I agree completely that AC coupled systems are far better off if they
have a battery charging method completely independent of the off-grid
inverter. Some DC coupled solar is the best way to go. The system I'm
considering already has 2820 W of DC coupled PV.
Drake
----- Original Message -----
From:
"RE-wrenches" <re-wrenches@lists.re-wrenches.org>
To:
<re-wrenches@lists.re-wrenches.org>
Cc:
Sent:
Thu, 31 Oct 2019 19:33:11 -0600
Subject:
Re: [RE-wrenches] Off Grid Optimizers
We've discussed AC coupled many times. Aside from the issues
Michael brought up, I need to remind that not having at least some
DC PV charging means that when the AC system shuts down for any
reason, so does all the PV charging. If Li+ batteries get discharged
to their low voltage shut off: Dark Starts anyone? With lead
acid, DC coupled PV is just as critical to keep the battery from
sulfating.
Which would you want?
Scenario 1:Come back to trouble shoot a system shutdown, try to
reboot, only to find no battery voltage to even test with. or
Scenario 2: You will have a battery that is being charged, if not
already at full charge.
For GTB?, you decide how important this issue is, but for Off grid
you are putting your customer in serious jeopardy without power.
Unless they have a manual bypass, the generator won't pass through to
the loads, or charge the battery either. This is not theory, We've
had to fix these, and in some cases replace the battery bank that was
damaged after sitting dead too long.
My previous post in favor of AC coupling was only as a supplement to
a solid DC PV system, or for module level optimization in partial
shade conditions.
Ray Walters
Remote Solar
303 505-8760 On 11/1/19 1:08 PM, Michael Morningstar wrote:
You know Murphy? That is Murphy of Murphy’s Law? He’s gotta
just love the idea of AC coupled off-grid systems. The OB, SB, Li
system Jay described is going to keep him (Murphy) and the installer
very busy at some point. The further away the system is from
civilization, the higher the odds of chicanery and headaches. Systems
that need backup safety controls seem inherently risky too.
On Oct 31, 2019, at 11:06 AM, jay <jay.pe...@gmail.com [1]> wrote:
HI Drake,
I was just talking with a colleague the other day about a project he
did.
New Radian, AC coupling, lithium batteries, SB inverters.
Everything is working just as it should with the GT inverters
tapering during AC coupling frequency shift mode.
I would say you are fine, and while I can’t say for sure if the
Enphase will work that way, they should as they are all designed to
the same parameters rule 21.
I always do recommend a aux relay for backup/shutoff should there
be some kind of issue.
With the Envoy you’ll be able to see that tapering as well.
Seems like a good option for your application
jay
On Oct 31, 2019, at 9:49 AM, Drake
<drake.chamber...@redwoodalliance.org [2]> wrote:
Hi Jay,
Between 2160 and 2880 Watts of added array. We will be using a new
Radian.
Drake
At 11:49 AM 10/31/2019, you wrote:
How many watts are you adding as ac coupling?
And presuming its an older 8k radian?
Jay
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