13.2 kw DIY broke ground

[Maitake]

Single orientation.
I looked at multiple orientation, mostly based on your posts ? and even vertical panels in N/S orientation.
These configs seemed to make sense to maximize self consumption, but in the end I chose to maximize winter production as I have a heat pump.
This means a 60° tilt and straight south.
String inverters are pretty cheap.
With storage, catching all that solar production around noon makes a big difference, especially with bifacials and snow cover. Wire size is ridiculous because of code. 10AWG per string. 3 strings. This would be required whatever direction the panels face.

Is your array going to be a single orientation?

Two orientations, e.g. 9:00 AM and 3:00 PM would reduce peak output but increase hours of production (also does reduce total kWh somewhat). That would reduce IR drop in wire and battery charge rate. Should match consumption better and keep battery more full later in the day (if off-grid).

On-grid, it may be power is worth more certain hours of the day. Or, a maximum backfeed power/current allowed.

 

[DurkaDurka]

32 panels, 3 strings? Or maybe you moved to 33 panels? 11 per string, 3 parallels?

 

[Maitake]

32 panels, 3 strings? Or maybe you moved to 33 panels? 11 per string, 3 parallels?

Was going to do 2x11 and 1x10 but at 35 below zero the 11's are over voltage, so 3x10. I may run a DC charger to the battery off the 2 extra panels.
3 sunny boy 3.8kw inverters on the 3 strings.

I've never seen that cold in 30 years here, but never know. It's the all time record.

 

[Maitake]

Ok so why did I buy 33 panels?
Because my racking supplier had them at a decent price with free shipping, racking is drilled for direct mount, panels have long wire for skip wiring, and bonus...mounting hardware included. Had to buy a whole pallet of 33. Works out to about where I wanted to be anyway power wise and removed a whole lot of fooling around and figuring how the F am I going to mount all this stuff....
Also a decent match for the SB3.8's
All kind of came together. Think I was looking at 12kw originally.

 

[Maitake]

More background on the project choices.
System will have 3x3.8kw sunny boy string inverters and 2 sunny island battery inverters split phase.
Reviews are they form a robust ac coupled system.
Was eyeing the new sol ark 15k, and it would do the job, but one transistor fails and its out of commission and I'll have no power until it's fixed.
I can have 4 of 5 inverters fail or the battery pack die or lose 2/3 of my panels, and I'll still get 2kw of 120vac when the sun shines.
This project is about resiliency as well as independence.

 

[Hedges]

2kW would be Secure Power Supply.

On-grid or off?
Off-grid, even one Sunny Island can manage the 10.6kW of Sunny Boy. On-grid, would have to turn off one Sunny Boy (or rewire direct to grid) due to Sunny Island relay current limitation.

With an auto-transformer to convert SI's 120V to 120/240V split-phase, if one SI goes down you can commission the other as a stand-alone master, close relay to connect transformer, and keep operating. I plan to connect one for load balancing between phases, but with a relay so disconnected when on-grid.

Not sure if temperature sensors are required in your (lithium?) system. They could be used to enable a fan, at least. Connect to both SI so already wired, nothing to do there when commissioning single SI.

Any data cabling? I don't think that is used with a SI and SB -41 system, other than the RJ-45 cable between two SI. In my case I have RS-485 from SI master to multiple SB. Also to Sunny WebBox or Sunny Boy Control. An RJ-45 connector can be installed in SI conduit knockout, allowing cable to be unplugged from decommissioned master and plugged into the new master.


Have you addressed "load shed" for low battery?
If AC loads run battery down until it disconnects, Sunny Island won't produce AC so Sunny Boy can't recharge battery.
SMA has "emergency charge" instructions regarding connecting AC source to output of Sunny Island, but I don't want to try that. Secure Power Supply could be an AC source for this "jumpstart", probably only so long as SI charging of battery was set sufficiently low to not exceed that power.


I configured SMA's load-shed contactor so all loads connect/disconnect under control of relay #1 in SI master (one more thing I need with a connector to swap if reassigning masters.) Default is load-shed at 70% DoD, but inverter continues operating down to 80% DoD so Sunny Boys can produce.

It is also good to have a way to bypass the inverter if down. I use interlocked circuit breakers in sub-panel. In my case, SB is told by SI whether to use "UL-1741" or off-grid "backup" parameters, so I do not want SB connected straight to grid unless I ensure SB is in "UL-1741" mode. So only loads panel, not PV aggregation panel, has interlock bypass. In your case, if your SB -41 model is left in "UL-1741-SA" mode, they could be switched to grid as well.

 

[Maitake]

2kW would be Secure Power Supply.

On-grid or off?
Off-grid, even one Sunny Island can manage the 10.6kW of Sunny Boy. On-grid, would have to turn off one Sunny Boy (or rewire direct to grid) due to Sunny Island relay current limitation.

