30kw DIY battery for $310/kwh, which hybrid inverter is recommended?

[Ampster]

well youtubers are showing off their 272ah lifepo4 batteries now.

Yes, lots of people on another forum have developed reliable sources for those 272's, and some 280 cells from EVE.
Did this thread discussion about surge loads inform you about the complexity of picking the right hybrid inverter? It really has nothing to do with the kWhr capacity of the batteries except the batteries need to be able to provide the kW discharge to serve the loads.
I was able to open that video after several tries. I have used that same vendor ( Emily at Shenzen Basen) before with good results. Search for Shenzen Basen to see more reviews.

[khanh dam]

well youtubers are showing off their 272ah lifepo4 batteries now. much better price of about $120/kwh of storage.

https://www.youtube.com/watch?v=j7ocFLUO_qo

[oregon_phil]

The Sunny Island split phase option can manage a generator. This is their off grid solution, but as far as I can tell, doesn't work with the SMA automatic transfer switch but will manage a third party transfer switch between the grid and generator. I didn't elaborate earlier because this is an expensive solution. But user Salts bought some sunny islands cheap and did the work himself to it turned out to be a nice system.

[Ampster]

Good to know that there is a 240 volt split phase option. Too bad there is not a generator input. That is a feature of the internal transfer switches of most hybrids that adds to their cost effectiveness.
i do know that the generator input on the SolArk is bidirectional so it can be used for AC coupling a GT inverter. That may give SolArk flexibility in meeting the calculations for busbar adequacy by not having to go through the critcal loads panel and with another breaker. That calculation did complicate my Skybox installation with regard to the busbar rating of my critcal loads panel.

[oregon_phil]

When I say phase, I had to find an SMA blog posting when talking about SMA battery inverters. The SMA high voltage battery inverter is a 240VAC output device. So one SMA high voltage battery inverter per 240 VAC; not 1 per leg of 240VAC. The other thing is that the SMA automatic transfer switch doesn't manage a generator.

Their offgrid solution is SMA sunny island is a 120VAC output device. So one Sunny Island per 120vac, but you can pair two together for 240VAC.

[RottenMutt]

3hp PUMP? I have a 225 foot deep well and it only uses a 1hp pump. maybe you have an above ground pump?

three HP at bottom of well, ~300 feet. mine consumes about 3.8kw running, says my true power meter.

[Ampster]

The SMA transfer switch spec says the following:
.........
3) Battery inverter AC connection: Maximum overcurrent protection of circuit breaker of battery inverter: 50 amp; (remember one battery inverter per phase so the max here would be 1 SMA 6.0 battery inverter)

You confirmed my suspicion why the SMA solution is more expensive than the All In One solution offered by hybrids like the SolArk or the Outback Skybox. If I understand what you are saying, the SMA transfer switch is optional, which adds cost. Additionally, a separate battery inverter for each phase is required which adds additional cost. When you say "phase", I assume you mean each leg of split phase? The All In Ones are true split phase inverters with included transfer switches.

Hopefully this helps the OP evaluate which hybrid is recomended? The answer involves a lot more analysis and understanding than the OP may have thought when he framed the question. For example my Skybox could not handle the surge loads of A/C and the typical deep well pump but it sounds like the SMA can do that easily. Yet each of them could run just fine on a 30 kW(h) DIY battery.

[oregon_phil]

Perhaps the transfer switch on the SMA works differently which may make the calculation simpler?

The SMA transfer switch spec says the following:

1) Connection to utility grid and household distribution: Maximum input and output current: 200 amp
2) Solar inverter AC connection: Maximum overcurrent protection of circuit breaker of PV inverter:50amps. Inverter AC restriction: 9600 Watt inverter power max (40amps at 240 VAC)
3) Battery inverter AC connection: Maximum overcurrent protection of circuit breaker of battery inverter: 50 amp; (remember one battery inverter per phase so the max here would be 1 SMA 6.0 battery inverter)

It looks like if you went to the trouble of installing the SMA automatic transfer switch, you could still have a 200 amp grid connection and 200 and household distribution when using an SMA battery inverter and SMA solar inverter.

[Ampster]

I don't think you are wrong about this. The only other possible thing I found is a "solar ready" 200amp meter panel that has 225 amp bus bars. That way the derating is already baked into the spec so people don't have to do the math.

