You might need to do a bit of conversion to/from metric units, but this link tells you how to size cable based on the cable length and current requirement:
so plug 14 amps into the formula quoted in the link:
Here are some conversions to get you going...To determine cable size you must know:
The total conductor length,
The current that the cable will carry,
The permissible voltage drop (0.36 volts is fine for most 12 volt purposes, 0.72 for 24 volts).
From that it is possible to work out conductor size in sq mm as follows.
Length in metres x current in amps x 0.017/conductor size in sq mm = voltage drop.
3.28 feet = 1 metre
1 inch = 25.4 mm