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  1. #1
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    Li-ion Charging indicator

    I ordered MCP73831/2 charging IC for my design and I would like to put charging indicator to android/ ios app. On the circuit, there are two LEDs to indicate the charging status( orange and green lights). MCP738312.pdf
    As you can see the attached file, there are few stages for charging battery: pre-conditioning, Constant-Current and then Constant-voltage. Constant-voltage is for topping up the battery when it is almost completely full. The battery will be fully charged when the current is dropped to 5% of Ireg(current regulation). When if is fully charged, green LED turns on.

    Charging Termination
    The charge cycle is terminated when, during Constant-Voltage mode, the average charge current diminishes below a percentage of the programmed charge current (established with the value of the resistor connected to the PROG pin). A 1 ms filter time on the termination comparator ensures that transient load conditions do not result in premature charge cycle termination. The percentage or ratio of the current is factory set. Refer to Section 1.0 “Electrical Characteristics” for charge termination current options and the ”Product Identification System” for standard options.
    The charge current is latched off and the MCP73831/2 enter a Charge Complete mode.

    My plan is to use ADC to indicate the charging status on my app(3.2 V to 4.2V). My app says 100% charged but orange led is still on. After 40mins, the led turn to green.
    Even if battery is charged to 4.2V, it does not mean "it is fully charged." Ireg must be decreased to 5% for fully charging condition.
    How could I indicate this to the app? I have no idea how to match the circuit LED indicator and app(mcu),

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  2. #2
    Super Moderator
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    Apr 2014
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    Re: Li-ion Charging indicator


    You already have recognized one important thing:
    The voltage across the battery does not tell much about charging status.

    Thus there are dedicated charging status ICs, they mainly are charge counters (integrating current over time).
    Do an internet search to find part numbers, then read through their datasheets and application notes.

    Please don´t contact me via PM, because there is no time to respond to them. No friend requests. Thank you.

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