[RE-wrenches] Sunny Island Failure and various related issues

Mac Lewis maclewis1 at gmail.com
Thu Feb 12 09:11:43 PST 2015


Hi William,

Yes the Outback shunt should be fine for this application.  See page 72
here for the calibration:
http://files.sma.de/dl/15216/SI4548-6048-US-BE-en-20.pdf
As far as verifying with your clamp meter, I'd say if you can verify within
15% (remember to check polarity) then it is properly calibrated.  It should
do a better job than your clamp meter, but that will help make sure you are
close.  Check parameter 120.06 TotBatCur to see what the Sunny Island
thinks the battery current is (in older versions of firmware it may be
elsewhere).  I have found that with my fluke DC clamp meter (don't know the
model off the top of my head), I am easily within 5% when the current is
around 20ADC.

Good Luck

On Thu, Feb 12, 2015 at 8:58 AM, William Miller <william at millersolar.com>
wrote:

> Mac:
>
> Thanks for the advice. We will install the shunt today. A few more
> questions:
>
> 1.  Will the Outback 50ma shunt be compatible. My research indicates the
> value is correct.
>
> 2.  DC clamps are notoriously inaccurate, particularly at low amperages.
> Will this be a problem, or is shorting the leads adequate?
>
> Thanks again.
>
> William Miller
>
> PS:  We looked at the Midnite cabinets but they put the OPCD too far from
> the batteries.
>
> William
>
>
>
> On Feb 12, 2015, at 4:45 AM, Mac Lewis <maclewis1 at gmail.com> wrote:
>
> Hi William,
>
> I want to talk directly to your problem at hand.  I think installing the
> shunt and properly calibrating it, will fix this system .  In a DC coupled
> system with a Sunny Island, it is imperative that you use a shunt, unless
> you are using the Midnite charge controllers with the communications to
> accurately report all charging (or the non-UL listed SMA charge
> controllers).  There are so many functions and calculations that the Sunny
> Island performs that needs accurate SOC calculations.  All of the shutdowns
> that you are seeing are resulting from faulty SOC measurements.  I wouldn't
> believe the reported state of health either, because it is using the faulty
> SOC measurements.  Don't believe state of health until you have a couple of
> months of operation with the shunt.
>
> *Right now, with the system as is, it isn't accounting for the charge
> coming from the charge controller(s)*.  It is shutting down because its
> only accounting for AC power processed through the Sunny Island.  I once
> had a Sunny Island system with an improperly calibrated shunt and it acted
> just as you describe, strange shutdowns, bad SOC output etc.  After I got
> it calibrated, it has worked flawlessly.
>
> Take your time when you are calibrating the shunt.  Follow the (odd)
> directions perfectly and it should work.  Verify Sunny Island readings
> match your DC clamp meter and you should be good.
>
>
>
>
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-- 



Mac Lewis

*"Yo solo sé que no sé nada." -Sócrates*
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