I made a quick calulation for 10 foot length and 14 volt 3 ampere maximum charge, I see about .25 voltage drop.  So from 14 to 13.75.   I believe your 16 gauge would be ok for this, BUT if we are talking heated things, etc,  I think some 12 gauge and fused for 20 amperes would be better.  I am not sure what the female receptacle is rated for, but that is a consideration also.