Battery charging

Discussion in 'General Electronics Chat' started by bogdanul2003, Apr 3, 2012.

  1. bogdanul2003

    Thread Starter New Member

    Sep 20, 2011
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    Hello,

    I made a ciclo-computer that measures the speed and distance you travel by bicycle (attiny microcontroller and 7 segments LED display). Currently it is running on one 9V battery which lasts for about 8 hours.

    My plan is to use a dynamo to charge the battery. To do this I have to cut off the power to the pic while the battery is charging ? If yes I would like to use 2 batteries and switch between them while one is charging. How could I switch between batteries and not make the microcontroller to reset? Do I use a capacitor?

    Thanks,
    Bogdan
     
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,754
    760
    How about use the battery as backup.

    What is ur dynamo power rating ?
     
  3. Audioguru

    New Member

    Dec 20, 2007
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    896
    Are your 9V batteries the rechargeable kind?
    Are they Ni-Cad or Ni-MH?
    Are they actually 7.2V or 8.4V?
    Do you have a charger circuit?
     
  4. bogdanul2003

    Thread Starter New Member

    Sep 20, 2011
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    The dynamo is a 12v 6W. My batteries are NIMH rechargeable 8.4 volts.
    The charging circuit is not the hard part ... I don't know if I can charge a battery and power my circuit in the same time. If this is not possible then how do you switch between the batteries without power interruption.
     
  5. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    with 6W you can charge and power a typical circuit like urs.
    But need to see ur circuit to say anything abt it's power drain.
     
  6. bogdanul2003

    Thread Starter New Member

    Sep 20, 2011
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    0
    I think that the dynamo will deliver 6W only at high speeds. During the time I stop at a semaphore or go slow I need to power my circuit with a battery.
    So I need to solve the problems from my first post.
     
  7. MrChips

    Moderator

    Oct 2, 2009
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    Can you switch from LED to LCD display?
    Your battery will last a lot longer.
     
  8. bogdanul2003

    Thread Starter New Member

    Sep 20, 2011
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    I thought about using a LCD but I want to do this battery recharging stuff to learn something about battery management.
    How dose a mobile phone keep functioning while it is charged?
     
  9. chrisw1990

    Active Member

    Oct 22, 2011
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    why not try and reduce the power usage of the current system e.g.: turning things off when not needed even for a couple of mS? then implement a charging circuit?
     
  10. bogdanul2003

    Thread Starter New Member

    Sep 20, 2011
    7
    0
    I want to build the charging circuit anyway regardless of how much power my system needs. I would like to use a battery and when I have the right speed to produce enough energy from the dynamo to power the circuit and charge the battery I would like to cut off the power from the battery and power my circuit from the dynamo.

    How do I make this switch between the battery and the dynamo without interrupting the power to the microcontroller?
     
  11. MrChips

    Moderator

    Oct 2, 2009
    12,440
    3,361
    Use a diode.
     
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