Two Inverters

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.

@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?

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.

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.

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

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

@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.

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

Hit the STAR button at the top

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.

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?

Hello folks.

I've been reading this post with great interest, as I am in a similar situation where I would like to add a second inverter to expand our Solar PV system.

Our existing solar PV system is south facing producing 5.5 kilowatts in good sunshine and is run using a Solax hybrid inverter which is connected to a 6.3 kilowatt hour battery. This PV system feeds into a sub-fuse board located in the utility room. The sub-board is connected to the main fuse board with a 16 square wire. The hob, oven, dish washer, kitchen and living room lights and sockets are wired from the sub-board - just providing this information incase it's relevant to my questions below.

I plan to add a second inverter which will either be a Solax inverter or a basic string inverter with two string inputs, the size of this inverter will be approximately 3.5 to 5 kilowatts and the solar panels supplying the second inverter will be West and East facing. The sum of the two systems working together could produce 9 - 10kw on a good day.

I don't know anything about installing solar systems so I have a number of questions I'd like information on just so I'm aware and have an understanding while speaking with the installer.

Questions:

(1) I've been doing some reading online and any of the things I've seen in relation to the installation of a second inverter they talk about wiring the inverters together in parallel or in series. Is it necessary to install or wire the two inverters together in parallel or series or can they be wired independently to the same fuseboard or as it is in my case the sub-fuseboard?

(2) The existing inverter has a CT clamp on the mains wire coming in so it can determine if we're exporting or importing, is it necessary that the second inverter would also have a CT clamp on the mains for the same reason to see if we're exporting your importing?

(3) Should the inverters be connected together in some way so they can communicate with each other (this may not be possible I imagine if the inverters are different e.g. Solax for the existing system and Hypontech for the second inverter)?

(4) When both inverters are generating power will they both send power to the house to satisfy the load while the excess goes to the battery and rest (if any left over) exported to the ESB network or could they inhibit each other in anyway?

Apologies for the long post and questions but any advice you can offer or answers to my questions would be greatly appreciated.

Thanks in advance and I look forward to your reply.

Kind

regards,

SE Galway

As for DIY, super easy. Panels are daisy chained, with the cable from each end plugged into inputs in the inverter. All connectors are MC4's. They all just click together.

The AC side needs to be connected to it's own breaker on the board (or subboard). No CT's needed

You are limited to 25 amps on the new regs, thread here https://www.boards.ie/discussion/2058288583/esbn-new-regulations-on-nc6-form-on-6kw-25amp-inverters-may-31-2023/p1

Hello folks,

Many thanks for all your input it's much appreciated. I've learned a lot through this and earlier posts on this thread.

Thanks for sending link to regulations.

Kind regards,

SE Galway

What's your MIC? It'll say on your connection documents in kVA. As you say, I'd definitely do the research first before paying anything. You can check if it's possible to upgrade your MIC by getting a quote with this process.

You could put in a separate 'new' hybrid with your exisitng grid-tie and they would work independantly of each other. If you're upgrading a grid-tie system to hybrid, most people in that situation would just replace the grid-tie inverter with a hybrid inverter that can do everything you want in one go.

Just another thing on the 25A limit, it should be possible to program your existing hybrid to only allow a max export of that. So, if you size your new grid-tie inverter at 25A or under, you won't go over 25A total as the hybrid will throttle back if it's done charging the battery and house demand is being met.

You just can't really have two hybrids