Calculation of 24V solar cable section?

Forum solar photovoltaic PV and solar electricity generation from direct radiation solar energy.
k-nich
I discovered econologic
I discovered econologic
posts: 4
Registration: 19/10/20, 20:45

Calculation of 24V solar cable section?




by k-nich » 19/10/20, 20:52

Good evening everyone.

I have an installation which poses a problem for me and, it seems to me to have found the cause, an underdimensioning of the cable between the panels and the regulator. If anyone was able to advise me, I would be grateful.

This is a 24 volt installation with 14 amps to pass through. The panels are 50 m away from the regulator. I put 6 cable and maxed out at 3A maximum.

How much should I put for this to work? Copper or aluminum to limit costs?

Thank you in advance.
0 x
User avatar
Forhorse
Econologue expert
Econologue expert
posts: 2485
Registration: 27/10/09, 08:19
Location: Perche Ornais
x 359

Re: Calculation of solar cable section.




by Forhorse » 19/10/20, 22:02

If you really want very little loss you will have to put 50mm² (copper)
0 x
Christophe
Moderator
Moderator
posts: 79112
Registration: 10/02/03, 14:06
Location: Greenhouse planet
x 10972

Re: Calculation of solar cable section.




by Christophe » 19/10/20, 22:47

a) You have 3A ok but how many volts do you measure (input and output?) and how many amps at the output of the panels?

b) Otherwise the low voltage DC formula for a copper cable:

Section = 0.017 x L x I / T

S = section of the copper conductor expressed in mm²
L = driver's outward + return length expressed in meters
I = the intensity expressed in amperes
T = voltage loss accepted at the cables, expressed in Volts


In your case with 1 volts of voltage drop (4%):

S = 0.017 * 50 * 2 * 14/1 = 24 mm² ...

So you have 2 solutions: quadruple the 6mm2 cables (not cool) :( or increase the tension or move your panels ...

There are converters 24V to 48V see 96V ...
0 x
k-nich
I discovered econologic
I discovered econologic
posts: 4
Registration: 19/10/20, 20:45

Re: Calculation of solar cable section.




by k-nich » 20/10/20, 09:17

Thank you for your answers.

I have 27,6 volts at the regulator. I did not measure the voltage at the same time exiting the panels but will try to do so today.
On the other hand, which is curious and that I cannot understand, I have the same value in amps at the output of the panels as at the input of the regulator.
Having multiple installations I took the panels from another building where everything works fine to try and get the same result. Approx 3A input and output.
The regulator (victron) is not involved since I swapped it with another for testing. The result is identical.
Moving the panels would involve cutting down a considerable number of trees and I don't care too much.
Today I will reassemble the panels moved the day before to see if they are still functioning correctly.
0 x
Christophe
Moderator
Moderator
posts: 79112
Registration: 10/02/03, 14:06
Location: Greenhouse planet
x 10972

Re: Calculation of solar cable section.




by Christophe » 20/10/20, 10:23

Ok now measure the voltage after 50 m of cables as well as the input and output amperage ...
0 x
izentrop
Econologue expert
Econologue expert
posts: 13644
Registration: 17/03/14, 23:42
Location: picardie
x 1502
Contact :

Re: Calculation of solar cable section.




by izentrop » 20/10/20, 12:05

k-nich wrote:which is curious and which I cannot understand, I have the same value in amperes at the output of the panels as at the input of the regulator.
Normal, it goes in the same thread
You will also be amazed to see that the panel output voltage is perhaps 36 or 40 V, which is also normal.

You don't put such a distance between PV and charger at such a low voltage, unless you put wire sections as big as my thumb. : Wink:
1 x
Christophe
Moderator
Moderator
posts: 79112
Registration: 10/02/03, 14:06
Location: Greenhouse planet
x 10972

Re: Calculation of solar cable section.




by Christophe » 20/10/20, 12:08

So what do you plug into when you measure the 3As?

If it is a nearly full battery, it may be that it simply does not draw enough A ... : Cheesy:
0 x
k-nich
I discovered econologic
I discovered econologic
posts: 4
Registration: 19/10/20, 20:45

Re: Calculation of solar cable section.




by k-nich » 20/10/20, 12:53

With a multimeter that I put in series on the starting line of the panels.

The result is identical to that displayed by the regulator.

Today the weather is not nice, the weather is stormy, I will not be able to take the values.

If I go up to 48 volts with an mppt regulator, how much should the cable section be for it to work?
0 x
Christophe
Moderator
Moderator
posts: 79112
Registration: 10/02/03, 14:06
Location: Greenhouse planet
x 10972

Re: Calculation of solar cable section.




by Christophe » 20/10/20, 12:56

No I meant: what is plugged into the solar system when you measure?

I suspect that you measure with a multimeter ...
0 x
Christophe
Moderator
Moderator
posts: 79112
Registration: 10/02/03, 14:06
Location: Greenhouse planet
x 10972

Re: Calculation of solar cable section.




by Christophe » 20/10/20, 12:59

k-nich wrote:If I go up to 48 volts with an mppt regulator, how much should the cable section be for it to work?


S = 0.017 * 50 * 2 * 14/1 = 24 mm² ... would become S = 0.017 * 50 * 2 * 7/2 = 5.95 mm² ... with still 4% or 2 V of voltage losses on 48V .. .so acceptable ...

So bingo for you! 6 mm² would be just enough 8)

Otherwise I just found this doc: https://www.econologie.com/fichiers/par ... XIhXTb.pdf

The maximum tolerable low voltage drop is 5%, recommended 2.5% ... With 4% this is considered a "non-professional" installation ...
1 x

 


  • Similar topics
    Replies
    views
    Last message

Back to "Renewable energy: solar electricity"

Who is online ?

Users browsing this forum : No registered users and 134 guests