AIO and Hybrid Inverter together?

Is it possible to run an All In One and a Gen 3 Hybrid Inverter/Battery together?

I'm considering moving to a heat pump and would want more stored electricity. An AIO would add another 13kWh capacity, which would ensure I can cover house load and heating between charging slots. The question is whether an AIO would play nicely with my existing dc battery/hybrid inverter system?
I know the inverter and AIO would be fine without the dc battery, but is the GE system integrated enough to avoid cross-charging if you mix the two?

Pete.J No is the short answer.

Pete.J As per @Vestas , plus this is not a supported configuration by GE - I know because I was going to add a DC coupled battery to my hybrid inverter to complement the AIO and was told no by GE

Pete.J This question has been asked before, have a search in the forum, the two will cross charge each other so you will need some form of automation to stop this happening.

Have a look at the speak to the geek youtube channel and his website, he shared a solution based on. home assistant automations that detected cross charging and stopped it happening.

A subsequent video then he explained that he had abandoned that approach with concern that excessive number of start/stop charging instructions being sent to the inverter could result in them failing prematurely. He now sets one inverter to a gentle discharge during the day and the other to pause charging. This prevents the cross charge but means you can’t take much advantage of solar generation.

A better solution would be just the AIO. Not least of which because of the better discharge rate for the heat pump and cooking, kettle, etc that you may have on at the same time.

Do the maths as to how much stored electricity you need to run your heat pump and the home, you may well find that practically you can’t store or charge as much as you need (or want to pay for the battery storage) and so the question becomes how do you minimise costs. Tariffs like Cosy or Agile (when the prices are more reasonable) you can do this.

My heat pump can typically consume 20-40kWh a day on top of a base load of 14-20kWh. I have 13.5kWh of battery storage (a 9.5 and a 5.2) and this gets me through the evening peak and most of the morning with an overnight and afternoon charge.

So how do two AIO systems run together? Since these are AC coupled they should both be indistinguishable from incoming mains, which should see the same cross charging that you would get with the hybrid inverter/battery and an AIO.

Pete.J multiple AIO's are controlled by the AIO gateway which sits across the two of them.

All control goes via the AIO gateway

GivEnergy are releasing an EMS (CEMS) to control multiple inverters, the first release is multiple AC coupled inverters. Maybe multiple hybrid will be next (who knows), whether AIO and hybrid/AC coupled, my guess is they won't see sufficient market for this and won't develop it as a product. But that's just a guess

Be nice if the gateway could connect to non-AIO's but this isn't an option

I've read about the EMS - it's been talked about for many years and seems to be something of a mythical beast as far as I can tell: promised but still not yet available.

The inverter with a battery attached is essentially the same as an AIO (which is a battery with an inverter built in). So whilst the Gateway has a PV inverter input (expecting ac input only) the hybrid inverter/battery could be connected as a second AIO - all the Gateway sees is an ac coupled device. I understand the communication protocols may be different and the Gateway may not be programmed to do this yet, but since the Gateway deals with ac this should be something that can be sorted with software.

The alternative would be to control any cross charging using an external system such as Home Assistant and GivTCP. Since the main problem would be one battery system running itself down to charge the other (and therefore wasting energy in inverter losses) the solution could be to charge the batteries independently once one is full. Both charging together from grid is not a problem because both are in charging mode, both supplying the house is not a problem because both are discharging. So charge both, and when one system is full hold the charge at that value. I know this means you are not able to use this charged battery to meet house load yet, but you can't if you are charging anyway. This approach should mean you can set longer charging blocks and avoid the excessive writes issues caused by micromanaging cross charging.

Pete.J the hybrid inverter/battery could be connected as a second AIO - all the Gateway sees is an ac coupled device. I understand the communication protocols may be different and the Gateway may not be programmed to do this yet, but since the Gateway deals with ac this should be something that can be sorted with software

Agreed it should be theoretically possible but likely need a firmware upgrade on the hybrid inverter to accept such remote control, and firmware upgrade on the AIO gateway to control a non-AIO device.
And whether GivEnergy see there is sufficient commercial market to develop and test such a device?

Pete.J The alternative would be to control any cross charging using an external system such as Home Assistant and GivTCP … Both charging together from grid is not a problem because both are in charging mode, both supplying the house is not a problem because both are discharging. So charge both, and when one system is full hold the charge at that value. I know this means you are not able to use this charged battery to meet house load yet

You could do something like this and that’s what Oli on speak to the geek has effectively done, but it means you don’t get full flexibility out of the batteries leading to more grid import and export as you can’t use Eco mode on both batteries together.

Both the hybrid and AIO grid charging overnight not a problem as you say.

During periods when you know there will be sustained demand you can set both to forced discharge, so meeting home demand with the excess being exported if you set the discharge rate higher than demand, or if there is a shortfall in the power discharge set, you’ll grid import.

Could set one inverter to Eco mode and pause the battery from charging and discharging on the other, let one supply the house and charge of solar if there is any, and then when that one is empty you swap round, pause the first device and set the second to Eco mode. When one device is paused and the other in Eco any excess solar generation gets exported, you can’t start charging the first device as that would lead to cross charging.

