Maximum Inverter Output Power on Battery Only

Hi,

New here and looking at three options for inverters/batteries to go with a just over 6kWp east/west solar array.

• SMA/SolarEdge inverter coupled with a Tesla Powerwall
• Huawei Sun 6 Inverter and Luna2000 ESS battery @ 10kWh capacity
• GivEnergy Hybrid 5.0 Inverter and 1 or more 8.2kWh batteries.

The Tesla can take over the whole house with a 5kW output and the Huawei can do 5kW through a backup box to chosen circuits. Both of these are automated.

When I look at the GivEnergy, which was my initial choice, I find an issue that the maximum output on battery is just 2.6kW.

Now that's not tiny, but it's not enough to keep the background load, boiler and fridge freezer going without things getting a bit close to 80%. The changeover is also manual.

I don't mind the manual changeover, so that's not world ending, but the 2.6kW vs 5kW is quite poor.
Am I looking at the wrong inverter for this and is there a more powerful version of the hybrid inverter that I'm not aware of?

Sadly due to the way the wiring in the house is, it would be that most circuits, minus the high loads such as immersion and cooker circuit would end up on the EPS (so all lights and sockets, plus fire alarms).

I know there is common sense, but it would be nice to be able to have some lights on, keep the boiler running and the internet, watch TV and support use of say a microwave (1200W).

Any help would be appreciated, as right now I think the decision on which to go for wouldn't be going towards the GE solution.

Installation won't be for a couple of months, but obviously I need to put a deposit down to get the panels etc in and therefor need to decide on which battery system.

Thanks

If you can afford the Tesla Powerwall then I suggest going down that route. As for inverters I am not convinced the solaredge is worth the extra cost unless you have a shading issue. If your roof space will not be affected by partial shading then I would go down the SMA route or even a Solis. I have a solis 5kw 4g and about to add a solis 6kw 4g on another array.

kram The output from battery alone in the event of a power cut is 3kW using one of our AC Coupled inverters or 6kW using 2 Inverters. You are correct at 2.6kW From battery alone on the Hybrid, however that is only if you get a power cut at night time and the solar is not generating. If you were to get a power cut during the day then the solar would ramp back up and continue to generate to feed your critical circuits up to either 3.6kW or 5.0kW dependant on the hybrid model. You mentioned above that this is a manual changeover. That's not correct, the inverter has this built in and automatically changes over when the grid is down. It just requires some additional wiring work by the installation engineer to ensure that the critical circuits can be powered in the event of a grid failure. This means that your essential circuits are permanently supplied by GRID/SOLAR/BATTERY until the battery runs down to its lower level.

Hi Dan
This is useful but not something that I was aware of when talking to suppliers. I didn't ask about what happens when the power fails and potential suppliers didn't volunteer the infomation. I admit that I had assumed that in the case of grid power failure the current solar generation plus stored energy in the battery would be availble to the house as part of a standard installation but now it seems that this is not the case. I wonder if the installation companies know this?

Not even EON a major GivEnergy installer mentioned about EPS and what happens in a power fail.

Danlambert (GivEnergy)

Most supplies state I need to have a manual isolator on the GivEnergy system to keep the solar generating and turn it into an island. Obviously the powerwall has the gateway and huawei has a backup box that drops it into island mode and powers a set of "critical" circuits up to 5kW (continuous) power from the battery alone.

When you say the critical circuits are constantly powered, as you saying the hybrid inverter would actually isolate the house from the Grid as required, but leave the critical loads, battery and power running?

In terms of 2.6kW from battery, it is usually during the dark (evenings) when we use most power and as power cuts are most likely during the darker months, the solar side doesn't come into play. As such it's not much use for our requirements s it stands, whereas something like 4-5 would be much more useful.

You mentioned putting two 3kW AC inverters together to get 6kW, how do you run those into the critical loads panel?

@THALL - I tend to agree the solaredge is fairly pointless and have the SMA sunnyboy as the primary choice if we went that way.

FYI the array will be 3.2kW east, 3.2kW west, but high up, so minimal shading bar a chimney flu that would cast a shadow away from the panels for 90% of the time on one side of the roof and wouldn't shade the other side of the roof.

On the suppliers, even advanced installers are saying manual changeover and some of the regular ones were telling me that the panels don't charge the battery from the inverter when power is down, you just run on what you have. (Even with the hybrid)

My main gripe with the powerwall it it's difficult to find somewhere to install it, and worse still you're essentially paying more, to get it back over the 10 year warranty period by my calculations.

Just looking at the datasheet for the Hybrid 5.0 and I saw this on the web-page:

"Generation 2 Hybrid - Wifi / LAN / 4G ( Coming Soon )"

Don't suppose anyone knows how soon and if there are any improvements to the power output do they?
That might well swing it in favour of the GivEnergy system if there's a reasonable improvement..

