Auteur Topic: Sunny Boys, with AC Coupling Later?  (gelezen 906 keer)

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Offline RyanCaleb

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Sunny Boys, with AC Coupling Later?
« Gepost op: 19 september 2017, 10:42:35 »
Hi there,

I've been thinking long and hard about the difficulties of a charge controller + battery system, mindful of all the warnings here about the immense cost and babysitting required. Even though the idea of having some independence from the grid is very appealing and a primary reason why I got interested in all this in the first place, I'm about ready to make this summer's project just hooking up a couple of SMA Sunny Boys to the four PV strings I'm planning, get the grid-tie interconnect wired and approved, and wait for further signs of the apocalypse (kidding--well, sort of) before doing the batteries plus big old 48V inverter plus critical loads panel.

I know that DC coupling is the best approach if you are planning on a battery from the get-go. But it seems that the Outback could AC couple the Sunny Boys just fine if I decided to add all that off-grid crap later on, and they don't cost any more than a pair of Morningstar TS-600V 60A charge controllers. It wouldn't be ideal; if the grid is down, the remote relay in the Outback's AC-coupling load center would be switching the Sunny Boys in and out to keep the battery from overcharging. But the 6000W PV power being well within the <90% of 8KW Outback power requirement. Also, if I'm actually having to run off-grid for any extended amount of time, I seriously doubt if I'd be getting much overcharging done, with all the loading of the PV power I'd be doing at that point. The challenge seems like it would be more one of giving the Sunny Boys a chance to backfeed the Outback's H-Bridge to charge the batteries instead of drawing from them, and running a generator when they can't keep up.

There would also be the Sunny Island option for AC coupling, for a bit more money. But, hey, what's a few thousand extra if you are willing to spend ten grand on a ton of expensive lead and sulfuric acid that gradually degrades into a pile of heavy toxic junk in less than a decade?

I didn't find the right solution from the internet.

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