user44903: My bot arm building is complete, I'm using it with Arduino and 2 joysticks with 4 servos ( mg90s), running with the 9v battery, but still, the servos could not lift the bot arm once it is going down and the servo keeps fluctuating. It is a 3d printed bot so it is not so heavy. please help?

user27653: Even if your device is not so heavy, a 9V battery has a maximum practical current draw in the 10s of milliamps. It's not a good choice for operating motors.
A better choice would be AA, C, D, or Lithium-Ion/Lithium-Polymer batteries, wired in series to produce the desired voltage.

44903: <p>My bot arm building is complete, I'm using it with Arduino and 2 joysticks with 4 servos ( mg90s), running with the 9v battery, but still, the servos could not lift the bot arm once it is going down and the servo keeps fluctuating. It is a 3d printed bot so it is not so heavy. please help?</p>
 27653: <p>Even if your device is not so heavy, a 9V battery has a maximum practical current draw in the 10s of milliamps. It's not a good choice for operating motors.</p>

<p>A better choice would be AA, C, D, or Lithium-Ion/Lithium-Polymer batteries, wired in series to produce the desired voltage.</p>
