Good question. In post 97 above I said doing so was a bad idea.
2x Sol-Ark 15K's + HomeGrid Stacks
- Thread starter 2TrevorJ
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Hedges
I See Electromagnetic Fields!
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- Mar 28, 2020
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The suggestion to reduce demand would be so two inverters aren't needed, could just use one.
I was thinking of that for while off-grid, but to provide automatic backup, would also need to limit pass-through current to less than 200A.
Or, one is separate while on-grid, but has transfer switch to be fed by inverter when grid down.
Because system already splits 400A service to 2x 200A panels, I would try having systems parallel except output. If that does work (each regulates AC voltage while supplying needed current on its branch), should avoid all issues of balancing current and switching not being exactly simultaneous.
When passing through grids to load, parallel can have issues.
I do that with 4x Sunny Island, stacked 2p2s. Each has 56A pass-through so this should support 112A on each phase of 120/240V.
I've got the pass-through current pretty well balanced, but I think at the moment of switching grid relay, it may have had excess current in one and shut down or tripped a breaker. It usually works, but I saw it trip when electric furnace and pool pump were together drawing more than 56A (no, I don't intend to run electric heat off inverter, but don't have it either automatically switched off or hard-wired to grid yet.)
Schneider doesn't even try to do that; they say to use larger external relay.
With SolArk, already has 200A internal relay. Parallel should be no problem if only for more inverter capacity, but could be a problem if pass-through current > 200A.
How would one 15K pass through current > 200A ?
Ok, re-read that. I’m not investing in 400A equipment. Too expensive.
Just distribution blocks supplying 2 x 200A panels. So potential of 400A, though I’m sure I’ll never get close to that.
DIYrich
Solar Wizard
In the Battery Setup, you can lower the Float and Absorption voltages. Maybe drop them by 0.1 or 0.2 volts so the battery doesn't hit 100% charged.
DIYrich
Solar Wizard
Common Battery:
If you split the system, then each system gets its own battery. They can't share capacity and draw rate when split.
Also, they can't share PV when charging (if a battery system is full, the excess pv is sent to the grid). Similarly, excess PV can't be shared across loads. In theory, DC PV charging is more efficient because the power doesn't have to be converted to AC (DC PV goes directly to charging DC Batteries).
Max power off grid:
One Sol-Ark can deliver a max of 12,000 watts off grid without PV. In parallel, they can deliver 24,000 watts without regard to which system needs it. With separate systems, no single system can use more than 12,000 watts. The excess from one inverter can't be shared with the other.
Unbalanced load off grid:
There is a limit to the amount of unbalanced load one Sol-Ark can handle (2kW?). Two Sol-Arks can handle twice as much.
Downside to parallel:
If one inverter goes down, they both go down. In separate systems, at least one keeps functioning.
Although, in a parallel systems, the working unit can be re-programmed to run as single (turn off the other), so you can have whatever critical loads on either system.
DIYrich
Solar Wizard
You would probably loose battery com, and have to go by battery voltage only. You then run the risk of both units drawing or charging at the same time. Ok if you limit draws/charging to 1/2 of max discharge/charge rate.
I’m with you on that one. My very first sentence in this thread started with “If you truly need 400 amps and are planning on dual SolArk 15ks, …” I’m always skeptical of these huge systems being built, especially when they have the grid to fall back on; but I’m not well prepared to question someone else’s needs or wants when I haven’t taken any steps in their shoes. If they want 400 amps and can pay for it, so be it.
2TrevorJ
Bend the Joules
I would need to take it out of closed-loop (SOC) mode...negating one of the best features that I spent extra money to ensure it works without drama. Besides...in closed-loop the battery stays at/under 51.7V 99.9% of the time...0.5V under the 52.2V max recommended voltage so I guess they already took your advice.
Keep in mind this is a 15 cell config...hence the low(er) voltage.
2TrevorJ
Bend the Joules
The Skyboxes came with my head units. From what I understand HomeGrid will send you SkyBoxes for free if you didn't get them initially.
Supposedly you can permanently install them inside of the outer panel but I'm skeptical there's enough room. I still have yet to install those panels as I need to flip my negative battery cable connector over for clearance and I've had no reason to take the system down. I leave the skyboxes in place but unpowered since their wifi radios are always transmitting and the HomeGrid monitoring app is WAY beta.