Something like this could be done with Home Assistant automations that wouldn’t lead to excessive inverter writes occurring. It gives you additional capacity which the starting question, but can’t give additional power discharge rate. Has limitations in terms of additional grid import and export over a truly EMS managed system - a mythical thing as you say.

Pete.J yes and no is the answer.
Technically it's doable wit external help or a slow discharge programmed.

Data will look odd in the native giv app and portal. But could be made to be ok in HomeAssistant.

The easy way is.
Charge the hybrid at night same time as the AIO. You'll see this as PV so looks wrong
Then in the day time. Set the hybrid on a low and slow discharge just below baseload.
Again this will show as PV. Any fluctuations in load will be met by the AIO.
Any PV will 1st charge the hybrids battery, but once it's full, it will export. Therefore seen by the AIO. It too will then charge from this now exporting PV.

HEMS is coming soon (Home Energy Management System) which should be able to manage the AIO and Hybrid and present data in a meaningful format. Just as you could in HomeAssistant.

The no bit, none of this workaround would be officially supported, but wouldn't affect your warranty. Just make support a bit more drawn out and the agents would not likly unsrtstand what's going on in this non standard setup

A few have done it, with AC coupled and AIO. A few with hybrids.
But it's not for the amateur.

As with all Giv kit. Most things are possible with a little thought, just not out the box.

TheDragon (GivEnergy) Thanks for the reply. It is good to know this combination is possible, and even better to know that it may soon become officially available - I'll keep my eyes open for the HEMS.

TheDragon (GivEnergy) I'm still looking at how I might couple either two hybrid inverters (first choice solution) or one and an AIO (second choice). The idea is to be able to supply a heat pump as well as the house load. With this in mind I was wondering how independent the EPS works within the Hybrid 5kW inverter.

Following your suggestion of running a low steady discharge just below baseload (say 250W in this case) to stop cross charging, I wondered if the EPS circuitry runs before or after this limit is applied: can I set the inverter to a steady 250W discharge and simultaneously run the heat pump (2kW) from the EPS, or does the discharge rate limit apply to the EPS circuit too?

This should let me use one hybrid inverter on ECO to run the house load above base level, and a second hybrid inverter to supply a steady 250W discharge and run the heat pump (independently) off the EPS side. Both inverters would charge from grid at the same time.

Pete.J I don't think you can do what you are trying to suggest. You can connect the heat pump to the inverter EPS output and when the grid is still live the inverter passes house grid through to the EPS connectors. If you set the battery to only trickle discharge then that's all the inverter will supply to the load, the rest will be expected to come from the grid import (or other inverter).

I'd also be concerned about max load of a heat pump on the EPS circuit. I get up to 5kW draw on my heat pump, especially if its very cold. This exceeds the EPS maximum on my inverter, Maybe not an AIO but it'd soon drain the battery,

Pete.J I'm still looking at how I might couple either two hybrid inverters (first choice solution) or one and an AIO (second choice).

Both geoffreycoan and myself have dual hybrid 5.0 inverters. I have the Gen3 and @geoffreycoan has the earlier model (Gen1 I think?)
Without ‘external’ inverter balance control I was getting severe cross charging; One battery discharges at max until it’s empty and the other one gets full!) From what @geoffreycoan has said previously, he wasn’t (isn’t?) getting it as bad on the earlier inverter model.

I have the GE balancer software running on my inverter pair which effectively stops the cross charging. It works well and stops the cross charging from running away pretty quickly - but isn’t perfect or as fast as the expected upcoming hybrid EMS. Occasionally I’ll see a bit of cross charging but not for very long at all (maybe a few minutes? and nowhere near max cross charging. Maybe 1.5kW max for a short duration). It does work well though.

If you can get on this beta software, you’d be good with a pair of 5.0 hybrids. Your other option would be to replace your inverter with a single, newer larger one that works with the new HV batteries. - although that might work out more expensive.

I think the former option would probably work out better for you as it’s far less “messy” in terms of controlling each inverter and battery (/AIO) to charge/ discharge to cover base load etc. and you wouldn’t effectively be throwing away a perfectly good battery and inverter if you went the HV route.

Lots of us are waiting for the hybrid EMS to be released. But there is a dual hybrid solution in the meantime (actually, more than one (other software products)). I’d recommend speaking to GE to make sure that you can get on the beta balancer software first before you order anything though. I’m sure they’d let you on it. After all they’d be unnecessarily turning down sales otherwise!

There was a thread on here (I think) with someone suggesting a hardware fix to introduce a small bias in measured load. I wonder if that could be used to avoid cross-charging. It was simply a small additional AC current passing through the CT clamp, making inverter think consumption was very slightly higher or lower than true.

Pete.J I'm considering moving to a heat pump and would want more stored electricity. An AIO would add another 13kWh capacity, which would ensure I can cover house load and heating between charging slots.

What size heat pump do you expect to need, and how big is the battery on your hybrid? Is it just extra storage you're after, or also extra power?

Pete UK I do get cross charging from my gen 1 hybrids, but as you suggested, it’s not that severe, up to 1.5kWh if I let it run. Possibly not as severe due to the speed of the inverters?

