Twin motors/controllers with 1 throttle HELP !!

[dumbass]

Calling all controller geeks. OK, I have a twin 24v brushed motor setup but normally only use of the 1 motors and the other is for added power when needed or a redundant. Currently each motor has it's own freewheel, on/off switch, controller and throttle. I would like to maintain the twin or redundant setup but change to a single throttle for both motors.

I have already tried connecting both controllers to one throttle with no success. I have been told that I would need to leave off the positive lead from one of the controllers to make it work. I tried this and the motor without using the pos. wire did not run at all. Of course even if I could make it work by leaving off the pos. wire from one controller this is not an ideal situation because it would require that controller to be active even if not in use. I am wondering if my solution is to use diodes. I say this because if I wire the 2 controllers to the single throttle each motor will work provided I only apply power to 1 of the controllers. But if I apply power to both controllers the controller that was switched on first is the only motor that will run. Therefore, I am thinking there is a voltage feedback causing the second controller to not function. By installing diodes this should correct the problem. Any thoughts?

The question is what type and size diodes do I use and where do I install them? Do I install them on each wire of both controllers? Just figuring out which wire is doing what is a big PITA. Here's the voltage reading across the wiring both in standby and with the test motor running at a slow rate of speed.

The throttle to my knowledge is a hall 3 wires; throttle using 1 each white, black and red wire

Motor IN STANDBY

WHITE TO RED = 3.54V

WHITE TO BLACK = .875V

BLACK TO RED = 4.42V


MOTOR RUNNING AT SLOW SPEED

WHITE TO RED = 2.26V

WHITE TO BLACK = 2.14V

BLACK TO RED = 4.42V


Thanks for any help you can give me,

Bob

 

[Rassy]

Hi Bob. I'm not currently running any dual (or tripple) motor setups from one throttle, but over the past several years had several of them for hundreds of miles. I always tied all battery packs together in parallel, and then tied all three throttle wires to both controllers. Never had a problem, but was also told some bad things could happen, but don't know exactly what. I never did any regen, but it sounds like you aren't either, with freewheels on both motors.

I assume both your motors are identical and in the same size wheel.

Anyway, for what it's worth, I would not worry about running just one at a time. Once they are both running from one throttle there is very little amps penalty to having both motors running (unless you always accelerate as fast as possible). I.e., it takes a certain amount of power to move a certain weight at a certain speed, whether one motor or two motors are supplying that power.

Good luck.

 

[BLUESTREAK]

Go back and check "methods" thread about his running this setup with dual 9C I belive.

 

[amberwolf]

Verify first if they are or are not hall throttles, by measuring the throttle with an ohmmeter with it disconnected from the controller. Many brushed controllers use pot throttles rather than hall, and more often than not the ones I have worked with "check the resistance" of the throttle via one method or another to determine if the throttle is "on" at startup (high-pedal lockout) so that the vehicle can't be started and instantly have the motor at speed, which could cause a serious startup accident in some cases.

Even hall throttle-using controllers might do high-pedal lockout, but they should only be checking teh voltage at startup, rather than resistance. In that case, they should work with both wired straight ot teh same throttle. (although it's possible for one controller to react differenly than the other by a smidgen, causing most o the load to be on just one).

The pot-using controllers that check resistance are also checking for proper throttle operation, which will give wrong values if there is something disconnected or shorted in it, forcing the controller to be disabled until it is reset after the pot problem is fixed. If two controllers share a single throttle and they are doing this check by one of several possible means, they will interfere with each other and only one will work right, if either does (it's possible neither will).

Diodes may work, but you might have to increase the input voltage to the throttle by the same amount as whatever the voltage dropped across the diode(s) is.

 

[markcycle]

I did this 1 battery, 1 Hall throttle and two controllers.
I used a opamp buffer for each controller to split the throttle signal and a very well layed out single point grounding system. I used the 5 volts from one controller to power the opamps and I verified the the throttle signal is ground referenced.

I hope this helps

Mark

 

[dumbass]

Thanks everyone for all the great info.

