Connecting solar panels

[Johnmahon]

Hello everyone!

Looking for some advice on connecting 3 solar panels where 2 of them are exactly the same and they are already connected together in parallel. Wanting to add a 3rd panel to the system that has been given to me, but the specs are different.

Here are the specs of the 2 panels already connected together in parallel:

Voc 71.0 v
Current at maximum power 5.65 a
Short circuit current 6.08 a
Voltage at maximum power 59.4 v
Nominal power 335 watts

And here are the specs of the 3rd panel I want to add to the system:

Voc 37.93 v
Current at maximum power 8.85 a
Short circuit current 9.15 a
Voltage at maximum power 31.03 v
Nominal power 265 watts

Is this possible and/or should I even do it?

thanks!

 

[Forbisher]

What is your charge controller and input specs?
Maybe add the 3rd lower voltage panel on its own controller?
What kind of battery are you charging?

 

[Johnmahon]

I have the Victron smart mppt controller 150/35 and a 24v/100ah lithium ion battery bank comprised of 2 battleborn batteries connected in series.

 

[Johnmahon]

Can you have two charge controllers charging a single battery bank using two separate panel systems? I do have another Victron smart charge controller 100/20 that could be used with the additional panel.

 

[Craig]

Can you have two charge controllers charging a single battery bank using two separate panel systems? I do have another Victron smart charge controller 100/20 that could be used with the additional panel.

Yes this is quite fine.and would probably give you highest output.

 

[Johnmahon]

If you have a sunny day producing a high rate of charging, and a significant load, say a heater or ac unit, will both SCCs feed the load via the inverter directly, or feed the battery, which in turn feeds the inverter while being charged? Coming into summer, trying to produce as much power as possible (with what I have) and run a small ac unit in the shed.

 

[Craig]

It will do a mixture of both the energy is going to flow path of least resistance. You should put a meter or two on it and make a video

 

[Forbisher]

Yes this is quite fine.and would probably give you highest output.

Can he series connect the 2 panels at 142 volts or is that too many
volts or watts for the Victron smart mppt controller 150/35? thanks!

150V absolute maximum coldest conditions 145V start-up and operating maximum
12V: 500W / 24V: 1000W / 36V: 1500W / 48V: 2000W

Voc 71.0 v
Current at maximum power 5.65 a
Short circuit current 6.08 a
Voltage at maximum power 59.4 v
Nominal power 335 watts

 

[Johnmahon]

Can he series connect the 2 panels at 142 volts or is that too many
volts or watts for the Victron smart mppt controller 150/35? thanks!

150V absolute maximum coldest conditions 145V start-up and operating maximum
12V: 500W / 24V: 1000W / 36V: 1500W / 48V: 2000W

Voc 71.0 v
Current at maximum power 5.65 a
Short circuit current 6.08 a
Voltage at maximum power 59.4 v
Nominal power 335 watts

I chose to parallel connect the panels as it was getting close to the 150 mark. Only leaving 8 v difference. Of course on cold circumstances, which here in Phoenix, it does not get that cold. But still pretty close to the threshold.

 

[JoeHam]

If you parallel panels of different amperage you will be limited by the lowest amp panel.

If you series panels of different voltages you will be limited to the lowest voltage.

* As I recall *. I will have to look up a reference.

 

[Johnmahon]

If you parallel panels of different amperage you will be limited by the lowest amp panel.

If you series panels of different voltages you will be limited to the lowest voltage.

* As I recall *. I will have to look up a reference.

Yes, I believe I recall reading this as well. I think I am going to just apply two SCC and two solar units to the system. Seems to be the best solution under the circumstances.

Thanks for the comment!

 

[tictag]

@JoeHam is 100% correct, you mustn't add dissimilar spec panels, well, I mean, you can, but it is ill advised!

The two SCCs will work just fine, in fact, if you had a Control GX/VX you could specify things like total charge current and they would both work together collaboratively.

 

[Johnmahon]

The dual SCC are working perfectly and in complete harmony with each other. I’m sort of a Victron fanboy, but this has made me even more so. What is amazing is when you see both charge controllers go to float mode and bulk mode at the same time as they begin to work in tandem. Also, now I’m getting 750w coming to the bank. Running my 8000 BTU air conditioner now with extra watts to spare, thanks to everyone’s advice.

Take a look: