Fuses between solar panels? Panel>fuse>panel?

[Harmony5000]

Hi everybody. I just read an article leading me to believe I should install fuses between each panel. Either this is a bad article or I’m seriously misunderstanding something?

I’m using five renogy 100 watt panels. Unsure at the moment of the configuration I should use. I called renogy and they said this would be ok with my 40amp mppt charge controller as it’s rated for 520watts.

I think the wire size coming out of each panel is 12awg. Mmm that would mean it’s only safe for 20amps of current is that right?

Wiring parallel makes amperage additive right? So if the wire from the panels is only 12guage it would make it unsafe to use 5 panels in parallel because of the -wire- it’s self not the 520watts mppt. Uhm is that right?

I came to this conclusion trying to figure out fuse size to put between panels and charge controller - If my calc is correct this would put me at 30.8125. Panel Amp 5.38 x 5 panels x 1.25 = 30.8125

Wasn’t sure wether to use optimum operating current (5.38amps) or short circuited current (5.86amps) for the figure?

Uh so lost.. If even the 4 solar panels packaged with the starter kit were wired in parallel it seems to me this would put it over 12awg wire safety limit..

What am I not getting? Please help?

 

[Ozark Tinkering]

show us your controller

 

[Ozark Tinkering]

delete

 

[rmaddy]

5 panels in parallel would require a combiner box. Each panel would be fused inside the combiner box. The outgoing wire (between the combiner box and the charge controller) would need to be able to handle the combined current of the 5 panels. But each panel's wire only needs to handle its own current so the 12AWG wire of each panel is just fine.

 

[Harmony5000]

show us your controller

Here he is

 

[TEV]

my 40amp mppt charge controller as it’s rated for 520watts.

what's the model of the charge controller?
Edit: nevermind, I was too late.

 

[Ozark Tinkering]

Here he is

So it looks like you have options...if you were only using 4 panels.
MPPT Voltage DC Maximum
75
Charging Current (Amps)
40
MPPT Voltage DC Minimum
14

 

[Harmony5000]

5 panels in parallel would require a combiner box. Each panel would be fused inside the combiner box. The outgoing wire (between the combiner box and the charge controller) would need to be able to handle the combined current of the 5 panels. But each panel's wire only needs to handle its own current so the 12AWG wire of each panel is just fine.

Ok I’ll look up this combiner box. Was under the impression I could simply use an extra Y connector thing the panels were packaged with (pictured)

The article was saying if one panel had a problem all the amps could be drawn to it or something which could create heat/fire and suggested I use fuses between panels.

 

[rmaddy]

Typical MC4 connectors are only rated for 30A and usually 10AWG wire. Normally you need to fuse each string of panels when you parallel 3 or more strings. The combiner box is a good place for the fuses and it eliminates the need for the MC4 connectors and lets you handle more than 30A.

 

[rmaddy]

So it looks like you have options...if you were only using 4 panels.

That 40A SCC can easily handle 5 panels in parallel.

 

[Harmony5000]

Typical MC4 connectors are only rated for 30A and usually 10AWG wire. Normally you need to fuse each string of panels when you parallel 3 or more strings. The combiner box is a good place for the fuses and it eliminates the need for the MC4 connectors and lets you handle more than 30A.

It’s so weird renogy would sell a package 4panels and mppt charger with mc4 connectors as if that’s all you need...

These will be installed on a van. I just researched the combiner box. Should that go in the van or on top of it?

If I wired 2s3p or 2p3s or something does that change the situation?

 

[Harmony5000]

Based on environment I wonder when parallel vs series or whatever combinations make most sense. Ppl seem to have their preferences but they don’t tend to say ‘becaaauuse, it’s always sunny’ or ‘because, I get shade from ****’ etc. difficult to draw conclusions.

 

[Ozark Tinkering]

That 40A SCC can easily handle 5 panels in parallel.

When there's only one way, it doesn't count as an option.

 

[rmaddy]

It’s so weird renogy would sell a package 4panels and mppt charger with mc4 connectors as if that’s all you need...

It's not weird if you wire the panels in 4S or 2S2P. Then you don't need a combiner box or fuses or larger wire. Though for 2S2P you need a pair of MC4 Y connectors.

Also note that 4S wouldn't be doable with that SCC in colder areas since Voc goes up as the temperature goes down. But it would work with temperatures close to freezing (I'm too lazy to do the math for the exact temperature at the moment).

 

[Ozark Tinkering]

Let me see, do I pick option #1 or do I pick option #1?

 

[Harmony5000]

It's not weird if you wire the panels in 4S or 2S2P. Then you don't need a combiner box or fuses or larger wire. Though for 2S2P you need a pair of MC4 Y connectors.

Also note that 4S wouldn't be doable with that SCC in colder areas since Voc goes up as the temperature goes down. But it would work with temperatures close to freezing (I'm too lazy to do the math for the exact temperature at the moment).

Gotcha it’s all making sense. So if I wired 2p3s that would put me at 18.83amps I guess? Safe for the wires, no combiner box, but now kinda wonder why I got an extra panel. Is that right? The wires going from the array to the controller is 10awg so 18.83 would be ok from what I understand.

I’m trying to charge 200ah daily in a mostly sunny environment rare or never below 40F

 

[rmaddy]

2P3S would be 6 panels. It would be 2 times the amps and 3 times the voltage of a single panel. Though most people might connect them in 3S2P since it would be easier. 2P3S would require 3 pairs of Y connectors. 3S2P only requires 1 pair.

2S2P would be 4 panels. 2 times the amps and 2 times the voltage of a single panel.

I don't know how you came up with 18.83A. But 10AWG would be fine at that current as long as the length wasn't too long. Otherwise you start to have too much voltage drop and your controller won't see all that it could from the panels.

 

[TEV]

4 solar panels packaged with the starter kit

If you got 4 panels with the kit, and a pair of Y connectors, that you have in the picture, then they were suppose to be two panels in series, and then parallel the 2 strings of two panels each (2S2P)
Trying to add only one more panel, won't work, and your charge controller is only 520W, so you can't add two more panels.

 

[Harmony5000]

2P3S would be 6 panels. It would be 2 times the amps and 3 times the voltage of a single panel. Though most people might connect them in 3S2P since it would be easier. 2P3S would require 3 pairs of Y connectors. 3S2P only requires 1 pair.

2S2P would be 4 panels. 2 times the amps and 2 times the voltage of a single panel.

I don't know how you came up with 18.83A. But 10AWG would be fine at that current as long as the length wasn't too long. Otherwise you start to have too much voltage drop and your controller won't see all that it could from the panels.

Ohhh when someone says 2p3s the numbers are referring to the connections not the panels? I have 5 panels

So 2 panels connected parallel= 1p
3 panels connected in series = 2s
So 1p2s

?

So 1p - Optimum operating current 5.38 amps x 2 panels x 1.25 = 13.45 amps

Plus+

2s - 3 panels in series amps say the same 5.38

1p2s = 18.83 amps

...is how I got that

 

[TEV]

Ohhh when someone says 2p3s the numbers are referring to the connections not the panels? I have 5 panels

So 2 panels connected parallel= 1p
3 panels connected in series = 2s
So 1p2s

?

So 1p - Optimum operating current 5.38 amps x 2 panels x 1.25 = 13.45 amps

Plus+

2s - 3 panels in series amps say the same 5.38

1p2s = 18.83 amps

...is how I got that

No