Having enphase micro inverter system installed, how to AC couple diy battery pack?

Hi all,

Bit stuck here, I've got quotes for solar installations (around 3kw) and am quite sold on an enphase system +LG 320w panels,but this will mean AC power coming off the roof, what kind of inverter/charger supportsthis scenario?

I keep hearing sunnyboy storage but I'd like to build a DIY powerwall just not sure how is hook it up. I'm assuming an AC poweredcharger, but with grid and solar AC coming in I'm not sure what Central device I'd need to manage all that and drive the AC circuitsin my home.


Very keen on grid disconnection in case of a black out too!

Thanks for any pointers!

PeterNemere said:

Hi all,

Bit stuck here, I've got quotes for solar installations (around 3kw) and am quite sold on an enphase system +LG 320w panels,but this will mean AC power coming off the roof, what kind of inverter/charger supportsthis scenario?

I keep hearing sunnyboy storage but I'd like to build a DIY powerwall just not sure how is hook it up. I'm assuming an AC poweredcharger, but with grid and solar AC coming in I'm not sure what Central device I'd need to manage all that and drive the AC circuitsin my home.


Very keen on grid disconnection in case of a black out too!

Thanks for any pointers!

Click to expand...

I have been searching for months for a hybrid inverter that will allow legal grid tie in the US, and the only opitions are SMA sunny island and outback GFX. outback radian series.
Sunny island supports lithium ion charging, I believe the GFX is user-configurable as well.
Magnum energy has some AC coupled systems as well.


"Very keen on grid disconnection in case of a black out too!"

Im not sure what you mean here, as any installation will have to have to UL1741 compliance aka automatic grid disconnect.

What I have found in my search is that AC and DC coupled systems are very expensive because they require more equipment, disconnect switches, two inverters, etc.

I was really impressed with the MPP solar hybrid inverters, which seem to do everything I want with just one inverter....but unfortunately they are not UL listed so grid tie in the US would not meet approval.

Hi Peter,

I have a grid tied system identical (different mfg.) to yours. I went with a Home Depot/Intermatic 240vac timer/relay to "disconnect" my battery box and critical load panel from the grid/house AC for a certain time period each day.

Paul

PeterNemere said:

Hi all,

Bit stuck here, I've got quotes for solar installations (around 3kw) and am quite sold on an enphase system +LG 320w panels,but this will mean AC power coming off the roof, what kind of inverter/charger supportsthis scenario?

I keep hearing sunnyboy storage but I'd like to build a DIY powerwall just not sure how is hook it up. I'm assuming an AC poweredcharger, but with grid and solar AC coming in I'm not sure what Central device I'd need to manage all that and drive the AC circuitsin my home.


Very keen on grid disconnection in case of a black out too!

Thanks for any pointers!

Click to expand...

This doesn't make sense .... the enphase micro inverters on the panels convert DC to AC which can only go to the grid (if the grid is down you cannot use this power) . but you want a powerwall so you haveto turn the AC back into DC , store , presumably to give you power if the grid goes down ...

Enphase site is very deceptive , they talk about an "AC battery" ... A powerwallwith electronics inside ... My opinion of Enphase is that it's for people with plenty of money that don't understand the science ..... those people will by emphases "AC battery" ... with a vague idea aboutselling power to the grid ...after 10 years of operation they will know it was a fake dream , and they've lost a lot of money.

Can I suggest you define very clearly what you want to achieve . Is the grid unreliable ?

ozz93666 said:

This doesn't make sense .... the enphase micro inverters on the panels convert DC to AC which can only go to the grid (if the grid is down you cannot use this power) . but you want a powerwall so you haveto turn the AC back into DC , store , presumably to give you power if the grid goes down ...

Enphase site is very deceptive , they talk about an "AC battery" ... A powerwallwith electronics inside ... My opinion of Enphase is that it's for people with plenty of money that don't understand the science ..... those people will by emphases "AC battery" ... with a vague idea aboutselling power to the grid ...after 10 years of operation they will know it was a fake dream , and they've lost a lot of money.

Can I suggest you define very clearly what you want to achieve . Is the grid unreliable ?

Click to expand...

He wants to do an AC coupled system.

Its possible with micro inverters. The main benefit of the microinverters is the minimizing of losses due to shading that you would have with series strings.

APD said:

He wants to do an AC coupled system.

Its possible with micro inverters. The main benefit of the microinverters is the minimizing of losses due to shading that you would have with series strings.

