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Battery Recharge In An AC Circuit

  1. May 14, 2007 #1
    Hello everyone. This should be a fairly simple question to answer because I should really already know. Anyway, I was just wondering how exactly a battery is recharged in an AC circuit. In particular, I was looking at an electric car's rechargable battery. I know when you plug the car in the alternating current in the first coil causes magnetic flux thus causing an induced current in the other coil. However, isn't this second current also alternating? And if so, how is an alternating current used to charge a battery. Thank you for your time.
  2. jcsd
  3. May 14, 2007 #2


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    Battery chargers use diodes to convert the AC to DC.
  4. May 14, 2007 #3
    The induced current in the other coil would also be AC, and you can't charge batteries with AC as it would look like a short. So we follow the AC with a diode rectifier that removes from AC the negative alternating component, then it is filtered with capacitors to give you a pure DC.
    Last edited: May 14, 2007
  5. May 14, 2007 #4


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    Just a little nit-picking: electric cars do not use simple diodes for rectification. Instead, they use switched-inductor boost/buck converters to store energy in or release energy from the battery pack, which is DC. Same concept as a diode rectifier, but much more efficient and much easier to build.

    - Warren
  6. May 14, 2007 #5
    Thank you much. I had actually suspected a diode, but I wasn't completely sure. And it turns out I was wrong, when it comes to electric cars at least. Again, thank you for the information.
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