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Two Inverters

  • 28-01-2023 2:14pm
    Registered Users Posts: 429 ✭✭

    Who here has two inverters?

    I have my install taking place in February (16 x 380w panels) and a Solis inverter. This setup is via an Seai approved installed and will avail of the grant.

    Separately I’m going to undertake a DIY install (14 x 405w panels) and a Sofar 6000EP hybrid inverter with batteries arriving from PWOD.

    I plan to install both inverters side by side in my garage.

    Is there anything i need to consider with having multiple inverter setups?

    I may try be a little cheeky and ask the installer of the first system to run the electrical consumer connection for the Sofar when they doing the install of the 16 panel system. If not I’ll source an electrician



  • Moderators, Home & Garden Moderators Posts: 5,752 Mod ✭✭✭✭graememk

    Should just work without Issue.

    The sofar will need (ideally) a cat6 cable going back to the meter cupboard, or the main consumer unit.

    Are you tying into the power already in the garage or running a new cable for the solis inverter?..

    Maybe get a new (large) supply cable ran to the garage and run everything from that. eg 10mm2 at least.

  • Moderators, Sports Moderators Posts: 18,644 Mod ✭✭✭✭slave1

    Agreed, run a 10sq, I ended up running two SWA runs as two inverters need a large single cable and 6sq not enough

    Bit obvious but ensure the first setup neatly leaves room for the next inverter and switches

  • Registered Users Posts: 2,222 ✭✭✭SD_DRACULA

    As long as you don't put two hybrid inverters (of different brands) on the same supply.

    I mean you can but just connect batteries to only one of them.

  • Registered Users Posts: 429 ✭✭jasgrif11

    I have SWA running from main house consumer unit out to my Garage where I have another fuseboard. Can everything we wired into this?

    I also have Cat6 in my garage and a router.

    However I thought cables had to go back to the main consumer fuseboard? If not then it will be much simpler for the install overall.

  • Moderators, Home & Garden Moderators Posts: 5,752 Mod ✭✭✭✭graememk

    Doesnt have to go back to the main consumer unit, If the SWA to the garage is heavy enough. SWA can be 1.5mm2, or 16mm2+ there is a huge difference. (

    The Cat6 is for CT's It cant be used for Data at the same time, so it needs to be a separate cable

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  • Registered Users Posts: 49 Sligobuck

    Why not....I run a Solax X1 Hybrid 5K Inverter with 16Kw of batteries and a separate Sofar HYD 6000-EP with 56Kw of (Seplos 280Ah Mason 52v x 4) batteries on the same supply!

    I could not get Solax to provide an upgrade path to increasing battery storage so I gave up on them and added the Sofar HYD 6000-EP with 56Kw of batteries recently. There was no point in de-commissioning the Solax and batteries since they are good quality LFP high voltage packs (3 batteries).

    All runs fine with night rate charging (Time of Use) setup to charge both battery banks in separate time slots.

    Solax gets full power 5Kw of charging from 11pm and is done by 2am and remains on Time of Use till 8am. Solax has 6Kw of panels and has feed-in but I tend to feed very little to the grid even during the summer with excess to water heating.

    Sofar gets 500 watts of charging from 11pm till 2.30am and then switches to 5Kw charging until 8am, it generally is done by 5am or later if the heat pump is working hard during freezing days. Sofar has Anti-Reflux (no feed-in) switched on.

    All of the above is in the attic.

  • Moderators, Home & Garden Moderators Posts: 5,752 Mod ✭✭✭✭graememk

    kWh!! kWh!!

    I thought myself and @unkel were OTT with 40kWh 😂

    How do you prevent them from "fighting?"

    Who get priority to discharge first?

    Why does it take longer when the heatpump kicks in?

  • Registered Users Posts: 64,693 ✭✭✭✭unkel

    @Sligobuck - you charge your Seplos / Mason 56kWh with 500W from 11PM until 2:30AM then with 5kW until 8AM. That's 1.75kWh + 27.5kWh = 29.25kWh, only using half your capacity? Or am I missing something here?

    That seems a waste, did you buy too much battery capacity or are you planning to get a beefier inverter that can charge your battery quicker?

    You have 6kwp of PV on your other inverter, how much do you have on this one?

  • Registered Users Posts: 49 Sligobuck

    Mea Culpa....lazy with the kWh and I am likely to make those mistakes again :-)

    They do not fight, I am no electrical engineer but I guess whichever inverter has a slightly higher voltage gets to deliver the power to the loads.