Of note for everyone with HomeGrids - there's new firmware on the website as of the middle of last month:
Thats great and thank you for that information. I shall request one. I did get the "Error 20" yesterday but a simple power cycle fixed it. I love the HomeGrid battery system as a whole. Just wish firmware updates were easier.The Skyboxes came with my head units. From what I understand HomeGrid will send you SkyBoxes for free if you didn't get them initially.
Supposedly you can permanently install them inside of the outer panel but I'm skeptical there's enough room. I still have yet to install those panels as I need to flip my negative battery cable connector over for clearance and I've had no reason to take the system down. I leave the skyboxes in place but unpowered since their wifi radios are always transmitting and the HomeGrid monitoring app is WAY beta.
Of note for everyone with HomeGrids - there's new firmware on the website as of the middle of last month:
I updated mine yesterday (via Skybox & USB drive) and both the head units and the individual slabs were updated. No new issues and I think it partially fixed the only (minor) issue I had where the master BMS reported 99% SOC when charged and hardly ever hit 100%. Now it's 100% about half the time. ?
6
629658
Guest
Why change the firmware? I’ve had my batteries going for 6-8 months now. Never touched them after installation.
My view of it is for 2 reasons I suppose:
1. To deal with the Error 20 message I got. Seems to be fixed with latest firmware. Although I dont see how I can determine my current version.
2. Potentially helping with efficiencies in battery management. Better firmware to improve battery standby loss or other code that hinders optimal operation.
Of course firmware can break things too.
6
629658
Guest
Yea I’d just say be careful. Easy to get caught up in the gotta have the latest everything. I once did a beta firmware upgrade on my NAS. It tanked my entire NAS required hours and hours to reconstruct. After that I leave it alone and if I update it’s months after release and only official public release.My view of it is for 2 reasons I suppose:
1. To deal with the Error 20 message I got. Seems to be fixed with latest firmware. Although I dont see how I can determine my current version.
2. Potentially helping with efficiencies in battery management. Better firmware to improve battery standby loss or other code that hinders optimal operation.
Of course firmware can break things too.
2TrevorJ
Bend the Joules
I haven't posted in here in a bit because outside of troubleshooting my Emporia EVSE charger's "excess solar" function the system has been working perfectly. Zero drama/issues/hiccups/weirdness.
The two HomeGrid stacks are staying in lock step with each other now...never more than 1% indicated SOC difference. As always, the batteries run the house when there isn't enough solar so they get plenty of exercise and I think the batteries have stabilized with use.
The BMS also consistently calls for 600A charging anytime below 90% SOC. It's been that way for quite a while now. Good turn of events as the charging current was weaksauce coming out of the gate (compared to the marketing).
April wrap-up and a better pic of the 20.4 kW array is attached.
Again, the only time I mix in the grid is when solar production is low and I have to charge my daughter's car at that time. Her car accounted for 403.6 kWh of April's load. I think that's a record in itself. We usually don't drive it that much.
Peak Records:
-- PV Production 22.9 kW
-- PV Charging 21.0 kW (407A @ 51.7V)
-- Grid Charging 20.8 kW
-- Export 20.5 kW
-- Load 15.4 kW (that's just natural load; I've never intentionally tried to push it)
-- PV Daily Production 118.9 kWh
Averages:
-- PV Daily Production: 82.3 kWh
-- Daily battery usage: 17.4 kWh
-- Daily battery usage as a percentage of total load: 35.6%
-- Battery efficiency: 85.9%
-- 2 kW PV Available from 8:04 - 19:26 on sunny days
Those big peak numbers are all attributed to cloud edge effect so don't think that your system is broken. ? Just cool that my setup can capture & distribute it in real-time with no clipping. Normal production peaks out at 16.5-16.7 kW due to my array's multi-plane arrangement.
Battery-wise the lowest I've seen is 22% after a few low production days. Most of the time it's in the 70's in the morning and they're at 100% around 11:30 or noon. The highest single night usage (coming off a 100% evening) has been 61% in the morning. It was a hot night and both A/C units ran throughout the night along with the dishwasher and doing a bit of laundry (reminder - gas dryer). Again - I never charge the car from house battery - makes zero sense considering the efficiency hit and the amount of credit I have with the utility. I'll save that for the zombie apocalypse.
