[kevinhorn]

Jacob,
Powerwerx is a good source for both wire and APP products. They offer a crimper for 50 amp APPs is just $15 and does a great job. In a pinch you might be able to use the crimper on the Brundy color code terminals as well.
When ordering the 50 amp shells be sure to keep to the red shells as they are keyed by color and only connect to like colored shells. While the you are making an order you might want to pickup some 50 amp contacts that are made for smaller gauge wire to convert your battery charger to direct plug to the battery.
The #6 AWG in red black pair seems expensive but remember that a 25' roll has 50' of wire and the pairing is handy if you place your battery any distance away from your PD.