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Cable size

Which cable cable size should be used for different components / product?
Here we go through how to do in the car's 12v system.



Check the product MAX current (Ampere)

Start by seeing what the product's MAX current (Ampere) is.
Depending on which part / product is to be connected and how long cable you are going to use, you need to use the right cable size and then you need to know how much current the product use as MAX.
The difference is large between a fan and a lamp e.g.

Example: Bosch 044 fuel pump use approximately 13.5A at ~5bar back pressure.
Here you can use a 1.5mm2 RK cable.
Then you can secure with a 15Ampere fuse


RK / RKUB cable size (mm2)

Cable area (mm2) - Max current (A)
0.5mm2 - 5A
0.75mm2 - 7.5A
1mm2 - 10A
1.5mm2 - 15A
2.5mm2 - 20A
4mm2 - 30A
6mm2 - 40A
8mm2 - 50A
10mm2 - 70A


Cable area R2 / TXL (mm2)

If you use finer cable such as R2 or TXL as an example, you can follow this table:

Cable area (mm2) - Max current (A)
0.5mm2 - 10A
1mm2 - 15A
1.5mm2 - 20A
2mm2 - 25A
3mm2 - 30A
4mm2 - 40A
6mm2 - 50A
8mm2 - 60A
10mm2 - 70A


Fuse size

A fuse is used to protect cable and products connected to it. Use the same or smaller fuse as in the table above.



To summarize this short guide in 3 steps:

1 - Check the product MAX current (Ampere)
2 - Check the size of cable you need (mm2)
3 - Secure by cable / consumer with suitable fuse


Extra - calculate yourself?


OHM:s law

The cable sizing differs depending on the length you use, but in a car where a maximum of about 5 meters is used, the voltage drop in the cable is okay using the tables above.
If you want to calculate the exact cable size for the products in your system, use OHM's law.