    There are no priorities setup for discharge on either from 8am.

    The Solax seems the leader here with it delivering most of its battery power during the day from 8am on with the Sofar adding to any loads over 5kW during that time, once the Solax runs out of juice the Sofar seamlessly takes on the load.

    When the weather gets down around freezing the Nibe Air to water heat pump becomes much less efficient and pulls much more power on those days so the Sofar batteries get pulled lower and take longer to get back to full charge.

    Hope that makes sense and I am learning as I go along....Will and Andy have been my main resources for learning.

  • Registered Users Posts: 49 Sligobuck

    Future planning with the excess on batteries, ROI was not used in the calculation and decided to go all in now so an electric car and such can be factored in later. I also do not trust the state of the grid for the next few years so if rolling cuts are ever rolled out I will be well covered.

    I will be adding solar panels to the Sofar soon but only about 6 x 400 watt for now, I have other ideas for ground mount but not just yet.

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  • Moderators, Home & Garden Moderators Posts: 5,752 Mod ✭✭✭✭graememk

    Good to know they get on well.

    You lucked out there, it's not voltage it's whoever detects and reacts first, it could be the solax has a slightly faster response time, and the sofar just never gets the chance to get going.

    Also the CT on the sofar could be trimmed too.(but I wouldn't touch yours as it's already working fine) it could be that the sofar runs on a slight import,

    Have you ever pulled more than the solax limit, I suppose the sofar kicks in then?

    With averaging 30-40kwh a night, your not too much over 2000 night units on the Energia ev tariff.

    Any plans for summer to use the excess battery power?

  • Registered Users Posts: 49 Sligobuck

    I should also mention that I have setup for a second Sofar beside the current one so I can split to 2 packs on each.

    I have applied for the upgrade to an enhanced 16kVa so hopefully get that completed soon.

  • Registered Users Posts: 64,693 ✭✭✭✭unkel

    @graememk - "With averaging 30-40kwh a night, your not too much over 2000 night units on the Energia ev tariff."

    That's just his batteries charging. There is a lot more use during night rate hours than that 😂

    In my case like charging all the EVs, heating a big cylinder of water, heating the house, running dishwasher / washing machine / dryer plus of course the base load of the house

    I went over 900 over the 2000 night unit limit last bill

  • Moderators, Home & Garden Moderators Posts: 5,752 Mod ✭✭✭✭graememk

    There is a way to wire up the CTs on the sofar to give one priority of the other, need 3 cts in total.

  • Registered Users Posts: 64,693 ✭✭✭✭unkel

    Isn't that all making things unnecessarily difficult for yourself? I'd say if you add a smart car charger (like a zappi) and / or a smart water heater (like an eddi), you could find yourself in trouble with two battery inverters

    That's the very reason why I want to upgrade my 5.5kW Sunsynk hybrid to a 8.8kW Sunsynk hybrid inverter (single phase). It can charge at 190A, say 9kW. That means it can fill 9 hours * 9kW is over 80kWh of battery during night rate.

    I have 2 other dumb PV inverters, you can have as many of those as you like, they don't interfere with each other.

  • Registered Users Posts: 6,053 ✭✭✭championc

    Dare I ask, what is consuming so much power ???

  • Registered Users Posts: 64,693 ✭✭✭✭unkel

    He kinda answered that. Future planning, getting an EV and not trusting the grid going forward so wanting plenty of backup.

    Not dissimilar to @graememk and myself having a big battery. Both of us are planning to replace our fossil fuel heating with a heat pump in the near future, which we plan to run as much as possible on renewables / night rate electricity.

    We would also like to upgrade our electricity supply, if it wasn't so damn expensive. This is mostly future planning as well. Now we have a 9 hour cheap electricity slot, but if / when we eventually and inevitably go to smart meters, that slot could well be reduced to 2-3 hours, so maximum battery loading and night use would then be essential with all the power you have. 20kW o'clock would be better than 15kW o'clock 😁

  • Registered Users Posts: 49 Sligobuck

    I regularly pull more than the Solax and the Sofar provides that additional load (green)

  • Registered Users Posts: 49 Sligobuck

    Fair point @unkel and if that turns out to be the case then I will look at the larger inverter option. Hopefully the industry will have them readily available by then.

    The difficulty of trying to purchase large off the shelf batteries during 2022 with money in hand is what drove me down the buying cells and building batteries at less than half the cost so I decided to go large with the savings.

    The changeover to heat pump drove me to the bigger batteries, I realised big savings over oil but the energy companies took some of that away recently after doubling the cost of electricity.

