Two inverters ??

Hi I have two inverters on my GE system with 14 panels. One inverter is a Solis S5, the other is a GE3.0. Can anyone tell me why I would have 2 inverters, as my understanding is that an inverter converts DC to AC and vice versa. It does seem that the system is only capable of converting 3.0-3.5 kW so why 2 inverters? I have a total of 7.8kWh (GE) batteries and am intending to add another 9.5kWh to also take advantage of Intelligent Octopus Tariff on cloudy days. tried to upload an image but it kept failing.

KeithMersh1955RuthMary1971 is it possible the Solis & panels were installed before the GE equipment, then a battery was installed later. GE kit only works with GE inverters, so the AC3 was installed to manage the battery?

This sounds like a standard 'AC coupled' setup. The Solis inverter converts DC from your panels to AC, which it feeds to the house/grid. The GE AC3 then takes AC from the house/grid and converts it to DC to charge the batteries (and then back from DC to AC mains when discharging). Mine is the same, except my panels go through a Fronius inverter.

Essentially it is two separate systems, working together.

I actually have 3 Inverters!
A 2kW Fronius in the loft connected to panels on the house roof fitted in 2013 which get FIT payments.
Then in 2021 I had 8.2kWh GE Battery fitted with a 3kW AC Coupled Inverter on an outside wall.
Then in 2022 I had additional panels fitted to the Garage roof and they have their own Solis 2kW inverter in the garage.
All play very nicely together!

ToothyChris

ToothyChris

ToothyChris

Thanks Chris. Seems to make sense I think. So the Solis does the converting from DC to AC for the house. Is that without limited capability? Whereas the GE AC3 takes AC from the house / grid and converts it to DC to charge the batteries (and then back from DC to AC mains when discharging). So on a sunny day, if the array (5.39kW) is producing more than the 3.0kW that the GE is capable of converting back to DC storage then it has to go back to the grid? Seems to me if all that is correct that the system was not properly designed and we need a 5KW GE inverter to prevent wastage. Am I right?

KeithMersh1955RuthMary1971 Not exactly. There is still a limit how fast you can charge the battery regardless of the inverter used. Inverters have limit and there is a limit depending on battery size too.

The AC3 is used to retrofit a battery to existing solar installs. I have 2 solar arrays both with solis inverters then a single AC3 (for now) charging my batteries.

KeithMersh1955RuthMary1971 You are kind of right. If your solar was producing 5kW, of which 3kW was going via the AC3 to the battery, then the remaining 2kW would be used by your house first, with any remainder then exported to the grid. So, under those conditions, you need to be ready to put the washing machine on, or the tumble drier, or the immersion, or the air-con or whatever else draws lots of power. Using that 'overflow' will always be preferential to selling it, or giving it away.

I have a pair of AC3 inverters, each with a battery, for this reason (and because I wanted to pull more than 3kW from the batteries).

But, having an 'oversized' solar array will mean that you are more likely to be able to fill your battery in less favourable conditions (e.g. overcast, winter etc.)

(As Thall says, some of the smaller batteries also have a power limit as well, to complicate matters).

Interesting that Thall points out that GE3.0 used for battery retrofits but maybe I haven’t explained the whole story. I had a 2.6kWh GE battery initially with the system and then had an extra 5.2kWh battery added subsequently. Unfortunately the installer didn’t seem to advise properly and I didn’t understand much at all. (I’m still struggling a bit)

I have a single string array of 5.39kW.

So now I’m adding a third 9.5kWh battery - to enable max storage both from PV and the grid, should I upgrade to a 5.0 GE inverter?

I do have a separate issue as well in that I’ve had a new full fibre broadband connection and need to reconnect the GE Dongle to the new network. I’ve been trying to do this using https://youtu.be/fva7-7QNyAc but when I go to settings and connect to the Dongle there is no internet connect to be able to connect to 10.10.100.254 and reset the Dongle Wi-Fi connections 😫 really appreciate help from you guys.

KeithMersh1955RuthMary1971 So now I’m adding a third 9.5kWh battery - to enable max storage both from PV and the grid, should I upgrade to a 5.0 GE inverter?

You can capture the full output of the PV array and put it to the house consumer unit as AC. Your existing AC3 can consume up to 3kW of excess and push that to battery, but only at the rate of 3kW, irrespective of the number of batteries. If you wish to add more battery to increase storage and reduce export, you could add it to the existing AC3 but it would take (2.6 + 5.2 + 9.5) 17.3kWh/3kW=5.7 hours to fully charge from empty (from PV or off-peak grid). You'd also only be able to put 3kW back to the house from the AC3 when there is no PV.

If you added a second AC3 to go with the Batt9.5, the charge time would reduce to just over 3 hours from grid (simultaneous charging) but as long as it takes from surplus solar; the 5.7 hours mentioned above.

