One Throttle For More Than Two Motors

[Stagyar]

Connecting one throttle to two BLDC hub motors is as simple, in the case of the heavy cargo quad we're building, as using a splitter cable from the company that makes the motors and controllers to connect the one throttle to both motor controllers. The splitter twins the wires and adds a resistor. The manufacturer doesn't make a splitter for three motors, or four. Also, the two-motor splitter feeds the temperature signal from only one motor to the cycle computer, which can't read two simultaneously.

All the individual power and signal wires could be broken out and wired directly. That's the most work. Would connecting the throttle to the motor controllers be as simple as getting the resistance right?

Has anyone tried using a component computer like a Raspberry Pi to build a bike computer?

 

[E-HP]

Do you have a link to the splitter? It’s unclear why a resistor is necessary unless it’s used to apply more power to one motor over the other.

 

[Stagyar]

These are the links to the current model and the previous model of the splitter, but the attached pics are more informative. Both models have resistors but it's easier to see in the older one. My understanding is that the motor controllers have reference resistors built in, but paralleling more than one decreases the overall resistance, so the splitter adds enough resistance to bring the total back to what the computer expects to see.

older - Dual Controller Shunt
newer - CA3-WP Dual Controller Splitter

 

[E-HP]

Based on the diagrams, for the Splitter, the throttle signals are straight paralleled without using any resistors. The resistance is used to combine the shunt current sensing voltages (current monitoring) when there are two shunts, one for each controller, so total power can be measured by the CA. This uses the shunts inside the controllers. The Dual Controller Shunt is external to the controller and simply combines the battery current through a single shunt. The throttle signals are straight paralleled in this case as well. The latter could be scaled to more than 2 controllers as long as the shunt rating can handle the combined current.

Shunts are cheap. The relative costs between a 100A shunt and a 500A is minimal, so you can replicate a high current version of the Dual (quad?) Controller Shunt for $15 plus the cost of a few JST plugs and some solder.

Amazon.com

Amazon.com

 

[Chalo]

The accepted/functional way to do this is to add a second plug to the throttle, in parallel with the first, but connected only to signal and GND. +5V should connect to only one of the two controllers.