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ctx32
12-25-2008, 11:40 AM
I need some advice about running 24v. 130w. Scooter motors on 12v.
The motors on 24v. are just too strong and they're tossing my R2D2 around like crazy.
If I run them on 12v. they're much smoother and function much better.
I know the 24v. will last longer as far as drive time, But I could wire 2 12v. 22.ah batts
together and stay 12v.
Do you think this will damage the motors?
And will it make them run hotter?
Thanks :wink:
Calvin

darkback2
12-25-2008, 12:23 PM
I'm not the best person to answer this...

I'm pretty sure running 24 volt motors at 12 volts is fine. As for battery time, that has more to do with watts and amphours than volts directly...That said, the closer motors are to stall, the more they draw.

Then again, the batteries you have are huge.

db

robologist
12-25-2008, 01:08 PM
Think of motors as a resistive element. They aren't purely resistive, but primarily inductive, but what is more likely to kill the motor is over-current. Ohms Law gives you Voltage equals Current times Resistance, so reaarannging for current gives Current equal to Voltage divided by Resistance. A brushed DC motor (like the typical scooter motors) can be modeled as a fixed resistance. So if you up the voltage, you up the current, which the motor wires can only carry so much of. Lowering the voltage will lower the current, which the wires can then easily carry.

Essentially, if the motors are rated to run continuously at a certain voltage. they will run twice as continuously at half the voltage. There is no harm in running a motor at a lower voltage. :)

Oh, and the batteries should last longer since lower current is being asked from them.

ctx32
12-25-2008, 01:20 PM
Thanks for the answers.
The 24v. was just too much power.
I could'nt hardly move R2 without him jumping all over the place.
I'm running a C6C controller: http://www.cheapcontrolsystems.com/
and I don't have all the adjustments that a regular RC remote has built in.
And I had turned down everything I could for a lighter responce,
So I wired the batts for 12v. and everything works GREAT now.
Thanks
Calvin

12-25-2008, 04:39 PM
I concur with Robologist: Half the voltage = Motors that are [effectively] twice as happy. :)

ctx32
12-25-2008, 06:35 PM
Long time no talk.
Glad your still here and I'm getting very close to finishing R2.
Calvin

12-25-2008, 06:39 PM
Heya, Calvin -

Good to hear you're finishing him up! Videos!

I'm like the forum's bad rash - hard to get rid of me... ;)

ctx32
12-25-2008, 07:21 PM
I have some Vid's on my blog: www.tomsr2.blogspot.com (http://www.tomsr2.blogspot.com)
I'll post some new pics here, Can I post video's in my album?
It was nice today to be able to drive R2 on 12v. without all the jumping on 24v.
I still have to finish the onboard comp and then I can really enjoy all the good stuff
and the code we were working on.
But with MegaCon so close I had to cheat alittle with some basic stuff.
After that I will finish the comp and I have a webcam I want to add.
SeeYa
Calvin