Rassy.......Yeah, I was thinking the same thing that it would only be maybe a 10% penalty for just running the 2 motors continuously. The idea for the 2 motors was not just to have the extra power but more for the redundancy value. Say a motor, controller or throttle failed on a long ride. I could just turn one off and the other on. Of course I would need to carry a second throttle that is quick and easy to replace. This is the reason I installed a freewheel on each motor.

I have considered just series wiring the motors and running one controller for both motors. This would be easy because the motors are only 24v so I would only need a big 48v controller and matching throttle. But my current controllers are 24v 35a. I wonder if I would actually need a 48v 70a controller to be equal size.

BLUESTREAK...I new I had read posts on twin motors but couldn't find anything in the search. I'll try looking for methods post.

amberwolf...I am ridding a heavily modified Ezip bike setup. Relocated twin motor (in the “V”) driving through a jack shaft to the rear Nuvinci hub. While there are a lot of mods the motors, controllers and throttle is standard Currie Ezip. I just assumed they used a hall throttle but maybe it's just a pot as you say. I will check it.

I am guessing the controllers is checking for a “throttle on” condition and therefore not allowing the motor to operate. Actually when testing I noticed that the second motor would nudge a little then stop. So this is a very possible.

Yeah, I was thinking I would have to add voltage to allow for the diode. Not sure how but.... The more I think about it I am liking the series wired motors more and more.

markcycle...Thanks for the info but your talking way over my head electronically. I considered just using a separate 5v supply. My thought was nether controller would see a feedback this way. Of course where do I get a 5v supply? Even using something like 4 “D” cell batteries it would be well over 6v. Hmm, maybe just 3 D cells. Wonder how long they wold last. Maybe rechargeable cells.

 

[HTB_Terry]

Your hunch was correct, you should use diodes to isolate the two controllers. Both controllers need to power the throttle in case you want to use one motor. Use schottky diodes to keep the voltage drop low. The specs for the diode are 12V or more, any currect, small ones are fine. The forward voltage drop Vf should be 0.5V or less. Connect each one series with the 5V supply wire from the controllers (red wire). The anode goes toward the controller and cathode (indicated by the stripe) goes to the throttle. Hopefully at that low current the voltage drop will be low and you will get full output voltage from the throttle. If you have a meter, you can measure the minimum voltage to obtain maximum speed, then check it after the diodes are in. The ground and output wires from the throttle get wired directly to to the two controllers. You could actually use any rectifier diodes, but you might not get the voltage required for max speed.

 

[dumbass]

Your hunch was correct, you should use diodes to isolate the two controllers. Both controllers need to power the throttle in case you want to use one motor. Use schottky diodes to keep the voltage drop low. The specs for the diode are 12V or more, any currect, small ones are fine. The forward voltage drop Vf should be 0.5V or less. Connect each one series with the 5V supply wire from the controllers (red wire). The anode goes toward the controller and cathode (indicated by the stripe) goes to the throttle. Hopefully at that low current the voltage drop will be low and you will get full output voltage from the throttle. If you have a meter, you can measure the minimum voltage to obtain maximum speed, then check it after the diodes are in. The ground and output wires from the throttle get wired directly to to the two controllers. You could actually use any rectifier diodes, but you might not get the voltage required for max speed.

Thanks Terry, I think as soon as I get a chance I am going to order the diodes ans see what happens. If I am inderstanding you correctly I should only install them on the red (Positive wire) and not the signal or neg wire. Correct?

Bob

 

[Hillhater]

Of course where do I get a 5v supply? Even using something like 4 “D” cell batteries it would be well over 6v. Hmm, maybe just 3 D cells. Wonder how long they wold last. Maybe rechargeable cells.

you have several options as used for RC reciever systems.
Alkaline pack.. 3x 1.5v = 4.5 v works
Rechargeable battery pack... (4 Nimh cells is most common =4.8v)
BEC ( Battery elimination circuit) supplies 5 to 6v from the main drive battery.
http://www.hobbycity.com/hobbyking/store/uh_viewItem.asp?idProduct=10313