General question for charging a LI-PO and using it to power another circuit

Discussion in 'The Projects Forum' started by chimera, Jun 4, 2011.

  1. chimera

    Thread Starter Member

    Oct 21, 2010
    122
    2
    hello!

    I am trying to develop the a charger for li-poly battary using MCP73833 by Microchip. The typical application is what im after. Now I have two general questions and its assumed that the battery will never leave the project case to be charged seperately:

    1- How can a circuit be powered by a battery that is simultaneously being charged? As in charging the battery and using the battery at the same time.

    2- How can that be achieved? For instance, employ a switch that allows the juice from battery to flow into another circuit?

    PLEASE SEE THE ATTACHED FILE FOR A BLOCK DIAGRAM IDEA. ITS A VERY SIMPLE DIAGRAM.

    Thanks for viewing
     
  2. #12

    Expert

    Nov 30, 2010
    16,343
    6,828
    Are you afraid the external load will be hurt by the charging voltage?
     
  3. chimera

    Thread Starter Member

    Oct 21, 2010
    122
    2
    No not really. But I am actually curious of the actual physical connections that I would make to achieve the desired effect. I'll explain. The output of the charging circuit is going into the li-po battery to charge. Now, how will i connect another seperate circuit to the output of the battery to power it up since the input terminals of the battery will be already be in use due to the charging circuit.
     
  4. #12

    Expert

    Nov 30, 2010
    16,343
    6,828
    solder another connector on?
    use a "Y" connector?
     
  5. Adjuster

    Well-Known Member

    Dec 26, 2010
    2,147
    300
    Your charging circuit would need to be able to detect how much current was flowing into or out of the battery, so the connection of the load would have to allow for this. There could be a compromise between getting a good low-impedance connection between the battery and the load and the conditions for accurate current monitoring.
     
  6. chimera

    Thread Starter Member

    Oct 21, 2010
    122
    2
    Firstly thanks for the replies everyone!!

    Secondly, the idea for the Y connectors is okay. But how will force current from the charger to the battery through one end of the connector and use the other end to flow the current out from the battery to the external circuit. I ask this because the battery only has two terminals (Positive and ground (Red and black)). Please view the attached block diagram if its not too much trouble.

    Also I dont know how to modify the charging circuit to keep track of how much current is being consumed by the external circuit from the battery. If you click on this link:

    http://ww1.microchip.com/downloads/en/DeviceDoc/22005b.pdf

    it will take u to the data sheet and it can give u better idea of its capabilities. I dont think i can configure a feedback loop back to the charging circuit. The above link is very useful for anyone who wants to develop a charger for a Li-Po battery based on a very small IC.
     
    Last edited: Jun 4, 2011
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