2 Systems tying to one main panel: eg4 18k pv + IQ7+

[400bird]

The main use of a battery and inverter is to store excess solar power in the battery then discharge it into your home as you need it when the sun goes down.

If that was the case, why are nearly every battery inverter in this class designed with pass through relays, grid forming, etc?

Sure, energy arbitrage is a valid use case (one that I employ), but I don't think this is the most common set up.
That's a lot of work and expense to not have grid down back up power.

You can have both, I do.

 

[400bird]

The problem with tying the microinverters directly to the main panel (as opposed to the hybrid) is that the hybrid AIO won't have a direct path to regulating the microinverter's pv production in case of grid failure. Could possibly be done with frequency shifting...

This is exactly what frequency shift does.

The hybrid can regulate the arrays connected directly to it but not necessarily the microinverters...whether they are tied directly or indirectly via a panel upstream from the hybrid AIO. So I'm researching the Hoymiles microinverters which may have a method of having their pv production regulated by a downstream hybrid inverter.

Can you draw it out? Which way is down stream? When you say regulate, is this with grid connected or not?

Hoymiles interface with open source software which yields far more flexiblity but also less purpose-built or tested features.

They also don't have the long history and track record of Enphase, so longevity is still a question in my eyes.

Best case scenario... It's possible the AIO can regulate the microinverters if they are tied into the main panel

It can't. In the main panel frequency is set by the grid, no inverter is going to influence grid frequency. When disconnected from the grid, then the battery inverter sets the frequency for your home micro grid.

or into the AIO's Generator input...but I'm yet to have that confirmed or denied. It's not documented in the eg4 manual.

I could be wrong and I haven't read the manual cover to cover, which I'd suggest you do before purchasing an inverter, but this section sure does look like it is documented.

 

[zanydroid]

That sort of suggests (in two places) that it will let the microinverters go out to grid rather than try to charge on excess to achieve self consumption let alone cut it off.

Somewhat disappointing if true since lower end AC coupled storage inverters (including one from LuxPower) can charge from the microinverter.

 

[k490]

The main use case of batteries has varied significantly over time. If that was the main case, then all the early Tesla Powerwall owners were lighting cash on fire, since there were no utilities at the time where time shifting makes enough money to cover the cost. Rather, they're paying premium for pride of ownership and having backup power.

There are several tiers of retrofit AC couple systems. Some cannot keep AC coupled up when grid goes down.


Also provides an option for enforcing zero export in one place if the AC coupled hybrid cannot absorb it, by cutting the relay.

This is likely more simple when using multiple brands than trying to get two independent zero export systems to work together in a sane way.

Actual shading.

Could use optimizers for shading, but also some debate that the built in diodes do just as good of a job as an optimizer or microinverter with regard to shading. Obviously, RSD is required for rooftop systems. Have to consider that why spend 70% cost of an optimizer on an RSD device.

 

[400bird]

That sort of suggests (in two places) that it will let the microinverters go out to grid rather than try to charge on excess to achieve self consumption let alone cut it off.

Somewhat disappointing if true since lower end AC coupled storage inverters (including one from LuxPower) can charge from the microinverter.

Doesn't Luxpower make this inverter?
I won't disagree with the lower end inverter comment.
I expected the inverter to charge from AC coupled solar. I wasn't looking for that info, so I didn't see that hole in the instructions. In my reading I think it would charge from AC coupled solar when off grid. That's why there is an end SOC. Once the battery is charged to 100% there's no where else to put the energy from the AC coupled solar.

 

[zanydroid]

Could use optimizers for shading, but also some debate that the built in diodes do just as good of a job as an optimizer or microinverter with regard to shading. Obviously, RSD is required for rooftop systems have to consider that.

Trading microinverters for the the bad interoperability (if SolarEdge, maybe also the new SolArk ones) and lack of forum experience of optimizers is not my jam.

 

[zanydroid]

Doesn't Luxpower make this inverter?

Yup, makes it more disappointing if true, though if folks asked maybe they can port over some code.

The LuxPower AC coupled battery inverter does not have MPPT, it is targeted for retrofit only on an existing grid tie system, to add self consume and TOU optimizing. IIRC it can’t charge from/turn on the microinverters when off grid, so the opposite problem. So it’s more of emergency power for short outages.

I won't disagree with the lower end inverter comment.
I expected the inverter to charge from AC coupled solar. I wasn't looking for that info, so I didn't see that hole in the instructions. In my reading I think it would charge from AC coupled solar when off grid. That's why there is an end SOC. Once the battery is charged to 100% there's no where else to put the energy from the AC coupled solar.

