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AC Connected Battery (separate to solar)

  • 22-08-2022 12:36pm
    Registered Users Posts: 118 ✭✭

    Hi all,

    Apologies if this is covered somewhere here but I have recently put in a 3kW solar array. I didn't get a hybrid inverter with it as I just wanted to get a basic system up and running initially.

    It's working great for the last 2 months (good timing with the seasons) and it's producing about 50% more energy than my average use. I've reduced my mains energy use by about half over this period and so there is plenty of scope to catch and use more of the solar energy with a battery system before it heads out to the grid.

    I like the idea of a standalone battery with it's own inverter so that as well as capturing and using more of the generated energy as any battery would, it can be additive to the power produced by the panels on sunny days to help cover some of the more energy intensive times - oven, electric shower or just a combination of lower draw devices at the same time.

    I'm having trouble finding an appropriate battery and a battery only inverter for this task though! I'm not looking for a powerwall but something like the LG chem resu I think?

    I'm confused about appropriate inverters though and I can't really see where in Ireland to get this or something similar. Would be very interested to hear of anyone else who went down this route if you're out there!

    I'm not eligible for the feed in tariff as I put this system in myself



  • Registered Users Posts: 72 ✭✭Punchin A Keyboard

    I am very interested in going this route myself but it is a bit of a bottomless pit of info out there. You want to look up ac coupled systems or ess energy storage systems. With ac coupled it sits alongside the battery invertor on the grid side so you self consume before putting excess into a battery or out on to the grid.

    Most sites tend to list them under off grid product listings for some reason.

    Now i understand that ESB Networks may have a requirement for an ac coupled system to be in the nc6.

    The big draw with the ac coupled systems is that a load higher than what could come from a solar invertor can be supplemented from the battery invertor. Hence why I think the ESB might be concerned with potentially 2 invertors combined sending more than 6kw out to the grid.

    There of course is ROI/pay back time to be factored in on having 2 invertors.

    If I lived in a rural location with periodic power cuts then i would be all over it like a bad rash but i am in a urban environment with all power lines underground.

    Victron has some stuff on YouTube on ac coupled and DC coupled systems and systems with both ac and dc feeds.

  • Moderators, Sports Moderators Posts: 17,886 Mod ✭✭✭✭slave1

    You are looking for the likes of a Sofar ME3000 which is a separate inverter to the PV inverter, there's a full thread on it if you search or page back a bit

  • Moderators, Category Moderators, Motoring & Transport Moderators, Regional East Moderators Posts: 62,634 CMod ✭✭✭✭unkel

    I've got a brand new Sofar ME3000SP (unopened) AC side battery inverter and a brand new Pylontech US2000 (unopened) battery that I am considering selling. These work very well together and are a popular choice. They are both very hard to get new and fetch high prices on the likes of eBay, even second hand. If anyone is interested they can PM me with an offer, but only serious offers please and familiarise yourself first with how much realistic prices for these are

  • Registered Users Posts: 118 ✭✭blue chuzzle

    Thanks everyone for the info above!

    The more I learn on this the more questions I have 🙄

    Originally I assumed this wouldn't be too complex, I have a solar array and an inverter and I just want to catch and re-use some of the power that would otherwise be sent out to the grid.

    I assumed there would be ac connected battery+inverter systems, like the powerwall but not as big but there doesn't seem to be? I thought I was on to something with this, but an inverter is still required:

    I can't figure out from this site (or the moxia site) if this is a self contained battery+inverter solution. I've asked for a call back on it but nothing yet:

    I'm sure it's way more expensive and not as capable as building your own, but if it just works, that's a big plus. If it requires a hybrid inverter, then that's no good to me!

    I can just admit defeat and abandon my Solis non-hybrid inverter and replace it with a hybrid and then connect a battery. If I did that, with my 3kW solar array, would it make sense to get a 6kW or so hybrid inverter so (as well as providing power when the sun's not shining) I can have the battery and panels providing power to the house in parallel, helping to cover peak loads or is that just not how the hybrid inverters work?

    Failing that, I can just get a 3kW hybrid and enjoy having up to 3kw of draw covered day or night.

  • Registered Users Posts: 118 ✭✭blue chuzzle

    Simplified question from above:

    Would you ever oversize the hybrid inverter with the intention of it providing the combined power of the panels+battery during times of higher demand during a sunny day?

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