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charging one battery from another (using a charge controller, natch)

Discussion in 'Electronic Design' started by [email protected], Mar 28, 2007.

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  1. Guest

    I'm thinking about the simple scheme of charging a portable device's
    rechargeable internal battery from an external battery (which should
    a little higher voltage, obviously). The portable device should have
    internal charge controller to protect its battery and manage the

    Find a suitable battery or stack of cells, and plug it in. Simple.

    Using AA cells in an product like Belkin's iPod charger is an
    Recharging your cell phone from your car's 12V battery could be an
    example. Emergency power for a cell phone would be an example.
    Instances of externally powering the dead device, without
    charging its battery, would be interesting as well.

    I'm looking for specific instances of products, or of people doing
    themselves and making the suggestion to others. One caveat, these
    instances have to be during the 1990s or before. Sorry! :) That
    out Belkin and their AA-cell holder, since Apple introduced the iPod
    2002 and they brought out their product sometime later.
  2. Joerg

    Joerg Guest

    Prior art search for a patent tussle?

    I remember a guy in Germany who had this setup around 1987/88: Mobile
    phone in his car. Back then mobile phones were "mobile" but not really
    portable unless you were a weight lifter. So, since he had to inspect
    construction on high rises he had another phone in his car. That one was
    a wireless phone just like most of us have at home. Only talks to its
    base. This base in turn was linked to his mobile phone in the car.

    The handset came with a cradle that had a 12V cigarette lighter plug and
    it was definitely some NiCd current limit scheme. Else the handset would
    have exploded I guess. The cradle was meant to be bolted to the dash and
    the phone clicked into it so it wouldn't fly about after hitting a
    pothole. Supposedly you could leave it on the charger indefinitely. Of
    course this guy didn't since he wanted his car to start after a few days
    of parking. Also, he was a smoker and needed that cigarette lighter once
    in a while ;-)

    I just don't remember who made this stuff. He had it installed at some
    pro-shop and it was a major European mobile phone brand.
  3. Joerg

    Joerg Guest

    Another idea: I have also seen radios in charger cradles which were
    mounted on fire trucks. Probably 24V and IIRC the brand was Hagenuk
    (Europe). Early 80's.
  4. john jardine

    john jardine Guest

    Yes. We had a Motorola 4800x in about '86. Battery powered luggable phone
    but with a 12V cigar lighter adapter for car charging. Vague memories of the
    battery pack being NiCad.
  5. Do you know if the charging-control circuitry was in the lighter
    adapter or in the phone itself?

    These days in a way it's in both, thatis the car adapter regulates
    the voltage down to about 6 volts and the phone controls charging
    to its battery from the 6-volt power from the adapter. A Belkin
    adapter I looked at current limits at 125mA, but others go all the
    way to 600mA, etc., providing high currents like the phone's
    regular ac-line charger / power adapter.
  6. Joerg

    Joerg Guest

    There definitely were simpler devices with the limiting circuitry in the
    device itself. I had one as a kid, a rechargeable flashlight. It could
    be plugged into the cigarette lighter of a car which has no limit other
    than its fuse. This was at least 30 years ago which unfortunately also
    means that I don't have it anymore. But of course I opened it back then.
    There was one resistor and a tiny bridge rectifier which explained why
    the packing slip said it could also be used on cars with plus on the
    chassis (they existed back then). Also, both 6V and 12V was allowed.
    Very handy around the campground.
  7. john jardine

    john jardine Guest

    If anywhere then in the 'phone
    The plug looked a standard black plastic, plug-in adapter on a curly lead.
    S'pose there could have been a resistor in there but with the shoebox size
    of those batteries, it would seem illogical and unsafe without assistance
    from some kind of external heatsink.
    Pity, nearly bought a 4800x off Ebay the other month, could have confirmed
    the charging and whether Nicad or not.
  8. DaveC

    DaveC Guest

    Hey, Win! Remember: cross-post, don't multiple-post!

    My Braun 5414 shaver runs from both 115vac and 12vdc using the same cord. The
    battery will charge on either voltage. Battery is NiCd AA "non-replaceable"
    (which I've replaced once already).

    It's pushing it (my memory) but it's about 10 years old, give or take a few.
  9. Joerg

    Joerg Guest

    Yep, got one of those as well. But it doesn't work as well as the old
    non-rechargeables :-(
  10. Guest

    I didn't. I canceled my first post within seconds of
    placing it, for further editing. Did you see two posts?
    Dave and Joerg, can you verify that the charging controller
    isn't in the 12V "adapter" plug? With an ohmmeter test?
  11. Joerg

    Joerg Guest

    Mine just came with the 120V cord, the 12V cord would be a paid
    accessory which I didn't need (and Long's didn't have it anyhow). Just
    measured the 120V cord. 0.6ohms each line, meaning it's the usual
    stranded wires, no built-in extra resistance. I bought this Braun razor
    last year but they've been around for many years.

    The old flashlight I had as a kid definitely did not use an adapter
    either because you could take off a protective plastic cap and then plug
    the flashlight body right into the cigarette lighter outlet of a car.
  12. Guest

    You can get one now on eBay for $3. :)
    Do you remember the brand?
  13. Joerg

    Joerg Guest

    Yeah, but I don't like to shave in the car. It drives me crazy when I
    see others do that while cradling a cell phone between shoulder and ear.
    Sorry, I don't. All I remember is that I bought it in Germany. It had a
    red body and a white cap for the plug. This flashlight was square, not
    round. That was unusual since most other flashlights were round in the
    70's, at least in Germany. It cost just a few Deutschmarks back then and
    it would light for about 30 mins on one charge when new.
  14. DaveC

    DaveC Guest

    I didn't. I canceled my first post within seconds of
    Yes, I did.

    Canceling doesn't work with most servers. Neither does Supersede. To my
    knowledge these haven't been supported by most servers for a very long time.
    No, I can't (c:

    But the shaver itself says:
    "12-240 V ac/dc 50-60Hz / 5w"

    Lost the 12 plug.
  15. DaveC

    DaveC Guest

    Dave and Joerg, can you verify that the charging controller
    My presumption -- and I think it's sound -- is that when run on mains voltage
    the charg is controlled internally, and when run on 12 DC the same is
  16. Bob

    Bob Guest

    I have a motorola bag phone in deep storage somewhere,
    despite the analog cellular networks here being switched
    off years ago.
    Havn't got it out for a while but I just found a picture
    of a 4800x with google and it looks like the one I have.
    I disposed of the battery because it was totally dead
    but I'm fairly certain it was lead acid.
  17. I had a tiny FM radio with an internal rechargeable battery. It was
    recharged from a battery pack containing 4 AA cells. I can't recall
    exactly when I bought it, but I'm sure it was at least 10 years ago.
    More like 20 years ago. It quit working a few years back and I'm not
    sure if its in my busted junk pile or long since thrown out
  18. jasen

    jasen Guest

    Does an automobile count as a portable device? I recall mention of a
    drycell pack that could be applied to recharge the car battery it it was
    accidentally depleted.

    another thing worth considering is the origin of the term "secondary cell"

  19. Joerg

    Joerg Guest

    Probably only this one does:

    Some kids hand-carried one into the lobby of our high school as a prank.
    Just lifted it off the ground and walked with it.
  20. joseph2k

    joseph2k Guest

    The oldest bag phones i remember had a fuse in the lighter plug, circia
    1993, all other electronics was in the "bag". The first cell phones that i
    remember having anything electronic beyond a fuse / resistor / some diodes
    was about 1998 Motorola / Nextel car adapters with some widget in the
    lighter plug.
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