Choose a higher ambient temperature when conductors are expected to pass through.
Car battery ground cable size.
For more detail though check with the national electrical code as well as your own zoning laws.
Heavy 2 gauge cable should be used to connect the battery negative terminal to the engine block or starter mounting bolt.
Battery wire size per voltage amperage load and length chart below shows minimum cable size to use awg wire.
Cable size ampacity chart.
I recommend building cables larger than stock.
In summary when selecting the correct size of battery cable you need to take into account the total maximum amperage your electrical system requires the voltage of your system usually 12 volts the total length that your cables need to be and the amount of voltage drop you are willing to accept versus the amount you want to spend.
A short ground cable of the same size can be run to the frame but another short cable of the same size should run from the engine to the frame to complete the ground circuit.
For very long cables for example 15 foot long battery cables to relocate your battery go one size larger.
Wiring sizes measure from smallest to largest on a numerical scale with zero for the largest size of wire and larger numbers as the wire size decreases.
As far as i know these values are valid as of today.
The photos and captions chronicle the installation of an optima battery in a bitchin finned aluminum battery box within the trunk of my deuce hi boy roadster.
Choosing the correct gauge automotive wire depends on the acceptable voltage drop length of the feeder branch circuit conductor load amperage and the ambient temperature of the compartment where the primary wire will pass through.
A braided copper ground strap is best attaching the engine to the frame.
The manufacturers make stock battery cables as small as possible but still get the job done.
The fine stranded wire will pass more amperage than course stranded wire that has a lower strand count.
Fine stranded stereo wire makes great battery cable giving the best gage wire for proper battery charge.
The following maximum amps versus cable size awg come from the nec version 2011.
Most of the cost is the ends and labor.
Copper conductor ampacity based on 75 c 167 f reference.
This diagram illustrates proper vehicle grounding both to the engine block and also directly back to the battery as your vehicle s steel frame has only 20 of the conductivity as.
A matching size ground cable needs to be connected between the engine trans combination and the frame for vehicles with short ground cables from the battery to the frame and those with a ground cable running all the way to the starter.
