The LiFePO4 battery came with a 4 hookup wires. 2 for charging and 2 for discharge. This is because charging must go through the battery management system whereas powering the motor comes directly off the batteries.

The discharge wires are 16 gauge and the charge wires are 18 gauge. Since the battery is used outdoors, I bought fully insulated nylon spade wire crimps (see project parts list). They are color coded to indicate the range or wire gauge they support.

The reason the charge wires use two different colors is because their wires are different gauge. This is okay because the current is limited by the battery management system (higher gauge is rated for less current).