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You can see from my sig that my system has evolved from the original 2012 installation of 16 panels facing WSW and installed capacity of ~4kW. 6.5kWh battery added Autumn 2021. Following joining Camelot and reading Joeboy's direct battery charging system I added 3 big panels on a flat roof pointing SSE and a battery charger directly to the Growatt battery, operational since January.

This all works well and I am able to make use of excess to heat all my DHW tank. The DC coupled new panels generally shut down by midday when the battery is up to 54V and the DHW tank is full at this time of year.

I am having a slight difficulty moving to Octopus from Eon but I hope to move to the flux tariff. As I have an approved application to export up to 5.6kW to the grid and have managed to find an MCS installer to fit a second (third if I count the ac coupled battery) inverter I need some suggestions for what to use.

My supplier wants to sell me a complete Victron ESS as this will give me independence from power cuts but is expensive.

I was thinking more on the lines of a hybrid inverter able to work off grid during a power cut and keep the ac coupled battery and FIT system working. I have a mains isolation switch with its own protective earth bonded to neutral but it is manually operated. When tested my inverter generator was not recognised by the other two inverters so they just hung during a recent power cut when the generator supplied the house.
A hybrid would enable me to add a bit more battery capacity and if I get it with two MPPT inputs I can still add another string but would have to be G100 approved to keep the export below 5.6kW.

I think the reasoning of going the ESS route is the bigger inverter could better deal with the need to keep the battery inverter and FIT system inverter behaving and not running away with the frequency. Does the "master" inverter have to be bigger than the combined battery and FIT system inverters?

Thoughts?

Not much interest then?

I was deciding to go with a Givenergy hybrid and battery but they have advised against this as an addition because it would "fight" with the ac coupled battery.

Now I have experience of the Zappi and Solis hybrid at my daughter's not playing nicely but, with help from here, a few simple changes in the Zappi menu have sorted this out. So has anyone else integrated a hybrid with an ac coupled battery?

The reason for looking at Givenergy is that they are UK based and substantially cheaper than Victron.

Having two AC coupled battery inverters unless designed to work in parallel is difficult but not impossible. But your going down the road that I did and you may end up with a dogs dinner. I eventually bit the bullet, sold existing kit on and redesigned with a single manufacturer and put in something that works nicely together. And ensured I was not tied into a single battery supplier.

I have 3 x PV inverters and a big battery inverter, all SMA kit, centrally controlled as a single system with G100 export control, works offgrid too. If you are going with Octopus Flux you probably want something that does forced discharge to grid to maximise the peak export rate.

My experience is with only one Hybrid inverter, a goodwe 3600SBP AC coupled. I think you are already beyond where I have got to to but for anyone passing through.

The Goodwe was installed June 2018 and I had zero experience. It has run flawlessly for the 5 years it has been on and that's the main thing.

Things i'm not a fan of with it.
3.6kW limit, I'd have went to 5kW straight off if id been aware how the 'life' would develop.

Software bounces back to China and there is a 5 minute delay for refreshing so you're not actually pulling that 1.5kW you thought from the grid. Wee Octopus has helped in this regard. Also if there is something off at the Servers China end you can be hung in limbo for an update.

This one's daft but it still bugs me. The inverter draws from grid to power itself. I wouldn't know if there are any grid tied AC coupled that don't but...

Also worth looking into the conversion losses of your chosen units and pick the lowest. It largely comes down to the price/performance balance.

Regarding grid drop out, my solution to this was to install a standalone DC inverter rated at a continuous 2kW discharge rate and its as simple as plugging a three pin plug reel into it and reeling out to where I need power. Not an elegant solution but its there for when we need it and we rarely have power cuts (sorry Fintray).

I know the feeling of mmmn when the second system shuts down. I am focused on running the system as close to flatout this month just to see what it will generate in the best month. My strategy for that has been to start the day as low in SOC as I can then run EVERYTHING possible to stay ahead of the Tsunami of power.

It helps being retired and having the EV as it is an outstanding store of the excess.

Are you looking to utilise the upgrade for export financial generation and to know that your second system (to be extended) won't be shutting down and get some money in the door for the investment? Fair enough but make sure that you have your current power cascade operating efficiently. I say this as it would be better to have a true excess figure to potentially go to grid rather than spend the money and have a later aha! sad moment.

Last time I gave thought to the 'what if' of excess power I err'd towards a second water tank. Hard to say though with the i'm sure very different roles (retired, kids away, house in use most of time and being North).

Keep us updated and i'm sure we'll have some input!

P.S The power cascade (have to say it in a He-Man voice) is vital. As is storage, hence my second water tank thought or even a set of Batteries from Colin Deng. Knowing how much you've got and how you can use it through a day so you can go again is essential. I know you'll know this but I thought it worth emphasising for anyone passing through who's not so sure. I'd also be wary of chasing export cash as its not consistent in production or price per kWh AND the gear bought to enable it will break eventually. Hopefully that's years from now and well into profit and not 1 day out of warranty with a 30% return. (Sorry but its worth saying).

