diy solar

diy solar

What to do after 5pm til dawn?

And now PG&E is moving peak time into the evenings starting next March...LOL (Everytime you try to get ahead the Uncle Sam, they pull the rug out) PG &E is getting hammered by daytime production and no way to store it.. Selling to other states or paying other states to take the excess? With fires year after year, and California moving to control PG&E or even take it over...

There is such good insight in this message!! Most folks focus on doing grid-tie because it’s the quickest path to payback. However, there will have to be major changes to our utility infrastructure as we all transition into electric Hummers and robotic lawn mowers. I think it’s worth investing in flexibility on the front end. Expect your usage to increase significantly over the next decade. Plan ahead. Governments will support utility companies before homeowners.
 
I've toyed with timers for frig and freezer from 12 midnight to 6am cutting them off. 30amp breaker now (21-24 amps) with 8 awg from ac to panel. That would be first option....timers
Looked last nite least expensive Sunny Island 2500 eBay new in box...
 
With time of use (my lowest tier is midnight to 3:00 PM) of course run the fridge at night. But to minimize battery usage during off-grid operation, I would shut it off as soon as PV production drops below consumption. Which might have been 5:00 PM today.

I figure grid-tie PV costs me $0.05/kWh to install today (amortized cost of equipment over 10 years.) AGM battery costs me $0.50 or $1.00/kWh (amortized over wear-out life.) Lithium DIY would beat that by a considerable amount, but is new and has complexity. Commercial offering are starting to drop in price. When my undersized AGM battery wears out I'll consider other options.

What I've done is oversize grid-tie, and during grid failures I run everything direct off PV, always curtailing production to match load (happens automatically with Sunny Island), and battery stays charged. My battery will barely make it to morning if I turn off a bunch of loads - haven't connected relays to shed refrigerators, yard lights etc. but could.

Yes, $2500. A decent price, considering they're about $5000 MSRP. I got mine at half that when I bought a pallet full, quick profit for someone who bought it at auction. I was surprised to see a pair at $1200 each last week, but listing isn't there any more. Funny, I don't find the under "completed listings" either.

Here are a couple transformers I thought would do the job:


You can also buy conventional 'E' core transformers, already packaged and properly labeled, but toroids are more efficient. I hadn't found an economical and suitably sized ones at the time. To use these toroids you have to mechanically mount them some how. Do NOT use a metal bracket what makes a complete circuit through the middle and back around the outside!
 
Here is the other SMA offering:


for backup, also needs:


(It takes two to tango)

Newer product, not at the liquidation prices of Sunny Island so no bargain.
Those use a 400V battery, which isn't cheap either.

Your Sunny Boy, assuming it is the newer -40 or -41, is on the Sunny Island compatibility list only for "grid tie" and "off grid", but not for "grid backup". That is because it doesn't have a compatible communication link. However, SMA told me it could be used set to "off grid" (which disables UL-1741) so long as it is behind Sunny Island (which takes over that role). If you use this setup, you ought to inquire of SMA support and have their response saying to do so.


I'm using older model 5000W and other Sunny Boy which are on the list, but had inquired about the -41 for a friend.

The newer Sunny Boys do have a communication link which works with Sunny Boy Storage.
 
We have a 41....I downloaded the PDF (7 pages) on the SMA tech sheet for Island compatibility. Thank you for that.
Checked the smart meter again...seems 10-11KwH over nite....seriously now thinking about a 24 hr timer on freezer in laundry, 120v plug easy to get to. My best friend just bought a generator lp/gas at Costco (7-9kw $700). He said they only had 2? And a lady was on the phone with her husband doing 40 questions...LOL...He grabbed one after asking the lady if she minded. She said go ahead. Another customer grabbed the other. So she was standing there with nothing....
3 days later PG&E shut the power off Sunday afternoon til Tues nite.....
My point here is what a pain to move the frig out and plug it in to the outside generator. Told him run it on LP as gas will clog the carb over time.

I thought I saw somewhere on the forum a guy in Michigan has 2 Sunny boys and 2 Sunny Islands and the frequency is controlled by the Islands.,
So if the sun comes up and the battery bank is charged or charging the frequency gets into the 60 range and the Boys open up and begin doing their thing.
You are way ahead of me on research. Haven't talked to SMA because right now this exploratory.
Yes, I would think if Sunny Island is primary and the Boy is secondary...that the Island could control what is going and get the Boy to produce?
 
