[Al Skierkiewicz]

Andy,
At first I thought you might just have a small problem (i.e. a defective breaker or loose wire)but after reading all the posts, this is what I think you have...
1. Your drive system is drawing so much current that you have to redesign it to run in the future. I have heard so few teams claiming they are tripping the 120 AMP breaker that I thought we finally have a workable device. Sorry to be the bearer of bad news on this one. You didn't mention your speed but I am going to guess you designed for maximum push and are not a high speed robot. I am guessing from your description that you are tank tread design as well and with few details about the match in question, I would bet you were doing a lot of turning. High power + treads + lots of turning + two motors on a shaft = the highest current draw of any design = breakers tripping, wire melting, motors failing.
2. Replace not only the melted wire but the 120 amp breaker and the smaller breakers as well. They may not test bad now, but they have been stressed beyond normal and will certainly fail in the future. (Murphy's Law "Anything that can go wrong, will, and at the worst possible time.")
3. The larger the wire, the less prone it is to melting, not greater.
4. Just because the battery didn't feel hot to the touch does not mean that the internal temp hadn't skyrocketed. It takes time for that heat to migrate to the outside case. It is likely that some of the fragrance you smelled was venting of the battery as well as hot wires. Everything that got hot did so because of the high current. That current was also passing through the battery as well.