Click to expand...

OK... so that's enphase grid tie inverters selling power to the grid ....Does he expect to make a profit on this ???? If so I can guarantee he will lose $1000's ....( if anyone doubts this hopefully Peter can give us the amount enphase has quoted and we can go through the numbers)

And if the plan is an "ac coupled system " why the need for a powerwall ????

Many people get drawn into solar out of a feel good factor ... no clearly defined goals .... easy prey for companies like enphase.

ozz93666 said:

And if the plan is an "ac coupled system " why the need for a powerwall ????

Click to expand...

Do you understand AC vs. DC coupling systems?

He wants grid tie with battery back up, so he can have power when the grid is down.

It is the "best-of-both worlds" configuration: Produce power to offset your bill and remain connected to grid, but still use your PV when the grid is down which you cant do with standard grid-tie.

APD said:

ozz93666 said:

And if the plan is an "ac coupled system " why the need for a powerwall ????

Click to expand...

Do you understand AC vs. DC coupling systems?

He wants grid tie with battery back up, so he can have power when the grid is down.

It is the "best-of-both worlds" configuration: Produce power to offset your bill and remain connected to grid, but still use your PV when the grid is down which you cant do with standard grid-tie.

Click to expand...

I wasn't familiar with the term "AC coupling" ...a search shows it just means battery backup with normal inverters ... so in addition to the enphase micro grid tie inverters you need a big normal inverter.
The worst of both worlds ... lot's more expensiveelectronic equipment that can fail ... if you do the figures the payback from the power company will never cover the cost... that's why I asked if the grid was reliable ... If the grid is constantly failing , well ok ... or if you like the idea of being free of the grid , just how much are you willing to pay ??

It can also fill in gaps from the battery bank when not having enough sun. Ie not for grid going down but for using battery when needed.

Regarding shading you can also go the route with power optimizer. They feed out DC instead and then you hook that up to a "normal" battery setup. Though once again im not that familiar what exist for the US market and it may be the wrong answer If so ignore my answer.

daromer said:

It can also fill in gaps from the battery bank when not having enough sun. Ie not for grid going down but for using battery when needed.

Regarding shading you can also go the route with power optimizer. They feed out DC instead and then you hook that up to a "normal" battery setup. Though once again im not that familiar what exist for the US market and it may be the wrong answer If so ignore my answer.

Click to expand...

I remember you posting you run at very high voltage ...ie many (all?) panels in series ....doesn't this give you less than optimum power? if some panels are facing at a different angle you won't extract max possible power, or if you haveone small leaf , or patch of dirt on one panel it will drastically reduce overall output.

APD said:

ozz93666 said:

This doesn't make sense .... the enphase micro inverters on the panels convert DC to AC which can only go to the grid (if the grid is down you cannot use this power) . but you want a powerwall so you haveto turn the AC back into DC , store , presumably to give you power if the grid goes down ...

Enphase site is very deceptive , they talk about an "AC battery" ... A powerwallwith electronics inside ... My opinion of Enphase is that it's for people with plenty of money that don't understand the science ..... those people will by emphases "AC battery" ... with a vague idea aboutselling power to the grid ...after 10 years of operation they will know it was a fake dream , and they've lost a lot of money.

Can I suggest you define very clearly what you want to achieve . Is the grid unreliable ?

Click to expand...

He wants to do an AC coupled system.

Its possible with micro inverters. The main benefit of the microinverters is the minimizing of losses due to shading that you would have with series strings.

Click to expand...

Thanks for all the replies!

So I aim to build a powerwall myself (have 1.2kwh of cells so far) but want to connect it to this house while I live here. In a few years I plan to move away and rent it out, then I'd like to take the powerwall with me, because this is a DIY tinker thing, I wouldn't expect a renter to watch their power usage and keep an eye on the battery (even though I'd automate it with software, you still are conscious of these things if you DIY!).

I was sold on the AC microinverter idea for panels because I'm not sure of the future needs here. I can only fit 3kw on the roof but have a garage I can put more panels on later so with micro inverters you can just grab any panel, connect it to a microinverter and plug it into your system.

With a string inverter I'd need to buy say a 5kw, plug my 3kw of panels in, and in future if I buy different kinds of panels for the garage it will (from what I read) no longer be optimal as they aren't matched (new panels may be less wattage, or by then the older panels may not perform the same) and due to them being in series you end up limited by the weakest panel.

