[RE-wrenches] off-grid AC coupling feasibility

[Howie Michaelson]

Hey Kirk,
This is something I've done a few times with success, although I've used an
XW pro instead of the Radian, with OB charge controllers. Having the mix of
DC and AC coupled is ideal, as the solaredge will do the bulk of the
charging, but then charge controllers will do the finish taper charge
instead of a relay switching the solaredge on and off (which as far as I
know, solaredge removed frequency shifting for tapering the finish charge
several years ago). It is also helpful in cases where the inverter shuts
down on low voltage, as the DC coupled array will bring the battery voltage
up enough to allow the inverter to turn on and start the solaredge again.
>From my point of view, the combination of AC and DC coupling is the ideal
off grid scenario.
Howie

On Sat, Jul 30, 2022, 12:31 PM Kirk Herander via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> All,
> Anyone out there successfully AC-coupled inverters in an off-grid system?
> Advantages vs. pitfalls?
>
> In my case I'm thinking of its practicality with a Solaredge inverter
> AC-coupled to an OB Radian inverter. OB firmware makes this pretty easy
> now. So effectively the Radian is always operating in a grid-backup mode.
>
> I already upgraded the system to the Radian, and soon to add 5kw of
> pole-mounted PV(currently only 1.8kw of 22-year old PV on the roof). This
> system also just got 16kwh of Blue Ion LFP batteries.
>
> This is a last-minute thought I have instead of investing in additional DC
> charge controllers for the new array.
> Cost-wise there's not much of a difference between several high-quality
> charge controllers and a smaller SE inverter w/optimisers. Thanks.
>
> --
>
> *Kirk Herander / **kirkh at vermont.solar <kirkh at vermont.solar>*
>
> *Owner|Principal, VT Solar, LLC*
>
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