Hello,

    maybe this is more [EE] related than [PIC] but...


    I'm doing a battery (9V) powered application that uses an swithing
regulator (that LT1173) to convert 9V to 5V. Also, the user have the option
to use an external 9V power suply, as it consume about 100mA/500mW.

    Now I would like to give the user the possibility to use NiMH
rechargables and use the 9V power suply to charge the batteries. How could I
do that? NiMH is recharged with a constant current? How can I don't
overcharge it? I understand that (like cell phones), the circuit have to
smartly:

        1) use the battery power when not using an external power suply.
        2) charge the battery when an external power suply is available and
power is off.
        3) charge the battery even when power is on.
        4) if the battery is at full charge, stop sending charging current
to it.

    Can someone please help me? Tell what I need to read? Where the
information is available? Other kind of batteries would be better than NiMH?

    Thank you,

    Brusque

-----------------------------------
Edson Brusque
Research and Development
C.I.Tronics Lighting Designers Ltda
Blumenau  -  SC  -  Brazil
www.citronics.com.br
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