AC coupled battery charger inverter

[JohnMo]

Looking to possibly add a battery but looking at charger inverters.

 

Looking for recommendations for an AC coupled in Inverter charger, FYI the battery will be in the 5-9kW range.

 

Must haves

1.  AC coupled, not directly connected to existing PV.

2.  Must work with existing PV inverters (X2) one Growatt, the other Solis. Not interested in getting hybrid inverters.

3.  Must work in a power cut (have had two power cuts this week, one for 4 hours the other for 2 hours)

4. A nice to have would be in a power cut, the existing PV inverters think there's still mains and keep producing.

[SteamyTea]

2 minutes ago, JohnMo said:

5-9kW

cough

[JohnMo]

1 hour ago, SteamyTea said:

cough

5-9kWh

[SteamyTea]

2 hours ago, JohnMo said:

Must work in a power cut (have had two power cuts this week, one for 4 hours the other for 2 hours)

That does beg the question as to how much power do you want this, basically off grid system, to be able to deliver.

 

2 hours ago, JohnMo said:

A nice to have would be in a power cut, the existing PV inverters think there's still mains and keep producing.

Think you would need some sort of safely cut off to totally isolate the house when there is a power cut, and I think that regular inverters use the grid impedance for that, not the voltage and frequency, they are second line of defence.

[JohnMo]

1 hour ago, SteamyTea said:

That does beg the question as to how much power do you want this, basically off grid system, to be able to deliver.

Just fill in the background loads really, so I don't have to rush and put the generator on. So basically keep the ventilation, sewage treatment tank and borehole pump live.  So couple of kW should be fine.

 

1 hour ago, SteamyTea said:

Think you would need some sort of safely cut off to totally isolate the house when there is a power cut, and I think that regular inverters use the grid impedance for that, not the voltage and frequency, they are second line of defence.

Did think it would be a nice thing to have, but probably not practical.

 

I do have generator change over switch, so when generator is on the mains is isolated.

[SteamyTea]

57 minutes ago, JohnMo said:

I do have generator change over switch, so when generator is on the mains is isolated.

I think you can get automatic versions of those, @Nickfromwales fitted one if I remember rightly.

[Nickfromwales]

8 hours ago, SteamyTea said:

I think you can get automatic versions of those, @Nickfromwales fitted one if I remember rightly.

Indeed. Do you think I can remember who / when / where....? Not a bloody chance! I know who to ask though, if anyone's looking for info?

[JohnMo]

I'm not really looking for an auto switch, as already have a manual switch, and the generator has to also be started manually anyway.

 

More interested in finding a recommendation for an AC coupled inverter charger and/or battery.

[Nickfromwales]

7 minutes ago, JohnMo said:

More interested in finding a recommendation for an AC coupled inverter charger and/or battery.

 

13 hours ago, JohnMo said:

Not interested in getting hybrid inverters.

We often get to loggerheads, so let me add one more to the list lol.

WHY? This is such an obvious thing to do, and would be the most sensible 'jump' IMHO. Sell the others on and swap over to a hybrid. The added losses of all of your (then) equipment will be 'undesirable', but the (a) hybrid would work perfectly for you. It even has (could have) an input for the generator directly. Utterly seamless with zero time 'off grid / in blackout'.

Please reconsider this, as it has huge benefits for your exact situation!! 

[Dan F]

 

13 hours ago, JohnMo said:

Must haves

1.  AC coupled, not directly connected to existing PV.

2.  Must work with existing PV inverters (X2) one Growatt, the other Solis. Not interested in getting hybrid inverters.

3.  Must work in a power cut (have had two power cuts this week, one for 4 hours the other for 2 hours)

4. A nice to have would be in a power cut, the existing PV inverters think there's still mains and keep producing.

Do you need AC-coupled PV to continue to run in a power cut? 

 

[kommando]

Use a std AC to DC battery charger to put the juice into the batteries, then an off grid DC to AC inverter to take the power out of batteries. The charger can be on the DNO side as its incapable of feeding AC into the grid but the off grid inverter can only be used when the mains is isolated. The quality of the AC from the off grid inverter needs to be good enough for the Solis/Growatt to think they are grid connected and so you can still utilise the PV output during a power cut.