My cross charging is almost always in one direction from inverter 1 to 2 so I stop most of my cross charging by setting inverter 2 charge rate to zero and/or setting battery to pause charge when the sun goes down. The cross charging occurs when there is discharge load on the inverters, so pausing charging overnight when there’s no solar is a good enough fix for me

I am unsure about whether I would get a hybrid EMS or not. Circa £1000 purchase and fitting cost and from what I’ve heard of the AC3 EMS, it’s not as fast to respond to changing load.
It would be nice to have a single large virtual inverter/battery but not convinced at the cost/benefit. If it were a couple of hundred for the EMS and I could get it all fitted for £500 then I’d be more tempted.

I guess with the RAM registers there's nothing really stopping someone making their own EMS box that just twiddles the inverters power settings to keep everything fairly even.

To fill in some figures: I have two 9.5kWh batteries and would be looking at a 7kW heat pump (I know this will heat the house to 20C, uses about 2kW when running and over the winter will take up to 40kWh).

My biggest problem at the moment is rate of import: only having one inverter limits me to charging at 3.6kW and this means I can only charge by 9 or 10kWh in a 3hr period and I potentially need 10.2kWh plus house load until the next charging slot.

Two inverters with one battery each is the lowest cost solution and would allow me to fully charge both batteries over 3 hours. It also has the option to expand by adding another battery (or two) later.

Pete.J 3 x 3.6 is almost 11kWh. Assuming you are modelling cosy, you have a total of 8 cheap hours, so can charge almost 30kWh hours off-peak. And of the 40kWh/day, 1/3 of them are during cheap rate, and can come directly from grid. So you only need 2/3 of 40 = 26 kWh from battery. And 40kWh is probably only on coldest days?
And you might set-back overnight

[unknown] I assumed I would lose some charge due to conversions so I'm working on 10kWh of useful power.

You are correct that 40kWh is only coldest days but I'm thinking it would be nice to not worry about running the heating.

I'm using figures from a friend with a similar sized house and the same heat pump so have a good idea of the ASHP power consumption over last year. I want to keep import to a minimum cost and charging in the Cosy hours would be ok for this provided I can run off battery for the rest of the time.

Pete.J I have solar panels, Gen 3 hybrid inverter, one 9.5kWh battery and a 7kW heat pump. There was one occasion over last winter where my total household use for the day was 38.6kWh. Using the cosy tariff my one battery covered this. If you haven't already done so, I would get a heat survey done to make sure that a 7kW heat pump is right for your property before committing to upgrading your system.

Agree with getting a heat loss survey and proper heat pump design and sizing done before committing to any upgrade.

But even with a heat loss survey there are lots of assumptions and guesses that have to be made.

My own survey indicated that for the coldest days I would need a 15kW heat pump which at the time didn't exist on the MCS scheme, so was sold 2 9kW heat pumps. The survey projection was for 7989kWh a year annual consumption.

Year 1 was 5331kWh, year 2 5936kWh and year 3 4330kWh so all of them were under the projected annual demand but last year's 1/3 saving was due to me optimising the het pump setup and operation.

So if I'd taken the MCS projection I'd have been over-provisioning the batteries by nearly double.

I have two Gen 1 inverters so max 2.4KWh battery charge rate, a 9.5 and a 5.2 (4.2 usable battery). My batteries run out in the morning and then again in the evening, resulting in day rate import, with typical winter daily running costs at around £10. More batteries would reduce this but the payback wouldn't be great

[unknown] 3 x 3.6 is almost 11kWh. Assuming you are modelling cosy, you have a total of 8 cheap hours, so can charge almost 30kWh hours off-peak.

The charge rate of the 9.5’s is a nominal 3.3kW (increases to 3.5kW as charging progresses)

So with 2x Gen3 5.0 inverters you only get 2x (3.3 –> 3.5)kW for charging with the three 9.5kW batteries.

So if the OP had 2 batteries on one inverter and one on the other;

The single battery on one inverter will charge at the full ‘3.4’ kW and the other 2 batteries on the other inverter will charge at ‘1.7’ kW each (‘3.4’kW total).

Pete UK The charge rate of the 9.5’s is a nominal 3.3kW (increases to 3.5kW as charging progresses)

Is that the limit if the inverter, or of the battery? I assumed the latter, which means with two batteries in parallel, it would max out the inverter's limit without troubling the batteries, even when they're cold.
(But I only have 1 battery.)

Currently I have two 9.5kWh batteries on a single 5kW hybrid inverter. The fastest charge rate I've seen is 3.6kW into the batteries. It looks like the batteries are in parallel on the connection (even though the wiring goes to the first and then jumps to the second) so the 3.6kW is feeding both batteries simultaneously. This is probably 1.8kW per battery and is limited by the inverter.
If I get a second 5kW inverter and put one battery on each then both batteries will charge at full rate instead of half rate and I can charge to full faster, which should in turn ensure I can bring in enough energy to cover the house load and the projected heat pump. It's also the cheapest way I can think of to boost the performance of what I have.

Ideally both inverters would run on ECO and cover the required load whatever the source. Managing this would need something like the HEMS that TheDragon mentioned. Or maybe the RTC update to the inverter means I can safely use Home Assistant for this. The situation is slightly more complex in that my PV would feed one inverter, so I want to cross charge the other inverter/battery from excess PV but not from battery.

