12v vs 24v with 1 or 2 panels

[Boisblancboy]

Ok this may be very trivial but instead of one 200 watt 12v panel would 2 100 watt panels in series for 24v be much better if the wire length to the controller was around 50-60’?

Trying to learn some pros and cons.

Thanks for your time.

 

[DIYrich]

200 watts at 12v is about 17 amps, or 9 amps at 24v.

Using 60ft of 10 awg wire, calculator was showing 25+% voltage drop at 12v 17a, and 5% drop at 25v 9a.

 

[Boisblancboy]

200 watts at 12v is about 17 amps, or 9 amps at 24v.

Using 60ft of 10 awg wire, calculator was showing 25+% voltage drop at 12v 17a, and 5% drop at 25v 9a.

Thank you for the explanation.

 

[740GLE]

The cost of two 100w panels isn’t that far away from one 300-450w panel and the voltages will be about the same once they hit the SCC.

 

[Mattb4]

Ok this may be very trivial but instead of one 200 watt 12v panel would 2 100 watt panels in series for 24v be much better if the wire length to the controller was around 50-60’?

Trying to learn some pros and cons.

Thanks for your time.

Not trivial at all. You need to know the specs for the panels and how it will work with any SCC (solar charge controller), plus wire size needed, plus fuses, combiners and disconnects to properly design your setup.

For instance panels are not 12 vDC. They are likely 22Voc and 18Vmp.

 

[robbob2112]

What is your battery voltage and what type SCC do you have? If you are using a PWM you will loose a lot of power as it clips to the 13.4 voltage to charge the battery. If you have a MPPT all is well.

Note: a lot of PWM controllers are marked as MPPT on the outside but are still PWM on the inside. If it has a usb port it is most likely a PWM. Post a pic.

 

[Boisblancboy]

What is your battery voltage and what type SCC do you have? If you are using a PWM you will loose a lot of power as it clips to the 13.4 voltage to charge the battery. If you have a MPPT all is well.

Note: a lot of PWM controllers are marked as MPPT on the outside but are still PWM on the inside. If it has a usb port it is most likely a PWM. Post a pic.

12v on the battery.

This much I do know at least.

I have a 75/15 victron.

 

[robbob2112]

Great then it is all about efficiency without exceeding 75v. So two or three series panels or a single higher voltage/wattage panel like a 300watt, whatever you can fit.

At higher voltage you loose less in the wire and a with larger wire size you loose less in the wire. Just don't get a wire that won't fit the victron.

If you only have one string then no fuse is required by the NEC.

Is this just a for fun build or are you working up to a house system slowly or a van?

 

[740GLE]

12v on the battery.

This much I do know at least.

I have a 75/15 victron.

Solid unit, with the recent price drops it’s hard to save a couple bucks and get a different SCC.

 

[Boisblancboy]

Great then it is all about efficiency without exceeding 75v. So two or three series panels or a single higher voltage/wattage panel like a 300watt, whatever you can fit.

At higher voltage you loose less in the wire and a with larger wire size you loose less in the wire. Just don't get a wire that won't fit the victron.

If you only have one string then no fuse is required by the NEC.

Is this just a for fun build or are you working up to a house system slowly or a van?

It’s to learn with for sure but it’s main purpose will be a power source for one small circuit in my house when power is out. Running my modem and what not. That way I can sit in the dark and mess around and yet I don’t have to fire up the genny.

 

[robbob2112]

Sounds like my system
Currently a ExpertPower 200w inverter/charger 40amp - plugged into the wall on a timer - I run the server/desktop/modem off it during the day and the night time timer charges it. DC prefered mode --- in ac prefered it has 5ms switchover.

This was to replace a 20y old UPS that needed new lead acid batteries every 2 years and I just can't see it.

just got some panels to add to it, 2 x 330w Qcell.... picking a SCC to use still - But I want one I can use later when I am house sized at 48v.