Series-parallel

[David B.]

I am in the planning stages of my solar design. Currently I have a question about series-parallel.
I'm using 12 canadian 46.8 v 390 watt panels. I think my first calculation is correct,
4 panels wired series-parallel=46.8v @ 16 amps 12ga wire to inverter.
Now this where I'm not sure what happens to volts and current(amps) when I add the remaining 8 panels using the same series-parallel wiring to complete the string. Does the voltage and amps change as I add panels? With 12 panels what would my numbers be?

 

[BentleyJ]

Series connections: Volts is additive and Amps stays the same.
Parallel connections: Volts stays the same and Amps are additive.

 

[Think About It]

What model inverter are you tying them to? What is the MAX MPPT voltage and wattage per MPPT?

 

[Bud Martin]

I am in the planning stages of my solar design. Currently I have a question about series-parallel.
I'm using 12 canadian 46.8 v 390 watt panels. I think my first calculation is correct,
4 panels wired series-parallel=46.8v @ 16 amps 12ga wire to inverter.
Now this where I'm not sure what happens to volts and current(amps) when I add the remaining 8 panels using the same series-parallel wiring to complete the string. Does the voltage and amps change as I add panels? With 12 panels what would my numbers be?

Is the 46.8V Voc or Vmp?
What is the full spec of the panel?
OP: "4 panels wired series-parallel=46.8v @ 16 amps" That cannot be right to get 46.8V from series-parallel connection, that Voltage of 46.8V means all 4 panels are connected in parallel.
Make, model, and the spec of the solar charge controller?

 

[Think About It]

Aside from the other info, how far is it from string to inverter?

 

[David B.]

Is the 46.8V Voc or Vmp?
What is the full spec of the panel?
OP: "4 panels wired series-parallel=46.8v @ 16 amps" That cannot be right to get 46.8V from series-parallel connection, that Voltage of 46.8V means all 4 panels are connected in parallel.
Make, model, and the spec of the solar charge controller?

Well there is my first mistake! Canadian voc51.7 vmp42.9 385w what I am trying to calculate is what my voltage and amps will be with 12 panels. Thanks for the help.

 

[David B.]

Aside from the other info, how far is it from string to inverter?

From last panel 25ft. Thanks for help

 

[BentleyJ]

Well there is my first mistake! Canadian voc51.7 vmp42.9 385w what I am trying to calculate is what my voltage and amps will be with 12 panels. Thanks for the help.

What is the max PV input voltage on the MPPT charge controller or All in One Inverter?

385Watt (STC) panels should produce 385/42.9V = 8.97Imp (lets call it 9A at max power point)

If you connect 2 panels in Series you will have 103.4Voc & 85.8Vmp, 9A.
If you connect 2 panels in Parallel you will have 51.7Voc & 42.9Vmp, 18A.

The above should allow you to calculate Vmp & Imp for any configuration.

 

[Bud Martin]

Well there is my first mistake! Canadian voc51.7 vmp42.9 385w what I am trying to calculate is what my voltage and amps will be with 12 panels. Thanks for the help.

OK, so Imp is 385W/42.9V = 8.97A.
Next we need the spec of the charge controller so we can figure what how the panels will be wired to get the most out off them.

 

[David B.]

Series connections: Volts is additive and Amps stays the same.
Parallel connections: Volts stays the same and Amps are additive.

So what would voltage and amps be with 12 panels

What model inverter are you tying them to? What is the MAX MPPT voltage and wattage per MPPT?

No decision yet, trying to figure roof space, solar panel size etc. I use 40kwh per day. So I'm sizing system from that. Will have 16kwh lifep04 48v battery. ATS from grid to inverter. Somewhere 6500w inverter 220v in and out, 48v charger like sungold and aims. Thanks for help

 

[David B.]

OK, so Imp is 385W/42.9V = 8.97A.
Next we need the spec of the charge controller so we can figure what how the panels will be wired to get the most out off them.

No decision yet on controller or inverter. Looking for charging 48v 16kwh battery and producing 40kwh per 24 hours. Of course looking also to reduce my kwh average. I only have room for 12 panels, but they face due south and get a good 6 hours of sun. So that's where I'm at. Just got hung up on this series-parallel calculation.

 

[David B.]

What is the max PV input voltage on the MPPT charge controller or All in One Inverter?

385Watt (STC) panels should produce 385/42.9V = 8.97Imp (lets call it 9A at max power point)

If you connect 2 panels in Series you will have 103.4Voc & 85.8Vmp, 9A.
If you connect 2 panels in Parallel you will have 51.7Voc & 42.9Vmp, 18A.

The above should allow you to calculate Vmp & Imp for any configuration.

Thanks for the help. Iet me use this for a while.

 

[Bud Martin]

No decision yet on controller or inverter. Looking for charging 48v 16kwh battery and producing 40kwh per 24 hours. Of course looking also to reduce my kwh average. I only have room for 12 panels, but they face due south and get a good 6 hours of sun. So that's where I'm at. Just got hung up on this series-parallel calculation.

Twelve 385W panels = 385W x 12 = 4.62kW x 6 hours = 27.72kWh per day, that is how much power you will produce from your panels, but in real world will be less, may be around 80%.
OP: Looking for charging 48v 16kwh battery and producing 40kwh per 24 hours.
Please clarify about 'producing 40kwh per 24 hours'. Or do you mean consuming per day?

 

[David B.]

Twelve 385W panels = 385W x 12 = 4.62kW x 6 hours = 27.72kWh per day, that is how much power you will produce from your panels, but in real world will be less, may be around 80%.
OP: Looking for charging 48v 16kwh battery and producing 40kwh per 24 hours.
Please clarify about 'producing 40kwh per 24 hours'. Or do you mean consuming per day?

I use 40kwh a day per my electric bill. So I started there. Then I checked my roof and I have enough room for 12 panels. That is what it is. So I am first seeing what I can produce from solar then determine the inverter. I can afford the 16kwh battery. So I need enough solar to charge the battery, and provide house power. Beginning to look like I can reduce my power bill but not eliminate it. Figure 12kwh to charge battery every morning then I'll have 15kwh for the rest of the day. ATS will switch from solar to grid. I'll make battery charge priority. Stll need to figure out the solar wiring size. Designing first. Also gotta figure how mant volts 12 panels will be pumping out.Thanks

 

[David B.]

Thanks for the help. Iet me use this for a while.

Hey man, I used your info and tried to do the calc. Tell me what you think,
4 panels in series voc 52vx4=208v amps=9
3 parallel strings of 4 panels= 208v and 27amps to combiner. Does this sound right?

 

[BentleyJ]

Hey man, I used your info and tried to do the calc. Tell me what you think,
4 panels in series voc 52vx4=208v amps=9
3 parallel strings of 4 panels= 208v and 27amps to combiner. Does this sound right?

Yes, although the actual voltage when current is flowing will drop to Vmp which is 42.9V x 4 = 171.6V.

Under normal operating conditions the PV array usually doesn't produce 100% of the STC rating due to temperature, sun angle, dust on the panels, aging Etc.

 

[David B.]

Yes, although the actual voltage when current is flowing will drop to Vmp which is 42.9V x 4 = 171.6V.

Under normal operating conditions the PV array usually doesn't produce 100% of the STC rating due to temperature, sun angle, dust on the panels, aging Etc.

Agreed, used the higher number as fail safe. Now looking at hybrid inverters that will carry 208v at mppt. Do you have any preferables looking at 6500 watts 48 volt charger