# JX Servos maximum current

Joined Dec 21, 2020
8
Hi, I work on a project where I need 2 servomotors to be connected to a 12V battery. As the motors can not handle 12V, I need to find a regulator with a 7V output.
To be sure not to undersize this regulator I would need to know the maximum current required by the two motors.

Here are the informations I have about the motors I will have to use:
JX Servos (PDI-HV2060MG)
6V : 0.15s/60° and 48kg/cm
7.4V : 0.13s/60° and 62kg/cm

Each motor is attached to a charge (35cm*19cm and 400g). The motors and their charges will be embedded on a vehicule (from 0 to 200 km/h max) so they may be subjected to the wind force.

I read that this is possible to find the maximum current using this formula ' P = Couple * Rotation speed ' but:
- it doesn't take into account the force that will be opposed to it (the wind)
- I also read that the power up consumption might be higher that this, thus requiring a safety margin

Here are my questions:
1. How can I get the maximum current ? (I can't just measure it as I don't have access to the motors)
2. I did not choose the motors but aren't they a bit 'overkill' ? How can I calculate the couple I need ?
3. Will a motor with a lower max couple consum the same current as these 60kg motors while the max couple is not reached ?

Please, try to explain like I'm 5 years old, I am a beginner Thank you

#### Alec_t

Joined Sep 17, 2013
12,248
1) Ask the manufacturer of the servo.
2) By 'couple' I presume you mean torque. Torque = load x distance of load from centre of rotation (which you haven't specified).
3) It would depend on the motor construction. For any one motor, torque is approximately proportional to current.

Joined Dec 21, 2020
8
1) Ask the manufacturer of the servo.
Ok

2) By 'couple' I presume you mean torque. Torque = load x distance of load from centre of rotation (which you haven't specified).
Yes I meant torque. The formula you gave does not take into account the forces opposed to the rotation. Here there will be the air which, with the speed, will force the charge not to move. To be more precise about this charge, it will be like a plane spoiler, the motor will rotate it and keep it against the wind. The higher is the angle, the higher the wind force will be. As the spoiler is really light (only 400g), the real problem with this calculation is the wind force.

3) It would depend on the motor construction. For any one motor, torque is approximately proportional to current.
Ok, I will ask the constructor too then.

#### Alec_t

Joined Sep 17, 2013
12,248
The formula you gave does not take into account the forces opposed to the rotation
Those forces, plus the 'charge', are the load.

#### LowQCab

Joined Nov 6, 2012
1,183
The most important part of this whole setup is going to be Current-Limiting.
Most RC / Hobby Servos can not be "Stalled" with movement commanded
for an indefinite period of Time.
You will smoke the Motors.

There are Extremely Heavy-Duty-Servos available for RC-Trucks,
but prices start at around ~$100.oo each. Or, You can use a Heavy-Duty Voltage-Regulator with built-in Current-Limiting, like this .............. Then You need to find out the maximum permissible "Locked-Rotor" Current from the Servo manufacturer. . . . #### Juhahoo Joined Jun 3, 2019 215 Just build a setup where you have the weight which the servo must lift with its arm, and measure current. Simple. Thread Starter #### pradel Joined Dec 21, 2020 8 Those forces, plus the 'charge', are the load. Ok I guess I have to do some more researches about the calculation of this load Thread Starter #### pradel Joined Dec 21, 2020 8 The most important part of this whole setup is going to be Current-Limiting. Most RC / Hobby Servos can not be "Stalled" with movement commanded for an indefinite period of Time. You will smoke the Motors. There are Extremely Heavy-Duty-Servos available for RC-Trucks, but prices start at around ~$100.oo each.

Or, You can use a Heavy-Duty Voltage-Regulator with built-in Current-Limiting,
like this ..............

View attachment 245510Then You need to find out the maximum permissible
"Locked-Rotor" Current from the Servo manufacturer.
.
.
.
Yes I need to find this current but the Servo manufacturer seems unreachable, no website, no email. So, I guess I need to find out with the informations I have