My alternative idea was to use one inverter in ECO mode as I already do and the other at a small steady discharge, and run the heat pump off the EPS on the small discharge inverter, but I don't know if setting an output limit on the inverter discharge also limits the EPS output power to that same value. Does anyone know?

Pete.J not sure what the benefit of using the EPs is.
One possible option might be to wire up the CT clamps on such a way that one inverter cannot see the other. In a similar way to hiding an EV chargepoint from the inverter.
With no pv, one of your inverters is just behaving as an ac-coupled battery. Putting its CT clamp first means it can see the true consumption, and will store anything exported by the other. But the other will not see what this one is doing, and so will not drain its battery just to allow one to charge.
Cross-charging could still happen the other way, but a very small bias to make the inverter tend to discharge should fix that.
The two batteries would not share the load equally, but I'm not you can reasonably expect them to if they are operating independently.

If the EPS is an independent limit to the inverter home output then I can use the same inverter to cover the base load of 250W (so it's not charging) AND supply 2kW to the heat pump (the 16A EPS output should easily cover an ASHP)

Pete.J I may be wrong, but I thought that while grid was working, eps output was just wired to the standard output. Only when there's a power outage do they separate.

[unknown] Is that the limit if the inverter, or of the battery? I assumed the latter, which means with two batteries in parallel, it would max out the inverter's limit without troubling the batteries, even when they're cold.

It seems to be the inverters DC charging limit. It’s a bit frustrating really with 2 batteries (or more) on one inverter. It’d be great to be able to charge each of them up at their maximum rate but that isn’t the case, unfortunately.
The only good thing is that it’s kinder to the batteries (only charging them at 1.75kW max each) I guess. Meh.

Pete.J The situation is slightly more complex in that my PV would feed one inverter, so I want to cross charge the other inverter/battery from excess PV but not from battery.

With my dual Gen3 5.0 hybrid inverters I have 4 PV strings. 2 into each. (I don’t have EPS). Do you only
Have one string of panels? is that why you’d only have the PV going into one of the hybrids? As wouldn’t it’d be better to have solar going into each?
Or is that because you’d want them on the one with the EPS?

Anyway….

In the early morning, my 2 east facing strings ramp up much faster and I’ll see, say 2kW generation on them initially and 400w from the North and South strings on the other inverter. BUT, the batteries on BOTH inverters will be charging ‘equally’ (almost). So I’ll see (as an example) perhaps something like this;
2400w total solar generation,
600w house load,
Inverter A; charging batteries 1&2 at: 900w
Inverter B; charging batteries 3&4 at: 900w (despite it only having 400w PV generation from inverter B!)

So, even if you only have one string and it’s going into only one of the pair of inverters, I THINK you should see the same. The inverter with PV attached has excess generation and instead of exporting it, it will start to charge it’s batteries and the other inverter should also see that excess and start to charge it’s batteries as well.

Now I can’t remember exactly what happens if you don’t have some sort of inverter balancer software running. If it will behave like that or not. I think it will but @geoffreycoan maybe able to shed some light on that as he isn’t running balancer software any more (but he is also doing some other clever tweaking stuff!) However, that being said, you WILL need that software running, as these inverters will cross charge like crazy if not. Obviously as in the example above they discharge in the same manner (‘equally’) under load.

With an EPS. In a power failure, I assume one inverter effectively shuts off completely. And that attached battery becomes effectively isolated and is no longer available to charge or discharge. But that’s just my assumption.

Hope that helps.

My cousin has just had a system installed with an AIO and a HY5 inverter.
The AIO is the battery storage and provides EPS. The HY5 is grid tied and uses the AiO battery somehow.
There is also a hypervolt EV charger hooked up. Not sure how it all works but he has 2 GivEnergy logins and GE seem to be OK with it.

I have two PV strings - one East and one West, 8 panels each, into my existing inverter. The system works well, and is happy charging the two batteries, although it does take time to do this. from PV.

I hav originally thought of using an AIO as the second power supply. The ability to feed more than 3.6kW into the house would be useful occasionally, and the extra capacity would help when I get a heat pump. Another hybrid 5kW inverter and using one of my existing batteries would give the cheapest way to add an ac-coupled battery - I would leave the PV arrays on the existing inverter.. The challenge is how to make it all work together nicely.

The idea behind using the EPS would be to allow the second inverter to discharge at a low level to avoid cross charging and let the EPS cover the heat pump but this only works if the EPS output is independent of the inverter limit on the main ac output.

I could just get another inverter and rely on Home Assistant to switch between them so only one runs in eco mode, but this wouldn't allow me to access the extra output a second inverter could bring.

Pete UK So, even if you only have one string and it’s going into only one of the pair of inverters, I THINK you should see the same. The inverter with PV attached has excess generation and instead of exporting it, it will start to charge it’s batteries and the other inverter should also see that excess and start to charge it’s batteries as well.

Now I can’t remember exactly what happens if you don’t have some sort of inverter balancer software running. If it will behave like that or not. I think it will but @geoffreycoan maybe able to shed some light on that as he isn’t running balancer software any more (but he is also doing some other clever tweaking stuff!) However, that being said, you WILL need that software running, as these inverters will cross charge like crazy if not. Obviously as in the example above they discharge in the same manner (‘equally’) under load.

