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Trickle charge mobile phone?

Discussion in 'Misc Electronics' started by IV, Sep 11, 2003.

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  1. IV

    IV Guest

    Hi all; I have a mobile phone but I am near my computer most of the time.
    According to the manufacturer you should not keep the charger plugged in
    continuously, so what I do is to charge the battery and let it drain until
    empty, then recharge again. The batteries are NiMH.
    The problem, of course, is that when I do need to leave the batteries will
    most likely not be full and may actually be close to empty. I'd like to
    keep the batteries fully charged.
    Now - I have one computer controlled power outlet that I can program to
    regularly switch on and off as often as I want. Does anybody know how long
    and at what duty cycle I need to charge these NiMH batteries to keep them
    fully charged and avoid overcharging/memory effect?

    Thanks in advance!
  2. Ian Stirling

    Ian Stirling Guest

    NiMH cells do not suffer from the memory effect.
    Most phones will terminate the charge when the battery gets full.
    The "don't leave charger plugged in" may simply be to reduce their liability
    in case of fire.
    Does it say why not?
    Does the phone get hot after extended charging?
    If not, then I'd just ignore the manufacturer.
  3. IV

    IV Guest

    Thanks Ian - the phone does not get excessively hot while charging but I
    never left it plugged in for a day or more and so I don't know how that
    would influence things. The manual says not to keep it plugged in 'to
    prevent damage to the battery'. No mention about fires :)
    Actually my shaver (also NiMH) has the same mention.

    Are you sure about the lack of memory effect with NiMH? I'm reading some
    conflicting things. On top of that my phone has a menu item to completely
    discharge the cells - I guess you wouldn't need that if there weren't any
    memory effects?
  4. Ian Stirling

    Ian Stirling Guest

    With dumb chargers, like you find in some cheapest powertools or shavers,
    then you do have to disconnect them pretty much after they are charged.
    All phones I've ever seen that can charge in under a couple of hours
    have them.

    If it was me, I'd insert an ammeter in the battery lead and see what happens.
    If it terminates charge properly, then don't worry about it.

    Manuals are not always written by people who know the product.
    They can often carry over cautions from some other manual they are cribbing
    from without really understanding them.
    There are reasons to discarge other than memory effect. For example
    overcharging can reduce the capacity of the cells (until a couple of
    discharge/charge cycles have been done).
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