Cables can only pass a certain amount of current, before they heat up too much. Therefore, if your Car's System and added accessories requires high current, then you would need to use lower gauge (larger) power cables.

Here are some general values for cable gauge vs maximum fuse size (current demands)

Wire Gauge - Fuse Size
2/0 gauge - 430 amps
0 gauge - 345 amps
1 gauge - 265 amps
2 gauge - 215 amps
4 gauge - 135 amps
6 gauge - 80 amps
8 gauge - 55 amps
10 gauge - 30 amps
12 gauge - 20 amps
14 gauge - 15 amps
16 gauge - 7.5 amps

Make sure that the voltage drop in the power cable is not too high. Keep the voltage drop below 0.5V. Resistance in the power cable will result in a power loss.

There are many ways to measure Voltage Drop. Look here for ideas.


Fuses are there to prevent fires in the case of short circuits.

Remember, that the fuse (at the battery) is there to protect the cable. This means that the fuse rating should not exceed the amount of current that the cable can pass safely.

Rather than fusing the cable by the maximum amount of current it can pass safely (continuously), for example 125 amps for a 4 awg cable. Instead, it is safer to use a fuse that is as small as possible, but that will still be able to pass enough current for the car's loads without regularly blowing.

The power wire that is used to provide additional battery maintaining capabilities from a High Output Alternator is usually used in addition to the original power cable. In this case you are providing two paths for current, it is not necessary that this power cable be large enough to handle full output of the alternators charging capabilities. But at least enough to handle its additional abilities when neccessary.

The Power cable used to power an accessory like an amplifier you can simply add up the fuse values on the amplifiers. So, if for example, you had two amplifiers, one had two 25 amp fuses and the other had four 20 amp fuses, and the cable needed to be 6 feet long, then you would ideally use at least 2 awg with a 130 amp fuse. While it may be unlikely that this system will draw a maximum of exactly 130 amps while playing music, it is better to err on the side of larger cables and smaller fuses, therefore if a 130 amp fuse was not available, a 120 amp fuse will most likely work fine anyway.

Please Post Your Comments or Questions

comments powered by Disqus

(214) 202-3250