Sunpower panel system + third party automatic transfer switch + batteries

[goshdurnit]

Hi there - I have a Sunpower solar system with 32 panels that got installed this year on my roof. I don’t have any batteries yet.

Sunpower’s Sunvault’s 13kwh battery system with a hub+ is $17.5k, and that should do whatever automatic transfer switch stuff it has to built in.

Alternatively, I could get a rack of 61kwh EG4LLV2’s for $25.6k from Signature Solar. Is there a way to connect a diy battery system like that with the Sunpower solar system with a third party automatic transfer switch? What automatic transfer systems exist that would work for this purpose?

Alternatively, can I get a hub+ and use it with third party batteries in lieu of sunvault batteries?

 

[Hedges]

Your sunpower system is probably GT PV. It probably does frequency-watts.
If so, an AC coupled battery inverter like Sunny Island could be added.
There are other brands as well.

What AC wattage can your system produce?

 

[goshdurnit]

Your sunpower system is probably GT PV. It probably does frequency-watts.
If so, an AC coupled battery inverter like Sunny Island could be added.
There are other brands as well.

What AC wattage can your system produce?

It’s a 12.8kw system

 

[Hedges]

Just within the limit of what 2x Sunny Island can pass through from the grid.
These are often sold new in the box on eBay for about $2500 apiece +/-
I use them with AGM, for grid-backup.
Some people use them open-loop with lithium and AGM settings. Others use REC-SI BMS which communicates.

 

[goshdurnit]

I’m trying to lookup all these products to understand what it all does and how they would connect together- bare with me as I’m just learning about it all

I am grid-tied on Southern California Edison under NEM 2.0, which means I get 75% of over-generation credits towards my bill. Would a Sunny Island do the auto transfer between grid power, solar power, and battery power?

Not sure what open loop vs REC-SI BMS means. Thank you!

 

[Hedges]

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Look at the data sheet, and example systems.

SI automatically transfers.
What it doesn't do is divert PV to batteries during times of low rate, then feed grid from batteries during times of high rate.

Sunny Boy Storage does that, but is less capable for backup of heavy loads, and uses high voltage batteries we haven't figured out how to DIY.

Sunny Island will close a relay to the grid and let your GT PV inverter work like normal.
If grid goes out of spec for voltage or frequency, SI disconnects from grid and runs downstream loads from battery. Your GT PV inverter makes power which supports loads and charges battery. If battery getting full, SI ramps up frequency. If GT PV configured for Rule-21 frequency watts, it responds by ramping down power.

There is a list of name brand batteries from BYD and others which are supported by SMA.
REC makes a BMS that some DIY people use for home made batteries, also compatible with SI. Some people here use it but I haven't.

There may be some issues with Rule-21 inverters, vs. older model Sunny Boy that switched between on and off grid settings. Nothing stated, just some recommendations to use off-grid settings which suggest some issues. I'm running the older models.

 

[goshdurnit]

My Sunpower system is “Equinox” and has a bunch of micro inverters under each panel btw, if that changes anything

 

[goshdurnit]

If sunny boy storage can’t handle high loads and sunny island can’t auto divert power, is there nothing aside from sunpower sunvault that can do what I want?

 

[Hedges]

What are your goals for a battery system?

I'm most familiar with SMA equipment. Other guys here use SolArk, Schneider, Outback.
Some have microinverters AC coupled.

I think SolArk may have the the most features and responsive support.
It is a high-frequency architecture, reportedly not as good at dealing with AC coupling, but it has a relay it can use to shed the GT PV if needed. It can be stacked to significant power levels.

Midnight Rosie is a new high frequency inverter. I think they are going to have all the desired features. It is from the guys who were pioneers of the PV off-grid industry and designed several of the big name brand inverters including Outback and Trace (now Schneider).

Excluding the feature of peak shaving by timed use of battery, SMA has a very robust product. They are the guys who invented grid tied PV and AC coupling.

 

[goshdurnit]

Things I'd ideally want out of a battery system are below- I tried to list out all the possibilities @Hedges.

1) When using Solar: If the grid goes down, auto switch to battery consumption, while charging the batteries at the same time.
2) When using grid power at night: If the grid goes down, auto switch to battery, until battery is depleted.
3) When using Solar: Auto switch to Solar + battery consumption when solar alone isn't providing enough juice for what we're consuming. This extends our power to be able to use power during the high grid cost time of use at 4-9 PM.
4) When using Solar: Auto switch to Solar + battery + grid when solar + battery isn't providing enough juice for what we're consuming. same as above, extends 4-9 PM timeframe.
5) When using Battery: switch to battery + grid power when battery alone isn't providing enough juice for what we're consuming, generally 4-9 PM, until battery is depleted.
6) When using Solar: If battery is full, feed solar back into the grid. (currently our system feeds into the grid when we're generating more than we're using, but we have just Solar, no batteries)

Something like one of those 61kwh racks of a ton of batteries as I mentioned looks very attractive, but I'd love to know if that makes sense given our use cases. Let me know if this is feasible (or prohibitively expensive), or which of these make more sense to do than others. I don't have a good handle on what is easier than others. Thanks!

 

[Hedges]

I think Sunny Island will only draw from battery if grid is down, or to limit draw from grid to configured maximum. It does let surplus PV backfeed grid. Or not, if configured "grid as generator". Manual has detailed wattage overload vs. time and wattage vs. temperature.

I would expect the European model SI to come to the US eventually, likely providing peak-shaving and time shift features. But that's just a guess.

SolArk likely can be programmed for various scenarios you want. Several people here use it so search for who and engage them. Also inquire directly of the company! Ask about compatibility with your particular GT PV. People are having more difficulty with Enphase IQ8, better success with IQ7.

Consider what max wattage you want to power, and what surge above that is needed to start motors. Make sure you get can do it.