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Circuit not charging when the battery is below a certain voltage

Discussion in 'Power Electronics' started by Mywk, Sep 25, 2018.

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  1. Mywk


    Mar 13, 2012
    Hello everyone,

    I have a simple battery charging circuit that seemed to be working perfectly, that is, until the battery was completely discharged, afterwards I'm unable to re-charge the battery.

    Charging controller is a MCP73831/2

    The battery is a tiny cheap 55mAh 3.7 V battery and the circuit is as follows:

    I set everything according to the datasheet, being the 20k resistor on R3 for a 50mAh battery.

    When the battery is fully charged it outputs 4.1V, when discharging it stays at 1.950V

    Here's the deal, if I take out the battery and charge it somewhere else (let's say up to 3V) then put it back in my circuit, it keeps charging, but not on the circuit.

    I'm not the most experienced in electronics and I'm out of ideas so I'm asking here: What could the problem be?

    Note: I think the problem may be related to the Undervoltage Lockout (UVLO), page 13 of the controller pdf.

    Thanks in advance!!
    Last edited: Sep 25, 2018
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Lithium cells can be damaged if you discharge then too far. Too far is something less than 2.8 to 3.0 volts. Chargers frequently refuse to charge over-discharged cells

    See my thread "playing with fire" for my own recent experience.
  3. Mywk


    Mar 13, 2012
    It seems that the controller is acting as it should, since the battery is way below what it should be it simply doesn't charge it.. And, unlike the battery specs say so, it does NOT have over-discharging protection, so the microcontroller will just keep trying to suck the battery dry.

    Could anyone suggest a good controller that offers over-discharge and over-charge protection?

    Thanks once again!
    Last edited: Sep 25, 2018
  4. Bluejets


    Oct 5, 2014
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