Below we reference the two things you must double check when sizing your battery cables.
What size cable to run for dual battery.
As far as i know these values are valid as of today.
Use 13 5mm as an absolute minimum.
For more detail though check with the national electrical code as well as your own zoning laws.
I always suggest a minimum yes i did say a minimum of 6 b s 13 5mm cable for linking batteries larger is even better any further improvements to the charging time and system as a whole will be gained by increasing the size of this cable i know that the larger cable is not cheap but bigger is always best in the long run.
If in doubt always opt for the larger size cable.
The battery cable is among the most important cables in a battery management system.
Regardless of the math we would never use 7 71mm battery cable in a dual battery system.
The following maximum amps versus cable size awg come from the nec version 2011.
Copper conductor ampacity based on 75 c 167 f reference.
It ensures you have power stay on task and avoid battery drain.
The century n70t deep cycle battery is rated at 100 amps.
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.