    I expect as you say that once a large percentage of people swap over to electric cars then the cheap night rate hours will diminish and bigger battery banks will be handy to have. Having the batteries built and in place now gives a lot of satisfaction as they open up lots of options, mainly for the winter months when there is not much solar available.

  • Moderators, Sports Moderators Posts: 18,644 Mod ✭✭✭✭slave1

    Diminishing of the night rate hrs will be a kick in the balls alright, still a few yrs out though I reckon

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  • Registered Users Posts: 64,693 ✭✭✭✭unkel

    Last year was a pretty decent year for buying cells from AliExpress alright. Given that a lot of stuff had gone up in price, particularly shipping from China. You bought the EVE 280Ah cells from PWOD official store? What made you decide on buying the Mason / Seplos cases instead of what most of us did, just buy the cells (most of use use CALBs) and stick them together in large numbers with 2, 3 or even 4 in parallel, just using a single BMS for the lot? Do you remember what a single case cost you, including shipping (without cells)?

  • Registered Users Posts: 49 Sligobuck

    @unkel bought the cells from OYE and they came in from Germany. The cases cost $600 each incl shipping with BMS in each and these came in from Poland. You have to purchase cables as well since they have the quick disconnect design which are very useful, and finally the cheap adaptor for the PC.

    Following Andy from Off Grid Garage and Maddy on the Digital Mermaid I was happy to go down the route of the prismatic cells and the Seplos kit. I bought 2 of the bases as well from Seplos and these are great for wheeling around 2 packs on each at over 200Kgs on each base.

  • Registered Users Posts: 429 ✭✭jasgrif11

    Is it essentially a case with integrated BMS? Will it work with the 200AH 3.2V Lifepo4 Battery? Really nice clean solution, but a bit on the expensive side

  • Registered Users Posts: 64,693 ✭✭✭✭unkel

    Well that's the one thing I don't understand. You said you have all in your attic, so I presumed nice looking cases and being able to roll them around added near zero value? Obviously Andreas in the off grid garage wants them to look good as he is looking at them every day (and so are his viewers 😂) and he needs to move them around his garage, to connect them up to different systems, use them for tests, etc.

    €600 incl tax and shipment for those huge boxes is not bad considering they come with a built in €200 BMS too. But you would have saved over €2000 if you hadn't gone for them and put your batteries on some big planks across your rafters in your attic, with a single BMS

  • Registered Users Posts: 83 ✭✭Dave_D_Rave

    Apologies guys new to forum; Can somebdy tell me How to subscribe without commenting ?

  • Registered Users Posts: 6,053 ✭✭✭championc

    Hit the STAR button at the top

  • Registered Users Posts: 21,316 ✭✭✭✭ELM327

    Anecdotal experience from myself and others online would point to some inverters "playing better with others" compared to the rest. For all the flaws of my solis I have no issues running multiple small dumb inverters alongside it. In time, hopefully this year, I'll be adding another inverter and 8kWp more. I've been talking with an irish victron installer who is going to help me as he's interested in my off grid project. Probably end up with a main victron based system but keeping the solis.

  • Registered Users Posts: 64,693 ✭✭✭✭unkel

    Big difference between hybrid / battery inverters and dumb inverters. The former need to know what they are supposed to do, so need at least CT clamps. But if two of them are supposed to do the same thing, they could conflict

    Dumb inverters on the other hand, are simple devices that just convert DC to AC and are connected to your house / the grid. You can have as many as you like, there can be no conflicts.

  • Registered Users Posts: 6,805 ✭✭✭Alkers

    I am considering pulling the trigger on a pre-made seplos mason battery pack and looking for a few clarifications.

    We have an existing array with a non-hybrid 2.5kW inverter, in the attic.

    I want to leave this as is so realise I'll need a stand alone inverter for the battery pack, which needs to be wired back to my distribution board.

    If I go with this setup, how do I arrange for my solar excess to go into the battery pack as opposed to manually charging it when it's sunny and programming it to charge overnight?

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  • Registered Users Posts: 64,693 ✭✭✭✭unkel

    The new inverter will do all this for you. It has a CT clamp on your mains incomer, so it will know when you are about to export, it will charge the battery instead. It can also be programmed to charge overnight. It would not have to be a stand alone "AC side" battery inverter. It can also be a "DC side" hybrid inverter. You can then attach more PV strings to this new hybrid inverter if you expand your solar system in the future

    Any link to where you plan to buy that pre made battery pack?