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 Two DC motors in series

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SenaiERI
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PostSubject: Two DC motors in series   Fri Apr 17, 2009 12:20 am

Does anyone know the proper way to run two dc motors in series with one speed controller? I have the banebot 20:1 28mm motors and want to run them with banebots 45 amp controller. It should be able to handle the amps but when I run it, one motor runs very slow and sometimes not at all.

Should I have them in parallel?

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Jeff L
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PostSubject: Re: Two DC motors in series   Fri Apr 17, 2009 12:23 am

Yes, they should be in parallel. We ran X-Contamination's two weapon motors off of one relay in parallel just fine.
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SenaiERI
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PostSubject: Re: Two DC motors in series   Fri Apr 17, 2009 12:26 am

Jeff L wrote:
Yes, they should be in parallel. We ran X-Contamination's two weapon motors off of one relay in parallel just fine.

Thanks. I'll try it and see what happens. This is gonna be a long night.

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Dan Curhan
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PostSubject: Re: Two DC motors in series   Fri Apr 17, 2009 11:45 am

yeah, running motors in series is definitely NOT what you want. When you think about using one thing to run multiple things, you want to think about splitting - which implies parallel.

Ask away if you have any more problems :]
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SenaiERI
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PostSubject: Re: Two DC motors in series   Fri Apr 17, 2009 1:17 pm

Thanks guys. It works great now.

Maybe I shouldn't be taking advice my opponents. Apparently not everyone wants to display good sportsmanship.

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MattTavares
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PostSubject: Re: Two DC motors in series   Wed Apr 29, 2009 4:38 pm

Actually guys. I ran blender mini last year with the front and back left drive in series and the front and back right drive in series. It halves the voltage going to each motor in an ideal situation. Also, Because the resistance of a torque stalled motor goes up, if one of the motors gets torque stalled then the other motor gets more voltage delivered to it. So basically it compensates for the torque stalled motor. It was amazing because I didn't even realize until the end of one of the matches last year that one of my banebots gearboxes had seized during the match. I had to look back at video to figure out when it happened.
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PostSubject: Re: Two DC motors in series   Wed Jun 10, 2009 6:20 pm

Hey, I know I'm coming in late on these discussions (as in well after the competitions!), but I felt like this one is worth comment:
Two DC motors in series will perform exactly as MattT has said, but one thing to keep in mind: Even if you load them such that they begin to spin at the same speed, the PAIR will only have about 1/2 the overall power of a single motor of the same type! See, wiring them in series means, essentially, half the voltage to each motor, which means half the current through each as well. Power (in DC) is voltage multiplied by current. Half times half is one quarter, but you do have two of them each operating at 1/4 power, so overall you've got half the output.
The upside is that you are also drawing only half the power out of your batteries and through your ESC, and each motor is only working at 1/4 the prior demand.
When we discovered the drive motors for SpiderPig were crap the night before we shipped it, we just wired every two in series and the smoke ceased. Fortunately (and $400 later) we got Traxxas motors from Towerhobbies delivered to SF, and switched them out (and back to one per ESC) before competition.
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PostSubject: Re: Two DC motors in series   Thu Oct 15, 2009 1:46 pm

The best way to use motors in series is how Brian Nave does it in Shrederator. He runs two dpacks in series at 48v. Simply being able to say you run dpacks at 48v is awesome enough.
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Cody
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PostSubject: Re: Two DC motors in series   Thu Oct 15, 2009 11:25 pm

minus the 24volt or so limit in the 15lb class
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