Rs550 electric motor help

shortbus

Joined Sep 30, 2009
8,593
A 6V DC motor will run just fine on 12V, and give twice the power and RPM. Brushed permanent magnet motors are pretty forgiving when over volted. Withing reason, and 2 times voltage is with in reason.
 

MisterBill2

Joined Jan 23, 2018
8,799
At twice the voltage you will come close to twice the current and thus closer to four times the power. Mostly, at some point the brushes and comutator become the limiting items. An overheated comutator can come apart and be a spectacular failure, while an overheated brush can melt the plastic mount for the brush holder and be a dismal disaster. And a melted brush holder mount is a huge challenge to repair in a lasting manner.
 

Thread Starter

Marka1977

Joined Nov 24, 2018
33
I'm a bit confused. 1 person said a 12v battery would double the motor power, and another person said it will quadruple the power. ?
 

Tonyr1084

Joined Sep 24, 2015
5,993
Speed takes power. Power costs money. How fast do you want to go? With speed comes safety concerns. How safe do you want it to be? Safe enough for your child? Or just faster; which?

Some time ago a friend built a go-cart. He used a belt drive. The clutch was a pedal that when you pushed it down an idler pulley pressed against the belt and made the cart go forward. Take your foot off the clutch and the motor was disengaged. Changing speeds was as easy as changing the pulley size(s) and belt lengths to match. The clutch pedal was operated by the left foot and the gas and brake pedals were on the right. The clutch worked in combination with the brake pedal. Press the brake pedal and you automatically disengaged the drive.

Like I said, speed takes power. Faster requires more power. We have no idea how fast you want to send your child hurtling across the back yard (or down the street). Care to elaborate?
 

Audioguru again

Joined Oct 21, 2019
3,206
Power equals voltage x current. If you double the voltage then you also double the current. Then 2x2= 4 times the original power and the heating in the motors is also quadrupled which is probably enough to destroy them.
 

Tonyr1084

Joined Sep 24, 2015
5,993
Power is the factor of voltage and amperage. 5 amps at 12 volts is 60 watts. 5 amps at 18 volts is 90 watts. A 50% increase in voltage is equivalent to a 50% increase in wattage.

The effective resistance of a motor remains the same. So if you have a motor that draws 5 amps at 12 volts then the motors effective resistance is 12V ÷ 5A = 2.4Ω. Increasing to 18 volts (my example) means the amperage increases as well. So at 18V ÷ 2.4Ω = 7.5A. So 18V x 7.5A = 135W. So we went from 60W to 135W. An increase of 225% (2 and 1/4 times) in power (wattage). If we double the 12 volts to 24 volts then we have 24V ÷ 2.4Ω = 10A (twice the amperage). 24V x 10A = 240W. From 60W to 240 W. So doubling the voltage will increase the wattage by a factor of 4X.

@Audioguru again BEAT ME BY 2 MINUTES!
 

MisterBill2

Joined Jan 23, 2018
8,799
My observation has been that when a 120 volt shop vac is plugged into a 220 volt outlet and switched on, that it screams instead of just roars. And within a minute smoke and flames exit the motor vent openings. This proves two things, first, that nobody reads a large red warning that the cord is connected to 220 volts instead of 120, and second, that almost doubling the voltage increases the power a whole lot. It also demonstrated that a shop vac will self-extinguish once the motor burns out and stops.
One additional comment is that kinetic energy increases with the square of the speed increase, and kinetic energy, similar to inertia, is what forces people to keep moving when their vehicle hits something. And my grand-nephew driving his battery powered little tractor routinely hits things. Other kids may have a similar skill set.
 

ArakelTheDragon

Joined Nov 18, 2016
1,353
The new motors might have a higher weight, not fit on the same place, the higher current is probably not supported by the electronics and I don't know if there are any legal concerns as the vehicle has to be under certain power, speed and etc.
 

MaxHeadRoom

Joined Jul 18, 2013
23,135
My observation has been that when a 120 volt shop vac is plugged into a 220 volt outlet and switched on, that it screams instead of just roars.
The reason being it is a Series field motor and operates in a run away condition normally, with double the voltage it attempts double the RPM, This is why the large shunt wound-field DC motors had field loss protection, as this loss would cause a run-away condition, often to destruction.
Max.
 
