Answers.Body: <p>As others have said, it's difficult know what is going without seeing your design. I would expect what you have described to work, but it is possible that your design is overloading the over current protection in the battery box.</p>
  
  <p>PF battery boxes are designed to provide 800mA. Any more than this, and they have protection built in to cut power and prevent damage.</p>
  
  <p>LEGO indicated that the XL motors draw 300mA under normal conditions, and <a href="http://www.philohome.com/motors/motorcomp.htm" rel="nofollow noreferrer">Philo</a> has the stalled current listed at 1800mA. A single stalled XL motor can overload the battery box, and two of them working hard can easily as well. See <a href="https://bricks.stackexchange.com/a/2127/708">this answer</a> for more information.</p>
  
  <p>As a quick check, if you disconnect the motors from your car so that they can just run free, are they able to both run as expected? This should work fine and draw only 160mA if everything is connected and working properly. If not, one of your components must be performing abnormally or not be connected properly. As others have said, a photo would help us diagnose connection or build issues.</p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2017-04-05T16:14:28.797Z
Answers.LastActivityDate: 2017-04-05T16:14:28.797Z
Answers.LastEditDate: 2017-04-13T12:47:56.390Z
Answers.UserDisplayName: jncraton
Body: <p>We are trying to run our Grand Prix racing car on the IR remote control and would like to use two PF XL motors for the drive. One motor works fine on its own, but when both are connected, they stop running. Could it be that the battery pack power isn't strong enough for two motors?</p>
  
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-04-05T11:44:00.193Z
Comments.Text: Welcome to LEGO Answers.  Can you show us a picture of how you have this wired up?
Comments.UserDisplayName: chicks
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-04-05T15:23:42.667Z
Comments.Text: You need to explain the circuit you have created or provide a picture of it so we can help you.
Comments.UserDisplayName: Timtech
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-04-05T20:01:49.953Z
Comments.Text: Thanks for your answers. I'll try to upload a picture tomorrow. We tried to let the motors run free without being built in and it's the same problem.
Comments.UserDisplayName: user8557
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-04-06T09:57:40.713Z
Comments.Text: We tested the motors directly on the battery box and the motors are running fine for 1or 2 sec and then they stop. one motor at a time is fine.
Comments.UserDisplayName: LegoFan
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-04-06T09:58:02.590Z
Comments.Text: after a few more tests..... it's the battery box. We tested the motors on another box and everything is running as it should.
Comments.UserDisplayName: LegoFan
Tags: <motor><power-functions><remote-control>
Title: Problem with running two XL motors
UserDisplayName: LegoFan
ThreadText: # Problem with running two XL motors
  
  (Asked by: username_0 on 2017-04-05)
  
  We are trying to run our Grand Prix racing car on the IR remote control and would like to use two PF XL motors for the drive. One motor works fine on its own, but when both are connected, they stop running. Could it be that the battery pack power isn't strong enough for two motors?
  
  **Tags:** motor, power-functions, remote-control
  > **Comments:**
  > **username_1**: Welcome to LEGO Answers.  Can you show us a picture of how you have this wired up?  
  > **username_2**: You need to explain the circuit you have created or provide a picture of it so we can help you.  
  > **username_3**: Thanks for your answers. I'll try to upload a picture tomorrow. We tried to let the motors run free without being built in and it's the same problem.  
  > **username_0**: We tested the motors directly on the battery box and the motors are running fine for 1or 2 sec and then they stop. one motor at a time is fine.  
  > **username_0**: after a few more tests..... it's the battery box. We tested the motors on another box and everything is running as it should.  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_4 on 2017-04-05. Score: 2
  
  As others have said, it's difficult know what is going without seeing your design. I would expect what you have described to work, but it is possible that your design is overloading the over current protection in the battery box.
  
  PF battery boxes are designed to provide 800mA. Any more than this, and they have protection built in to cut power and prevent damage.
  
  LEGO indicated that the XL motors draw 300mA under normal conditions, and [Philo](http://www.philohome.com/motors/motorcomp.htm) has the stalled current listed at 1800mA. A single stalled XL motor can overload the battery box, and two of them working hard can easily as well. See [this answer](https://bricks.stackexchange.com/a/2127/708) for more information.
  
  As a quick check, if you disconnect the motors from your car so that they can just run free, are they able to both run as expected? This should work fine and draw only 160mA if everything is connected and working properly. If not, one of your components must be performing abnormally or not be connected properly. As others have said, a photo would help us diagnose connection or build issues.
  
  
  ---
  
  