 

Choice of off grid inverter will depend on the type of battery chemistry and voltage plus confirmation grid tie inverters will be fooled.

[JohnMo]

On 20/07/2023 at 22:21, Nickfromwales said:

 

We often get to loggerheads, so let me add one more to the list lol.

WHY? This is such an obvious thing to do, and would be the most sensible 'jump' IMHO. Sell the others on and swap over to a hybrid. The added losses of all of your (then) equipment will be 'undesirable', but the (a) hybrid would work perfectly for you. It even has (could have) an input for the generator directly. Utterly seamless with zero time 'off grid / in blackout'.

Please reconsider this, as it has huge benefits for your exact situation!! 

Reason I thought to go AC coupled was I have 2 PV inverters at remote locations from each other. One is routed to a consumer unit in an outbuilding the other in the house attached to the main CU.

 

If I put a hybrid inverter on the outbuilding it would be good location for the battery, but I would need something like a wireless CT clamp - not seen anything that solves that issue - anyone any ideas.

 

The other solution is leave the outbuilding as it is and replace the inverter in the house with hybrid and locate the batteries there, CT clamp will be an easy route.

 

So if I go hybrid any suggestions on make or models? 3.7kW would be right for the solar array.

[kommando]

Wireless CT is not available but if the Inverter is setup to connect to a RS485 Meter then I use HyFlying EW11's to transmit the RS485 signals via wifi. You will need one on each end, I use them with my SMA Sunny Boys both for monitoring and for setting of parameter's, just the occasional reset required but latest firmware seems to have sorted that issue.

 

I have a Sunny Island on route but before buying it I had this Hybrid Inverter on the radar. G99 cert in place. Next step was to see what the reviews were like but did not get that far. UK designed but made in China, also known as Deye in US.

 

https://www.bimblesolar.com/ongrid/hybrid-inverters/Sunsynk3.6kW-ECCO?sort=p.price&order=ASC 

[sharpener]

On 20/07/2023 at 08:52, JohnMo said:

Must haves

1.  AC coupled, not directly connected to existing PV.

2.  Must work with existing PV inverters (X2) one Growatt, the other Solis. Not interested in getting hybrid inverters.

3.  Must work in a power cut (have had two power cuts this week, one for 4 hours the other for 2 hours)

4. A nice to have would be in a power cut, the existing PV inverters think there's still mains and keep producing.

 

Victron is the go-to brand, it will do all the above using its ESS software with fully automatic changeover, no external switches or relays required. Can connect an equal amount of PV to the o/p and they will keep going in a blackout. What size are the two you have got?

 

I have had the MultiPlus II GX 5kVA for 18 months now, DIY install, is large enough to supply the whole house, works a treat with 10kWh of Pylontechs. I have 3.68kW of AC PV and another 3.24 of DC connected via an MPPT converter.

 

Good support and excellent user forum here.

[JohnMo]

4 minutes ago, sharpener said:

What size are the two you have got?

Just over 3.4 and 3.1kW, one south eastern and the other south western directions.

 

6 minutes ago, sharpener said:

PV to the o/p

What's the o/p?

[sharpener]

28 minutes ago, JohnMo said:

Just over 3.4 and 3.1kW, one south eastern and the other south western directions.

 

What's the o/p?

 

Output. You could connect the 3.4 to the output and that would keep going and the 3.1 to the input and it wouldn't.

If you had the 8kVA unit then both could be kept going. Or sell the 3.1 and use an MPPT like my setup. Depends rather on the value you place on riding through blackouts, and whether you need more than 5kVA (4 kW continuous) to power your loads.

 

If you want to integrate yr generator then the Quattro range have a Grid input plus a Generator input, they can be configured in all sorts of ways e.g. autostart the generator according to state of charge etc. But more expensive.

 

5-9kWh of battery strikes me as small, I put in 7.1 to begin with but upped it to 10.65 as it wasn't enough to keep everything going until the E7 cheap period. Also I needed more capacity to use all the current available from the second PV array. 2 hrs endurance in a blackout is a good rule of thumb for min size.

 

On 24/07/2023 at 18:59, JohnMo said:

but I would need something like a wireless CT clamp - not seen anything that solves that issue - anyone any ideas.

