After about 100 flights my switch melted. I found arcing marks on the contacts inside the switch (they were hard to find with all the melted plastic). The switch can handle the current fine if the contacts aren’t damaged. Several people are looking for a bigger switch to prevent this issue but that doesn’t fix the arcing and even a bigger switch will arc and degrade.
The arcing happens when the switch is turned on because there is a rush of current to charge the capacitors inside the ESC. Several people have talked about using a precharge circuit where the current flows through a resistor to slow down the rush of current. Once the capacitors have the same voltage as the batteries the main switch can be turned on without arcing occurring inside the switch. This is the route I decided to take. I tested several resistors and found 22 ohms to work well. With anything higher than that I could hear arcing inside the switch. This is because the higher the resistance the lower the voltage gets inside the capacitors so when the switch is flipped there is still a rush of current.
Paul is supplying two switches with the kits now so we can use both switches at the same time with half the amps running through each one. He sent me two switches and another bracket. But then the question of how to wire two switches. There are several ways to do it. One way is to have one set of batteries run two motors and the other set run the other two with a switch between each. The method I came up with is to have a switch between each battery set but either set would run all four motors. If one switch goes out I will still have power to all four motors but that power would all be coming from one battery set. This is preferable, in my opinion, over having two motors not running.
Having two switches is a good thing but the first switch flipped will still arc so one switch needs to be connected to a precharge system. Here’s what I came up with: I designed a replacement knob for the switch that has a precharge switch built into it. All I have to do is twist the switch about 10 degrees to precharge the system, hold it for less than two seconds until the motors beep, then turn the switch 90 degrees to fully power up with no arcing. There is a spring inside the knob that disconnects the precharge circuit when I let go of it. It’s nice because it can be done with one hand as opposed to using a separate button.
All the knob does is press two wires together to run the current through the resistor. The resistor is covered in heat shrink on the orange wire:
Here is how I wired the two switches… the battery leads come in on both sides and run to the nearest switch and to the nearest motors. This makes the wires as short as possible. The two wires running left and right join the two circuits (I ran out of red so both are black). Power won’t really even run through these wires other than to discharge the batteries evenly. But if a switch goes out they will feed the other side:
While I was rewiring my whole machine I 3D printed covers for my electrical junctions:
Here are the files for anyone who wants to use them:
Pre-Charge Knob - Part 1.stl (255.3 KB)
Pre-Charge Knob - Part 2.stl (383.1 KB)
Pre-Charge Knob - Part 3.stl (1.9 MB)
Connector Cover - Top.stl (582.7 KB)
Connector Cover - Bottom.stl (582.7 KB)