I'm a little confused if I'm honest as the 8kWh battery can put out 85A @51.2v which is 4352W, so 3.6kW continuous output should be possible even at 80% of that.

GrahamShaul The power can be available to power the whole house, however this would need an auto/manual changover switch. You need to ensure that the GivEnergy system is on the supply side of the changover switch and that there is a complete disconnect from the grid supply to ensure safe operation. there are multiple, GivEnergy approved methods for configuring this found below:
https://kb.givenergy.cloud/article.php?id=12&oid=1

THALL Eon dont offer this as a solution due to the regulatory difficulties in the earthing and safe operation in the event of a grid failure.

kram With a Dual AC Coupled system in Island Mode, youd require a split load board or two separate consumer units each powered from an inverter. When grid connected it can allow upto 6kW of available power to power standard house loads. in the event of a power failure it will provide 3kW to each side of the backup board to power essential circuits. Please note, the two inverters cannot connect together into a single board in the event of a powercut to provide 6kW.

In terms of positioning a Giv Battery, our two options are outside in porch storage area (Bins currently in there) or in the kitchen, as these are the only two sensible routes to get to the meter etc, without digging up half the house.

Are there are restrictions on where the battery should be placed?
I'm aware the GE battery is LFP vs NMC for the Tesla, so obviously it's less of a bang if it goes, but still a bang.
The Huawei is LFP, but the manual states not in any living spaces, but neighbours have one in their office.

Danlambert (GivEnergy)

Thanks 🙂
That would essentially be two AC inverters, two batteries, a solar inverter to get 6kW output then?
The fuse box is split, but would obviously have to have the non-required loads moved off the RCD onto their own RCBO.
(I'm thinking cooker, immersion etc).

kram Please do have a read through the forum for issues people are having with multiple inverter givenergy / battery setups. Don't get me wrong I really like my givenergy setup, but more complex systems are causing people some issues.

I would suggest that you don't dismiss the advantages of the SolarEdge inverters with optimisers out of hand.

My installation (December 2020) has 19 panels on a nearly south-facing roof, which has no shading. So in theory the panels should all produce the same. However, there is a noticeable variation between panels, perhaps manufacturing tolerances. The upper row of panels does seem to start outputting before the lower ones at dawn, and after rain, dew etc the panels don't all start producing (drying out?) at the same time.

The 'best' panel has a lifetime production 14% higher than the 'worst'. The average output is 6% higher than the worst - ie the SolarEdge optimiser benefit is equivalent to an extra panel.

This is with quite new panels, and I expect the panel variation to grow as the panels age.

I hear what you're saying about optimisers (The Huawei has the option to use them too).

If I go with the SMA with shadefix built into the inverter, then whilst I don't get all the advantages I get some.
My issue with the optimisers is that we have a 3 floor house (Thin and tall), which makes getting up to replaced a failed optimiser an expensive (Scaffold) job.

I'll probably take one string east, one string west and I might lose a bit without optimisers and not be able to monitor in the same way... but one scaffold expense would add 1200-1500 to the cost of the system. That's why I'm very cautious about electronics in places which are hard to reach.

I had a think and to be honest the dual AC GivEnergy solution isn't attractive as I end up with loads of boxes (which I don't have space for) and a headache.

It's a real shame as I like what GE are doing, but the inverter is clearly hobbling what that 8+ kWh battery can do in terms of backup supply.

So we're down to the GivEnergy Hybrid or the Powerwall and an SMA after a talk with the installer.

Can I just confirm what I believe was stated earlier please?

The GivEnergey Hy 5 inverter will automatically switch over without me needing to isolate the grid for the critical loads in the event of a grid failure?
Or have I misread that the EPS functionality is there, but in the event of grid failure a manual process (or automated changeover switch) is required in the event of grid failure.

Essentially Method 2.

I have a split distribution board, so I am thinking that the EPS would feed one RCD with the creitical loads on it and the rest would be on a different RCD or RCBO.

Those connected to the EPS RCD would carry on when the grid went without a changeover switch in grid failure and those on the rest of the board would have no power.

When the grid is live the circuits behind the EPS RCD are powered by grid power as are the other items in the board.

That's my understanding - but I don't have an EPS (yet) installed. There is a few seconds delay from when the grid goes and the EPS output loses power and then it restarts, providing power from the battery only. On an AC inverter this will NOT include solar. On a hybrid I think it does.

A manual change over switch is not needed if the circuits in question are always only on the EPS side of the inverter - i.e not grid side ever. By being on the inverter side (i.e not directly grid connected) they are limited to max 3kw, irrespective of whether the grid is supplying the power or the batteries. That's my understanding.