Thanks Nowty.

I have the Growatt ac coupled inverter and like Joeboy apart from needing a firmware update soon after fitting it has worked well for two years, it is slightly too small for my wants and not readily upgradable. Again like Joeboy I do not like it always calling home.

Yes I can see two dissimilar ac coupled inverters fighting but I was suggesting adding a hybrid and battery to feed my extra PV panels into and with two mppt inputs being able to add yet another string. I cannot see what conflicts they may have other than the hybrid discharging into the Growatt battery which should be fixable with an export margin set.

Yes selling the Growatt and going hybrid with a bigger (>10kWh) battery makes sense but I am only wanting to re invest my FIT money if possible.

The MCS accredited installer I found has gone a bit quiet on me.

openspaceman wrote: ↑Mon Jun 26, 2023 9:36 am Yes I can see two dissimilar ac coupled inverters fighting but I was suggesting adding a hybrid and battery to feed my extra PV panels into and with two mppt inputs being able to add yet another string. I cannot see what conflicts they may have other than the hybrid discharging into the Growatt battery which should be fixable with an export margin set.

Yes selling the Growatt and going hybrid with a bigger (>10kWh) battery makes sense but I am only wanting to re invest my FIT money if possible.

The MCS accredited installer I found has gone a bit quiet on me.

I said its difficult, not impossible.

The hybrid inverter will likely be DC coupled to the batteries, but it still ends up being an AC coupled unit to the grid after the sun goes down. You can maybe change the mode of the hybrid to only charge from the PV. But once you start discharging both battery units thats when the problems start. People have modified the wiring of the CT clamps to force two units to work as a master / slave configuration, example here for two Sofar ME3000SP battery units,
https://camelot-forum.co.uk/phpBB3/view ... =14&t=2013

The hybrid will work ok if just adding PV to it.

Thanks yet again Nowty.

Much of that linked thread was a bit beyond me but did illustrate the difficulties.

So as long as I can find a hybrid inverter that will keep my FIT string and solarmax inverter alive and generating and be G100 compliant, to keep my total exports to within the 5.68kW I have approval for it should be okay to be fitted minus a battery.

Then perhaps I can go for a homemade battery, as long as no soldering is required (I find that difficult now with monocular vision) at a later date. I can then simply switch off the Growatt if problems are insurmountable and sell it.

I have so far mostly copied what Joeboy has done and all is good except I thought I would be sanguine about the extra panels being curtailed much of the summer, once the battery voltage is high, but it does seem a bit of a waste and now I am with Octopus I could get paid for it. It would be good if the cost of my winter imports were exceeded by the payments for summer exports.

Have you thought about the future. When your younger things get modified / replaced.

Here I had half the house off grid running all fridges / cooking / television +++

The amount of people that came round and would say. Whats that. ? When walking about.

Have gone back to on grid with battery inverters. If the inverters / battery fail I have to pay for electricity.

Last month had to pay 0.5 units cheap rate and 1.0 unit day rate.

The average electrician would have come here years ago and have no understanding about whats going on.

Im now with Mr Joeboy. Ref. “ Regarding grid drop out, my solution to this was to install a stand-alone DC inverter rated at a continuous 2kW discharge rate and its as simple as plugging a three pin plug reel into it and reeling out to where I need power. “

Now over 70 and.

Have ripped out all the tech stuff. Gone back to Grid. Fitted a 3kW inverter for grid failure. Run a extension lead to the fridge.

Still got every light in / outside house working off 24 volt battery system.

It took over 70 years to Know / learn what. “ Keep it simple means. “

ALAN/ALAN D wrote: ↑Mon Jun 26, 2023 1:50 pm

Last month had to pay 0.5 units cheap rate and 1.0 unit day rate.

Similarly I pay for about 1/3 kWh daily because the system doesn't quite react fast enough plus occasionally if there is no PV output and the load exceeds what the battery inverter can supply, 3kW. The thing is the standing charge at £154/annum becomes significant in the equation of whether it is worth attempting. My total spend on electricity aside from the standing charge is £135.

Im now with Mr Joeboy. Ref. “ Regarding grid drop out, my solution to this was to install a stand-alone DC inverter rated at a continuous 2kW discharge rate and its as simple as plugging a three pin plug reel into it and reeling out to where I need power. “

I can activate the EPS on the inverter and do that, the problem is that PV generation stops as I currently do not have a hybrid inverter and my generator is not recognised by either inverter.

Now over 70 and.

Me too, well into extra time. Some of what I do is to keep active and my brain in gear.

Ref " Last month had to pay 0.5 units cheap rate and 1.0 unit day rate. "

That was for the month. Not per hour.

Fully agreeeeee. The standing charge is definitely a WIND UP.