It will charge from off grid by my reading. And the bunch of UI settings they screenshotted sort of double confirms it.

Take a look at the two paragraphs for on-grid though, it makes no such promises.

 

[zanydroid]

No statements about charging behavior and no UI showing ways to customize it.

 

[the.shining]

Can you draw it out? Which way is down stream? When you say regulate, is this with grid connected or not?

the hybrid is downstream from the microinterter because it receives the microinverters output as its input.

They also don't have the long history and track record of Enphase, so longevity is still a question in my eyes.

Yes, dependability is a big asset, but micorinverters I'm general appear to have less issues with failure rates because they are simpler machines which is one big reason to build with micros, any brand.

It can't. In the main panel frequency is set by the grid, no inverter is going to influence grid frequency. When disconnected from the grid, then the battery inverter sets the frequency for your home micro grid.

on grid: if batteries are full, no load is present, and micros are outputting pv, the eg4 needs to be able to shutoff micros. This can't be done by frequency shifting. BUT, there may be an alternative relay control mechanism. IF an alternative exists, then no other solutions need be entertained. Otherwise, Hoymile may be the answer.

Off grid: frequency shifting can certainly be implemented. No problem here for eg4.

I could be wrong and I haven't read the manual cover to cover, which I'd suggest you do before purchasing an inverter, but this section sure does look like it is documented.
View attachment 184937

This section dismisses Frequency Shifting as a regulating mechanism when ON GRID. It doesn't explicitly rule out other alternative relay control (regulating) mechanisms. It's likely safe to assume there is no alternative...thus Hoymiles are the defacto alternative

 

[zanydroid]

Yes, dependability is a big asset, but micorinverters I'm general appear to have less issues with failure rates because they are simpler machines which is one big reason to build with micros, any brand.

I am not sure they are simpler. They’re passively cooled in a more inclement environment. I would guess they are more complex than a grid tie string inverter.

This can't be done by frequency shifting. BUT, there may be an alternative relay control mechanism. IF an alternative exists, then no other solutions need be entertained. Otherwise, Hoymile may be the answer.

What I was looking for was some discussion about implementing zero export/self consume against the current output of the microinverters. This is certainly doable by turning on the charger and modulating it until the net power is zero.

 

[k490]

If that was the case, why are nearly every battery inverter in this class designed with pass through relays, grid forming, etc?

Sure, energy arbitrage is a valid use case (one that I employ), but I don't think this is the most common set up.
That's a lot of work and expense to not have grid down back up power.

You can have both, I do.

Yes, I agree it can pass through but you're not going to have 100% of your home's circuits on the critical load backup panel. If you move everything over to that sub panel might as well just go with an off-grid inverter which isn't exactly true, the off-grid inverter does have a grid input. The only difference with a hybrid is it can back-feed to that grid input where an off-grid inverter can't. I think I was kind of talking about a way which gives the homeowner the ability to permit a string of microinverters then later add a DIY inverter / Battery which you can expand.

 

[zanydroid]

Yes, I agree it can pass through but you're not going to have 100% of your home's circuits on the critical load backup panel.

This is exactly the setup that you pay a premium for on the SolArk 15k and EG4 18kpv. As long as you have all your home circuits on 200A or smaller service you can splice the inverter in between the 200A subpanel with all house loads and the meter/main combo. These have an internal 200A bypass / transfer relay.

The only difference with a hybrid is it can back-feed to that grid input where an off-grid inverter can't. I think I was kind of talking about a way which gives the homeowner the ability to permit a string of microinverters then later add a DIY inverter / Battery which you can expand.

Technically many POCO will also require the battery to be permitted if the storage inverter is to be paralleled with grid (IE any kind of grid assist mode). It’s stipulated in the interconnection rules for almost all California POCOs. Either you try to fly under the radar, set up an inverter that can carry full system load from battery and inverter, or pull off a few circuits into a CLP/the only circuits legally allowed to self consume.

 

[FilterGuy]

I really don't see a good reason to even use the microinverters if you want to permit entire system.

The main use case for Micro-inverters with the 18Kpv is when the customer has an existing grid-interactive solar system that they want to add batteries to. Rather than re-wire the array, you can just take the AC out from the existing system and feed it to the correct port on the 18Kpv.

Yes, dependability is a big asset, but micorinverters I'm general appear to have less issues with failure rates because they are simpler machines which is one big reason to build with micros, any brand.

Micro Inverters have a terrible reputation for having a High failure rate. (All of them, but particularly EnPhase).

1) They are sitting under the hot panel and heat is not good for electronics.
2) You have a lot of them, so even if the absolute failure rate is low, you have to multiply that failure rate by the number of them you have for the failure rate of one of them going out.