About the only (sorta) issue I have is external. Voltage has always been high in this house...248-252V before my system was commissioned. I'm seeing it occasionally creep up to just over 254V indicated while exporting big numbers. I've seen no issues with my household equipment, but I know it's technically out of limits. Trying to decide if I want to reach out to the utility. I mean...their engineering fully approved my setup but I still don't want to stir the pot and have them potentially ask me to limit my export (booooo!). Is there anything they can do with the transformer (other than replace it)? One variable is there are still 6 or 7 houses on my street that are vacant; brand new and unsold. Local load is sure to increase once they're occupied.
The two HomeGrid stacks are staying in lock step with each other now...never more than 1% indicated SOC difference. As always, the batteries run the house when there isn't enough solar so they get plenty of exercise and I think the batteries have stabilized with use.
The BMS also consistently calls for 600A charging anytime below 90% SOC. It's been that way for quite a while now. Good turn of events as the charging current was weaksauce coming out of the gate (compared to the marketing).
April wrap-up and a better pic of the 20.4 kW array is attached.
Again, the only time I mix in the grid is when solar production is low and I have to charge my daughter's car at that time. Her car accounted for 403.6 kWh of April's load. I think that's a record in itself. We usually don't drive it that much.
Peak Records:
-- PV Production 22.9 kW
-- PV Charging 21.0 kW (407A @ 51.7V)
-- Grid Charging 20.8 kW
-- Export 20.5 kW
-- Load 15.4 kW (that's just natural load; I've never intentionally tried to push it)
-- PV Daily Production 118.9 kWh
Averages:
-- PV Daily Production: 82.3 kWh
-- Daily battery usage: 17.4 kWh
-- Daily battery usage as a percentage of total load: 35.6%
-- Battery efficiency: 85.9%
-- 2 kW PV Available from 8:04 - 19:26 on sunny days
Those big peak numbers are all attributed to cloud edge effect so don't think that your system is broken. ? Just cool that my setup can capture & distribute it in real-time with no clipping.
Normal production peaks out at 16.5-16.7 kW due to my array's multi-plane arrangement.Battery-wise the lowest I've seen is 22% after a few low production days. Most of the time it's in the 70's in the morning and they're at 100% around 11:30 or noon. The highest single night usage (coming off a 100% evening) has been 61% in the morning. It was a hot night and both A/C units ran throughout the night along with the dishwasher and doing a bit of laundry (reminder - gas dryer). Again - I never charge the car from house battery - makes zero sense considering the efficiency hit and the amount of credit I have with the utility. I'll save that for the zombie apocalypse.
About the only (sorta) issue I have is external. Voltage has always been high in this house...248-252V before my system was commissioned. I'm seeing it occasionally creep up to just over 254V indicated while exporting big numbers. I've seen no issues with my household equipment, but I know it's technically out of limits. Trying to decide if I want to reach out to the utility. I mean...their engineering fully approved my setup but I still don't want to stir the pot and have them potentially ask me to limit my export (booooo!). Is there anything they can do with the transformer (other than replace it)? One variable is there are still 6 or 7 houses on my street that are vacant; brand new and unsold. Local load is sure to increase once they're occupied.
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Transformers have multiple taps. You should call and ask them to check; adjusting it isn't that hard. Damage from over-voltage is long-term degradation, so you do not see the effects right away.
How many homes are fed by the one transformet?
2TrevorJ
Bend the Joules
Looks like there are six 50 kVa 14.4 kV transformers on my street feeding roughly 30 single family houses. So...maybe 5 houses?
I did some reading and looks like those taps are usually 2.5% increments. Does that mean they could potentially drop the voltage to ~243v?
EDIT: just put a service request in.
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It depends on if the distribution circuit is over-voltage or just the local transformer. The distribution transformers often have automatic tap changers which work in smaller increments.
The ANSI standard is +/-5% at the meter and +4/-8% at the load. Most utilities want to keep it tighter than that under normal circumstances to allow for extrordinary conditions.
2TrevorJ
Bend the Joules
Utility just got done. Shot power with a fluke and it was 1.8V under what the Sol-Arks report. This jives with my cheap multimeter. Found meter base connections well under-torqued on the transformer/curb side. ? The meter base has been sealed since the house was built (we did all the solar work on the house side of the main 200A breaker next to the meter). Also used a suitcase like load tool to load each leg between the house and transformer and everything behaved as expected.
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