If you replaced the existing PV inverter with a Givenergy HY5 and Batt9.5, the time to charge etc would be the same as if you added an AC3 but with fewer inverters overall. However, if you currently receive FIT payments for your existing PV, you'd have to liaise with your FIT provider to agree on what is required for you to continue to receive FIT with a hybrid inverter and battery attached (usually just a certified import/export meter).

The HY5 inverter would only increase your charge/discharge speed by 0.6kw over your AC3. Adding a second AC3 with the 9.5kw battery would double your charge speed. But there are various issues running dual givenergy inverters at the moment. My installer will not install dual inverters due to the issues. There is a fix coming, an extra device called an EMS. Then I think you can have 1x AC3 with the 9.5kw attached then the other AC3 with your 5.2 and 2.6kw attached. Total charge discharge about 6kw.

Basically your question "should I upgrade to a 5.0 GE inverter?" nah not for an extra 0.6kw charging speed. The cost is about the same as adding a second AC3. Not to mention the paperwork will be simpler by just adding an inverter rather than changing one.

THALL The HY5 inverter would only increase your charge/discharge speed by 0.6kw over your AC3

As I read the question, I don't think the suggestion was to replace the single existing AC3 with an HY5. It was whether to just add the battery to the existing AC3 (not worth it), or to add a second AC3 (maybe), or to swap out the original solar inverter for an HY5 (also maybe).

If the solar inverter was replaced by an HY5, the AC3 would behave exactly as it does now; diverting export to charge the batteries and discharging the battery to reduce import. AFAIK having an AC3 which isn't connected to another inverter works quite simply; it's when there's another AC3 in the picture when issues arise. An HY5 independent of an AC3 on the same system should work perfectly fine. That said, whether Givenergy can get the customers' portal sorted with sensible readings is another thing but at least the energy savings and load shifting should work just fine.

Tim That is interesting. I had not considered a AC3 and HY5 package before. I have a friend this might work perfectly for. Do you think both inverters can be on 1 account? Bit more faff setting each separately but gets round the problem of plant based systems.

THALL Do you think both inverters can be on 1 account?

No idea. I know our dual HY5s are on one account and the portal looks right in most places, just not on the summary banner at the top of the portal.

The house consumption is from one inverter only, but the other data looks right enough.

Tim I shall enquire with GE. Be interesting if a hybrid and ac can be managed together.

Loving the charge rate you have there. I really want dual AC3's as soon as possible. I would put up with data issues if I knew cross charging would not happen.

THALL I'm investigating this configuration at the moment too.

Would love to understand what if anything you were able to find out from GE.

Current set up is a Gen1 HY5 with 16.4 of batteries - that is accepting input from a south facing array. I'm looking at an another east/west array that the AC3 would be connected to. Do folks feel this configuration would work?

NiallKilleen Not supported by GE, can not manage the 2 different systems on a single site. You could add a second hybrid for the new east/west array and move 1 of your batteries to that. But there are issues with dual inverters but they are working on solutions. EMS device due etc.

THALL Thanks for the quick response. Its a bit disappointing. So two HYs would appear to be the route to go. Have you any thoughts or insight on timing for the EMS device?

@Tim - did you encounter many issues with your duel install? Are both of yours the same generation? Current one is Gen1 5.0 - do folks think i need to match that with another Gen 1 or does it matter?

NiallKilleen It is in testing, not everyone with dual inverters have issues however. Some installers will not install dual inverters until this EMS box appears but they can explain better than I can.

So you can't run a GE hybrid and an AC3 in the same property. Is this just a GE thing? Could you run a GE AC3.0/GE battery and someone elses hybrid feeding someone elses battery? Long term I am thinking bout changing my flat roof extension to a shallow pitched roof - this would enable me to fit an additional 4 panels (south facing). When I had the AC 3 installed I didn't realise that the panels would stop generating in a power cut and I could only run from battery backup. I understand that with a hybrid they can continue to generate and supply house and battery. So I am thinking that I would quite like this option on any future panels. Would 2 seperate systems on one house be possible or is this just too complicated?

Karen Don't think so, the systems would fight each other to supply the house. You can have the EMS wired up to auto switch over in a powercut with your AC3. Your AC3 can monitor 2 PV's, but you don't need to monitor at all. I have 3 PV systems with a single AC3 and it only monitors generation from 2 because I didn't want to pay several hundred for a lora device etc. The AC coupled will just grab any power it see's trying to go out to the grid.

Karen Do you have an EMS to switch the power supply? If not then you wont be able to get any power in an outage. These systems are grid tied so need that feed to be able to supply the house. The new Gateway looks to do what the Tesla system does and can isolate you from the grid if needed. Apologies if I misread your comments but thought I'd raise it in case you thought you had battery backup (you may have it and not said so).

I'm also looking into having 2x AC3's with one solaredge inverter feeding them. From reading this it seems like it may not work. Main requirement is higher input/output with the ability to add a second battery to allow some sort of electric heating (ASHP or air-to-air).

