[RE-wrenches] EG4 18kPV Correction - does have frequency shift AC Coupling

Tue Nov 7 12:12:31 PST 2023

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 at 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.peltz at gmail.com <mailto:jay.peltz at gmail.com>]
> *Sent:* Saturday, October 28, 2023 1:58 PM
> *To:* william at millersolar.com <mailto:william at 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 at lists.re-wrenches.org 
> <mailto:re-wrenches at lists.re-wrenches.org>> wrote:
>
>
>
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