The Sunny Island and Sunny Boy work great together. So long as grid is up, frequency is between 59.4 and 60.4 Hz. Sunny Boy delivers all power available from PV for net metering. If grid goes down, after about 30 milliseconds Sunny Island lifts a relay and produces AC. Almost all appliances, computers etc. ride through, don't notice the dropout. Sunny Boy probably drops off, and Sunny Island powers loads from battery. In a couple minutes, Sunny Boy comes back online and everything runs. If battery is full and loads are less than PV production, Sunny Island increases frequency. Up to 61 Hz, Sunny Boy produces 100% of available power. Linearly up to 62 Hz, Sunny Boy decreases power to 0%. So as I add or remove loads, frequency moves between 61 Hz and 62 Hz, and Sunny Boy adjusts output to match load (air conditioner, fridge, etc.) Sunny Island takes care of starting surge current for motors. At night, things run on batteries. Sunny Island puts out < 59 Hz for a while to mechanical timers average out to correct time.

That all works if inverter is set to respond to frequency shift. Other brand grid tie inverters drop off above 60.5 Hz. A Sunny Boy set for on-grid UL-1741 does the same. The new "grid support" parameters allow some frequency/voltage excursions and may have some power adjustment in response, but not as good. The various model Sunny Boy either need an RS-485 cable and adapter or setting changed to "off-grid" a.k.a. "island". SMA started shipping Sunny Boy already configured with backup mode "on all phases" so just plugging in hardware enabled the function.

My Sunny Boy were SWR2500U, from 15 years ago, and couldn't be set with the necessary parameters. I picked up some 10000TLUS which are listed as compatible. With parameters set and RS-485 connected, they recognized off-grid and stayed connected up to 62 Hz, but didn't reduce power output. SMA support told me to set the for off-grid. That works fine, and no RS-485 needed. They just can't be wired directly to grid, because they don't have UL-1741 enabled, have to be connected through Sunny Island.

Your -41 model don't even have an RS-485 interface. They have an interface like Ethernet which would work with Sunny Boy Storage. I think the new Sunny Island models in Europe may support them. Those are also rain tight, don't have the breaker or SD card. For the US Sunny Island, SMA support told me to just configure -41 for off-grid.

If you can wire additional circuit breaker panels, you can set up a protected loads panel with things like refrigerator, internet, some lights. It would always be connected through Sunny Island, total of about 50A 120V available. With only one Sunny Island you need the transformer, to deliver 25A 240V & 50A 120V. You should also have the "load shed" relay to disconnect loads but leave Sunny Boy connected; otherwise if battery is drained Sunny Island will shut off and never turn back on. You would need a battery charger to recover from that.

To use your generator as well, need a transfer switch so input to Sunny Island is connected to either grid or generator. Use a switch or extra relay contact to tell Sunny Island which. It will let Sunny Boy backfeed the grid but not the generator. It closes a relay to autostart generator, or that could signal you to manually start.

For 11 kWh at night you would need 400 Ah 48V battery, $5000 for AGM like mine. If you could get that down to 3 kWh then $1200 for 100 Ah. Or less money for FLA like golf cart batteries.
 
The Sunny Island and Sunny Boy work great together. So long as grid is up, frequency is between 59.4 and 60.4 Hz. Sunny Boy delivers all power available from PV for net metering. If grid goes down, after about 30 milliseconds Sunny Island lifts a relay and produces AC. Almost all appliances, computers etc. ride through, don't notice the dropout. Sunny Boy probably drops off, and Sunny Island powers loads from battery. In a couple minutes, Sunny Boy comes back online and everything runs. If battery is full and loads are less than PV production, Sunny Island increases frequency. Up to 61 Hz, Sunny Boy produces 100% of available power. Linearly up to 62 Hz, Sunny Boy decreases power to 0%. So as I add or remove loads, frequency moves between 61 Hz and 62 Hz, and Sunny Boy adjusts output to match load (air conditioner, fridge, etc.) Sunny Island takes care of starting surge current for motors. At night, things run on batteries. Sunny Island puts out < 59 Hz for a while to mechanical timers average out to correct time.