If you only have PV feeding into one inverter then the second inverter is effectively acting as an AC coupled inverter.

During PV generation all of the PV will go into the battery of the inverter with the PV input. When the battery is full the first inverter will convert the DC PV to AC and start to “export” the excess, at which point the second inverter (without PV) will see the excess AC and start to convert it to DC and charge its battery, again until full and then all solar will be exported.

Where it gets messy is when house load occurs that exceeds the PV generation. What happens then is that both inverters will try to respond to the load, will discharge their batteries, there will then be an excess that’s being exported, so they will stop discharging and start charging with the excess. The two inverters don’t respond as fast as each other so what happens in practice is that one starts charging, the other discharging, and this can ramp up to full rate energy transfer from one inverter to the other.

Hence why you need some form of balancing software to stop this happening.

alan_johnston My cousin has just had a system installed with an AIO and a HY5 inverter.
The AIO is the battery storage and provides EPS. The HY5 is grid tied and uses the AiO battery somehow.
There is also a hypervolt EV charger hooked up. Not sure how it all works but he has 2 GivEnergy logins and GE seem to be OK with it.

What this is is that the HY5 inverter is acting as a solar inverter, converting the DC from the panels to AC that the AIO can then charge into the battery. It’s an expensive way of getting a solar inverter. GivEnergy now sell their own PV inverter (probably in essence a hybrid inverter with the battery stuff ripped out), or could have installed any other solar inverter such as SolarEdge.
The two accounts is to ensure that the AIO graphs look sensible. If the hybrid and AIO are on the same account the solar PV gets counted twice as its reported by both devices and all the energy graphs are screwed up

[unknown] Where it gets messy is when house load occurs that exceeds the PV generation. What happens then is that both inverters will try to respond to the load, will discharge their batteries, there will then be an excess that’s being exported, so they will stop discharging and start charging with the excess.

My suggestion above should break that symmetry... The "outer" inverter is responsible for fine-tuning to get grid activity balanced, and the bias on the "inner" means it always leaves a little work for the other one to do.

Can have various major modes of operation without requiring detailed micro-management to balance.

Pete.J I'm considering moving to a heat pump and would want more stored electricity.

Clearly you'll have far more storage than you'd need for most of the year. How would you plan to utilise it during the non-winter months? Flux, and just dump the extra battery to grid every day? Or are you hoping predbat can manage both inverters with agile?

@geoffreycoan If you only have PV feeding into one inverter then the second inverter is effectively acting as an AC coupled inverter.

Yep. That’s it. All of the above. Hence my suggestion to put one PV string into each inverter to even things up a bit.

@geoffreycoan Hence why you need some form of balancing software to stop this happening.

Yep. And if he puts one string into each inverter, then it’ll be acting as more of a hybrid inverter with the solar from the lower PV input string being topped up with excess AC (from higher PV output) from the other inverter, keeping the charging up of both balanced.

Ideally in a perfect world you’d split E/W into 4 strings and put one string of 4 west panels and one string of 4 east panels into inverter A and the same remaining east and west strings into inverter B. Then they’d have a matched PV input all day on each inverter. But that’s going to be a lot more work that nobody will want to do. Let alone pay to have modified after the event!

Pete.J I could just get another inverter and rely on Home Assistant to switch between them so only one runs in eco mode, but this wouldn't allow me to access the extra output a second inverter could bring.

Personally, if it was me, I’d try and make it as cheap as possible, as easy as possible to operate with the highest charge and discharge rate possible, whilst allowing maximum use of the systems capability. Which IMHO would be dual Hybrids with a 9.5 battery and one string of solar on each, some kind of inverter balancing software and the heat pump on the EPS circuit of one of them.
One string into each inverter will also avoid any possibility of any clipping occurring from your 16 panels during the cross-over time when the sun is highest. (Assuming your panels are more than 310watts each). I’d put the 8 west facing panels on the inverter with the EPS.

An AIO and hybrid inverter running together won’t play nicely without a significant level of buggering about. And even then the result may disappoint you because this will mess about with and possibly compromise your system’s maximum operating capabilities, which is what you’ll be wanting to use >99% of the time; rather than just the rare <1% grid out occasions that may allow you to have everything running and cook a meal at the same time once in a blue moon.

If you don’t have loads and loads of power cuts a year that last more than 3 or 4 hours, I wouldn’t worry too much. The HP would run off a single 9.5 battery for about 4+hours at 2kW with a few LED lights, WiFi router and probably the TV on at the same time (assuming it’s full). And even after that your house will retain some heat for a reasonable amount of time. If you have other critical items that absolutely need to remain on you can buy separate UPS power supplies for them from Amazon. Maybe one even exists for heat pumps? as that would likely be the main priority.

It’s all a bit of a compromise at the end of the day. If you do however get day long black outs regularly then that’s a different story. if not; I’d focus on the >99% of the time rather than the <1% !

With the dual gen3 5.0 hybrid set up (you propose as your preferred option), you’d get;
1) 7.2kW max discharge rate to cover house load,
2) 8kW max discharge rate to grid and/or house (forced export), Or up to 10kW if the suns out. Both subject to DNO limitations.
3) ‘7kW’ battery charge rate from solar or grid or combination of both.
4) ‘19kWh’ to last between off peak slots. Or maybe even for the majority of the winters day from 05:30–> 11:30pm on IOG…?

