🚀 go-pugleaf

>In article <1992Oct12.031200.15821@cube.handheld.com> jmd@cube.handheld.com (Jim De Arras) writes:
>>In article <dillon.0p24@overload.Berkeley.CA.US> dillon@overload.Berkeley.CA.US

>>     current == no heat.  For example, diodes are often used in battery
>>     charging circuits like this:
>>
>>	+12V from supply ----*DIODE*----x----> system power
>>					|
>>	+!2V from battery --------------/
>>
>>     When AC is available it charges the battery.  When AC is not available
>>..

>Where did you get this dangerous mis-information!!  Do not EVER, repeat, EVER
>attempt to charge a standard lithium cell.  You are looking at a nasty mess at
>BEST, if the seals blow, and a VERY REAL, blow a hole in the board and you,
>explosion if the seals fail to blow.  Lithium cells do not take a joke!

    Silly person, you didn't read the article very closely.  The above was
    an EXAMPLE of what is one of the most common charging configurations
    for batteries... a regulator and a diode.  It has nothing to do with
    lithium cells (the above circuit is actually used to charge lead-acid
    gel cells).  To charge a lithium cell, and you *can* do it, you have to
    be much more careful.

    The above example was simply illustrative of one of many uses DIODES
    are put to, in response to an earlier comment by someone who was
    worried that reverse biasing a diode would destroy it eventually, which
    is nonsense.

>>     I presume that NeXT is using a similar circuit to power the real time
>>     clock and prevent the battery from trying to power the system +5.
>>
>Let's hope not!

    Believe it or not people use trickle charge circuits all the time to
    extend the life of lithium batteries in backup situations.	This is
    usually necessary only when the battery would discharge due to current
    requirements long before it's normal shelf life expires.  With a proper
    charging circuit you can extend the lithium batteries backup
    capabilities all the way to its shelf life limit (5yr or 10yr usu).  In
    applications where the shelf life would expire before the nominal mAH
    of the battery is used up such a circuit is not required.

>(Will this topic ever end?  :-) )  I cannot let dangerous misinformation remain
>as the final word, though.  When it comes to putting batteries in ANYTHING
>backwards, "Just say no!"
>
>Jim

				    -Matt
--

    Matthew Dillon		dillon@Overload.Berkeley.CA.US
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