wire gauge for mech boxes.

[Mike H.]

I did some reading and see that it takes 10g copper wire to handle 30 amps and, not understanding why some would use anything less than that..I can understand maybe that large of a wire would be hard to solder but, how is 14g (common gauge used /rated 15 amps) handling dual parallel batteries on .2ohm loads or lower when it takes at least 12g copper wire to handle 20 amps?

.2 ohm load at 4.2v is 21 amps...so shouldnt the wires get pretty warm on 14g wire?..Its my understanding if the wires get warm then its not the proper wire gauge to be using.