 

[zanydroid]

2) You have a lot of them, so even if the absolute failure rate is low, you have to multiply that failure rate by the number of them you have for the failure rate of one of them going out.

That just yields the expected number that will die. I wouldn’t say this is worse than a string inverter since it is still incremental where a string blows up all at once (albeit it also restores all at once… note that RSD for strings are connected in series and they themselves can degrade reliability) . Arguably progressively losing microinverters could be considered a cost of doing business just as panel level degradation is.

They are parallel wired so if they fail the rest will stay up, unless the failure also breaks the disconnect/isolator between the AC output and trunk and wrecks the whole branch.

 

[zanydroid]

The main use case for Micro-inverters with the 18Kpv is when the customer has an existing grid-interactive solar system that they want to add batteries to. Rather than re-wire the array, you can just take the AC out from the existing system and feed it to the correct port on the 18Kpv.

Do you know if 18kpv properly factors in the output of microinverters in on-grid self consumption mode? The manual suggests it does not, which is surprising because other Luxpower products can do it, and clearly says it in their manual.

 

[k490]

The main use case for Micro-inverters with the 18Kpv is when the customer has an existing grid-interactive solar system that they want to add batteries to. Rather than re-wire the array, you can just take the AC out from the existing system and feed it to the correct port on the 18Kpv.

Micro Inverters have a terrible reputation for having a High failure rate. (All of them, but particularly EnPhase).

1) They are sitting under the hot panel and heat is not good for electronics.
2) You have a lot of them, so even if the absolute failure rate is low, you have to multiply that failure rate by the number of them you have for the failure rate of one of them going out.

I have heard that EnPhase can be a problem trying to get it to AC couple to an inverter. Also have a limit how much PV power you can AC-couple. Why I was saying just leave it tied into the main panel and setup an inverter battery back feed the same main panel. Obviously would need to make sure the busbar can a handle the amount of current. I understand would lose that string if power went out could also connect more panels to the 3 MPPT inputs of an 18PKV.

 

[the.shining]

Enphase provides 25 warranty on their microinverters. Eg4 provides 10 yr warranty. Whether these warranties can be depended on is anyone's guess, but all else being equal, enphase microinverters appear to be the cheaper and longer life inverter at the present time.

And it sounds like the original system I proposed with the microinverters feeding into the main panel (instead of the eg4) could be feasible for ON grid AND OFF grid (using some relay system in additon to eg4). However, the relay system specifics have not been specified as of this time, that I've seen. Perhaps this is a basic workflow but I'd like to see some exact hardware suggested that would accomplish this workflow.

Whether on or off grid, the hybrid should be able to guard against backend to the grid, no?

When the grid is off, hybrid can frequency shift to control all connected arrays.

But when grid is on, batteries are full, and we don't want any backend to grid...then the hybrid MUST have a way of communicating to microinverters to shut off. It can't be done by frequency shifting while grid is on, so it would have to be done by some relay (regulatory) system. What hardware/component would accomplish this regulating action?

 

[the.shining]

...and because this is a daily load sharing system, sub paneling isn't an option. Worst case scenario I can limit loads or cut off breakers at main panel, but neither I nor the common customer wants to rearrange their circuit breakers into sub panels. I'm trying to design a system that is turn key not only for me but for common scenarios where people value inverter diversification, multiple power paths, seamless load sharing, on and off grid solar power.

 

[400bird]

Enphase provides 25 warranty on their microinverters. Eg4 provides 10 yr warranty. Whether these warranties can be depended on is anyone's guess, but all else being equal, enphase microinverters appear to be the cheaper and longer life inverter at the present time.

And a John Deere costs more than a Ford.
You're comparing two inverters with very different features and functionality, unless you're getting into the Enphase battery. In that case it's more like comparing a kit car to a new car off the lot.

Comparing the value of each company and their ability to back their products, I'd go with Enphase every day of the week. EG4 imports inverters designed and manufactured by another company, they just get custom paint and stickers. Enphase has their own products and engineering. One has a long history with honoring warranty even early on when the failure rate was higher. The other is a new company with nearly daily complaints in this very forum.

That said, all of this is a mile away from where you started this thread.

 

[ksmithaz1]

The thread is about creating a Frankensystem. There is no way I would ever intentionally mix micro inverters with an AIO on a new install. It just sounds dumb, and now you are all worried about weird interactions, why would you want to intentionally create something so complex? I see dubious benefit and the likelihood of strange behavior. Heck throw a couple of windmills in there while your at it. Rube Goldberg would be proud.