I actually was interested in the enphase "AC" battery, except I feel it's quite expensive. I don't know why oz93666 is against it, I think it's a great setup because it apparently uses the same enphase microinverter inside that you have on the panels. In future this might be a really good way to tinker with these things - if we could create a BMS and battery, but it's all plugged into a microinverter, the rest of your system may not even need to know it's got a battery in there, it might just be surprised to be receiving solar power at night!!

The one thing I can't get my head around is if you have AC coming in at 50hz, and you have 10 microinverters on your roof all making AC, clearly they'd somehow have to detect the existing AC and produce the same waveform... and you'd also need your battery inverter to do this too.

Until now it seemed you'd just plug all of this into a single big inverter box that takes care of any of these issues internally, but I'm not sure what I need to do what I described above (battery+bms+some kind of DC->AC inverter that can sit in my solar setup along with the microinverters). Which could then easily be detached from the system (remove a single 240V AC component) and it continues running as a grid-connected solar system.

Might need some diagrams to make what I'm saying clearer?

ozz93666 said:

I remember you posting you run at very high voltage ...ie many (all?) panels in series ....doesn't this give you less than optimum power? if some panels are facing at a different angle you won't extract max possible power, or if you haveone small leaf , or patch of dirt on one panel it will drastically reduce overall output.

Click to expand...

Yes i run large strings. My main inverter have 2 MPPT charge controllers and therefore i run 2 strings. 1 string at 21 degree angle to South and the other at 15 degree to west. My system is a HIGH VDC system. This is alot more efficient when it comes to grid tie systems than running it at 48v.
With that said. Yes, shadowing is an issue... But not for me If you have looked at my images you will see that my roof is totally free from chimneys. I do not have a single tree around to shade nor do I have issues with leafs The only shadowing is from the clouds itself but that is negligible in the whole context.

Micro inverters and power optimizers is something you should use either if you want to build some at the time or you have heavy issues with shadows due to objects around you. Micro inverters makes it easy since its just a matter of hooking up to the grid. Easy to expand and if 1 fail its easy to fix since not all go down. BUT its more expensive!

Power optimizers is something you stick in between your inverter and your panels and helps you with shadowing problems but still enables you to run some kind of inverter that then takes care of the battery/off/on grid power.

Yes you can stick such devices to micro inverters as well today but as always the more conversions and devices you have the more expensive. (My current though of it...)

Im about to do some installs later this spring and then i hope to get the knowledge needed to actually help you guys out when it comes to above. Right now i have no clue on what exist or how to hook it up im afraid

PeterNemere said:

I was sold on the AC microinverter idea for panels because I'm not sure of the future needs here. I can only fit 3kw on the roof but have a garage I can put more panels on later so with micro inverters you can just grab any panel, connect it to a microinverter and plug it into your system.

With a string inverter I'd need to buy say a 5kw, plug my 3kw of panels in, and in future if I buy different kinds of panels for the garage it will (from what I read) no longer be optimal as they aren't matched (new panels may be less wattage, or by then the older panels may not perform the same) and due to them being in series you end up limited by the weakest panel.

I actually was interested in the enphase "AC" battery, except I feel it's quite expensive. I don't know why oz93666 is against it, I think it's a great setup because it apparently uses the same

Click to expand...

I have no problem with the design of the enphase system ... it's that I think most people who buy it don't give close attention to the economics ....you say you are thinking of first getting a 3KW system from them ... this ( I understand) is designed solely to sell electricity to the grid ... it won't do this in powercuts and you can't use the power in power outages ...

A 3kw system will produce on average (depending on location)2,550kWHr per year ..if you can sell this for 10c/KWHr that's $250/year ..

It's an economic consideration does a return of$250/year warrant the initial cost .... the cost of any government inspectors .... and cleaning the panels regularly .....

As for matching panels this shouldn't be a problem put the panels in parallel...many advantages in a low voltage system that's what I run...

If you are into making powerwalls this changes the parameters greatly .... my suggestion would be forget selling power to the grid , aim to be off grid , no expensive grid tie inverters , just feed the DC into powerwall and use a large standard inverter.

p.s....I'd be very interested to know the figure you were quoted for the 3kw grid tied system.... and if the grid guarantees to buy your power , and at what price.

Its not just about selling. Its about how much you actually save using the power too. In most places you only get a fraction for selling compare to what you save in using it directly. And hence the powerwalls

Hey all,

Sorry I missed a few posts when I wrote the last reply, just saw people asking about my quote.

