its input current tracks its input
voltage. There is no input protection (except a fuse); so if the input
voltage is too high, the input current gets too high and it blows a fuse.
The one that doesn't work is in a 24v microsine inverter. With a battery
input, it ramps up to full power over a period of a few seconds; then
shuts down for a few seconds; and repeats. It doesn't appear to be
damaged; but it's also not particularly useful.
Off topic. Maybe.
Perhaps you can comment on some trouble I've run into.
After observing that some microinverters worked on battery input and
that string inverters worked well with combined strings of both east and
west facing panels, I became convinced that a single microinverter could
serve one east facing panel and one west facing panel. The two panels
connected in parallel to the microinverter. Tests were disappointing
with generally a microinverter, over a day, producing less energy than
had it been attached to either a single east facing panel or a single
west facing panel. Slopes on the panels are 15-20 deg from vertical so
that panels are shaded around 30% of the day and both E and W receive
sun about 30% of the day. It is semi-clear that even a shaded panel
interferes with production from the not shaded panel.
String inverters can do "double duty", producing from east facing panels
early in the day and west facing panels late in the day. With a smooth
change over at mid-day. Microinverters seem unwilling to do that
"double duty".
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