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Curious about cable thickness

corporal_Canada

corporal_Canada

New Member
Joined
Aug 29, 2023
Messages
599
Location
Philippines
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Hi I have this solar panel it is roughly 15-20m away from me.. my question is .. it indicates that it needs 12 awg.. and that will allow me to get something close to 320 watts.. but let's say that one day I get greedy and I want another identical panel.. or 3 or 4.. all linked together in parallel.. so all the positive cables of all the panels going to 1 cable that I will indicate POSITIVE and same for the negative side, I'm simply curious if I need thicker cables each time I double the wattage output, me being super cheap.. I wanna buy the extra thick cable now in lieu of me wanting to have more panels.. .. and how does the 12awg double ? Do I need 24 awg for 2 panels ? 36 for 3 panels.. etc..

I am sorry if this is a dumb question but I've recently moved to another country so my mind is overflowing with new data and a new language.

Cheers
 
Those panels should be safe with two parallel sets on #12, but for voltage drop you might want 10 or 8.

9.2A max amps, max power output would be 8.6A, so #12 is generally rated for 20A
10 for 30A
8 for 40A

Be w
Aware, every panel has to be fused if you go over two in parallel.
 
thank you.. so which awg should i look for for (2 panels for example).. .. and fuse where ? on the positive side going from solar panel to the positive line going down the side of building wherer i reside ???.. right before i join the 1 solar panel to the 12 awg (not cerain yet, i might as well get 8) or more cable going down into my home....

PS i apprecieate your answers
 
20m of awg... roughly 70-80$.. for 1 cable... . according to a ampacity chart (i bet you made that word up... awg 8 can handle 55-60 amps).. so not an issue if i just take each positive end of 2 solar panels and link it to 1 awg 8 and same for negative ? the picture im trying to paint is just copper making contact and all twisted together.. i mean for each polarity.... of course ill try getting a nicer cable link thingy to make it cleaner.. there are copper pipes that you can slide all the polarity cables into and kinda crimp it.. OR.. a thing where you insert the cables into and screw them in place.. of course, once everygthing is linked, ill wrap it in electrical tape in case positive and negative make contact and also because.. Philippines gets more rain than Canada gets snow...
 
If connecting in series, 12awg is fine for the amperage. If you start connecting strings in parallel, you will need to evaluate your needs based on how many strings you want to put together.

Parallel adds the amperage, series adds the voltage. Wire size is based on amperage.

anBn
 
thank you.. i am familiar with "series connection" however since the only thing i can remember from DC electricity stems from automobile mechanics in military training...i am simply more comfortable using 12v .. so "parallel" for everything.. after replacing the 2 caables coming from the roof to my household.. i intend to replace the inverter with one that outputs pure sine wave.. id like to plug in my overpriced ups to it... and power my computeter/monitor/modem/ electric fan and external hdd's
at this very moment.. the ups (the thing that all the above are connected to) is drawing 157 watts from city power.. so if i even get 200 watts from the panel during daytime.. im in the ballpark... and its 2x 50ah batteries.. so unlesss my math is WAY off.. i believe i have 1200 watts stored if both batteries are full.. but i believe that figure changes once the voltage drops.... learning process :).. the reason why i want pure sine wave inverter is because one individual compelled me to daisy chain ups's and the first one was outputting modified sine save and my overpriced ups started chiming at 0600...not a fun way to wake up...

but.. im certain ill go for 8 awg..since i want that security buffer.. and im still confused because i treat amps and watts like water flow.. so if i want to pull more power.. the cable should be thicker
 
im using the big panel again.. since i received a scc that can read up to 48v.. but i dont really feal the power.. the voltage kinda stays at 10v.. despite the power in at (holdon will verify now).. 12.74... i tested the + and - of the 2 screws on the SCC that the cable go to the battery terminals...
 
You say you're only comfortable with 12v hence why you are connecting in parallel but your solar panel is 37V. If you do connect in series you need to ensure the VOC (in the coldest temperature you're likely to see) of them added together doesn't exceed the max input voltage type mppt can take.

I said in your other thread as well about the mppt, if you can link us to the model we can help you.
 
corporal_Canada said:
think i did.. hmm.. i dont see it :(


View attachment 282444
Click to expand...
I'm gonna go out on a limb here and say that there's a 0% chance that thing is actually an MPPT.
It's a PWM, which means that all it can do is reduce voltage from the PV input.

corporal_Canada said:
the voltage kinda stays at 10v.. despite the power in at (holdon will verify now).. 12.74... i tested the + and - of the 2 screws on the SCC that the cable go to the battery terminals.
Click to expand...
This is what PWM's do... So the maximum power you could possibly get from that panel is limited to the current it can put out (Isc = 9.2A) multiplied by your battery voltage (about 12-13 V). So, something like 110W.
A real MPPT will be able to take full advantage of the power that panel can make.
corporal_Canada said:
it has usb ports on the bottom but it should deliver on its claims that it can read 48v...
Click to expand...
That claim is that it can work with a 48V battery, not a 48V panel.
 
corporal_Canada said:
i know its a fake mppt.. it has usb ports on the bottom but it should deliver on its claims that it can read 48v...
Click to expand...
Sorry to be harsh but you really need to do more research before buying things. Did you read the description of the item? That cannot work with your panel VOC when using a 12V battery.
 
so.. you think i should go series ???.. i mean i could just remove the parallel and place both .. 2x6 gauge ??/ cables going from negative to positive to another battery...

as for the mppt.. i did use my crappy 2$ multimeter on the 2 scfrews of the solar panel input and im not sure if its an error or calibration fault but i think i saw 51v for a second.. then it went to -1 which typically means error... .. i always had trouble plugging in the red and black terminals in the correct plug of the multimeter.. the black is on the bottom near the ground symbol.. the red.. should be on fused .. i think its a 10 amp fuse.. sorry.. DC class was nearly 30 years ago
 
ShaneC said:
Sorry to be harsh but you really need to do more research before buying things. Did you read the description of the item? That cannot work with your panel VOC when using a 12V battery.
Click to expand...
i didnt really read every detail... but i did see it can read UP TO 48v.. so if my panel puts out 46v.. seems good to me... .. although based on my last post i should move it up to 60v.. another person even suggested 100v...
 
