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

[Ray Walters]

Actually its much more cost effective to use charge controllers than GT 
inverters for the PV input.   Just price out a 4 Kw GT inverter of your 
choice compared to a Midnite Classic for instance.  It's in the ball 
park of 25 cents/ watt savings, and that's not chump change.
I only use AC coupling when the GT system is already in place, and we're 
adding battery backup.

R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760

On 6/6/2015 8:49 AM, Jeff Clearwater wrote:
> Hi Mark
>   Seems a shame to spend the money on a charge control etc when SMA 
> has carefully provided a built in solution.
>
> If you do decide to go that route you'll need to install a Shunt and 
> set up the DC Current Sense circuit so the inverter knows what other 
> current is flowing to and fro the batteries.
>
> Best,
>
> Jeff
>
>
>
>
>
> Sent from my iPhone
>
> On Jun 6, 2015, at 7:23 AM, Mac Lewis <maclewis1 at gmail.com 
> <mailto:maclewis1 at gmail.com>> 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  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 <markf at berkeleysolar.com 
>> <mailto: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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