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Mouse and two 1.5V batteries.

Discussion in 'Power Electronics' started by eptheta, Mar 20, 2011.

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  1. eptheta


    Dec 20, 2009
    My mouse runs on two 1.5V batteries and it dies out pretty fast. The rechargeable batteries that I get here are pretty useless and stop working after maybe 5 charges.
    This is what immediately came to mind:
    If I can acquire a spare mobile phone that no one uses and take its Li-ion battery, could I fit it into the mouse and use it ?
    When it needs charging, I can put it back into the mobile and let it handle the complex charging mechanism I've heard so much about.

    Most of the mobile batteries are 3.7V so can I just use a voltage regulator (LM317 say) to bring it down ?
    I really don't know how much current the mouse circuitry will draw, but since normal USB devices work with its 500mA supply and the LM317 can give up to a 1.5A max current, that shouldn't be a problem.

    I just wanted to be sure that I'm not thinking stupid because I have no desire to blow up my mouse.

    Thank you.
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    The problem with Lithium cells in this type of application is over-discharge. I would certainly be wanting to incorporate something to prevent that. And you need to be very careful as power is always applied, so you need a very low power (at least low quiescent power) solution.

    The problem with an LM317 is that it requires approx 2V higher input than the regulated output, AND it has a rather high quiescent current requirement. Add to this the range of resistances allowed in the voltage divider, and it adds up to way too much current.

    You would be far better off looking for an ultra low power, low dropout, 3.3V (or even lower) regulator.

    Another option would be to get some better quality batteries.

    Have you considered the option that it may be your charger that is killing the batteries and not poor batteries?
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