GrahamRead

Thanks Graham,

I'd be interested to find out if that means when the grid is working just fine they can only cope with 2.6kW of power draw, as that would knacker my plan 🙁

If it's only 2.6 when on batteries only, but normal grid draw when grid is live, life would be happier.

Anoyingly the fridge and kettle being on the same circuit won't help me.
If it's as you suggest then that's a no go for automatic failover for the fridge freezer and a few essentials on such a small total load.

The changeover switch is also useful should there be a fault with the inverter. You can power from the mains until the inverter is fixed. Hopefully rare, but you never know!

I’m sure it is indeed useful as you say it gives you options to bypass a faulty inverter etc.

I wish they’d hurry up and release the v2 inverters though as if the power was at 3.5 or more I’d go GivEnergy.

Annoyingly I also realised that whilst the inverter output from battery alone is only 2.6kW, then using a kettle with anything else going will result in a draw from the grid.

That’s sub-optimal in winter though when you would charge a battery up off peak and try to use it to power the house all day.

kram Hi, we've got two of the current model 5kW Hybrid inverters and we had our consumer unit replaced literally a month before the system was installed. Had I known then what I know now, I'd have asked for lighting and the boiler power circuits to be put into a separate board. But I didn't know about EPS and I didn't take the opportunity to do that. What we did do was to ask the installer to put a 13A outlet where I can plug in our broadband/phone router and a supply for the boiler. In the event of a power cut, we'd still have the phone/broadband and the heating on. We would still have to use torches during the evening (as we always have in the past), but at least we'd be warm and the VOIP landline would work. For a few hours, it wouldn't be an issue but when the power disruption is prolonged, as happened a few months ago in the North East, I'd be wanting to minimise my battery drain to extend the services as long as possible. Only one of our inverters has a 13A socket on the EPS outlet but if the power cut was prolonged, it'd give me time to get the other system sorted out too. As regards the kettle, we have a gas hob and our stove kettle takes about 6 minutes to boil; much slower than a 3kW electric. However, when we had a caravan, we had a low power kettle to keep our use below the 10A that was available on hook up at some sites. I guess for me, EPS is Emergency Power System, and I'm happy to compromise on a number of things during a power cut for the convenience of keeping available those things that I consider essential. A bit of lighting on EPS would be good too.

If only battery power could be fed into the PV side which has more spare capacity on the Hy5 😀

hoggy

Do you know something I don’t?

Out of interest my plan if I went GivEnergy would be to have one RCD on the EPS and the other plus rcbo just on mains.

Juggle the circuits so the lights, kitchen plugs (fridge and freezer are all on main circuit) and boiler plugs are all on the EPS then the rest can stay off.

kram sorry wasnt trying to be cryptic, just that as with most hybrid inverters its a shame so much spare DC capabilty is left on the table when on battery alone.

For further reading, it is "technically" possible to use a seperate DC/DC converter & a battery on one of the PV strings to essentially either top up (during the day) or flatout "fake" PV at night to get more out of inverters on battery alone.

hoggy
Ahh ok, I thought I’d missed something obvious 👍

Faking input and the getting a way to charge too is a headache I can’t be bothered with, particularly when plenty of other manufacturers offer solutions off the shelf.

THALL

I just wondered why you said if you can afford a Powerwall to go that route?

Any thought would be appreciated as it’s a straight GE vs Powerwall now.

kram exactly

kram Well, basically its just better. Whole home backup power by default without any extra setup and no need to ask the installer it is just done. Higher default capacity both storage and output etc. Access to special tariffs. Their whole system is polished rather than a work in progress like GE. I went GE for costs and liked the fact the system is still being developed and it integrated with Octopus. BUT if i had the funds I must say I would of went Powerwall. Oh 1 of my personal bug bares is how fast the GE system responds to load going up and down. You might of seen posts on here of people saying how much grid they draw even though their battery is charged. The Powerwall responds much much faster.

In another example, I am buying a Vauxhall Mokka E as my EV, but if I had 15 - 20k more I would get a Tesla Model 3. Simply its just better. Sorry GE if you read this, your system is still in development though :-)

To be honest the difference isn’t small but it’s not huge either. EV wise I’ll probably look lower down than a Tesla, but it does look polished.
Shame as I like the API.

My biggest gripe right now is everyone installing knows there are new inverters and batteries, but there’s nothing from GE at all.

Just to finish this thread we are going for rec panels and a Tesla Powerwall.

Partly due to the Tesla functionality, the tariff and the fact it is physically in stock. The drivers against GE were the long battery lead times and low battery output power, with no lead time on the g2 inverters.

I’ll stick around as another family member is looking at solar and the GE would work there.

Wish me luck 😂😂