According to my understanding of the busbar rule when backfeeding, the sum of the breakers cannot exceed 120% of the busbar rating. That would be 240 Amps of breakers for a 200 Amp busbar and 270 Amps of breakers for a solar ready panel.

The SMA high voltage battery inverter is 6.0 kW

That would be a 30 Amp breaker for the SMA. I checked my notes and my electrician calculated that we had plenty of room for the 5kW inverter capacity of the Skybox back feeding the 200 Amp panel. After moving the critical loads to that subpanel there was only 220 Amps of breakers on my 200 Amp panel including the 60Amp breaker feeding critical loads which passed through the Skybox. The inverter on the Skybox would have only required a 30 Amp fuse but it was capable of passing through 60 Amps to the critical loads panel. . Could that same theory apply to a 8kW SolArk? Perhaps the transfer switch on the SMA works differently which may make the calculation simpler?

[oregon_phil]

Just went through this exercise for a customer that wanted a Sol-Ark hybrid inverter. One thing that stood out about this relatively new design is that it has a grid output AC max current over 32amps which means it can't be used for backfeeding without modifying a typical 200A breaker panel. I like the all-in-one design for being easy to set up and it looks like a nice user interface, but even the 8kW version is too powerful for a simple grid tie. Am I wrong about this??
I'm still recommending with the SMA storage bundle using a 10kWh BYD battery. Solidly engineered, proven quality, can be added to an existing grid-tied system, not cheap...

I don't think you are wrong about this. The only other possible thing I found is a "solar ready" 200amp meter panel that has 225 amp bus bars. That way the derating is already baked into the spec so people don't have to do the math.

Or is it that the SMA solution just has less capacity?

The SMA high voltage battery inverter is 6.0 kW

[J.P.M.]

If people could read and understand that information and integrate that into an optimum system; there would not be much demand for forums like this.

People can read and understand, but most are too lazy to make the effort and would rather be spoon fed fast answers from places like this. That inherent laziness ensures there will always be a place for forums such as this.

Q: If all places like this went away how would folks know pump curves exist and how to use them ?

A: The same way they always have - pick up a book and get informed. Alternately these days google "pump curves" or "pump lift + GPM", get swamped with hits and spend 10 minutes learning.

[Ampster]

.....One thing that stood out about this relatively new design is that it has a grid output AC max current over 32amps which means it can't be used for backfeeding without modifying a typical 200A breaker panel........

I am not sure what modification would be necessary to use a hybrid inverter as a backup other than adding a critical (essential or protected) loads panel. For sure the SolArk needs a 60 Amp breaker but installations I have seen have worked around the busbar rule in a variety of ways. I am not versed enough in the details of that rule to give an example. What is unique about the SMA solution that makes it able to accomodate a 200 Amp panel in a way that the SolArk cannot?
Or is it that the SMA solution just has less capacity? If that is the case there is a smaller SolArk or the Outback Skybox if one wants to consider an All In One inverter. I have heard good things about SMA offerings but as you mentioned have not seen anything that is competitive with All In One hybrids. I am more interested in understanding the options and relative costs of the solutions. In one sense this may get us back to the title of the thread which was about "which hybrid inverter is recommended?'

[solarix]

Just went through this exercise for a customer that wanted a Sol-Ark hybrid inverter. One thing that stood out about this relatively new design is that it has a grid output AC max current over 32amps which means it can't be used for backfeeding without modifying a typical 200A breaker panel. I like the all-in-one design for being easy to set up and it looks like a nice user interface, but even the 8kW version is too powerful for a simple grid tie. Am I wrong about this??
I'm still recommending with the SMA storage bundle using a 10kWh BYD battery. Solidly engineered, proven quality, can be added to an existing grid-tied system, not cheap...

[Ampster]

That's why pump mfgs. publish pump curves for their offerings.

Yup, and inverter manufacturers publish specs showing surge capacity of their inverters. If people could read and understand that information and integrate that into an optimum system; there would not be much demand for forums like this.

[J.P.M.]

Yes, I looked up a table for pumps and it suggested as @oregon_phil mentioned that it also depends on how much flow one wants. For example a lift of 225 feet could be done with less than a 1 hp pump but the flow would be less than 5 gallons per minute. At that rate you would need a larger tank on the surface depending how how long you want to take showers.

That's why pump mfgs. publish pump curves for their offerings.