Tweet
Hi AussieAndy and you will find most auto electricians use 6mm AUTO cable and they call it HEAVY DUTY cable or another name they use is 50 amp cable.
Both are wrong and if you are talking to an auto electrician about getting a dual battery system fitted and he uses those terms for the cable he recommends, you would be better off going elsewhere.
Hi amts, while keeping a voltage drop of no more than 0.3v in an ordinary 12v circuit is best practice, it actually does not apply to dual battery circuits.
The reason is that in an ordinary 12v circuit, like one powering a fridge or to power some lights, you will have a known constant maximum current requirement for the circuit.
With a dual battery cabling circuit, the current is continually varying, depending on the state of charge of the auxiliary/house batteries and the voltage level being applied at the supply end of the cable.
As a number of you have posted, 6B&S ( 13.5v ) is the most common CORRECT size cable to use in a 12v.
While you can go thicker, there will be little advantage but if you use thinner cable, there is a huge disadvantage.
6B&S just suits 12v dual battery circuits.
As to voltage drop, if you had say 3 x 100Ah house batteries in a low state, over a 10m run of 6B&S, you could see well over a volt drop at the batteries, but they would most likely by drawing anything up to 70+ amps, depending on how low they were.
A voltage drop of this size is irrelevant when the batteries are drawing 70 amps while charging, and as the batteries charge, their current draw will reduce, and so will the amount of voltage drop.
Both are wrong and if you are talking to an auto electrician about getting a dual battery system fitted and he uses those terms for the cable he recommends, you would be better off going elsewhere.
Hi amts, while keeping a voltage drop of no more than 0.3v in an ordinary 12v circuit is best practice, it actually does not apply to dual battery circuits.
The reason is that in an ordinary 12v circuit, like one powering a fridge or to power some lights, you will have a known constant maximum current requirement for the circuit.
With a dual battery cabling circuit, the current is continually varying, depending on the state of charge of the auxiliary/house batteries and the voltage level being applied at the supply end of the cable.
As a number of you have posted, 6B&S ( 13.5v ) is the most common CORRECT size cable to use in a 12v.
While you can go thicker, there will be little advantage but if you use thinner cable, there is a huge disadvantage.
6B&S just suits 12v dual battery circuits.
As to voltage drop, if you had say 3 x 100Ah house batteries in a low state, over a 10m run of 6B&S, you could see well over a volt drop at the batteries, but they would most likely by drawing anything up to 70+ amps, depending on how low they were.
A voltage drop of this size is irrelevant when the batteries are drawing 70 amps while charging, and as the batteries charge, their current draw will reduce, and so will the amount of voltage drop.
Comment