That all works if inverter is set to respond to frequency shift. Other brand grid tie inverters drop off above 60.5 Hz. A Sunny Boy set for on-grid UL-1741 does the same. The new "grid support" parameters allow some frequency/voltage excursions and may have some power adjustment in response, but not as good. The various model Sunny Boy either need an RS-485 cable and adapter or setting changed to "off-grid" a.k.a. "island". SMA started shipping Sunny Boy already configured with backup mode "on all phases" so just plugging in hardware enabled the function.

My Sunny Boy were SWR2500U, from 15 years ago, and couldn't be set with the necessary parameters. I picked up some 10000TLUS which are listed as compatible. With parameters set and RS-485 connected, they recognized off-grid and stayed connected up to 62 Hz, but didn't reduce power output. SMA support told me to set the for off-grid. That works fine, and no RS-485 needed. They just can't be wired directly to grid, because they don't have UL-1741 enabled, have to be connected through Sunny Island.

Your -41 model don't even have an RS-485 interface. They have an interface like Ethernet which would work with Sunny Boy Storage. I think the new Sunny Island models in Europe may support them. Those are also rain tight, don't have the breaker or SD card. For the US Sunny Island, SMA support told me to just configure -41 for off-grid.

If you can wire additional circuit breaker panels, you can set up a protected loads panel with things like refrigerator, internet, some lights. It would always be connected through Sunny Island, total of about 50A 120V available. With only one Sunny Island you need the transformer, to deliver 25A 240V & 50A 120V. You should also have the "load shed" relay to disconnect loads but leave Sunny Boy connected; otherwise if battery is drained Sunny Island will shut off and never turn back on. You would need a battery charger to recover from that.

To use your generator as well, need a transfer switch so input to Sunny Island is connected to either grid or generator. Use a switch or extra relay contact to tell Sunny Island which. It will let Sunny Boy backfeed the grid but not the generator. It closes a relay to autostart generator, or that could signal you to manually start.

For 11 kWh at night you would need 400 Ah 48V battery, $5000 for AGM like mine. If you could get that down to 3 kWh then $1200 for 100 Ah. Or less money for FLA like golf cart batteries.
Thank you for all the information. You are a wealth of knowledge.
Have things to do so adios for now..
 
@Hedges it sounds like your Sunny Boy is on the grid side (AC2). Why is this? It seems like you'd put it on the load side (AC1) and then let the excess feed the grid. This way you never have to worry about whether the grid is up or down and the PV will supply power regardless of the grid's state.
 
@Hedges it sounds like your Sunny Boy is on the grid side (AC2). Why is this? It seems like you'd put it on the load side (AC1) and then let the excess feed the grid. This way you never have to worry about whether the grid is up or down and the PV will supply power regardless of the grid's state.
My Sunny Boys are on the island side, on their own load panel. It has a breaker going to a load-shed relay, feeding detached house.
Input side comes from a breaker panel connected to grid, which powers the garage. That shuts off during grid failures, but I have set up interlocked breakers as a manual transfer switch, so I can disconnect grid and power garage as well.

SMA written documentation says Sunny Boy can be set to "off-grid" a.k.a. "island" for completely off-grid use with Sunny Island.
It says must be set to "backup" e.g. "backup = on all phases" if used for grid backup. If that option isn't available in a Sunny Boy, must be set for on-grid UL-1741. Doesn't explain why, given that it is behind Sunny Island. I have some theories why the engineers from Germany said that. The support people in the U.S. have said it is OK to use "off grid" settings in that case.

You do have to limit Sunny Boy capacity on load side AC1, 6.7 kW per Sunny Island due to the 56A relay in each. For a time I considered having 5 kW of Sunny Boy (with a transformer) on load side of a single Sunny Island. Another 5 kW of Sunny Boy would be on the grid side. During power failures I would transfer the second 5 kW to load side. (Sunny Island can manage 12 kW of Sunny Boy, but can't feed that much through its relay.) But I've since put in four Sunny Island, 2S2P. I had to address imbalanced current so they could pass through 56A + 56A = 112A. Now it works well.
 
