Solar Panel mixing Optimization

[hgg]

Hi,

I currently have a small 2kW solar array in a series/parallel configuration as in the diagram below,
together with the Phocos 3kW hybrid inverter and a custom 6.7kW LiFePo4 battery.



Everything is working fine but I need just a bit more solar power for the perfect balance.
The solar panels are from Eco Delta, they are shingled and are working amazing under
all conditions. Unfortunately they have decided to stop exporting to Europe because
of the cost and the lower priced normal panels.

So I am looking to add another two panels to my existing configuration.
I have narrowed them down to the Hyundai 440W and the Sharp 415W.
The new configuration will be three panels in series (two EcoDelta plus the new one)
and two series in parallel.

With the Hyundai I will get a theoretical total of 2773 W and with the Sharp 2807 W
Even though the Sharp has less watts than the Hyundai it will give me more power
because its current is closer to that of the EcoDelta. (on the negative side, if I choose
the Sharp I will loose the performance of the shingled technology.)

My concern is that the Vmpp difference of the EcoDelta and the Sharp is 7.51V while
the difference of the EcoDelta and the Hyundai is only 2.7V and I do not know how
the MPP charge controller will respond.

So, my question is, what is the actual result of a higher Vmpp difference if you mix
panels in series, will it bring my whole system down to a lower wattage?
Which panel do you think is most suitable ?

Thank you.

 

[sunshine_eggo]

3S on a 145Voc limit MPPT is asking for trouble. You need to be WELL under Voc limit to allow for cold temperature voltage effects. If it ever gets below freezing, you're going to pop the MPPT.

Is there a reason you're not just putting 2S hyundai panels in parallel with your existing 2S2P array? Of all possibilities, that's the most practical.

 

[TomC4306]

^That

 

[hgg]

3S on a 145Voc limit MPPT is asking for trouble. You need to be WELL under Voc limit to allow for cold temperature voltage effects. If it ever gets below freezing, you're going to pop the MPPT.

Is there a reason you're not just putting 2S hyundai panels in parallel with your existing 2S2P array? Of all possibilities, that's the most practical.

Because it will produce even lower power at 2743 W.
I also want to minimize the cable loses and voltage drop.

It has a 7.7V margin with the Hyundai and 13V with the Sharp panels.
How much lower should the array total Voc be in order to compensate
for freezing temperatures?

 

[sunshine_eggo]

Because it will produce even lower power at 2743 W.

Is it worth destroying your equipment for 34W?

I also want to minimize the cable loses and voltage drop.

Is it worth destroying your equipment for a very small improvement in losses?

It has a 7.7V margin with the Hyundai and 13V with the Sharp panels.
How much lower should the array total Voc be in order to compensate
for freezing temperatures?

I already told you:

If it ever gets below freezing, you're going to pop the MPPT.

Literally - 0°C, and you run the risk of destroying the MPPT. Are you in an area where freezing isn't even a possibility? Ever?

 

[hgg]

Nobody wants to destroy its equipment but I want to squeeze out of the system as much power as possible
because I do not have more space for solar panels.

I found this online calculator: Max Voltage Calculator
In my area we don't get temperatures lower than -5C and according to the above calculator,
the Huyndai will give me a Max of 149V (bye bye MPPT..) but the Sharp will give me 142.3 Max.

Its so easy to incorporate an over voltage protection in the MPPT units that makes you wonder.

So getting back to my initial question, if I choose the Sharp panels what is the actual result of the higher
Vmpp difference if you mix panels in series, will it bring my whole system down to a lower wattage?

 

[sunshine_eggo]

So getting back to my initial question, if I choose the Sharp panels what is the actual result of the higher
Vmpp difference if you mix panels in series, will it bring my whole system down to a lower wattage?

The above question is irrelevant, and it indicates that you lack even a basic understanding of voltage and current in an array.

What you're planning is foolish.

If you want to increase the size of your array, wire 2S hyundai in parallel with your existing array. It presents no risk to the controller.