Quote:
Originally Posted by apalrd
Al, at 400a, what are the losses of a #6 vs #4 battery cable? We always keep the length short (never adding length to the 12" COTS cable and using a ~6" wire between Main Breaker and PD), and wondered if switching to #4 on one or both ends would help.
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Assuming that you are talking 12" on both sides of the Anderson connector, the resistance of #6 would be roughly 0.002 ohms. Moving to #4 would cut that in half. So all things being equal, moving to #4, 400 amps would give you another 0.4 volt available at the PD terminals. We choose to trade off the free weight of 12" of battery cable for the slightly higher loss. Then try to keep all wiring short to minimize losses and balance the loads.
I can't tell you how many teams over the years have come to me trying to make their autonomous run straight. By far most of these teams had several more feet in the wiring feeding one side of the robot then the other side. To all teams, your robot design should try to keep the PD centered in the robot base so that wire runs to drive hardware is short and similar lengths. All other loads are secondary to the drive. The cRio doesn't care where it is located, neither does the DSC, compressor or other loads. When a team asks if I can determine a problem with their drive, one of the questions will be "how fast did you design your robot to move and does it move as fast you expected?" When the answer is "no, it doesn't go as fast as we expected" then I look for where the PD is mounted and the length of the wiring to the speed controllers and motors. While mounting to make things pretty is great, it is not always the best choice for electrical losses.