I’d go for that if it was me. Just one extra inverter to purchase, run both in eco mode and use some balancing software. Fairly straightforward and does exactly what you need I presume?

I don't think it's worth splitting my PV - East and West arrays of 8 panels each. Eight panels is great for charging one battery, but four would be less than ideal and I can't fit more panels on the roof.
This is why my original post was about running a Hybrid inverter with an AIO. Anything extra I add is probably going to be an AC coupled battery (or at least act as one). The AIO is the neatest solution but another Hybrid 5kW inverter and move one battery across is the most cost effective solution so far.

At the moment it looks like the best way to manage two inverters will be Home Assistant because the GE Home Energy Management System seems to be longer term product: it gets mentioned occasionally but not often enough to believe it is likely to appear soon and I've not seen any mention of beta tests. I know Predbat can cope with two inverters so presumably this could manage them (especially after the RTC update to reduce writes). An alternative would be to use one inverter in ECO and keep the other in standby and switch between them when the battery gets down to a lower limit (say 20%?). Thsi should be possible through givTCP.
If the latency is low enough, HA could turn the second inverter on (enable ECO) if the home load exceeds the output of the first inverter, and disable ECO when the extra load ends. This should minimise cross charging if the changes can be made fast enough.
This setup would allow me to charge each battery independently, which means I would be able to charge the full 18kWh system in the 3 hour Cosy slots to run home and heat pump (assuming a maximum of 6kWh for home and 12kWh for heat pump over a six hour interval between slots - I doubt I'd reach this very often so it should comfortably cover most of the year).

I think it's doable. If there is not too much work to do to add the second inverter then it's probably affordable too.

Pete.J If the latency is low enough, HA could turn the second inverter on (enable ECO) if the home load exceeds the output of the first inverter, and disable ECO when the extra load ends. This should minimise cross charging if the changes can be made fast enough.

My proposal from above is implementing almost exactly this strategy, but needs no additional software running to achieve it - it happens entirely automatically using the standard inverter firmware. I can add a followup with more details if it wasn't clear.

Pete.J I don't think it's worth splitting my PV - East and West arrays of 8 panels each. Eight panels is great for charging one battery, but four would be less than ideal and I can't fit more panels on the roof.

No I don’t think it is worth you doing that either. That was just an “in an ideal world starting from scratch scenario comment”. In that hypothetical scenario, you wouldn’t have just 4 charging each battery though; you’d have 16 charging both batteries concurrently; 8 charging each battery (4 east and 4 west charging one battery) and the other 8 charging the other battery (4 east and 4 west). So they’d charge equally requiring less balancing and also minimising all clipping (wasted PV). That was the idea. Not really cost effective splitting your 2 arrays now I suppose. Even if you didn’t split the strings like that though but went for a second HY5 you’ll still have the same output from the 16 panels charging 2 batteries equally as above and they would charge up faster and equally between cosy slots because you’re got 2 inverters (from solar with balancing software) or from the grid. Which seems to be what you wanted for winter operation.

The method of operation that you are describing seems very convoluted, just to solve a potentially avoidable self induced problem.

In my mind I’d doesn’t make sense to operate either a second hybrid inverter (or AIO) independently, ie charging one then charging the other or having one just discharging at a fixed rate to cover you base load (which is ever changing). As you’ll be defeating the point of having the extra input/output capacity you want to add!
Just let the system work normally with some balancing software, then you’ll achieve what you want easily and simply.

The EPS function is only an off-grid mode. Effectively you don’t “run” stuff through just the EPS in normal day to day operation. In normal day to day operation your heat pump would effectively be supplied by both batteries (or solar, or grid or a combination). The EPS circuit is just what is left powered when you get a power cut.

You can operate each inverter separately to do what you suggest using home assistant. You can do all sorts of clever stuff. But the question is why would you want to do it like that when you don’t need to?
You’d be introducing all sorts of complications and limitations unnecessarily for no gain, only pain !

DD My existing CT clamp for the inverter is after the meter and before the Y connector that separates for the distribution box and the inverter. Where would you put the other clamp?

Pete UK I have a different opinion on some of those points.
My HA server and home network run off the EPS all the time and are very happy. I have a small UPS to ensure the transition during a power cut is smooth.

The point of adding another hybrid 5 inverter is to be able to charge faster. This is definitely not a "no gain" scenario because it would allow me to charge both batteries in 3 hours instead of taking 6 hours as they are configured now. In turn this would make it possible to cover the load for the house and a heat pump until the next 3 hour charging slot: that's a big saving at the peak rates.

Pete.J

home --+--a---+--b----(meter)---grid
       |      |
       A      B

where A is the hybrid inverter with PV with CT clamp at a, and B the AC-coupled inverter with CT at b. A is unaware of B, and sees everything to the right of 'a' as "the grid". (Could potentially add an EV between 'b' and the meter, so that neither inverter attempts to power it.)

A is the primary and (by default) doing all the work. B just catches anything A cannot do,

Cross-charging is eliminated because ECO mode on A means it doesn't want any current passing through 'a'. Even if B was to respond more quickly than A to an increase in consumption, A would choose to (also) cover it, then B will back off (because it will become export to the grid across 'b'.)

