Santa
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Don't know yet...But can you estimate 10 feet maybe? Subject to change when installing...
How do I connect 5 solar panels?
- Thread starter Santa
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MisterSandals
Participation Medalist
If your longest run is less than 20 feet then ~23 amps would require 12awg. Up to 30 feet 10awg. So you're good!
Longer than 30 feet you need 8awg.
Santa
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I got 28 amps...? but 10AWG is good. It won't be more than 15 feet I would assume.
MisterSandals
Participation Medalist
oops, i see your suitcase is 2 panels. I got your total amps at 29.28.
Up to 30 feet you need 10awg. (still good)
Up to 50 feet you need 8awg. (same)
Just saw your post above, yep, you're right. You don't need us anymore!
Santa
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Are you counting the Imp or the Isc?
Justin Laureltec
Bay Marine Supply Tech Support Manager
Very important to note (since I don't see it noted on that chart anywhere) that those length measurements must be for round-trip circuit length, not one-way. So if the panels are literally 30' away, round-trip distance is 60', and the wire must be sized accordingly.
MisterSandals
Participation Medalist
Holy crap, i learned something very valuable today.
Santa
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Thank you! I too learned something new. It won't be over 30 feet roundtrip.
Justin Laureltec
Bay Marine Supply Tech Support Manager
It's amazing how many wire gauge calculators don't tell you that, particularly given how bloody critical of a consideration it is...
MisterSandals
Participation Medalist
I'm not a fan of my chart anymore. Do you have one you recommend, one for dummies like me?
Here in California, we like to (need to?) park in the shade so having your carry out panels 25+ feet from your RV is not uncommon. Just consider your real world use case.
Santa
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I will be mounting 4 on the roof. The suitcase will only come out sometimes. So, for argument's sake, I will be connecting them with the mc4 Y 1-4 combiner and then connect the suitcase with a MC4 1-2 combiner. If I use 10AWG to connect the 4 panels, and let's say I have to move my suitcase panel 25 feet (50 feet roundtrip). Would I need to get 8AWG wire for the suitcase panel to the combiner?
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Justin Laureltec
Bay Marine Supply Tech Support Manager
I mean, the chart is still good (albeit a little optimistic in my view), you just have to remember that "circuit length"=ALL wire used in the system. Alternatively, we have a decent calculator and some relevant charts on our site, but you still have to remember to input round-trip length (although at least ours mentions that). I've found, in practice, that our calculator tends to spec heavier-gauge wire than Blue Sea's, which I personally like because I'm a big believer in overkill when it comes to wiring, but I suppose that could be argued.
Bottom line, the chart you posted is perfectly valid, it's just someone needs to put CIRCUIT LENGTH IS ROUND-TRIP in big bold letters across the top of it :D
MisterSandals
Participation Medalist
I'm feeling really unqualified to answer this now...
I "think" that with the addition of 50 foot round trip you would require ALL of the wires to be 8awg. (Justin?)
Alternatively, if you disconnected the roof panels when you add the suitcase, you would be 6.48 amps and good to 100' roundtrip.
What is the use case for the suitcase? To augment the rooftop panels or for use when rooftop not in use? (parked in shade for example).
For the latter, i think you'd be disconnecting the rooftop panels to be safe (trees do fall and shadows move...)
Santa
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In my OP, I explained the reason for only sometimes using suitcase. I want as much power as possible, when stealthly possible. Disconnecting the roof panels defeats why I would even mount them in the first place.
Justin Laureltec
Bay Marine Supply Tech Support Manager
Ahhhhhh worse than all that... 30A at 50' needs 2AWG to keep the voltage drop under 3%, though 4AWG puts you at 3.2%, which... eh... could be lived with I guess.
8AWG at that distance puts your voltage drop at 8.08%, which is simply untenable. Then again, running 2ga wires 25' out is also pretty untenable... I strongly recommend just not putting your suitcase that far away, @Santa .
EDIT: I'm an idiot... what voltage are your panels running at? I was using 12v as the voltage in my calculator and on the panel side of the controller, that's obviously not the case.
8AWG at that distance puts your voltage drop at 8.08%, which is simply untenable. Then again, running 2ga wires 25' out is also pretty untenable... I strongly recommend just not putting your suitcase that far away, @Santa .
EDIT: I'm an idiot... what voltage are your panels running at? I was using 12v as the voltage in my calculator and on the panel side of the controller, that's obviously not the case.
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MisterSandals
Participation Medalist
Does that apply to ALL the wiring in parallel? So even the rooftop solar panel leads become woefully inadequate?
Justin Laureltec
Bay Marine Supply Tech Support Manager
Waaaaaiiiiiiit I'm an idiot... hang on, what voltages are we talking about here? I was thinking 12v, but obviously at the panel side of the controller the voltage is way higher, and the amperage way lower, which of course means you can use lighter-gauge cables.
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Justin Laureltec
Bay Marine Supply Tech Support Manager
Okay, I've read back... the panels on the roof are roughly 18.2v, 5.5A, so in parallel they're fine all the way to 12AWG.
The suitcase is a little funky... does it have an SCC built-in, or is it just the panels? If it has an SCC built-in, then it's stepping down the voltage/up the amperage, in which case you're back to using 2AWG at 50'. If it's just the panels out 25' away, then you're still high-voltage low-amperage, in which case you're good to stay at anything heavier than 12AWG going to the SCC, then of course heavier gauge from the SCC to the battery.
