Choosing Cable Cross-Section for 12V DC, 8A Car Fridge: Installation Distance of 120m

Question

I have a 12 V DC car fridge; 8 A. I would like to carry a large piece of the installation to it, as much as 120 m. What cable cross-section should be chosen? I searched a lot on the Internet, I found various calculators, but the results range from 1 to 6 mm sq. Could someone explain it to me...

alekt77 · Accepted Answer

What is the minimum voltage at which the refrigerator will work? 11V, 10V? Take from the tables for cables with different cross-sections the resistance of 1mb of the cable, count the resistance of the cable for 240mb of length (2x120m), multiply by 8A, you will have a voltage drop on the cable, subtract from 12V and check if this value is above the minimum operating voltage of the refrigerator, take a wire with a cross-section a little larger than in the calculations (just in case and for plug losses).

^ToM^ · Accepted Answer

So on quickly: 120 m distance, therefore 240 m of cable where some voltage drop will occur at 8 A. How will you use a wire with a cross section 2.5 mm2 then the resistance of a 240 m cable will be 1.6 ? R = ??L / S R = 0.0168?240 / 2.5 R = 1.6 ? Therefore, by giving such a wire and passing 8 A through it, there will be a voltage drop U = I * R, i.e. 8 A x 1.6 ? = 12.8 V Will you be able to learn from this?

Szyszkownik Kilkujadek · Accepted Answer

I don't know where these results came from? They are wrong. If you want 12V, send 8A DC over 120 meters, now be careful: You need a cable with a minimum cross-section of 25mm2. If you want to know how to solve this problem, please ask. Write where you get the power from and why such a long cable. Basically what are you up to?

alekt77 · Accepted Answer

Here: Link you have a calculator, you can convert for different assumptions

Szyszkownik Kilkujadek · Accepted Answer

If we apply the most stringent safe voltage criterion, we can give a maximum of 30V. Then you can go down to 6mm2 cross-section.
So you install a 230V / 24V DC power supply at the beginning of the cable, and a converter lowering the voltage to 12V next to the refrigerator.

https://pl.wikipedia.org/wiki/Napięć_bezpieczne#Wartości_napięć_dotyczki_dopuszczalnych

zworys · Accepted Answer

24V is also a safe voltage. Only half of that voltage would be lost to heat in the cable. Next - the 8A refrigerator is charging continuously or periodically? I think that periodically such a simple method is omitted because with lower power consumption, for example, 19V will appear on the refrigerator and this can be fatal for the refrigerator. A converter should be used at the end of the cable, which would supply some 12V to the refrigerator when the load changes. I don't know if it would be cheaper to use a set of solar panel + controller + 12V battery.

alekt77 · Accepted Answer

Due to the fact that the refrigerator probably consumes 8A continuously, the matter becomes more complicated because the voltage at the end of the cable from the refrigerator side will change in a fairly wide range.

Szyszkownik Kilkujadek · Accepted Answer

Do lorry trucks run in the pool? Did you read what the author wrote? Here: 48V DC can be used, but it requires deep analysis. I would not suggest it in the dark.

anchilos · Accepted Answer

Is the author going to let bare wires through the pool? Will he use the correct wire - a cable buried in the ground? More like a second version. I greet everyone. By the way They traveled in Cyprus. Directed by our so-called elite. greetings again.

CYRUS2 · Accepted Answer

Why ? Everyone has the right to ask on Elektroda. In the electrics section for everyone. Refrigerator - max voltage 15V because this voltage can be on the car battery. The minimum voltage on the refrigerator should be 11.5V. This is the output for the calculations. But what do you want to power it from? You need to purchase a DC 15V 10A-15A stabilized power supply. 15V- 11.5V = 3.5V 3.5V / 8A = 0.437? 0.437? / 240 = 0.0018 ? / m The conductor cross-section is 12 mm? You will need a cable with a conductor cross-section of 16mm2. This is enough for a current at engine start of approx. 11.6 A.

zworys · Accepted Answer

When I wrote my post, yours was not visible yet. I also mentioned the converter.

anchilos · Accepted Answer

However, difficult. maximum load 10A (continuous load up to 8A 70W)

anchilos · Accepted Answer

12x8 =? W

mar_uda · Accepted Answer

Maybe it is worth for the author to write what kind of refrigerator it is about.
There are models in which cooling takes place using a Peltier cell. Thus, there is no increased inrush current and the sensitivity to voltage changes is lower. Then you can choose a power supply with a correspondingly higher voltage and the converter will not be necessary, and the cable cross-section will be smaller.

acso · Accepted Answer

Or maybe two 230 / 24V transformers?
One at the beginning of the cable and one at the end.
A current of about 4A will give a voltage drop of about 6.5V with a conductor cross-section of 2.5mm2.
The second transformer is connected to the wire by a secondary winding
it should give you about 165V on the primary one.
Most of the 12V switch mode power supplies can handle this voltage without any problems.

freebsd · Accepted Answer

Can it do something like this: a 1: 1 transformer and a 230 V earth cable (although located on the cornice)? In this thread, electricians familiar with the standards should have the final say

^ToM^ · Accepted Answer

But there is no choice here because the author already has a refrigerator! Read in the first post.

mlewan · Answer

I feel like it won't go. I suspect that from a practical point of view it is impossible to do this? And does this table: is authoritative?

mlewan · Answer

I take the power supply from 230 V AC, the problem is that it is a wet environment where a lot of people hang around (swimming pool). There is a place to lay the cable, but generally wet and a lot of people. If no construction works are to be carried out (and they are not), only safe voltage is involved.

Szyszkownik Kilkujadek · Answer

Mates @zworys and @ alekt77 please note that at the end of the cable I proposed a converter that reduces the voltage to 12V. Read the whole thing with understanding. Doubtful.

anchilos · Answer

48VDC is widely used as safe voltage even with direct contact (see industrial trucks). Solution . 230VAC / 48VDC converter, on the other side a step down converter to 12VDC with a continuous current of at least 12A (lower heating)

mlewan · Answer

Rather not, the cable is going to be placed on the cornice, 2 m above the ground, in a protective tube. It will definitely be wet.

alekt77 · Answer

I am reading, which does not change the fact that it is troublesome to find a converter with a wide range of voltage changes at the input. For example, I found something like this on the web: Link It works from 15V input voltage, so with a power supply of not less than 24V DC on the primary side of the cable, you could be tempted to use a 4mm? cable, which is a reasonable size.

Szyszkownik Kilkujadek · Answer

Difficult? Added after 3 [minutes]: Or: Added after 5 [minutes]: Which does not change the fact that perhaps the best and most economical solution may be a gas-powered camping refrigerator:

alekt77 · Answer

Maybe not so much If you read my post # 17 carefully about an hour ago, you would see that I found something suitable on the network and in a ready housing for about PLN 73 (gross)

alekt77 · Answer

8A x 12V = 96W> 70W

Szyszkownik Kilkujadek · Answer

Right. Anyway. The inverter is no problem.

Szyszkownik Kilkujadek · Answer

Generally, we have a consensus: you need to increase the voltage at the beginning of the cable and lower it at the end (at the refrigerator).
It is also possible not to lay the cable and use a gas-fired refrigerator instead.
The choice is up to the author of the topic.

[Solved] Choosing Cable Cross-Section for 12V DC, 8A Car Fridge: Installation Distance of 120m

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