Building a whole home system but have questions

[Shamoke]

Hope this is the correct forum for this.
I am rehabbing a double wide mobile home and want to build a whole home solar backup system. I've been looking to use EG4 inverter(s) and battery(s) along with solar panels on an adjustable ground mount. I am undecided on the equipment I am going to use and have concerns about compatibility.

1. On the inverter side I am thinking about using 2 x eg4 6000XP or 1 x 12KPV. I know the 12KPV is newer and more capable but costs a lot more too. I can buy two of the 6000xp's for less than one of the 12KPV's and have a safety backup if one stops working, I.E. Still have some power if/when one goes down.

2. The battery I'm thinking about is the EG4 Powerpro. I can start with one and expand later as I can afford to.

3. Panels: I have 10 370 Aptos DNA-120-BF26 370 watt panels now and had planned to buy more but they are no longer available. this leads me to question if I could use another panel in conjunction with the 370 watt panels with the inverters listed above, would it create any issues with different amp and voltages coming into the inverters.

If I have two inverters and max out one with a single solar array could I use a second array with different amp and voltage ratings with the other inverter without causing any issues? Would that cause any issues with having more than one battery? If I have two inverters and two batteries do I connect both batteries to the first inverter or have a single battery for each inverter?

I know I am throwing a lot of questions out there and I do appreciate any and all responses.

 

[Hedges]

You can use totally different PV panels if connected to independent MPPT inputs, or to separate inverters.
You can parallel strings of different PV panels if Vmp of the strings are similar, ideally within 5% of each other.
Parallel strings do not have to be same orientation as each other, regardless of what manufacturer says. Panels in series do have to be same orientation.

 

[DIYrich]

Consider the new growatt sph 10k. About the same price as two 6000xp.

 

[Lawrence_SoCal]

Hope this is the correct forum for this.
I am rehabbing a double wide mobile home and want to build a whole home solar backup system. I've been looking to use EG4 inverter(s) and battery(s) along with solar panels on an adjustable ground mount. I am undecided on the equipment I am going to use and have concerns about compatibility.

1. On the inverter side I am thinking about using 2 x eg4 6000XP or 1 x 12KPV. I know the 12KPV is newer and more capable but costs a lot more too. I can buy two of the 6000xp's for less than one of the 12KPV's and have a safety backup if one stops working, I.E. Still have some power if/when one goes down.

Will just released a video 9days ago on the EG4 12pv with specific commentary at the end (time marker 11m38s) on the 18K vs 12K vs 2x 6000XP
a big factor is grid-tie functions... which I'm assuming you are now? or is this a full off-grid system?
And a quick check at one well known vendor on these forums indicates an approx 10% premium ($400?) for the 12K vs 2x6000XP kit, and that does NOT include any extra installation costs for extra wiring for a 2nd inverter, much less professional electrician labor if you go that route

If I have two inverters and max out one with a single solar array could I use a second array with different amp and voltage ratings with the other inverter without causing any issues?

Solvable issues, but biggest factor will be whether
1. grid-tied system or not? and if yes, are you looking for grid-forming capability (ie power house while grid-down? [vs just time-shifting/increasing self-consumption]

Would that cause any issues with having more than one battery? If I have two inverters and two batteries do I connect both batteries to the first inverter or have a single battery for each inverter?

This is NOT may area... but for sake of discussion.. I'd assume 2 inverters gets tricky (to not recommended/ sometimes not possible/compatible?) to coordinate in a grid-forming situation. Again, I'm simply doing a SWAG, but I'd assume typical recommendation would be to have one inverter be capable of local grid-forming, and the other simply follow the lead of the 'primary' inverter. And connecting batteries to that would probably be easier, BUT driven your situation (example covering both 'phases' of a 240V main load center and or inverter output capacity and your load ... ex 1 INverter not enough to power desired loads, in which case you must also power 2nd inverter from battery).

all of which to me would say, long walk off short pier... get the 12K or similar and save yourself a whole load of hassles/complications
but I'll watch this thread to learn... as I could easily be completely wrong

 

[Hedges]

2 inverters in parallel for grid forming is pretty common. One serves as master, other as slave.
If master goes down you probably have to reconfigure slave as sole master and move any communication cables.
Connectors rather than screw terminals could make it easy enough do in the dark. (I gotta set mine up that way. And second temperature sensor too because I have AGM not lithium battery.)

Bigger difficulty can be pass-through from the grid. If you split the grid out through 2 breakers to 2 inverters and recombine, current may not split evenly, so no guarantee you can have more load than what one inverter can pass through. I had such a problem until I changed breaker type (and enclosure to fit it.)

Since your system is backup to the grid, not offgrid, you could go with the single larger inverter (does it have higher pass-through current?)
Have a mechanism to bypass inverter if failed and get power straight from the grid. I used an interlocked "generator" breaker in my panel.

 

[Shamoke]

I appreciate all the information and I am still trying to wrap my head around it. If I use the EG4 12k, which has a nominal voltage input of 360 volts and 25 amps usable then I should be able to use a string of ten of the Aptos 370 panels one input which would have 345 volts at 10.72 amps on that string. If I am reading this correctly.
Is the rated input for the 12K listed per MPPT or both MPPTs together? If separately then I can use two strings of panels with the same or close to the same ratings on the same 12K?

 

[Shamoke]

I need to clarify that I am planning this system to not feed back to the grid but run the house off of solar with the grid as supplemental when the sun doesn't shine or we just need more power. Eventually I will have a backup generator to supplement the solar as needed. If we have a grid down situation then I want to be able to run the whole house from a solar and generator combination.

 

[Hedges]

You could put 10s2p of those panels on one MPPT input, and 10s2p on the other MPPT input. 40 panels total. Maybe 44.

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Looks like Voc = 41.4V, so 10s is 414V, which is fine given 500V max for the inverter (allows extreme cold with temperature coefficient -0.28%/°C)
Could probably accept 11s but have to check the numbers.

https://www.aptossolar.com/wp-content/uploads/2023/05/DNA-120-BF26_370W_Datasheet52623.pdf

 

[Shamoke]

Ahh so I need to use open circuit volt ratings instead of rated voltage. So with the 370 watt panels I wouldn't want to exceed the 12k watt usable on the 12K, so 30 panels to leave a bit of head room. So those max inputs listed on the data sheet are per MPPT and not combined?

 

[Hedges]

You can usually get away with more watts of panels than the data sheet says. Inverter won't draw more than it wants.
In particular, if you parallel PV strings oriented SE with strings oriented SW, you can overpanel to maybe 140% or so of what it says and not even waste anything.

(It can be OK to exceed current specs. To be done carefully, with understanding. Especially, don't also connect the panels reverse polarity.)

Never exceed max PV input voltage. You have to calculate how much voltage rises in record coldest temperature. Or assume a conservative +16% increase above Voc.
The current and voltage given for its MPPT inputs look like each can take about half the total wattage it says. Check the math. I don't think you could put 12kW or 15kW on a single MPPT without exceeding current or voltage.