120volt battery bank

[Forbisher]

So if the charge controller doesnt add up volts just Amps, then it seems it's only benefit would be reducing my wire size coming from the panels to charge controller. That way it can stay at 10guage

Your 6 panels in Series is 240V 10A

Your 6 panels in Parallel is 40V 60A

You can also wire 3 in Series 2 Parallel for 120V 20A output.
Or
2Series 3Parallel

Your MPPT scc also needs higher than battery voltage and to be in a working voltage range.
Look at the specs on MPPT scc's.

 

[Sunray]

My system will be off grid so i dont think a grid tie will work for me? I plan on having a generator for backup power with transfer switch. I live alone so my wattage need isnt crazy high. I'm just trying to design the most efficient system possible even if it cost a little more upfront.

Buy maybe a small effi

Your 6 panels in Series is 240V 10A

Your 6 panels in Parallel is 40V 60A

You can also wire 3 in Series 2 Parallel for 120V 20A output.
Or
2Series 3Parallel

That is correct

 

[John Frum]

@Sunray the place to start is with an energy audit.
Have a look at my signature for a helpful link.

 

[Sunray]

@Sunray the place to start is with an energy audit.
Have a look at my signature for a helpful link.

Will do. Thank you.

 

[Sunray]

I think what you're saying is if a have a battery bank at 48 volts then my inverter will be 48 volts and my charge controller will need a output slightly higher then 48 volts to push the current but on the charge controller side could be up to 250 volts. Or am I way off to what your were trying to say?

Maybe I'll just get a micro inverter for each panel. Convert at the panel and I keep my 240volt 60 amps

 

[Forbisher]

Maybe I'll just get a micro inverter for each panel. Convert at the panel and I keep my 240volt 60 amps

Nope.
240V x 60A is how many watts?? 14,400 watts!!!!
You are Never getting more than 2400w.
You still dont get it.
At 240V it will be 10A on 6 x 400w panels is 2400w
Volts x Amps = Watts
240V x 10A is 2400 watts.

 

[Sunray]

Nope.
240V x 60A is how many watts?? 14,400 watts!!!!
You are Never getting more than 2400w.
You still dont get it.
At 240V it will be 10A on 6 x 400w panels is 2400w
Volts x Amps = Watts
240V x 10A is 2400 watts.

Okay if it's all the same then wouldnt 6 in series be the best way to go? Keep the voltage high so you can use smaller cable size? Or should it be a little more balanced at 120volt20amp?

 

[John Frum]

Okay if it's all the same then wouldnt 6 in series be the best way to go? Keep the voltage high so you can use smaller cable size? Or should it be a little more balanced at 120volt20amp?

Higher voltage means smaller guage wire for the same wattage.
However your solar charge controller will have an upper pv voltage limit which must not be exceeded.
Which solar charge controller are you planning on using?

 

[Sunray]

Good point!

A charge controller CAN take 240V and output 60A from 2500W of panels... but it will output 40V...

if the battery being charged was 240V, it would only output 10A...

So one advantage having the combiner box would be if one panel goes out it doesnt bring down the other 5 since they are not in series. But you achieve the same voltage

 

[Sunray]

Higher voltage means smaller guage wire for the same wattage.
However your solar charge controller will have an upper pv voltage limit which must not be exceeded.
Which solar charge controller are you planning on using?

I've been looking at midnite, victron and outback. I'm pretty sure all three of those companies make 250 volt charge controllers

 

[Forbisher]

Okay if it's all the same then wouldnt 6 in series be the best way to go? Keep the voltage high so you can use smaller cable size? Or should it be a little more balanced at 120volt20amp?

Try shopping for a 240V input MPPT SCC.
Also is 40V Vmp or Voc on your panels??

If your Voc is 50V then you will need a 300V max input MPPT and cold temps will raise that voltage.

 

[Forbisher]

I've been looking at midnite, victron and outback. I'm pretty sure all three of those companies make 250 volt charge controllers

Yes but is that 40V Vmp or Voc???
I suspect your Voc is higher.

 

[Sunray]

Try shopping for a 240V input MPPT SCC.
Also is 40V Vmp or Voc on your panels??

If your Voc is 50V then you will need a 300V max input MPPT and cold temps will raise that voltage.

My voc is 49

 

[Sunray]

Yes but is that 40V Vmp or Voc???
I suspect your Voc is higher.

Charge controllers are hard to find over 250volt. Good point. Seems like series parallel for 120 volt20amps is best

 

[Sunray]

Charge controllers are hard to find over 250volt. Good point. Seems like series parallel for 120 volt20amps is best

Unless I find a combiner box that has 2 outputs and have 2 charge controllers

 

[Forbisher]

My voc is 49

Ok so 49V x 6 is about 300V so you can not wire 6 panels in Series on a 250V MPPT.
3S2P would work in even cold temps.
That would be 150Voc

 

[Forbisher]

Unless I find a combiner box that has 2 outputs and have 2 charge controllers

2 charge controllers would not need a combiner box with 3 panels in Series on each MPPT.
But 3 in Series is about 150Voc so too much for a common 150V max input SCC.

 

[Sunray]

2 charge controllers would not need a combiner box with 3 panels in Series on each MPPT.
But 3 in Series is about 150Voc so too much for a common 150V max input SCC.

I know the combiner box isnt necessary. I just like the fact that if one panel goes down it wont bring the others down as well.

 

[Sunray]

I know the combiner box isnt necessary. I just like the fact that if one panel goes down it wont bring the others down as well.

I think I'll do 2 sets of 3 panels is series. So I'll have one set of 120volt10amp going into a 3 string combiner box and another identical. Then each combiner box with feed there own individual charge controller. I'll get 200volt charge controlles to account for voc. Then each charge controller will feed my battery bank which then feeds the inverter

 

[Forbisher]

I know the combiner box isnt necessary. I just like the fact that if one panel goes down it wont bring the others down as well.

With 3 panels in Series i dunno if that is true.
Panels rarely "go down."
Combiner boxes are expensive and 3 in Series is very simple wiring.