In the case that A's battery fills up and A is forced to "export" the excess across 'a'. B will charge from it. And if ever A cannot fully cover consuption (because battery has run out, or it exceeds its max or configured output), B will step in to make up the difference (since it doesn't want anything flowing across 'b')

If you want to try to utilise them a bit more equally, you might choose to reduce A's max discharge rate, to say 1kW. Then for any consumption exceeding 1kW, B would chip in. However, would need to keep an eye on B's SoC - if it was to run out, A would not automatically increase output to cover the shortfall. So that's something you could tweak by API every hour or so. And if consumption exceeded what B could provide, A again wouldn't automatically increase its output.

But as has been noted, more efficient to charge A's battery from solar than to send it to B, so you'd want to keep that asymmetry,

This is why I was asking about how you planned to use B outside of the heating season - it doesn't really have much to do. Though I guess on Flux it's probably still better to store excess solar until peak time than to let it out earlier.

Neither inverter can provide accurate stats: only B knows true import/export, but only A knows true generation/consumption.

DD I like your solution, very clever, extending the concept of how to wire an EV charger up so the battery doesn’t discharge into it.

Pete.J I know Predbat can cope with two inverters so presumably this could manage them (especially after the RTC update to reduce writes). An alternative would be to use one inverter in ECO and keep the other in standby and switch between them when the battery gets down to a lower limit (say 20%?). Thsi should be possible through givTCP.
If the latency is low enough, HA could turn the second inverter on (enable ECO) if the home load exceeds the output of the first inverter, and disable ECO when the extra load ends. This should minimise cross charging if the changes can be made fast enough.

Just picking up on a couple of points from the above. Predbat can manage multiple inverters and it basically manages them as a pair of devices that both receive the same instructions. It doesn’t (natively) do things like start one inverter charging and the other discharging or holding, you can do some of that by manipulating inverter charge and discharge limits (and this is what I do to trickle charge my batteries at different times of the day), but generally both inverters are controlled the same.
There is inverter balancing but that’s effectively a separate bolt-on.

r/e HA latency. It’s not really HA’s latency, it’s how often GivTCP polls the inverters via modbus. If you crank this up to too high a frequency then the inverter spends all its time talking to HA and none of its time sending data to the GE cloud or being able to respond to commands from the portal. I have run my GivTCP at 20 second polling frequency, but now run it at every 30 seconds which is the recommended maximum.
So yes you could do more dynamic stuff in HA, but limited to about 30 second response time

DD that is how my two are setup - duty & standby. Only if duty gets saturated does standby step in to help.

Off topic I know but you did build a virtual inverter at one point.
I guess a virtual EM115 meter could equally be made, such that whatever the true reading of the meter is, the value gets divided by however many inverters need to know and then they see that instead?
(I'm assuming this will be how the Hybrid Cems thing will work)

Pete.J The point of adding another hybrid 5 inverter is to be able to charge faster. This is definitely not a "no gain" scenario because it would allow me to charge both batteries in 3 hours instead of taking 6 hours as they are configured now. In turn this would make it possible to cover the load for the house and a heat pump until the next 3 hour charging slot: that's a big saving at the peak rates

Agreed. But that wasn’t what I was saying. (One HY5 vs 2x HY5’s).

What I meant by it’s a “no gain” scenario is compared to running the two hybrids as a ‘normal’ plant set-up with balancer software running! You’d achieve exactly the same without increased complexity and limiting functionality.

Pete.J This should let me use one hybrid inverter on ECO to run the house load above base level, and a second hybrid inverter to supply a steady 250W discharge and run the heat pump (independently) off the EPS side. Both inverters would charge from grid at the same time.

You were describing setting one hybrid to have a slow discharge to cover the base load and when one gets empty swapping over to the other, having one operating in eco and then swapping them over when one battery got “really low” etc. I can’t see how this method of operation provides any significant extra advantages. And you’d be reducing the ability to cover spikes in load demand; instead you’d potentially import from the grid during those times.

ie you’d likely be ‘hobbling’ your system to some extent.

For example; If one battery is full and one empty you can only charge the empty battery at “3.5kW”. If both are half full you can charge both at “7kW”. Same logic for discharging!

You can still use home assistant to do all the other clever stuff. It just seems to me that it makes more sense to operate them together, charging and discharging equally and hence having all the max charge and discharge ability. Does that make sense?

Pete UK Thanks for the reply. My ideas have changed a bit as we've explored this conversation and I've probably not been clear enough about this.

The idea of using one inverter to cover baseload comes from TheDragon's reply (9 Feb). Although this originally referred to a Hybrid 5kW and an AIO, it could possibly have applied to two hybrid inverters. Running the heat pump off one inverter that also covers the house baseload would balance the battery use more evenly so I wondered if this could be done using the EPS output on a slow discharging inverter. I now know this won't work because I've learned that limiting the output to cover the base house load would also limit the EPS output.

This brings me back to the original idea of adding some form of AC coupled battery, either AIO or hybrid 5 inverter and battery. My current system probably has enough battery capacity to run the house and a heat pump between Cosy charging slots in winter, I just can't charge the batteries fast enough to use it this way.