So it's 10 320W LG Neon2 panels, Enphase 270w microinverters, Envoy-S controller for the whole thing for $6100 (after the STC rebate thing). The most I can get is 11c/kwh if I sell to the grid but that's not why I'm doing it. Our 2 bedroom townhouse averages 9kwh/day so 3kw solar during the day would more than cover our usage, at night we'd be using the grid. I just can't mentally deal with turning on light switches and knowing it's run by a coal plant any more so I want to be as close to off-grid as possible.

Enphase make their "AC Battery" which is a 1.2kwh LiFePO4 I believe, with a ~300w charge/discharge rate. If I install 2 (so can output ~600w) it will cover my fridge (180w when on) and all other night-time lighting/fans/phone chargers. I'd want to heat hot water during the day (when solar is available).

My only issue is that 1 AC Battery installed is $2000. In total I'm looking at $10,100 and I would very rarely draw from the grid, while excess solar would go back in maybe slightly lowering my $1/day grid connection fee.

Now you'd probably say this is insanely expensive, but look at the options - Tesla Powerwall 2 is $10k installed, but needs a solaredge storedge for $5k and I still need panels and other hardware - comes to $18k. I'd be paying 1/2 that and still cover my needs.

The only thing that really bugs me is this won't work when the grid is down. There are off-grid installed Enphase setups where the "grid" is an LG Chem storage battery, so when the Enphase AC battery depleats the system draws from the LG, but I'm not made of money! If I were I'd just get the Tesla Powerwall 2.

I'm looking for a way to build my own battery and still connect it to a modern AC solar setup for minimal cost.

To lower my costs I'm now looking at second hand 3kw solar setups (plenty on Gumtree for around $700 just panels). Perhaps I can pair second hand panels with a cheap inverter and spend more on the battery inverter?!

I've read about the Pip 4048 or whatever, it seems commonly used by people on this forum, but there are a LOT of bad reviews out there saying it's not reliable, etc so I'm a bit put off by that.

Anyway, that's my brain dump for tonight. Please if you have any suggestions or have gone through similar thinking share your thoughts! Thanks!

Thanks for that info Pete ... interesting ... It should be remembered 9kwHrs /day is only the average output from 3KW of panels , on cloudy days maybe only 2KWHrs and there maybe a few of these days one after the other. Since you are a DIY er have you thought about doing the solar thing yourself ??? It's a lot easier than many think . It should be possible to buy 3KW of new panels for $1,500 ,build your own big powerwall , and a standard inverter (forget grid tie) .. I wouldn't rush things , you say you plan to move , maybe wait a while ... second hand panels are a very good idea , when you have the space it makes sense to buy lots of these.

I feel I must say a few words about your main motivation "I just can't mentally deal with turning on light switches and knowing it's run by a coal plant any more " ...We're talking anthropogenic global warming ...evil fossil fuels ... carbon emissions ...this is something I've been studying very closely for over two decades ,and can say without any doubt it's a lie , a con trick , pushed by conspiring bankers and politicians ... the biosphere is desperately short of CO2 ...some commercial greenhouses pipe in CO2 to increase their yields ... The main pushers of the global warming lie , like AL Gore have already become Billionaires through "carbon trading" ...it's a very long story , and here is not really the right place to cover it ... Search "lord monckton" for the truth on this matter.

ozz93666 said:

I feel I must say a few words about your main motivation "I just can't mentally deal with turning on light switches and knowing it's run by a coal plant any more " ...We're talking anthropogenic global warming ...evil fossil fuels ... carbon emissions ...this is something I've been studying very closely for over two decades ,and can say without any doubt it's a lie , a con trick , pushed by conspiring bankers and politicians ... the biosphere is desperately short of CO2 ...some commercial greenhouses pipe in CO2 to increase their yields ... The main pushers of the global warming lie , like AL Gore have already become Billionaires through "carbon trading" ...it's a very long story , and here is not really the right place to cover it ... Search "lord monckton" for the truth on this matter.

Click to expand...

Ok, its all clear now.

ozz93666 said:

Thanks for that info Pete ... interesting ... It should be remembered 9kwHrs /day is only the average output from 3KW of panels , on cloudy days maybe only 2KWHrs and there maybe a few of these days one after the other. Since you are a DIY er have you thought about doing the solar thing yourself ??? It's a lot easier than many think . It should be possible to buy 3KW of new panels for $1,500 ,build your own big powerwall , and a standard inverter (forget grid tie) .. I wouldn't rush things , you say you plan to move , maybe wait a while ... second hand panels are a very good idea , when you have the space it makes sense to buy lots of these.

