I wanted to make Ipod charger.

Discussion in 'General Electronics Chat' started by Sonoma_Dog, Oct 20, 2008.

  1. Sonoma_Dog

    Thread Starter Active Member

    Jul 24, 2008
    99
    0
    I wanted to make a Ipod charger using a 2 AA rechargeable battery. Will this be possible? I wanted the device charge up both the Ipod and the AA battery when it is plugged in the the wall. Otherwise the 2 AA battery will charge up the ipod.

    should i supply 5 volt to the USB possitive terminal? and how to make a 5 volt out of only 2 AA battery.

    I have the sechmatic in my mind right now. but wanted to make sure it is doable before i take any further action.

    Thanks!
     
  2. tmd_63

    Member

    Oct 20, 2008
    13
    0
    What you are going to need is a boost converter to take your battery voltage of around 2.4V and boost it to 5V.

    If you do not require a lot of current or a stable supply then you could try a voltage doubler. A simple circuit using a CMOS NE555 and some caps and diodes should do the trick.
     
  3. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
    1
    Typical ipod battery is 550mAh @ 3.6V, therefore ~2W/h of energy. Using a NiMH or NiCad battery (you'd be environmentally irresponsible to use a non-rechargeable battery for this, they're a horrible waste), you can easily find 2200mAh 1.2V batteries. These will give ~2.6W/h. Assuming about 80% efficient for the boost converter, you can transfer about 2.1W/h, so it is feasible.

    I don't have a clue what your capabilities are when it comes to actually making something, so I don't know if it is doable. You can find very low voltage input boost regulators/

    Steve
     
    Last edited: Oct 20, 2008
  4. Sonoma_Dog

    Thread Starter Active Member

    Jul 24, 2008
    99
    0
    All right. Well, to reduces the complexity, I am going to 4 AAA rechargeable battery. That will give me roughly 5-6 volt, and it will be going through a 5 volt regulator.

    when you are saying "Typical ipod battery is 550mA @ 3.6V"

    is that mean i only need to supply 3.6v to the Vdd of USB?

    one more question. Let say if i wanted to recharge 4 AAA battery, do i just apply voltage across them? do i need to use any resistor or is the internal resistance of the battery will take care of it?


    Thanks
     
  5. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Four AAA rechargeable cells make only 4.8V. Most 5V regulators have a minimum input of 7V but low-dropout ones need only 5.5V.
    The four AAA cells need more than 6V to charge them through a battery charger IC.
     
  6. Sonoma_Dog

    Thread Starter Active Member

    Jul 24, 2008
    99
    0
    I thought the rechargeable batteries are 1.5 volt each. the non rechargeable ones are 1.2.
    What is a battery charger IC?
     
  7. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    No.
    A Ni-Cad or Ni-MH battery is 1.2V per cell. It is 1.25V per cell when the output current is very low.
    They are almost 1.5V when almost fully charged and are still charging.
    A lithium battery cell is 3.6V to 3.7V and is 4.2V when almost fully charged and are still charging.

    No.
    Old carbon-zinc and newer alkaline cells are 1.5V to 1.6V per cell when brand new and with a very low current.

    All semiconductor manufactures make battery charger ICs. They detect that a battery is already charged and do not begin an overcharge. They detect when the battery is fully charged then shut off.
     
  8. Sonoma_Dog

    Thread Starter Active Member

    Jul 24, 2008
    99
    0
    Great! looks like that is something i would consider! I will do some research on it later tonight, do you have the part number for that IC? it may save me a lot of time if you have a part number in mind :)

    Thanks!
     
  9. HarveyH42

    Active Member

    Jul 22, 2007
    425
    5
    The Ipod likely already has the charge controller built into it, to protect the battery+Ipod. For the money they charge, it would be disappointing to find out it doesn't. Remember seeing a kit some place online for what you are doing. Will take a look later and post a link.

    http://www.ladyada.net/make/mintyboost/index.html
     
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