[RE-wrenches] Any thoughts on this approach to adding battery backup to an existing grid tie system will be appreciated.

[Andrew Truitt]

Anyone have any experience with the SMA Sunny Boy Storage for this
application?  Li+ compatible, HVDC bus, black-start capable... looks like
no generator input though.  I wonder how well it works when AC coupled with
with non-SMA inverters.



*Regards, *


*Andrew Truitt*

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On Thu, Sep 13, 2018 at 6:21 AM Will White <will at solarenergy.org> wrote:

> I agree with everything Ray has said when you're using a system with
> lead-acid batteries, however this doesn't apply to lithium-ion. Li
> batteries don't need multistage charging like LA batteries do so they would
> be a perfect fit for a retro-fit battery backup system that can only bulk
> charge.
>
> I'd also suggest people check out the Enphase IQ8 system which allows the
> inverters to operate without the grid with no storage. They should also be
> able to black start an AC coupled system with no grid unlike other AC
> coupled designs. I haven't seen it in person but two of my co-workers
> toured their demo project and it seems to live up to everything Enphase is
> claiming.
>
> Thanks,
> Will
>
> On Wed, Sep 12, 2018 at 8:38 PM Ray <ray at solarray.com> wrote:
>
>> I didn't watch the whole thing, but it looked like a standard AC couple
>> set up with an Outback Radian.  My understanding is that Outback no longer
>> supports AC Coupling, BTW.  I would never use that for an off grid system
>> or  for longer outages.  In a very brief explanation,  it essentially
>> bypasses any charge controlling to the batteries, and puts full Array power
>> into the batteries until a relay (or phase shifting) disconnects the
>> array.  No three stage charging, no taper charging, no float, no temp
>> compensation.  Its like trying to fill a 5 gal bucket with a fire house, or
>> drive a car with a throttle that's either off or at full throttle, no in
>> between.  The other issue is that if the batteries get low and the inverter
>> shuts off, the system will not recharge, and after a couple of weeks the
>> batteries will be sulfated beyond recovery.
>>
>> My guess is that manus that advocated this approach got into trouble from
>> end users that fried expensive battery banks during longer outages.  I
>> would consider it the equivalent of cheap backup generators: a great backup
>> system for folks that don't need it.   There are probably thousands of
>> those out there with happy customers and installers, because its never
>> actually been used for more than a few hours, and the batteries are
>> properly charged from the grid 99.8% of the time.
>>
>> Ray Walters
>> Remote Solar
>> 303 505-8760
>>
>> On 9/12/18 6:11 PM, Ken Schaal wrote:
>>
>> https://www.youtube.com/watch?v=eyhkIfS5Z-Q
>>
>>
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