The suitcase is a little funky... does it have an SCC built-in, or is it just the panels? If it has an SCC built-in, then it's stepping down the voltage/up the amperage, in which case you're back to using 2AWG at 50'. If it's just the panels out 25' away, then you're still high-voltage low-amperage, in which case you're good to stay at anything heavier than 12AWG going to the SCC, then of course heavier gauge from the SCC to the battery.
MisterSandals
Participation Medalist
Yea, and after I just read back, I am wondering why we didn't suggest connecting the 4 roof panels in series?
Is there a limitation on the SCC for input volts?
(panels in series add the volts, and as we discussed, panels in parallel add the amps).
Is there a limitation on the SCC for input volts?
(panels in series add the volts, and as we discussed, panels in parallel add the amps).
Just keep an eye on amps...dont go over the current rating of the wire.
Santa
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You seem pretty smart to me. ;-) 18 on the (4) 100 watt panels and 18.2 on the suitcase
Yes. There is a limit of 30 amps on this SCC. I HAVE to wire them in parallel with this system. Adding the 5th panel is not what Will recommended in his blueprint and will be close to the max the SCC can handle, and not feasible if the weather is cold, according to what I am understanding, the voltage will rise.
Justin Laureltec
Bay Marine Supply Tech Support Manager
...okay, so for the purposes of calculation, I'm figuring a max of 9A per panel (and the suitcase has 2?) so I figure 18A @ 18.2v @50' and come up with 8AWG being perfectly fine, but don't go lighter than that... sooooo basically, right back where we started
On the other end, between your SCC and your battery, you'll need heavier gauge depending on the distance from SCC to battery, since the SCC is putting out higher amperage at lower voltage, which requires heavier cable. But your panel-to-SCC wiring is all good at 8.
Santa
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Guys and/or Ladies, this thread has become a little complex for me here. I am not stupid, but sometimes I am ignorant and need to study things when life isn't hitting me over the head with other things like my bathroom flood twice from the neighbors and the many complications after (I am dealing with now). I am trying to figure this out AND I WILL. Thank you for helping and your input, each and every one.
JeepHammer
Solar Wizard
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With all due respect,
That's not correct.
Parallel panels won't have an issue with a damaged/defective panel,
The parallel wiring simply skips the defective panel.
Current, following the path of least resistance, will simply avoid any resistance that could cause a fire.
The traces in a solar panel will be the first to go, being panels *Usually* have 10-12 Ga wire.
Once a pan trace opens (which can't start a fire) the circuit to that panel is dead, open since this is DC, not AC, there is no 'Live' wire left to start a fire.
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Facts First,
Fuses, Breakers, Diodes have SPECIFIC functions.
Less & less panels are coming with blocking diodes.
Blocking diodes are 100% effective in stopping back feeding and 100% reliable when used within tolerance.
Using the WRONG component for the job is the builders fault 100% of the time.
The panels in a COMBINED parallel string CAN NOT back feed each other, it's impossible.
DC circuits REQUIRE a completed circuit, both positive and negative.
Like charging a 48 volt battery as 2 each 24 volt batteries,
4 each 12 volt batteries,
8 each 6 volt batteries,
Any single panel in parallel WILL NOT accept current from the other panels.
The only way a panel can do ANY damage is *IF* it becomes a 'Load', at which time a trace will burn and open the circuit entirely...
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*MY* (personal) usage/method.
TEST EVERYTHING, EVERY TIME.
*YOU* don't know what the manufacturer did unless you inspect & test.
Know the difference...
A phenolic (plastic) diodes used in combiner boxes & panels will BLOW OUT, break/burn, open the circuit, when overpowered.
It's a makeshift 'Fuse' of sorts.
A steel case diode will not.
The ONLY way to kill a diode is over volt, or over amp.
Common Diodes *Usually* come with 150 to 300 volt limit,
The amperage limit is what you seriously need to watch.
Charge controllers have input diodes that do the blocking.
This is so when the sun goes down the batteries don't heat the panels, blocking battery current from reaching panels, which would defeat the purpose of a charge controller...
Adding extra diodes at panels or combiner boxes with diodes simply drops the voltage production from the panels to batteries.
Every diode in the line will drop the line voltage between .2 and 1 volt.
You can tell how good of diodes were used by checking the voltage drop through the diode,
Cheap diodes will drop about a volt (line losses), the better diodes will drop voltage .2-.3 volts.
The more diodes you add, the more inefficient your system becomes, line losses stack up.
When parallel panel wires come into a combiner box, the panel wires are 12 or 10 Ga, while the wire FROM combiner to charge controller MUST carry the combined power of the panels...
See above, separate completed SOURCE circuits CAN NOT back feed each other, unless the panels becomes a 'Load' not 'Source'...
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Notice size of main (combined) lines on left, and right in image below.
Both are 'Parallel', two different ways to wire Parallel...
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Santa
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RE; Suitcase panel: I would LOVE to directly answer your question of "does it (suitcase panel) have an SCC built-in, or is it just the panels" but cannot. Originally, about 2012, I bought an "all-in-one" along with the suitcase panel. The battery/all-in-one was since stolen. I still have the suitcase. This was my introduction into solar/backup power. I don't know or understand what they used as a charge controller. I tried to ask them (Lion) about it, but never got an answer. Is there something on the back of the panel that can answer this?
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