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

Sun Nov 12 16:27:22 PST 2023

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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