I see. Thank you for the correction. I misunderstood the earlier comment.

In my case I have Enphase microinverters. They run on the AC1 side.
 
I see. Thank you for the correction. I misunderstood the earlier comment.

In my case I have Enphase microinverters. They run on the AC1 side.
Do those Enphase respond to frequency shift, smoothly adjusting power output?
Or just bang offline and wait 5 minutes before coming back?

When I set up the 10000TLUS as "grid backup", they stayed on line at 100% until 64.5 Hz, dropped off, and came back on at 100% when frequency lowered to 61 Hz. Constant cycling, which is why I contacted SMA and changed setting to off-grid.

Do you use a load-shed relay? SMA documentation does give emergency charging instructions, but those made me nervous about damage if anything went wrong. I could use DC coupling with a small PV array, but that would be slower, because I have a lot of AC coupling that can charge fast. The way I have it set up, battery has to come back up from 70% DoD to 50% DoD for my load-shed to reconnect the house. Goal is to manage loads so it doesn't disconnect in the first place.
 
I wish that I could answer your questions but I have no idea. I literally assembled the system for the first time yesterday as a test. I ran it for about 8 hours to ensure that basic functions worked (PV comes up, charges battery, feeds excess to the grid, stress test running the entire house from the 2x6048-US). I monitored the grid and PV in realtime to ensure that it worked and never saw the PV go down after they came up. Unfortunately after looking at my panel I realized that I had under-estimated the wiring difficulty, so I just Macgyvered the setup to test for the day and then took it all down so I can get the correct parts.
 
Welcome as a new inhabitant of Sunny World! ?

With grid disconnected and large amount of PV production, exceeding consumption, wait until Sunny Island says battery is charged.
Display will show zero or 0.1 kW going from PV to battery. Turn on a space heater, like 600W or so. PV should supply that so still zero to 0.1 kW from PV to battery. If display shows battery to load is 600W, Enphase isn't supporting it yet. Wait and see if they come back online after 5 minutes (UL-1741 operation).

It may be the PV just cycles on and off 100%. Enphase has some products of their own for zero-export and for off-grid operation.
I think lithium batteries with their cycle life may be OK smoothing out on/off PV cycling, if they can accept the full current.
AGM or FLA would be worn out faster with constant cycling, more important to be able to curtail PV to match load.
I have a way undersized AGM bank, so if PV came on 100%, battery couldn't accept the current and Sunny Island would raise frequency to where PV was knocked off again.
(Default charge rate was 0.55C when I did quick-start configuration for my battery, so I altered a parameter to 85A, about 0.2C)

The latest "Rule 21" functions may provide some frequency control of power, but I think it has a time limit for high frequency, after which is is required to disconnect. So off-grid or backup settings would work better. But I haven't tried using any inverters with Rule 21.
 
Thanks! I'll check it out. That experiment didn't occur to me yesterday when I had it configured. I've ordered some more wires, etc for a more stable setup so my next chance to try again is this weekend. What I did see is that with the grid attached during battery charging I had a huge excess PV, but the battery charging seemed to come entirely from the grid. When I disconnected the grid I saw the battery charging from PV, but then I turned the grid back on before the battery finished charging to see the PV feed the grid. So, one of the experiments now is to run without the grid when the battery is fully charged. I think that I just need to be able to leave it assembled for a couple weeks so that I can get a feel for how it runs and all of the settings.
 
What happens if battery runs down to low-voltage disconnect at night?
If loads and Enphase inverters are directly connected to load/island side of Sunny Island, it will shut off and stay off.
Some provision is needed for Sunny Island to get the battery charged back up to where AC can be produced again.
 
Yes, this problem has occurred to me and I don't have a solution right now. I think that I will need to configure the Sunny Island to fail before the battery gets to 0. Presumably there should be a voltage setting to do this. I really struggle with the settings though because the description in the manual rarely matches the observed behavior when I try a setting.

For reference I only have 10KWh of battery right now, so I wouldn't expect the system to make it through the night without the grid. If things go well I expect to buy at least 10-20KWh more battery.