I feel I must say a few words about your main motivation "I just can't mentally deal with turning on light switches and knowing it's run by a coal plant any more " ...We're talking anthropogenic global warming ...evil fossil fuels ... carbon emissions ...this is something I've been studying very closely for over two decades ,and can say without any doubt it's a lie , a con trick , pushed by conspiring bankers and politicians ... the biosphere is desperately short of CO2 ...some commercial greenhouses pipe in CO2 to increase their yields ... The main pushers of the global warming lie , like AL Gore have already become Billionaires through "carbon trading" ...it's a very long story , and here is not really the right place to cover it ... Search "lord monckton" for the truth on this matter.

Click to expand...

Dude what capacity have you been studying this in? I'm shocked. I can't understand how anyone on earth can think climate change is a conspiracy. Who will benefit? Huge fossil fuel corporations have their vested interestsin governments, corruption everywhere... Who will profit from the world switching to solar? Evil big solar? Al Gore?

This is the most mind blowingly stupidargument... so we shouldfight for the poor oligarcs running their loss making charity providing us with fuel?

You've got the whole thing backwards.

Firstly, fossil fuels are a stupid solution. You realise how much effort and energy is wasted trucking and shipping materials around the world as fuel?

Secondly of course burning all that has an effect, if you run your car in a garage you die. How many cars and power plants are running around the world 24/7? The problem is sitting at home we can't even comprehend how much fuel is burning all the time. The World is a big garage but we've been enthusiastically burning fuel for about 150 years

How do you explain that CO2 levels at Mauna Loa are above 400ppm permanently now and riding? Is Al Gore there with his evil conspirators making a case against fossil fuel by burning something near the sensor? He'd have to do that at a heck of a lot of sensors globally...

If you told someone in 1880 that will pump sludge from the ground all over the place, ship it to refineries then spend fuel sendingit all over the world so every citizen can fill their tank, and burn coal away from people do they don't notice how polluting it is...

You'd be laughed out of town.

And yet we built this insane system.

Now we have the solution to this and the pollution problem and I feel it's my mission and duty to get off coal a stick my finger up at every petrol station once I get an ev.

Over the years I've seen several forums I really enjoyed destroyed by political wrangling.

What we have here is a technical challenge; produce, store and efficiently utilize as much of our own energy as we reasonably can, the politics of it all are or at least can be divisive, the technical challenge unites us. Politics are largely bulshytt anyway so they shouldn't enter into this discussion.

These days practically everything reminds me of a song, the soundtrack of my life.

I love it that they aren't wearing helmets...

PeterNemere said:

I can't understand how anyone on earth can think climate change is a conspiracy. Who will benefit? Huge fossil fuel corporations have their vested interestsin governments, corruption everywhere... Who will profit from the world switching to solar? Evil big solar? Al Gore?

Click to expand...

This is not about us switching usto solar, governments and corporations are doing their best to hold back solar (despite what they say)... it's about keeping us mostly on fossil fuels , but bringing in a global tax on any carbon emissions ...surcharges on plane flights etc.

There is a massive global conspiracy headed by powerful families (rothschilds , royalty) they control the politicians and media , hire 'climate scientists ' who soon realise keepingtheir jobs depends on global warming being real ... they fix the numbers...they've been caught fixing the numbers ... all AL Gores predictions of doom from 15 years ago have failed to materialise .... but this scam goes back further than that .

In the 1970's these same people were pushing 'global cooling' and blaming fossil fuels for that! http://www.populartechnology.net/2013/02/the-1970s-global-cooling-alarmism.html ... then as time went on figures showed the planet was warming very slightly so the switch was made to global warming ...still fossil fuels were to blame .... now latest figures show a slight cooling , so now it's"climate change" ....they tell usany change in the climate is due to carbon emissions and we must be taxed....

True climate scientist , not reliant on a pay check from the government say these slight variations in temperature are due to the sun.

The massive coal, oil(and chalk/limestone) deposits contain carbon that was once circulating as CO2 in theatmosphere thisis now buried and locked up out of use , hence the biosphere is operating at low efficiency...responsible custodians of the planet have a dutyto put this back in circulation ...The controllers know this but they are literally satanists who seek to destroy life.