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KidsWheels
Gruber
HobbyMasters
M.L. Toys
KidsWheels
HobbyMasters M.L. Toys
Gruber
KidsWheels
Anything that doesn't fit somewhere else & general forum updates
#150402
If 2 electric motors are running off the same power source and you load one motor up more than the other, will more power transfer to the motor with less load on it ?
To clarify some, my daughter has a 24v Disney princess carriage, stock. Both back wheels have their own motor/gearbox assembley. When she drives it, if one wheel gets in the air, it spins and the other one doesn’t. Almost like it has a differential of some sort but it obviously doesn’t. I don’t know if the motors are wired in parallel or series, or what’s typical or what difference that makes. All of this just makes me wonder if one motor is stealing power from the other motor when one of them is able to turn more freely. Is that possible? Sorry I’m not up on dc motor theory. The company sent me 2 new motor assemblies but I haven’t replaced them yet. If what I’m saying isn’t possible then what is most likely the problem, or is there a way to make it a true 2 wheel drive so it doesn’t get stuck all the time?
Thanks everybody


#150404
Thank you for letting me know it’s working properly, I don’t have to waste my time replacing motor assemblies that are just fine. But I might spend time on it doing other things. The batteries need replacing.
I know you said there’s nothing I can do but I have to ask lol, If I were to change the wiring to be in parallel, then each motor would get too much voltage, right? (I’m thinking in series the 24volts gets divided across the 2 and that the motors are probably 12v motors.) So what if I changed the batteries or added some sort of voltage reducer or even added or changed a motor controller? I guess my questions boil down to:

1) if I figured a way to make them work in parallel, would one tire still spin when it’s in the air or would that problem be solved?

2) if that problem would be solved, what’s the best way to go about getting them to work in parallel?

3) now instead of the voltage being split, wouldn’t the current be split? Although I didn’t think the power source determined the current except for a max rating, and that each device in a circuit would draw whatever current it needed.
Anyways, if the current is split, will that reduce the speed?

Again, thank you for your help.
#150413
You're generally correct -- in the current configuration it will be 12V per motor when they're both on the ground. The reason you get the 'open differential' effect when one wheel is off the ground is that the current needed to spin up the in-air wheel is much smaller than the one on the ground and it will build up enough RPMs to use all of the voltage (via. back-EMF). So if you had actually measured the voltage across the motors in that configuration you'd see ~24V on one motor and ~0 on the other one.

If you rewire them so they are in parallel, that 'open differential' behavior would disappear since both motors are forced to have 12V on them. But you'd have other effects:
(A) The top speed would be 2x
(B) Peak torque on each gearbox will be 2x
(B) The peak current load at the switch/battery would be 4x (!) vs. your current configuration

And depending on how well-built components are, that could lead to breakage or switch failure pretty quickly. Wiring it for 12V in parallel would give you the same speed and torque as your current setup but remove the open-differential problem. Note that even at 12V it would still use 2x the current, which could be a problem. I don't know why they went with a 24V-series configuration other than that it can be run with wimpier wire.
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