MarkyG82 Just to be clear your solaredge inverter will not "feed" the AC3's it will supply the house and the AC3's basically grab power they see. As they are AC coupled they don't care if the source is PV or wind etc. So this will work fine. The only issue will be if you want emergency power in a power cut, the AC3's can not stack on the emergency circuits, so about 2.5kw per circuit which is not enough for a ASHP

MarkyG82 EPS? EMS is something different!

TX200 Oh yeah of course. What does EMS stand for then? I'm getting my acronyms mixed up. Comment re. the power outage holds true though.

THALL Yep I follow now. So my setup would be as follows: Solaredge receiving array juice > House < 2x AC3 each with 9.5 battery. Would both AC3s manage the load and charging independently or do they talk to each other to balance the battery levels. I guess as long as it's plumbed right they act as separate setups. So when the house needs 5kw both inverters will supply power instead of one AC3 supplying 3kw and the grid supplying 2kw. Is that correct? So the next question (I think asked up there ^ somewhere): can you view both systems on one dashboard or could you have two?

MarkyG82 energy management system. The thing that'll allow two inverters (or more???) to operate nicely together, without cross charging each other etc.

MarkyG82 Not sure how they appear on the dashboard, I have given up on the idea of getting a second AC3 for myself so stopped looking into it. Though I am keeping an eye out for a second hand AC3 now AIO's are appearing..... But yes dual AC3's will cover a house load up to 6kw providing the grid is connected.

MarkyG82 mine do the 6kw discharge without a problem.

NiallKilleen Are both of yours the same generation?

They are but if they're at the same property, they don't communicate at all. They just see a demand and start ramping up to supply. The fact that two inverters see this at the same time simply means that they both do half the work. Ramping down is the same. The actual hardware performs brilliantly. The only issue is that the portal charts/reports aren't quite right but the way they operate is absolutely fine.

THALL the systems would fight each other to supply the house

I don't think they would. The AC3 would monitor grid connection and divert to charge battery if exporting, or supply house load if importing. The hybrid would do exactly the same. If the response times were the same (as gen 1 hybrids are) they would share load equally.

Tim the problem seems to be when one AC3 notices an export and the other starts grabbing that export to charge the battery, thus one discharges into the other - which is lossy.

The original AC3 keeps discharging to meet what it thinks is house demand, but it’s really charging the others battery.

TX200 The response was about whether dual hybrids or one hybrid and an AC3 could work cooperatively. I get the confusion with dual AC3s cross charging.

Tim could it still happen with a mix of hybrid and AC3?

Hybrid battery is full, solar is being exported
AC3 sees the export and starts charging it's battery
Sun goes in.
Hybrid sees a house demand (it doesn't know it's the AC3?)
Hybrid continues to discharge to meet house demand
AC3 continues to charge it's battery, now being charged from the hybrid battery?

I know the beta firmware is more responsive to grid import/export changes - I can't 100% recall, but I think it makes it worse for multiple inverter setups.

Can check with GE support. But I was given various reasons why I could not have a hybrid inverter with its own battery on a separate PV array and an AC3 with battery attached else where. I had hoped this would be a way to double my battery throughput when I asked about it.

TX200 I don’t have that setup but I get what you mean. The only thing is that I’d hope the AC3 would reduce draw if the sun went in causing grid import. Given this situation, slowing down response time on the hybrid would help, but obviously people want faster not slower responses.

I wasn't allowed to add a GE hybrid inverter to my existing AC3.0 and 8.2kwh battery. Therefore I do have two separate AC3.0's each feeding their own battery. I don't seem to have any conflict between the two although the GE app struggles at times to show the actual values when you first open it up. On the portal, I can see far more data but have gone to GivTcp / Home Assistant to try and refine control around Intelligent Octopus charging slots.

Tim The response was about whether dual hybrids or one hybrid and an AC3 could work cooperatively

I have two Gen 1 Hybrid 5kW inverters both with their own battery and they play fine together. The reports in the app and the portal seem OK and as has been said the two inverters don’t know about each other and so both will ramp up or down when they see changes to the house load.
Occasionally I have seen one battery reporting as discharging and one as charging but I think that’s more due to the position of the sun (one inverter is the panels on the house front, the other inverter is the garage front and a few on the house rear). I’ve not seen prolonged periods of one battery discharging to the other.

And yes, according to the GivEnergy website FAQ’s, this multi-inverter (“plant”) setup isn’t a supported configuration. I only found this out after the system had been installed.

I did originally have problems with one inverter recording over-voltage situations and tripping out on sunny days. This was caused by the installers putting both batteries on one inverter and no batteries on the second. Balancing the batteries over the inverters resolved this.

I also have an older FIT array with a Growatt inverter which of course the GE inverters know nothing about. These do confuse the GE inverter stats as there’s house generation where the inverters expect to only see house demand. On sunny days I have some very confused data in the app. e.g. for the month of June I have recorded 316kW solar to battery generation, 403kW solar to grid export and -160kW solar to home! For the cost and hassle of changing the Growatt FIT inverter to a GE inverter I’ve just learnt to live with the weird data. The system seems to work as expected and the import figures are low so that’s the critical bit!