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Tonyr1084

Joined Sep 24, 2015
5,993
The new motors might have a higher weight, not fit on the same place, the higher current is probably not supported by the electronics and I don't know if there are any legal concerns as the vehicle has to be under certain power, speed and etc.
Another point this made me consider; higher current may be beyond the switches that are used to control the motors. As I recall, the switches in one of my kids toys - got it second hand - were pretty badly burned up. Possible someone tried a higher voltage, which lead to a higher current, which lead to greater arcing and burning of the switches.

Remember, a good engineer's design is only as good as the weakest link. If a switch is rated for 10 amps and you use it for 5 amps - you're well within operating range. But when you go up to 10 amps - you're right at the edge of failure. Given the nature of how kids may overload the toy they may overload the motors which will overload the switches.

If you want bigger motors and higher voltages then you're going to need switches and wiring that can handle it all. Not to mention - as Arakel already did - bigger motors are not likely going to fit in the same place as the original motors.
 

MaxHeadRoom

Joined Jul 18, 2013
23,135
Once you get into high current DC switching with relay/contactor, then some kind of arc quench types are needed and typically used in industry.
Otherwise plasma conduction destroys the contact surface.
Max.
 

Audioguru again

Joined Oct 21, 2019
3,206
The extra weight of kids today (fast and too much food) already overloads the electric car's motors, before doubling the voltage.
Four times the normal power might result in the motor or wiring catching on fire.
 

MisterBill2

Joined Jan 23, 2018
8,799
We need to keep in mind that the vehicle in this discussion is a blow-molded polyethylene race car, and that the relays in the picture, while rated 12 amps at 120VAC, do not show a DC current rating. And there is no room for a real power contactor, anyway.
 

Thread Starter

Marka1977

Joined Nov 24, 2018
33
Ok guys. Looks like I will be leaving it as is. I wanted about 6 mph as it is not really brisk walking speed as is.
This was bought at smyths toys and is the bmw i8 trin motor 12v model.
They do the 6v single motor model but I believe it is the same motor in 1 wheel only and a 6v battery. It also has 1 relay and not 2.
I just wanted to have the car but a little quicker now that he is older.
 

MisterBill2

Joined Jan 23, 2018
8,799
Ok guys. Looks like I will be leaving it as is. I wanted about 6 mph as it is not really brisk walking speed as is.
This was bought at smyths toys and is the bmw i8 trin motor 12v model.
They do the 6v single motor model but I believe it is the same motor in 1 wheel only and a 6v battery. It also has 1 relay and not 2.
I just wanted to have the car but a little quicker now that he is older.
One possibility that can provide better performance is to apply an anti-slip treatment to the wheels. On my grand-nephew's tractor the wheels slip a lot when it starts.
Also, you can evaluate the present arrangement because it may be that changing the connections to a motors in parallel will give the performance that you seek. I just reviewed all of the posts and I see that it was never mentioned as to what voltage was presently applied to the motors, which were described as six volt motors.
After another examination of that photo in post #7 it looks like the two motors are in series, so changing to a parallel connection will provide a lot more speed. It seems that I was not fully awake when I originally looked at that photo. You can verify the series connection by unplugging one motor and checking if the other motor still runs.
 

Audioguru again

Joined Oct 21, 2019
3,206
It is too dangerous to see if the motors or the wiring catches on fire first if the 6V motors are powered from 12V.
The ride-on car probably does not even have a seatbelt to keep the driver kid from flying when an overheated motor suddenly gets jammed.
 

Chris65536

Joined Nov 11, 2019
270
Most of you guys are just too funny for words. Your assumptions on how PM DC motors work.
I figure, torque is proportional to current, and max RPM proportional to voltage. I think the TS should leave the motors alone, and upgrade the battery to lithium. Lower internal resistance would give more torque, and 4 cells would give from 16.8v - 14.8v, giving a little more speed, without frying anything. He could also use even more cells along with a PWM motor speed controller. Full power would only be used intermittently. You have to make sure to buy the real brand name cells, to get the max amps. There are a lot of fakes out there! (which I have bought by mistake)
 

MisterBill2

Joined Jan 23, 2018
8,799
To put the two motors in parallel will not be very difficult, since there are connectors that can be unplugged. BUT you do need to verify the rotation, since the two currently spin in opposite directions because of the mounting arrangement.
Most of you guys are just too funny for words. Your assumptions on how PM DC motors work.
I certainly agree on this one, S.B., almost to the point of making remarks about other's concerns. But I will not make fun of anybody this time.
 
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