Hi Folks,
Just wanted to make a correction on the EG418kPV of a statement made
during the AC Coupling thread.
The EG4 18kPV does have frequency shift based AC Coupling. The
confusion comes from the fact that like Sol-Ark there is a SOC set-point
override feature for AC Coupling but the video William referred to
seemed to imply it is the only control. It is not and EG4 is fixing this
video.
William Miller wrote:
EG4: I read the manual and it looks like the EG4 works just like the
Sol-arc: You program the generator input to actually be an output. The
EG4 abruptly disconnects that output when battery SOC reaches a
programmed level-- There is apparently no frequency shift function.
Hope that helps,
Jeff
Clearwater
Village Power Design
www.villagepowerdesign.com <http://www.villagepowerdesign.com>
William Miller via RE-wrenches <mailto:re-wrenches@lists.re-wrenches.org>
October 28, 2023 at 10:49 PM
Jay:
I am not sure how it would be possible for a grid-tied inverter to
operate with any battery inverter if it was not connected to the
battery inverter AC output. The grid-tied inverter needs to see
correct voltage and frequency before it can start up. How else could
this work?
I looked up all of the inverters you cited. In each case it may look
to you like you are connecting to an input, it is really just
reprogramming the inverter to turn the generator input into an extra
output. All of the manufacturers provide warnings about doing this.
Here is more information from each of the manufacturers:
Sol-arc: From the manual for the Sol-arc 15K-2P-N: You convert the Gen
input to an output and make that your connection point. “/A full AC
coupled solar system is not recommended as power control and
monitoring is limited.”/
EG4: I could not find an “ev4” inverter anywhere online. There is an
EG4 inverter. I read the manual and it looks like the EG4 works just
like the Sol-arc: You program the generator input to actually be an
output. The EG4 abruptly disconnects that output when battery SOC
reaches a programmed level-- There is apparently no frequency shift
function. The manual is pretty inadequate on this point but they do
provide a video
<https://www.youtube.com/watch?v=vRAq9g34VcI&ab_channel=EG4Electronics>.
Fortress: The same as above is true about using the generator input
for AC-coupling on the Fortress FP-Envy-12k. From that manual/: It
is forbidden to connect the Generator in Gen Port when AC Coupled.
/That is because when AC-coupling, the generator input is no longer an
input.
So while it appears one connects an AC-Coupled inverter to battery
inverter inputs, it is just a reprogramming of the generator input to
be an output. In all cases that I can see there is still no voltage
control of AC-coupled battery charging.
I am aware that to try and provide some modicum of control over the
battery charging from AC-coupled sources, a scheme was invented to
shift the output frequency and taper or shut down AC-coupled power.
This is a work-around, not a design. In each and every one of these
systems it is pretty clear there is little control over battery
charging voltage. These systems do not support three stage battery
charging like a DC charge controller can.
When AC-coupled charging is connected to batteries with BMS in certain
conditions battery voltage spikes can occur. See section 2.2 of this
article. <https://www.victronenergy.com/live/ac_coupling:start>
There are limited advantages to AC coupling:
·AC coupling allows reduced wire gauge for long-haul feeders. This is
no longer as necessary with new 600 volt input charge controllers.
·AC Coupling allows an easier upgrade path for a customer that has
grid-tied inverters and wants to add batteries. I am not sure most
batteries can survive for long with the crude charging algorithm
provided, so I would hesitate to recommend this.
In my opinion AC-coupled battery charging with even the newest
inverters is a crude affair. I am not a fan.
William
Miller Solar
17395 Oak Road, Atascadero, CA 93422
805-438-5600
www.millersolar.com <http://www.millersolar.com/>
CA Lic. 773985
*From:*Jay [mailto:jay.pe...@gmail.com <mailto:jay.pe...@gmail.com>]
*Sent:* Saturday, October 28, 2023 1:58 PM
*To:* will...@millersolar.com <mailto:will...@millersolar.com>;
RE-wrenches
*Subject:* Re: [RE-wrenches] AC Coupling
I’m going to both agree and disagree
Agree The older inverters ( Schneider, Outback, etc) your drawing is
correct.
Disagree For many new inverters ( sol ark, ev4, fortress) they bring
ac coupling into the inverter directly.
Usually on the generator input and not in the backup loads panel.
And I will also disagree about the statement that these inverters are
not designed for ac coupling.
Agreed that the earlier non rule 21 compliant versions didn’t have any
internal control and required external relay control to prevent
overcharge.
Newer versions of Schneider, OB, have frequently shift which works
with newer gt inverters to address the ac coupling overcharge
concerns. While creating potential new issues for loads with up to 64 hz.
Jay
On Oct 28, 2023, at 2:15 PM, William Miller via RE-wrenches
<re-wrenches@lists.re-wrenches.org
<mailto:re-wrenches@lists.re-wrenches.org>> wrote:
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