Way way way back when the Anderson SB-50 connector was selected and apparently Anderson approved the higher current rating, the kit (this is back when you could only use parts from the kit or Small Parts) contained 2 Bosch drill motors and 2 Fisher-Price motors, and an assortment of small motors. The batteries were the same as they are now, but they used a 60a main fuse instead of the 120a main breaker we now use. Shortly after, the Victor was used, then the IFI control system. Now the rules allow 18 motors of similar power to those 4 drill and FP motors, robots have nearly tripled in speed, and the games are significantly more complex.
Now, we design to the 120 amp breaker, and put a lot of effort into keeping that breaker from tripping. Sometimes we design a bit too close, and it safely trips, and we take steps to prevent it from tripping again. We know what it will take, thanks to data sheets and trip curves. We already do a lot of design based on the main breaker and 40a branch breaker trip curves. We know when they will trip, we can run simulations of accel events, travel times, and distances to optimize our gear ratio to our strategy. We know how far we want to push the main breaker and we certainly know that when we exceed it, we have to scale back a bit but the failure is safe (even if it could cost us a match). In addition, in our pursuit of perfection, we design to push the robot as hard as possible during a competition. Maybe we push too hard. Then we go and drive the competition-designed robot for hours to practice, or at fast pace off-season events, and the issues show up.
We don’t have a number or ‘melt curve’ for the 50 amp plastic connector (and I can not design my robot to 50a instead of 120a and stay competitive) so we can’t design around it. Sure, we could empirically melt a whole bunch of connectors with a several hundred amp current limited lab power supply and huge load (the only reasonably safe way to do it) to get data on connector melting vs time vs load, or we could spend $5 more and buy a properly sized connector so the engineered electrical limiting device (the breaker) trips first and safely instead of the undersized connector.
The whole point of the main breaker is to safely cut power when we exceed the electrical limits imposed by the FIRST electrical system. We shouldn’t rely on a plastic connector to fail (possibly shorting and causing several hundred amps from the battery to start a fire) as an energy limit. The connector is far too small for our application (even if it was approved for the current draw way back when) and the company even makes a connector the right size for us.
It’s not the robot, it’s several robots over several years of practice and off-season events, designed at relatively common FRC speeds with quite efficient drivetrains. We run them (on the practice bot) for hours at a time, running roughly 50% duty cycle, but we can’t upgrade the connector on the practice bot without upgrading all of the batteries (which we also need to take to competition, and plug into the comp bot).