With an auto-transformer to convert SI's 120V to 120/240V split-phase, if one SI goes down you can commission the other as a stand-alone master, close relay to connect transformer, and keep operating. I plan to connect one for load balancing between phases, but with a relay so disconnected when on-grid.

Not sure if temperature sensors are required in your (lithium?) system. They could be used to enable a fan, at least. Connect to both SI so already wired, nothing to do there when commissioning single SI.

Any data cabling? I don't think that is used with a SI and SB -41 system, other than the RJ-45 cable between two SI. In my case I have RS-485 from SI master to multiple SB. Also to Sunny WebBox or Sunny Boy Control. An RJ-45 connector can be installed in SI conduit knockout, allowing cable to be unplugged from decommissioned master and plugged into the new master.


Have you addressed "load shed" for low battery?
If AC loads run battery down until it disconnects, Sunny Island won't produce AC so Sunny Boy can't recharge battery.
SMA has "emergency charge" instructions regarding connecting AC source to output of Sunny Island, but I don't want to try that. Secure Power Supply could be an AC source for this "jumpstart", probably only so long as SI charging of battery was set sufficiently low to not exceed that power.


I configured SMA's load-shed contactor so all loads connect/disconnect under control of relay #1 in SI master (one more thing I need with a connector to swap if reassigning masters.) Default is load-shed at 70% DoD, but inverter continues operating down to 80% DoD so Sunny Boys can produce.

It is also good to have a way to bypass the inverter if down. I use interlocked circuit breakers in sub-panel. In my case, SB is told by SI whether to use "UL-1741" or off-grid "backup" parameters, so I do not want SB connected straight to grid unless I ensure SB is in "UL-1741" mode. So only loads panel, not PV aggregation panel, has interlock bypass. In your case, if your SB -41 model is left in "UL-1741-SA" mode, they could be switched to grid as well.

On grid AC coupled, flip interlocked breakers to go off grid whole house backup. I think you are doing this as well.
Not doing load shed. The SI will sleep at X% of charge, the REC BMS will disconnect everything at X-10% charge. I can live without power or flip to the grid if the batts get low.
With a low battery the SI will wake up every 2 hours and form a grid, if the SB's have sunshine it will all start charging again. If that doesn't work, I will have a DC charge controller from the 2 extra panels to charge the battery. Might do this anyway to catch the extra power.

I'm not using the internal relay (I think) nothing connected there.


Looks like my utility accepts CA rule 21 settings so I'll use those so the SI and SB play nice together.

 

[Hedges]

Yes, I use interlocked breakers. One puts garage on backup, rather than straight to grid as usual. Another for the house, normally powered through SI as UPS. Originally I had SI powered from garage panel and also interlocked to backfeed garage panel. Now it is fed by something like a line-side tap, so garage can be fed through SI from grid, working as UPS.
If yours also switch SB, allow 5 seconds off before connecting to a possibly out of phase source.

DC charge controller will eventually awaken it.
In a lead-acid system, battery shunt would be used so SI is aware of charge current. I would think with lithium, BMS provides that info.

At X%, does SI sleep until dawn? I know it has some sleep functions, haven't played with them.
When it does start producing AC again, with sun low in the sky, PV output may still be less than loads. It could be a race for the sun to get higher before battery discharged to shutdown level.

If some of your major loads have a low power control signal (e.g. thermostat of AC or heat), that could be switched by the load-shed relay. You get two settings to control 2 relays, and there are 4 relays total in 2x SI.

Relay 1 in master defaults to "start generator". Relay 2 defaults to "load shed at 70% DoD"

Rule 21, with frequency-watts enabled (may require firmware update if earlier version?) should work well.
For some reason, SMA has a video recommending instead using offgrid setting when SB -41 is behind Sunny Island; that disagrees with written documentation.
I can see the need if a generator is used (tolerates wider frequency range) but wonder why they suggest that for on-grid.

You can get a power relay to load-shed some or all loads. I plan to also do that at a higher SoC like 20% DoD for dryer, water heater, A/C.
The control relays are good for 120/240VAC or 48VDC. 1A ptc fuses on battery+ and battery- can be used to supply it. If you use a 48VDC power relay, you want a good "economizer" which limits current after closing. I ordered the SMA branded one (made by ABB?) from a UK vendor.

 

[RV10flyer]

What are your montly kWH numbers?

I'm at 38 deg Lat, all electric with wood stove backup, off grid 3+ months, 20.6KW pv, wood/unistrut ground mount at 45 deg angle, two SA12K and 134kWh LFE.

 

[Hedges]

There's a thread with many people's figures:

Average Consumption?

As I've been planning a potential move off-grid I have become very curious to know more about the average annual consumption for those who are already doing it. Obviously minimizing consumption is key to success, but how has that worked out for everyone? Would really love to hear from some folks...

diysolarforum.com

 

[Maitake]

Yes, I use interlocked breakers. One puts garage on backup, rather than straight to grid as usual. Another for the house, normally powered through SI as UPS. Originally I had SI powered from garage panel and also interlocked to backfeed garage panel. Now it is fed by something like a line-side tap, so garage can be fed through SI from grid, working as UPS.
If yours also switch SB, allow 5 seconds off before connecting to a possibly out of phase source.