LakeHouse said:
I'm gonna go out on a limb here and say that there's a 0% chance that thing is actually an MPPT.
It's a PWM, which means that all it can do is reduce voltage from the PV input.


This is what PWM's do... So the maximum power you could possibly get from that panel is limited to the current it can put out (Isc = 9.2A) multiplied by your battery voltage (about 12-13 V). So, something like 110W.
A real MPPT will be able to take full advantage of the power that panel can make.

That claim is that it can work with a 48V battery, not a 48V panel.
Click to expand...
agree with you but i said fake mppt, so beatyou to it...

if i get 110watts ill call that a good day... its enough t o run 2 electric fans if i even get 110 watts... and with current prices of kwh here, im not exactly using the AC.. im simply trying to establish a baseline of something that functions.. so that i can build off that foundation...
 
corporal_Canada said:
i didnt really read every detail... but i did see it can read UP TO 48v.. so if my panel puts out 46v.. seems good to me... .. although based on my last post i should move it up to 60v.. another person even suggested 100v...
Click to expand...
I'm not sure what you mean. Are you talking about adding more panels in series? That would blow up your solar charge controller. You're already feeding far more voltage into it than it can take while charging a 12v battery. Do you understand that the voltage it can handle differs based on the battery it is charging?

If you could change your battery configuration to 48V then it would work, but you'd need a 48v inverter. Your best option is to get a solar charge controller that can take in your panels voltage while charging a 12v battery. We would be happy to help you if you post possible charge controllers that are available in your area and their detailed specifications.
 
ShaneC said:
I'm not sure what you mean. Are you talking about adding more panels in series? That would blow up your solar charge controller. You're already feeding far more voltage into it than it can take while charging a 12v battery. Do you understand that the voltage it can handle differs based on the battery it is charging?

If you could change your battery configuration to 48V then it would work, but you'd need a 48v inverter. Your best option is to get a solar charge controller that can take in your panels voltage while charging a 12v battery. We would be happy to help you if you post possible charge controllers that are available in your area and their detailed specifications.
Click to expand...
no.. the batteries:) qalthough i have intensions to get more panels that will be next year after the roof has fimished construction for 2 additional studios
and yeah ill stick to parallel :)
 
corporal_Canada said:
so if my 2 batteries are linked in series creating 24v... the mppt or rather FAKE mppt will actually deliver some kind of power ???
Click to expand...
The specification of your charge controller states:

"15-25V(12V Battery);30-50V(24V Battery);45-75V(36V Battery);60-100V(48V Battery)"

So yes, your panel voltage is within the 30-50v range, it should work. I wouldn't have much faith at how well it will work but it's worth trying if you can reconfigure your battery to 24v. You will need a 24v inverter though unless your current one can handle either 12v or 24v.
 
ShaneC said:
The specification of your charge controller states:

"15-25V(12V Battery);30-50V(24V Battery);45-75V(36V Battery);60-100V(48V Battery)"

So yes, your panel voltage is within the 30-50v range, it should work. I wouldn't have much faith at how well it will work but it's worth trying if you can reconfigure your battery to 24v. You will need a 24v inverter though unless your current one can handle either 12v or 24v.
Click to expand...
thank you.. so.. if i understand you correctly.. (forgive me if i sound dim) when i shift both cables from pos to pos and neg to neg.. and use both those cables together to link pos to neg(2 cables cuz i hate wasting stuff...) and then the negative of the fake mppt to negative terminal of battery 1.. and positive of fake mppt to positive of battery 2... i will actually get a power flowing INTO the batteries ? and please remind me.. because i do keep forgetting.. will i still have 1200 watts total with the 2 batteries linked in series.. i know the voltage doubles.. therefore it is 24V x 50 AH. .. awesome.. 1200.. that was one of he reasons i hated series.. but the watts does actually double with each battery.. but what happens if i go crazy and buy a 250 or 400 ah sla battery cuz ya.. still hesitant to use lifepo4.... .. can i add said imaginary 400ah battery in series.. itll be 12v 50ah... 12v 50ah and 12v 400ah.. how do you do the math on that ?
spank you very much for putting up with my thick skull.. i blame it on too many hockey injuries.. not playing.. but jumping off the balcony when the Washington Capitals score ....
 
When connecting in series the battery capacities need to match. You should also ensure they are at the same charge. Given they have been connected in parallel that should be fine.

To expand your capacity you'd need to build another 24v battery and connect that in parallel. In that case all you need to do is ensure they are the same chemistry.

Your maths on the watt-hour capacity of your battery is correct, it doesn't change as it's multiplying the voltage by amp-hour capacity.

Are you using a 12v inverter now? Do not connect it or any other 12v devices if you change your battery to 24v.
 
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