Parallel inverter setup questions

[Dinobot248]

Some newbie questions

Current setup

- Single EG4 6500EX
- Second EG4 6500EX needs to be setup
- 6 Lifepower4 batteries and rack
- 8kw array
- Grid is available but it's not connected
- All circuits moved to critical load panel and it is completely separate from original house panel / load center.
- I use 120v. No need for 240v, don't have anything that takes 240v. I am open to setting up up split phase but not right now.
- Worst case scenario requires more than 6500 watts eg if microwave, hair dryer, air fryer, multiple portable heat pump or AC, washer dryer are on at the same time. It's unlikely but it can happen when the rest of the house is oblivious and lacks basic electricity knowledge (eg kids and wife).

MPPT 1 has 2p12s. Two parallel sets of 12 panels x 170w at 20v 8a in series.
MPPT 2 has the same setup





Now the questions



1. Does the PV array need to be the same or similar PV for both inverters?

I'm thinking the answer is NO since one array could go down for whatever reason and your setup should still work.

Also, I don't want to rush and get the additional 8kw of PV to match or maximize all 4 MPPT controllers. I have about 4kw in boxes for something else, see questions below.

2. Can the second inverter not have any PV, meaning no solar at all? It just connects to the battery. Is the 6500ex smart enough, designed or capable to properly apply and use up the existing PV from inverter 1 before either inverter 1 and 2 draws from the batteries?

I have my ground mounts setup for the 8kw array ( actually two 4kw arrays) and I don't want to rewire them.

I want to setup the second inverter but don't want to be rushing to get the necessary PV array in place. I may want to get some fancier (bi-facial) or larger panels than the existing 170w panels for the 3rd and 4th MPPT channels on the second inverter.


3. I have 4kw of spare solar panels (24 x 170w) in boxes right now.

House is oriented North and trees are on both east and west side. PV array is in back yard. I get 80% of my solar from around 12 noon to 4pm.

Can I over provision one MPPT to have say 6kw when spec is 4kw? More specifically, can I overprovision the array and set them in parallel to collect sun at different key times of the day.

I think it is doable and relatively safe but need a sanity check.


Hear me out if it is not clear. 2kw portion will face east to collect morning sun, 2kw will face south to collect afternoon sun 12-4pm, and 2kw will face west to collect evening sun. The individual 2kw arrays will be 12 panels set in series or 240v at 8a.



Or would it be better to simply setup a 4kw array facing south and call it a day for the 3rd MPPT channel. Keep the 4th MPPT channel open. Save the extra effort for something else.


Thanks for reading if you made it this far.

 

[FilterGuy]

1. Does the PV array need to be the same or similar PV for both inverters?

No. They are totally independent

2. Can the second inverter not have any PV, meaning no solar at all? It just connects to the battery. Is the 6500ex smart enough, designed or capable to properly apply and use up the existing PV from inverter 1 before either inverter 1 and 2 draws from the batteries?

I assume it is only one battery bank and you are not trying to use two separate battery banks. (I don't think the 6500 supports split banks)

The inverter without solar will use the battery any time it is called on to generate power. I don't think the 6500s will coordinate and only use the inverter with solar input.

However, if the inverter without solar has more solar energy than it needs, it will be putting the extra energy into the battery as the other inverter is pulling it out.
.

Hear me out if it is not clear. 2kw portion will face east to collect morning sun, 2kw will face south to collect afternoon sun 12-4pm, and 2kw will face west to collect evening sun. The individual 2kw arrays will be 12 panels set in series or 240v at 8a.

No. if they are all in series it won't work. All the panels on a string should face the same direction.

If each set of 4 was it's own string and then the 3 strings were wired in parallel it could work.

Or would it be better to simply setup a 4kw array facing south and call it a day.

I would lean toward doing this. The total production would probably be more than the separate facing panel arrangement.

Note: All this assumes you have the battery or load to take the energy. If the batteries fill by 1:00 and there is no load that needs the energy the 'extra' generation is wasted.

 

[Dinobot248]

Thanks Filter Guy

When the idea moves out of my head and onto paper / smartphone, it's more easier to point out the flaws.

I can see for question 3 above, setting up a simple 4kw array facing south is now the easier and best overall course of action for the second inverter.

I figured the 6500EX and probably most other inverters in this price range would not coordinate with each other when set in parallel.

The best solution for PV array setup that minimize the impact of inverters not taking to each other is to setup as equal as possible PV arrays for each inverter.

 

[Mattb4]

...

2. Can the second inverter not have any PV, meaning no solar at all? It just connects to the battery. Is the 6500ex smart enough, designed or capable to properly apply and use up the existing PV from inverter 1 before either inverter 1 and 2 draws from the batteries?

...

Having both AIO's hooked to the common DC battery bus means that the one without PV input thinks it is drawing from the battery. However the battery does not give out any power if the other AIO's incoming PV is putting out enough amps to cover all the loads for both AIO's. It is not a matter of them coordinating it is simply the potential of PV is higher than the battery in the circuit. If at any point the PV incoming potential drops to the point the battery potential is higher than the battery it begins discharging.

My first sentence however has some importance in the way the AIO displays input and output. Because it has no PV input of its own it will always show a drain from the battery. It does not know that the common DC bus is supplied by another AIO's PV source.