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Can you measure voltage of AA batteries while they operate?

  1. Feb 24, 2016 #1
    I'm wanting to know if I can and if so how to measure the voltage of two AA batteries whilst they are in a device with the device turned on. This device is a vibrating toothbrush so if anyone could help with an answer, it would help teremendously with my science project as I am testing the effects of temperature on batteries.
     
  2. jcsd
  3. Feb 24, 2016 #2

    berkeman

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    Welcome to the PF.

    Yes, you can certainly monitor the voltage while the device is operating. The challenge is how to connect physically to the ends of the 2-battery stack.

    Can you post some pictures? Are you okay with drilling some holes in the toothbrush, or do you want to try to do it non-invasively? Do you have access to copper tape? :smile:
     
  4. Feb 24, 2016 #3
    Will do tomorrow, and I wouldn't be against it as long as it doesn't change the functioning capacity of it, I'd just like to do what works? What can copper tape be used for?
     
  5. Feb 24, 2016 #4

    berkeman

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    You can use copper tape to make very thin strips that you can put at the two ends of the battery stack and solder wires to in order to route the wires out of the end of the toothbrush.
     
  6. Feb 25, 2016 #5
    image.jpeg
     
  7. Feb 25, 2016 #6
    What kind of voltmeter do I need to use? That is if there is a specific type, preferably at a lower price.
     

    Attached Files:

  8. Feb 25, 2016 #7
    So as you can see the battery can be held in without the cap due to the design and can also operate without the cap screwed in place and yes I would like to do it non-invasively or rather without drilling holes in it haha. But I would like to know what you think would work as far as testing the voltage while it runs and what to test the voltage with?
     
  9. Feb 25, 2016 #8
    Also now the question arises? How might I measure the amps being put out?
     
  10. Feb 25, 2016 #9

    berkeman

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    Well, you can go from just measuring the average DC voltage of the batteries during operation, all the way to using an oscilloscope and clamp-on Hall-effect current probe to get a more accurate picture of what is going on with the batteries.

    What grade level is this project for? What electronics test equipment do you have access to? You mentioned making these measurements over temperature for your project -- how are you planning on setting and measuring the temperature of the batteries?

    I would use an external 2xAA battery holder and rig up some expanding stick-type thing to make contact with the two battery terminals in the toothbrush. That will be easier, and more flexible than trying to rig up test pads inside the toothbrush. Something like this:

    http://www.seeedstudio.com/depot/images/product/P3192320.jpg [Broken]
    http://www.seeedstudio.com/depot/images/product/P3192320.jpg [Broken]
     
    Last edited by a moderator: May 7, 2017
  11. Feb 25, 2016 #10
    I'm finishing my 12th grade year and I'm very passionate about my project, just a bit clueless when it comes to some things. So I have a multimeter and my toothbrush but I don't know how I'll be able to touch the red (positive) chord to the positive end of the battery while it is inside the toothbrush or if that's what I'm even supposed to do?
     
  12. Feb 25, 2016 #11
    I again want to thank you very much for the help, I'm a bit lost but I love learning this stuff. And I'm about to upload a picture of the multimeter I have so you might better understand the situation.
     
  13. Feb 25, 2016 #12
  14. Feb 25, 2016 #13

    davenn

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    good :)

    that's what the copper strip is for that berkeman was talking about

    set it up like this have drawn a nice pic for you :smile:

    batteries and tape.JPG



    cheers
    Dave
     
  15. Feb 25, 2016 #14
    Alright so where does the other end of tape lead to? And it's actually just 1 battery thankfully so less waste.
     
  16. Feb 25, 2016 #15

    davenn

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    The left end, the one bent up is where you touch the positive lead probe tip of your multimeter to
    the negative lead probe tip of the meter you can place against the negative end of the battery(ies) there will be a coil spring there just like in that battery holder berkeman had shown you

    I had shown 2 batteries as that's what you said in your opening post :wink:


    Dave
     
  17. Feb 25, 2016 #16
    True haha that was my bad guess, but much thanks, I'll be testing and I'll probably let you guys know how it goes, thanks again guys!
     
  18. Feb 25, 2016 #17

    dlgoff

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    image-jpeg.96436.jpg
    Doesn't this tooth brush only have one AA battery? I recently took apart one like this to get the motor and it only had one battery.
    toothmotor.jpg
    edit: oops. davenn beat me to the 2 battery thing.
     
  19. Feb 25, 2016 #18

    berkeman

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    Nice DMM! What model is it? It looks like it has an AC current sensing loop, but the toothbrush current will be mostly DC.

    You can make measurements of the DC and AC voltages once you get the probe points on your battery figured out. Keep in mind that as a battery discharges, its characteristics change a bit. You should look around at the Duracell website to find a datasheet for the AA batteries you will be using in your project. :smile:
     
  20. Feb 25, 2016 #19
    Here's another question since you guys are so good at answering them lol, where can I buy some copper tape? And what exactly does it look like?
     
  21. Feb 25, 2016 #20

    berkeman

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    In Silicon Valley, you can get it at Halted or Anchor Electronics... :smile:

    It's pretty expensive to buy a roll of copper tape, so we may need to figure out an alternative for your project. You need something wide enough to be a good contact, and made of copper so you can solder a wire to it. Do you have a soldering iron?
     
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