Also, I have ~9KW of panels and I get a peak output of ~6KW. Total energy on a sunny day ranges from ~28KWh to 60KWh. I estimate that in the worst case I use 24KWh sun down to sun up (when not charging the EV). My thinking is that 40KWh of battery would get me through 95% of the time in a real power outage situation. I'd like to build up to that though as opposed to buying everything now. As a guess (I didn't stress test the batteries yet) that the current configuration would get me through the day and then I'd need to shut of everything but a few circuits overnight. I haven't set up any circuits for load shedding and I have not decided whether I will do this or not.
 
So for now, alter the low battery shutdown to happen at about 70% DoD/30% SoC.
If that occurs, turn off all loads and change low battery shutdown back to default, which I think is 20% SoC, 80% DoD.
(I'm assuming you can change the settings then.)
With Sunny Island restarted, it should recharge from AC coupled Enphase, and once it reaches 50% SoC and you have sun, you can set the limit back to 30% SoC and connect loads again.

Hardware solution is add a relay to shed the house loads, but keep Enphase connected. One of the switching relays in Sunny Island defaults to that function, at 70% DoD. Alternate is to add DC coupled PV. Could be Midnight Classic with a data interface, or any brand with a shunt so Sunny Island can count the electrons.

Your 10 kWh battery gives you 7 kWh usable. If you can eliminate enough nighttime loads when running off grid, that might be enough.
You have 200 Ah at 48V. SMA recommends 100 Ah per 1 kW of PV, 600 Ah in your case for peak 6kW. I have only 1/3 or 1/4 of their recommendation. I think the issue would be if 6 kW was going to house loads, and all turned off suddenly. Sunny Island takes several seconds to ramp frequency and cause Sunny Boy to curtail production. Sudden connection of loads it can supply from battery, 11 kW for 5 seconds from each Sunny Island. But sudden disconnection it can only stuff so much into the battery, so maybe AC voltage rises an GT inverters drop off line. But typically only a couple kW turn off at a time. It hasn't caused a problem for me.
 
First, thank you so much for sharing your knowledge and experience. It's been a bit of a slog to get here by myself, so please know that you are appreciated.

Because of my battery configuration (posted elsewhere) I'm not sure that my SOC is being tracked correctly. My understanding is that Lithium Ion would be tracked by voltage. Also, I have not setup the battery current monitor yet. For reference, I have LiFePO4 batteries with an internal BMS, so for now I tell the SMA 6048-US that I have a VRLA battery.

I'm with you that best practice should be to configure load shedding with a separate panel. I just haven't made it there yet. Once I have the system working and understood I hope to make improvements over time.

It's interesting that they have a sizing of battery capacity per generation (PV). Is this intended for off-grid systems? In my mind the ideal usage of a system like this is for buffering combined with not losing all power sources (including generation) when the grid fails. From there you can build up to off-grid, but unless you are attempting to protect against long grid outages, there isn't much reason to use that much storage. Over time I expect to add more storage, but there's no immediate reason to guarantee fully off-grid.

I plan to experiment with off-grid modes once I get everything reconnected. I was thinking that float mode might eliminate the shutdown problem, but I just need to see it for myself.
 
Sunny Island manual says,

"SMA recommends the following minimum battery capacities:
• Minimum battery capacity per Sunny Island inverter:
– Sunny Island 4548-US: 190 Ah
– Sunny Island 6048-US: 250 Ah
• Minimum battery capacity per 1 kW output power of the PV system: 100 Ah (C20)"

Configuration allows you to set 100 Ah minimum lead-acid battery, 50 Ah lithium.
I noticed what when I did the quick configuration of my battery, default charge current from grid was reasonably low, but from PV or other sources was 0.55C. In your case with lithium that might be acceptable. If my PV was 100 Ah per 1 kW of PV, that wouldn't exceed about 0.2C. Because my battery is so much smaller, I altered the charge current setting.

I don't know how well Sunny Island will estimate your battery's state of charge. It can count amp-hours, but the voltage may confuse it. You will have to compare what BMS says with what Sunny Island says. (Lithium state of charge not shown by voltage at least in the middle range, but cutoff at low end might be clear.) Maybe the appropriate minimum voltage could adjusted from default VRLA settings.
 
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