[RE-wrenches] SI/SB MicroGrid - Recovery From Low Battery Shut Off

[Drake]

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:allan at sindelarsolar.com>allan at 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:markf at berkeleysolar.com>markf at 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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>>--
>>
>>
>>
>>Mac Lewis
>>
>>"Yo solo sé que no sé nada." -Sócrates
>>
>>
>>
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