Battery Charger

Discussion in 'General Electronics Chat' started by vindicate, Jun 30, 2010.

  1. vindicate

    Thread Starter Active Member

    Jul 9, 2009
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    I saw this:

    <snip>

    My question is why use a transistor at all? Why not just use resistors to lower the current to the 63mA or w/e?
     
    Last edited by a moderator: Jun 30, 2010
  2. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
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    because. duh...

    Actually I dont see anything... ;)
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    The link in the original post has been removed. The projects were not valid, nor was the site one we would care to have members exposed to just because of the language.

    The Op is going to get more useful information from the link - http://www.batteryuniversity.com/

    Notice that alkaline batteries are not in the list of rechargeable batteries. http://en.wikipedia.org/wiki/Alkaline_battery

    There are some alkalines that are rechargeable, though - http://en.wikipedia.org/wiki/Recharg...kaline_battery
    __________________
     
  4. vindicate

    Thread Starter Active Member

    Jul 9, 2009
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  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    You must not attempt to recharge primary batteries like alkaline, carbon zinc, etc. You will receive poor performance, and there is a risk of fire/explosion, or the battery case otherwise rupturing and ruining the device it's used in.

    A constant-current charger is just too simple for rechargeable battery charging. The charger should change modes from current-limiting to voltage regulated when the battery approaches fully charged. Failing to do so will result in overcharging and short battery service life.
     
  6. vindicate

    Thread Starter Active Member

    Jul 9, 2009
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    Well it wasn't so much that I wanted to build that circuit as much as I was curious as to why it was built the way it was. If anyone knows the original circuit and wants to explain I would appreciate it.
     
  7. Dx3

    Member

    Jun 19, 2010
    87
    7
    Using a constant current supply makes the charging rate steady, as in, same amps, all the time. Using a resistor would make the charging current decrease as the battery gets filled up. That might be a good thing when trying to charge a battery that isn't meant to be charged!
     
  8. vindicate

    Thread Starter Active Member

    Jul 9, 2009
    158
    0
    Why does the current get less with a resistor setup? As the battery fills, does the battery itself have more resistance?
     
  9. retched

    AAC Fanatic!

    Dec 5, 2009
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    Yes. The internal resistance changes as the battery charges and ages.
     
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