 

Various solutions to this on the Victron forum.

 

 

Edited July 26, 2023 by sharpener

[JohnMo]

Decision made

1 x 5.5kW hybrid inverter on the house array (3.1kW) with 10kWh of batteries. Have chosen Sunsynk for the inverter and batteries.  The Sunsynk inverter will push any excess PV to the batteries if they are full excess will be pushed to the immersion.

 

Pretty much out the box solution.

 

The other PV array will remain as is. Little efficiency loss, but... To much digging and running cables to do anything else, that is cost effective.

 

I have installer lined up to install begining of September.

 

Octopus are having to install a new smart meter, so no smart tariffs until that is fixed.

 

 

[sharpener]

Out of interest does the Sunsynk provide the full 5.5kW to the house in a blackout or have you had to compromise with only a few circuits on the EPS output?

 

On 04/08/2023 at 13:16, JohnMo said:

The other PV array will remain as is. Little efficiency loss, but... To much digging and running cables to do anything else, that is cost effective.

 

I think if you put the CT on the grid side of the tee to the outbuilding the Sunsynk will manage the installation as one.

 

Edited August 5, 2023 by sharpener

[JohnMo]

From what I can tell you wire so it will give the 5kW output in an outage or you can use dedicated EPS function, for a few circuits.

 

But have just sent an email asking the question 

[sharpener]

1 hour ago, JohnMo said:

From what I can tell you wire so it will give the 5kW output in an outage or you can use dedicated EPS function, for a few circuits.

 

But have just sent an email asking the question 

 

Looks like from this there are a lot of connection options inc genny but I can't say I have got my head round it all! Seems they will need to fit an external relay for earth-neutral bond in island mode, also you will need an earth electrode if you are not on TT supply already. Lots of info and several Sunsynk users on this forum https://camelot-forum.co.uk/phpBB3/viewforum.php?f=11.

[JohnMo]

Just spoke with the electrician and if I want the whole house in a power outage it would have to be via a manual change over switch. Which isn't really what I wanted.

 

So we are now going Givenergy all-in-one with gateway. The only limitation is inverter doesn't like generators, so once battery depleted and I start the generator the grid / generator change over switch will disconnect the battery/inverter as well as the grid.

 

He said I need an additional earth spike.

 

More money, but bigger battery, less faff.

[JohnMo]

Thanks @sharpener for questions prompting me to think about different things and ask the right questions.

[sharpener]

1 hour ago, JohnMo said:

Just spoke with the electrician and if I want the whole house in a power outage it would have to be via a manual change over switch. Which isn't really what I wanted.

 

If the whole house is behind the inverter it might be worth installing a switch like this anyway to allow bypass of the inverter for maintenance/in case of fault. Will go in an ordinary CU and much cheaper and neater than the free-standing ones often fitted. I have a second one for the garage as well, allows me to have the EV charger direct on the grid while I am using it. They are in the CU on the rhs of this pic

 

 

However I wish now I had made the house switch a changeover relay so it would fail over to the grid automatically, to keep the freezer, alarms and router  going if the inverter packs up while I am away.

 

GivEnergy gateway is a good solution as it gives much more freedom with equipment placement and IIRC has got a built-in bonding relay. So much to think about, will have to evolve further to accomodate the HP...

 

Edited August 6, 2023 by sharpener

[kommando]

You can't get away from needing a changeover switch.

 

I woke one morning to what seemed like a powercut, what was odd was the LED bulbs would put out a dim glow but nothing else worked. DNO helpline reported no faults in our postcode area so rang to get a person online. The DNO guys came quickly and replaced the 100A fuse but that made no difference, they then when to the overhead line and traced the fault to a link that was coming loose and incapable of carrying current but was in contact. So we were getting 240v but not amps to power anything other than the LED's.

 

So a G99 Inverter without being islanded in a powercut would be putting out 240V with the CT limiting the amps being output to near but not quite zero. A voltmeter used on the supplying line would show 240v with little if any amps which I am sure would be an issue to the repair crew.

 

[JohnMo]

Thanks for that will discuss with the electrician. He said he has installed the Givenergy all in one before and is a registered installer, but I am the first to ask for a gateway. So he is off to do the online training course.