That is what we did for our home system. The main
impetus was to keep the batteries charged without
having to charge from the grid using the on-board
battery chargers. Grid charging uses a lot of utility power.
This system has stacked Outback inverters. We
keep the backup inverters turned off at the Mate,
but with the instrumentation running. If we did
have a low battery situation, the voltage would
rise enough to start the system back up from the 80 W of DC coupled PV.
Another way to recover from low battery shutdown
would be to program the shut down parameters
below battery voltage when the sun came back out.
Also, it is likely that if the system were
completely turned off at the DC breaker, the
battery voltage would rise enough to start the
inverter(s) when solar resources improved.
At 05:51 PM 6/6/2015, you wrote:
Years ago, when I was researching SB/SI
microgrid solutions for a Ted Turner high-end
off grid rich man's lodge, John Berdner (at that
time the head of SMA-America) had made me the
same recommendation: that a small amount of PV
be wired as a DC charge-controller-based input.
This was a final fail-safe approach, in case the
array was insufficient and the gennie didn't
start. It would bring the batteries to a minimal
voltage level, such that the SB/SI system would
return to operation once the batteries recovered.
Allan
Allan Sindelar
<mailto:al...@sindelarsolar.com>al...@sindelarsolar.com
NABCEP Certified PV Installation Professional
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder (Retired), Positive Energy, Inc.
505 780-2738 cell
On 6/6/2015 8:23 AM, Mac Lewis wrote:
Hi Mark,
The Sunny Island has various battery protection
modes and will shutdown based on user
programmable state of charge levels. Level 2
battery protection will start the Sunny Island
every 2 hours in an attempt to get charge into
the batteries. You should set this level up at
times when energy input is likely. See page
113-114 here:
<http://files.sma.de/dl/15216/SI4548-6048-US-BE-en-20.pdf>http://files.sma.de/dl/15216/SI4548-6048-US-BE-en-20.pdf
If it doesn't get any charging to the batteries
for 10 minutes, it will shut down and wait again.
This is an advantage of having at least some DC coupled solar input.
On Sat, Jun 6, 2015 at 7:39 AM, Mark Frye
<<mailto:ma...@berkeleysolar.com>ma...@berkeleysolar.com> wrote:
Hi Guys,
Just wondering about how a SI/SB microgrid
works. If all the PV is connected to SB
inverters, what happens if the loads manage to
drain the batteries to their low voltage
shutdown? Wouldn't the SB stop providing the AC
sync so then the SB wouldn't have anything to
sync to even if they had power available from the PV?
How is this handled? It seems to me you would
always want to have some amount of PV DC coupled.
Thanks,
Mark Frye
Berkeley Solar Electric Systems
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