[RE-wrenches] Integrating Fortress E-vault maxes into an SI AC-coupled system

Sun Nov 12 17:31:55 PST 2023

William,

     I agree that AC coupled input power can't be "directly" regulated by
the battery inverter, but it *can* be indirectly regulated using techniques
such as telling the downstream PV inverter(s) to back off via a
frequency-watt change, or turning on a diversion load, or worst case simply
shutting off the battery inverter AC output connected to the PV inverters
(so-called bang-bang control).  However, I thought the battery charging
parameters were part of the equation when the inverter is making the
decision about what to do if the batteries are nearly full?

    And in my case, with the SI master set to EXT-BMS (most recent
firmware), the battery parameters *could* be set and appeared to make a
difference in operation.  My (possibly incorrect!), assumption was that the
closed loop communication was primarily for SOC and fault conditions.  If
there is any documentation for what the closed loop communication consists
of that would be really interesting!

Cheers,

Kirk Bailey
kirk at abundantsolar.com
541-231-8072 x1

On Sun, Nov 12, 2023 at 4:38 PM William Miller <william at millersolar.com>
wrote:

> Kirk:
>
>
>
> There are a lot of misconceptions about AC Coupling in the industry.  I
> think you may have fallen victim to one:
>
>
>
> When you are feeding AC power backwards through a battery inverter, that
> inverter cannot exert any control over the charging parameters.  You can
> set bulk, absorption, float, EQ, any charge setting you can find, but if
> your power source is AC-coupled (coming in through the out door), those
> settings do not affect the charging at all.
>
>
>
> Someone please slap me if I am wrong on this.
>
>
>
> Those settings do apply if you have an AC source like a generator or grid
> that is connected to an AC *input*.   We cannot connect grid-tied
> inverters to any input because AC inputs do not create a mini-grid.
>
>
>
> Furthermore, if you set a Sunny Island for battery type “Ext BMS”, you
> cannot adjust those settings.  Pressing the buttons elicits wonky
> responses. Pressing up arrow jumps to zeros…  Pressing the down arrow can
> reduce settings but they will not be saved.  I have seen this and while
> Fortress cannot replicate this in the lab, they have heard this reported.
> (This Ext-BMS setting is only available with the latest firmware and by
> initiating New battery or New system in the quick programming function.)
>
>
>
> Until this moment I did not realize that this is another reason Closed
> loop on a
>
> Sunny Island is a non-starter:  If you can’t set charge parameters for
> generator or grid battery charging then you have a system that cannot be
> set to charge batteries from AC sources with precision.  If closed loop
> does not work for this reason, and open loop does not track the critical
> SOC values, then we may be out of options.  Maybe this is why SMA will not
> talk to anyone with lithium batteries.
>
>
>
> Hmmmmm…
>
>
>
> William
>
>
>
> Miller Solar
>
> 17395 Oak Road, Atascadero, CA 93422
>
> 805-438-5600
>
> www.millersolar.com
>
> CA Lic. 773985
>
>
>
>
>
> *From:* Kirk Bailey [mailto:kirk at abundantsolar.com]
> *Sent:* Sunday, November 12, 2023 3:05 PM
> *To:* william at millersolar.com; RE-wrenches
> *Subject:* Re: [RE-wrenches] Integrating Fortress E-vault maxes into an
> SI AC-coupled system
>
>
>
> I went back and looked at my notes on my recent adventure with closed loop
> SI to eFlex Fortress, and one thing I had noted at the time is that
> Fortress recommends 2.2V, 2.26V, and 2.3V for the setting for ChrgVtgFlo
> (220-10), depending on which of three Fortress docs I read.  I think I
> ended up setting it to 2.26V after some experimentation.
>
>
>
> I can imagine a scenario where the voltage gets *slightly* too high,
> activating the most trigger-happy of the battery's BMS's, and the resulting
> sudden partial loss in load then causes a transitory voltage surge from the
> SI, which then...
>
>
>
> Cheers,
>
>
>
> Kirk Bailey
>
> kirk at abundantsolar.com
>
>
>
>
>
> On Sun, Nov 12, 2023 at 2:36 PM William Miller via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
> Jay:
>
>
>
> Good question. I assumed some kind of FET circuit but that is only my
> assumption.
>
>
>
> However an open relay exhibits some fairly high impedance.
>
>
>
> The symptoms indicate the SI shuts down but the batteries remain
> connected. Something allows 69 volts on the battery terminals…
>
>
> William Miller
> Miller Solar.com
> 805-438-5600
> www.millersolar.com
>
>
>
>
>
> On Sun, Nov 12, 2023 at 2:22 PM Jay via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
> Maybe someone else knows differently but it was explained to me that the
> fortress batteries have a relay that disconnects the battery if the voltage
> gets to high or low. There isn’t any electronic  device to change battery
> impedance besides what the actual cells are doing.
>
>
>
> Jay
>
>
>
> On Nov 12, 2023, at 12:50 PM, Jerry Shafer via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
> 
>
> Regarding the SI Inverters,for me it works best to eliminate the bat temp
> sensor and put in a resister set to be 75 degrees, this will prevent the
> charger over under charge issue.
>
> Fun times
>
>
>
> On Sun, Nov 12, 2023, 12:36 PM William Miller via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
> Friends:
>
>
>
> I am still working on getting the E-vaults to play nice with the Sunny
> Islands and Sunny Boys.
>
>
>
> With Open loop I was getting significant discrepancies in the reporting of
> SOC in the e-vaults versus that reported by the SI inverters.  This
> discrepancy did not diminish over time.  The discrepancy caused
> unacceptable charging and generator operations.
>
>
>
> I got Closed loop hooked up, but I found that every few days the SI
> inverters would shut down due to a battery over-voltage condition.  I
> believe that when the e-vaults are near 100% SOC the BMS units increase the
> battery impedance which means any charging current applied will cause the
> voltage spike I have been seeing.   I was able to measure these conditions
> myself on site, although they were very fleeting and required recording
> with the Fluke87 Min-Max function (love this meter!).
>
>
>
> I was able to extract log files from the Sunny Island primary inverter and
> perform some analysis.  It appears when I turned on remote BMS on the SI
> (as part of the Closed loop protocol) it disabled the Frequency-Shift Power
> Control.  This means the SI inverters have gone from having poor control
> over battery charging to having no control over battery charging.
>
>
>
> I have documented my research here
> <https://millersolar.com/MillerSolar/case_studies/36_SIFortress/36_SunnyIslandFortressIntegration.html#Inhibit>.
> There is a table of contents to take you to the latest information.  I
> appreciate pertinent comments any of you might have.
>
>
>
> By the way, if anyone has called SMA tech support for help on a Sunny
> Island system, you have likely been asked to extract log files, zip them up
> and send them off for review (and waited a long time for a reply).  I am
> the kind of guy who does not like to wait for solutions and who likes to
> figure out things for himself.  I have taught myself how to evaluate those
> log files. I will be posting a web page on the subject.  In the meantime,
> if you are interested, two of my analysis Excel sheets are linked in the
> case study.  I will be expanding on this and providing resources to any
> integrator that wants that knowledge.
>
>
>
> Thanks in advance for any insight.  I hope I am wrong about this and I am
> just missing something.  I also hope revealing my headaches will help
> someone someday…
>
>
>
> William
>
>
>
> Miller Solar
>
> 17395 Oak Road, Atascadero, CA 93422
>
> 805-438-5600
>
> www.millersolar.com
>
> CA Lic. 773985
>
>
>
>
>
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