Energy dump while being grid tie with IQ8

[Alvarote]

Hi All, I have a 6kW system with IQ8+ inverters. So far the system is saving us money during the off peak hours. However, my energy company adds an on demand charge if your consumption goes over a threshold during the on the peak hours...
I was thinking about adding some extra grid tie inverters connected to Lipo4 batteries (120v soyo ones from Amazon) to offset my energy usage and that way avoid the on demand charges if possible. I've seen some videos and I know they can put from 650w to 750w. The caveat is that my solar array is using IQ8s so I don't know if having a 240v grid tie micro inverters will complicate this setup. Also, would it be possible to run those 120v soyo inverter while my panels are producing? Or should I wait until is dark and no enphase sync is happening with the grid?
Thanks!

 

[Hedges]

On grid, you can have multiple GT inverters all stuffing power into it. Grid is such low impedance they won't disturb each other.

You're thinking of something this?

Amazon.com: Customer reviews: SOYOSOURCE 600W Grid tie Inverter PV-Input 50v-88v Adjustable Output Inverter on Grid for 48V Battery Output Adjustable

Find helpful customer reviews and review ratings for SOYOSOURCE 600W Grid tie Inverter PV-Input 50v-88v Adjustable Output Inverter on Grid for 48V Battery Output Adjustable at Amazon.com. Read honest and unbiased product reviews from our users.

www.amazon.com

Whatever you get for grid backfeed should have genuine UL (or NRTL) listing.

That Soyo inverter is meant for PV. Some people have fed batteries into a PV inverter.

you can probably find a good hybrid to do what you want, that can AC couple to IQ8 while grid is down (may require some DC coupled PV.)
SolArk is one that does it.

There are also some bidirectional battery inverters. But hybrids may be more economical as well as more features.
I'm starting to use Sunny Boy Storage for same purpose.

 

[Alvarote]

Thanks for your reply, I was considering this one
1000w grid tie inverter with battery input

 

[Hedges]

Is this the extent of documentation?

https://m.media-amazon.com/images/I/A1t+pOY1-ZL.pdf

I would not use a grid-interactive inverter that didn't have UL-1741 listing from UL or another NRTL.
words to the effect of "tested to UL-1741" are not sufficient, must actually be listed by a recognized lab.
Don't trust off-brands when safety is involved.

If an inverter is on California's CEC website, it will have passed the tests required for it to be safe.

Solar Equipment List - CA Energy Commission

solarequipment.energy.ca.gov

Not all equipment on the list is still able to be granted permission to operate by the utility. If you download spreadsheet (near upper right of page), there are additional columns with more grid-support features. Those won't matter if you're doing it without permission, but if you backfeed while the sun is down utility could figure out you have batteries. One older PV inverter I picked up wasn't allowed so I had to get a newer one.

Some vendors will say "UL Listed" but the equipment was simply tested by an unrecognized party. Some had received listing, but vendor was shipping inverters with "UL" sticker and inspectors in some locations wouldn't accept a copy of listing document.

An inverter like SolArk will couple with IQ8, if firmware on IQ8 is updated. SolArk recommends DC coupled PV wattage exceeding the PV you have on your microinverters. That brand is expensive, but if you look around you may find others or less from EG4, Growatt, etc.

I'm using SMA Sunny Boy Storage, which I got cheap because discontinued, but compatible high voltage batteries are expensive (I found a discontinued one.)

You may do best with an inverter that takes a 48V LiFePO4 server rack battery, many economical choices.

That was thinking about ability to operate as backup, and AC couple with your existing microinverters.
To simply shave peaks, you could use any grid-interactive battery inverter, with it and the microinverters connected to grid. Connect loads downstream of battery inverter and program it to limit current draw on its input. It will charge and discharge batteries as needed.

 

[Alvarote]

Is this the extent of documentation?

https://m.media-amazon.com/images/I/A1t+pOY1-ZL.pdf

I would not use a grid-interactive inverter that didn't have UL-1741 listing from UL or another NRTL.
words to the effect of "tested to UL-1741" are not sufficient, must actually be listed by a recognized lab.
Don't trust off-brands when safety is involved.

If an inverter is on California's CEC website, it will have passed the tests required for it to be safe.

Solar Equipment List - CA Energy Commission

solarequipment.energy.ca.gov

Not all equipment on the list is still able to be granted permission to operate by the utility. If you download spreadsheet (near upper right of page), there are additional columns with more grid-support features. Those won't matter if you're doing it without permission, but if you backfeed while the sun is down utility could figure out you have batteries. One older PV inverter I picked up wasn't allowed so I had to get a newer one.

Some vendors will say "UL Listed" but the equipment was simply tested by an unrecognized party. Some had received listing, but vendor was shipping inverters with "UL" sticker and inspectors in some locations wouldn't accept a copy of listing document.

An inverter like SolArk will couple with IQ8, if firmware on IQ8 is updated. SolArk recommends DC coupled PV wattage exceeding the PV you have on your microinverters. That brand is expensive, but if you look around you may find others or less from EG4, Growatt, etc.

I'm using SMA Sunny Boy Storage, which I got cheap because discontinued, but compatible high voltage batteries are expensive (I found a discontinued one.)

You may do best with an inverter that takes a 48V LiFePO4 server rack battery, many economical choices.

That was thinking about ability to operate as backup, and AC couple with your existing microinverters.
To simply shave peaks, you could use any grid-interactive battery inverter, with it and the microinverters connected to grid. Connect loads downstream of battery inverter and program it to limit current draw on its input. It will charge and discharge batteries as needed.

Thanks Hedges for your detailed explanation. When you mentioned grid interactive battery inverter, you meant the EG4 or Growatt ones
Or are there any other type of inverters you recommend for the shaving peak purposes you pointed out?
Thanks

 

[Hedges]

"Grid interactive" meaning synchronizes to grid and adds power by pushing in current following the voltage is sees.

I think there are some by SolArk, EG4, Growatt, Outback, Schneider, SMA, bunch of other names.
Some also make off-grid inverters which can't do that.

One that connects CT (current transformer) at grid connection point can monitor power in/out and adjust its output to change current through meter, but doesn't have to carry heavy loads through it.

I don't have experience with any peak-shaving inverters (except Sunny Boy Storage, which I don't recommend for you) but other people here do.

searching for Peak Shaving I find threads on SolArk, EG4 18kpv, etc.