DC charge controller will eventually awaken it.
In a lead-acid system, battery shunt would be used so SI is aware of charge current. I would think with lithium, BMS provides that info.

At X%, does SI sleep until dawn? I know it has some sleep functions, haven't played with them.
When it does start producing AC again, with sun low in the sky, PV output may still be less than loads. It could be a race for the sun to get higher before battery discharged to shutdown level.

If some of your major loads have a low power control signal (e.g. thermostat of AC or heat), that could be switched by the load-shed relay. You get two settings to control 2 relays, and there are 4 relays total in 2x SI.

Relay 1 in master defaults to "start generator". Relay 2 defaults to "load shed at 70% DoD"

Rule 21, with frequency-watts enabled (may require firmware update if earlier version?) should work well.
For some reason, SMA has a video recommending instead using offgrid setting when SB -41 is behind Sunny Island; that disagrees with written documentation.
I can see the need if a generator is used (tolerates wider frequency range) but wonder why they suggest that for on-grid.

You can get a power relay to load-shed some or all loads. I plan to also do that at a higher SoC like 20% DoD for dryer, water heater, A/C.
The control relays are good for 120/240VAC or 48VDC. 1A ptc fuses on battery+ and battery- can be used to supply it. If you use a 48VDC power relay, you want a good "economizer" which limits current after closing. I ordered the SMA branded one (made by ABB?) from a UK vendor.

The sleep restarts are time determined. A window is programmed for restart attempts. This would be when you are expecting sun. It will run for 10 min, this gives the SB's time to wake up and run. If charging current is less than 3 amps at 10min it shuts down again, rinse repeat. Manual start is also possible. Page 150ish in the manual.

I may do some smart load control, but honestly I'm looking forward to see what it can do. I'll be the "load shed controller" heat pump, oil and wood are the three heating options. Lights, electric appliances, I'll manage electric use as I see fit. Not that big of a deal. 43kwh battery could last a day+ or a week depending on what's running.

Manual switchover is a small inconvenience, but it allows whole house backup which I wasn't willing to go without. The wimpy internal relay doesn't cut it in this regard. Sol ark nailed that one with the 200A Internal ATS.

This is 90% grid tie with backup. I'll probably run off grid one week a month to keep the batteries happy. Leave them at 70% or so SOC so there is juice in the tank for outages, but not get beat up from high voltage.

The heat pump in winter will be the major single power user. I may hook this to the 70%DOD relay in the SI to turn it off and have electricity for other things. Good idea ?

 

[Maitake]

What are your montly kWH numbers?

I'm at 38 deg Lat, all electric with wood stove backup, off grid 3+ months, 20.6KW pv, wood/unistrut ground mount at 45 deg angle, two SA12K and 132kWh LFE.

0 production it's not complete yet.
Avg usage is 400kwh/month. Conservation is possible, have incandescents still mostly.
Heat pump is new 1 ton mitsu, will add 8000kwh per year per my calcs.

 

[Maitake]

Batteries arrive from 18650batterystore

 

[Hedges]

Is that what dunce caps looks like after a pallet sits on its head?

 

[Maitake]

Shippers must get joy from smashing those.....like an 8 year old popping bubble wrap.

 

[Maitake]

They look good, crating is exceptional. Dec 2021 date code.
Still waiting on EVE test data....
Edit: Jan 22 date code read it wrong

 

[Maitake]

Here is EVE test data for the cell with the date code pic.
I read the date code wrong, its jan 2022
excel headers are in chinese, did a google translate and they are what you would expect based on the recognizable values.
The cell voltage is as of the ship date. It will be a couple months before I get them hooked up.

2022-01-14
19:35:34
04QCB76831400JBCJ0001080
MB0027
3.2962
0.149
286537.1
K55J
4700006750
0
17
0
082389
1/15/22 10:15
LF280K

 

[Maitake]

Forms are built.
Was going to level them, but think I'll let them run on grade. Might feel different in the morning ?
Posts will be trued up and that's what counts.

 

[Hedges]

I see daylight under the closest form, sloppy concrete bleed expected.
My foundation is pier & grade beam, so dirt erodes and lets in water and rodents.
Is that dirt actually compacted per proper engineering of earth?

 

[Shimmy]

Is your array going to be a single orientation?

Two orientations, e.g. 9:00 AM and 3:00 PM would reduce peak output but increase hours of production (also does reduce total kWh somewhat). That would reduce IR drop in wire and battery charge rate. Should match consumption better and keep battery more full later in the day (if off-grid).

On-grid, it may be power is worth more certain hours of the day. Or, a maximum backfeed power/current allowed.

Bifacial panels.