Wiring Y-cables & robot batteries

Hello Vex Forums, I would love any advice on how to wire y-cables, or wiring subsystems in general. Whenever my team has used y-cables, the subsystem(mostly a 4 motor lift) it is used in stalls frequently. Also, whenever we used y-cables, our battery drained quickly(within 30-45 secs of using the lift; just going up and down). Would love to know your thoughts and any advice you have. Also, this is certainly not a mechanical issue because we have tried using y-cables on the drive and other robots in the past, and it has been the same situation.
When I say “drained quickly”, i mean the robot indicator on the cortex turns red.

y-cables really shouldn’t be doing that… we never have any problems with ours… maybe a cortex issue? or the y-cables aren’t working?

Thanks for the feedback @To_Bi_As . I updated the cortex’ firmware, tried other charged batteries; same result.
Our lift is 7:1 4 motor H.S by the way.

try swapping out the y-cables. it could be something wrong with those.

When using any y-cable (or any 3 wire extender for that matter) you need to make sure that the cables are plugged in red to red, black to black, etc. Another thing to check is that you are not overloading any one circuit breaker and, because you are using a y-cable I assume you have 12 motors, you need a power expander to have extra battery power. It is important to split up all the motors on your robot so there is not so much current being drawn from a single circuit break which from your description I assume is happening and it is tripping.

If the current drain were high, the PTC device would go non-conductive, and current flow would stop until it reset. So that’s not it.

Probably shouldn’t always make that assumption, though it may well hold here. In my experience, most people use y-cables for convenience in wiring and programming, not because they’re out of ports.

Good advice, but not the problem here. As mentioned above, triggering a PTC into non-conductivity will shut down the circuit, thus now current flow and no battery drain.

to my knowledge the y cables split the voltage between the two stands so your motors may just not be receiving enough power, try plugging them in one at a time and testing it.

Wires don’t work that way. Y cables don’t and can’t split the voltage. Y cables are just wires with very little resistance. The same voltage is delivered to each branch of a Y.

Think of the 8 motor ports 2 through 9 in the cortex. (Ports 1 & 10 are different) Each one of those is connected to the same “wire” on the circuit board. So the motor ports themselves serve as an 8-way splitter. Yet the motors don’t receive only 1/8 of the voltage.

Am I the only person who avoids using ports 1 and 10 even though I’m using 12 motors and ends up using 4 y cables?

Comments on how “that is illegal” are predicted.

Thanks for all your comments. I will try getting new y-cables and see what happens.

My recommendation on y-cables and power consumption is to run two y-cables from the Cortex to a Power Expander. Then run individual cables from the four Power Expander outputs. That puts the four motors that would draw power through only two ports back onto four ports. It’s not really critical, but it’s a safer practice.

As @kypyro said, the y-cables to not split the voltage. That will be essentially unchanged. They split the current, which means your single end of the y-cable carries theoretically double the current that goes out either of the two ends.

Another possibility with this happening is the battery. We’ve had a few batteries that went bad. What will happen with said bad battery is that it will hold a charge (say at 7.5V or so) but as soon as any resistance comes to the motors at all it will drop drastically (to something like 3.0V) for just a fraction of a second.

@Jake_B That is what I am experiencing with the lift. As it gets close to the highest point, it slows down and the battery indicator slowly turns red.

Test multiple batteries and check their voltages. We just used an lcd screen. I can provide the code if you need it in a little while.

It’s fine, I already made one, thanks. We have had those batteries for about 3-4 years now. @Jake_B

That would make sense.

Yep. I ordered new y-cables as well. Thanks for your help