I agree that adding complexity is rarely a good idea. DD's suggestion for positioning the CT clamps looks to be a simple solution that should work.

DD Thanks for the detail.

Please can I check I understand this correctly.
Inverter A is my current setup - solar and battery. I understand that eco mode will meet house load and charge from solar etc just as it currently does. Once battery A is full any excess PV will be exported towards grid (and therefore B). Inverter A can pull from the grid to charge the battery if required. Presumably it would charge from B if B is exporting while A is charging because effectively inverter B and grid are the same source in this setup.

Inverter B is upstream from A. It sees any demand for energy from "grid" that A can't meet and can respond accordingly (assuming ECO mode is on). Inverter B can pull from the grid to charge.

What I'm less certain about is how B knows when to charge from any excess PV coming through position a because this is effectively mains "out" from the house load rather than DC in from solar panels from the viewpoint of this inverter. Does a hybrid inverter behave this way automatically in ECO mode or does this require extra control?

Pete.J Inverter A is my current setup - solar and battery. I understand that eco mode will meet house load and charge from solar etc just as it currently does. Once battery A is full any excess PV will be exported towards grid (and therefore B). Inverter A can pull from the grid to charge the battery if required. Presumably it would charge from B if B is exporting while A is charging because effectively inverter B and grid are the same source in this setup.

Yes. You'd want to ensure B is not (able to) discharge while A is charging. (It would supply power if it's in eco mose ) Probably charge them both at the same time? To avoid races, could configure a pause-discharge on B to overlap A's charging time. Or charge B for an extra minute or two either side of A, since their clocks won't be precisely synchronised.

Inverter B is upstream from A. It sees any demand for energy from "grid" that A can't meet and can respond accordingly (assuming ECO mode is on). Inverter B can pull from the grid to charge.

Yes. And A would have no knowledge about B charging from grid, and wouldn't interfere.

What I'm less certain about is how B knows when to charge from any excess PV coming through position a because this is effectively mains "out" from the house load rather than DC in from solar panels from the viewpoint of this inverter. Does a hybrid inverter behave this way automatically in ECO mode or does this require extra control?

It did surprise me a little that hybrids did this - automatically consuming any "stray" export as an ac-coupled battery would. But it must do for cross-charging to be a problem - one must be consuming AC without knowing where it's coming from (and the other supplying it without knowing where it's going.)

But worth checking. The usual scenario would be if you have an ac-coupled solar inverter (or micro inverter) with a hybrid, will the hybrid store the additional solar?

If not charging from solar, I would be looking to charge both batteries at the same time, for example during Cosy slots. It doesn't matter if the two batteries are not exactly the same SOC as long as they both take in enough energy between them to get through to the next charging slot without the need to import at a higher cost.

I can sort something with Home Assistant to stop one battery charging while the other discharges (for example during a calibration) and I should be able to use data from clamp b to monitor actual export to grid.

DD It did surprise me a little that hybrids did this - automatically consuming any "stray" export as an ac-coupled battery would. But it must do for cross-charging to be a problem - one must be consuming AC without knowing where it's coming from (and the other supplying it without knowing where it's going.)

This ability to charge off stray export wasn’t how the hybrids originally worked.

My Gen 1 hybrids on the stock 450/451 firmware charged only on DC power, any excess AC was ignored and exported. In my case this could happen either from a GivEnergy inverter that was maxed out on battery charging or my pre-existing AC FIT inverter.

But, the Gen 2 and Gen 3 hybrids didn’t do this, they would charge off stray export. This feature came to the Gen 1 hybrids along with the fast-response and battery pause functionalities. i.e. beta firmware 191/193 onwards.

And yes I can confirm that on the newer gen 1 firmwares it does AC charge, in fact it will AC charge as well as DC charge off the panels.

Right now for example my inverter 2 is charging the battery at 1kW but there’s only 0.9kW of solar from its panels. The extra 0.1kW is coming from inverter 1 and the FIT inverter with the balance being exported.
(inverter 2 is currently limited to 1.0kW charge rate to trickle charge the battery, inverter 1’s battery is full)

Gen 1 on the old 450 fw does hoover up excess AC from other sources but only if you turn ECO off (which is a bit weird but that's what mine does)

So I finally plucked up the courage and financing to talk to my installer about a second Hybrid inverter to be connected to one of my existing batteries. They said it's not a recognised GE setup and so can't do it, which is a shame.

A HEMS would solve the problem (because that would then be an officially supported set up) but I've not heard any news for a long time - has anyone heard anything new on this?

Pete.J So I finally plucked up the courage and financing to talk to my installer about a second Hybrid inverter to be connected to one of my existing batteries. They said it's not a recognised GE setup and so can't do it, which is a shame.

Your installer is not quite correct. It is perfectly possible to have multiple hybrid inverters each with their own batteries on the same electricity phase, there is a risk of cross charging as already discussed, especially with the newer (faster) firmware although there are ways to minimise this. This is precisely the setup I have.

GivEnergy have an FAQ on this https://givenergy.co.uk/faq/my-electrical-consumption-is-high-what-are-my-options-ac-plant-systems/?asp_highlight=multiple&p_asid=3

It is a recognised GE setup, its fully supported by GE, its just not recommended (because of the cross charging issue)