Re: NiMH Battery

[whittle@usc.edu (Randy Whittle)]

At 3:42 PM 1/10/96, Joseph Christie wrote:

>>>         Did you leave it plugged in a lot with the battery in the machine?
>>>
>>>         On my 750C (before I sold it), that did *terrible* things to the
>>> battery.  It would constantly drain to about 90% and then re-charge to
>>> 100%.  Lots and lots of mini-cycles like that will simply destroy your
>>> battery life.  I presume the 360 would do the same, since they are very
>>> similar machines.
>>
>>I've used NiMH batteries for years, in RC racing and now laptops.
>>That mini charge, as Randy pointed out, definitely _kills_ batteries.
>>I believe the term battery "memory" applies to NiMH unlike Lithium
>>batteries.  When partially discharging a NiMH battery repeatedly
>>to a similar level, i.e. leaving the laptop unplugged overnight or
>>every weekend and then recharging it, the battery eventually refuses
>>to recharge beyond that point.  (This fact was actually much more
>>important racing RC cars than traveling with laptops :-)
>>
>>Guy W. Farrell                Vox: (860)486-0964 My Desk

>NiCad batteries are notorius for the "memory" phenomena. The docs I got
>with my 701C and the NiMH specifically states that not only is it
>unnecessary to discharge the battery completely between charges but that
>doing so may do damage to the batteries.
>
>I often leave the battery in while running off the charger and check the
>battery level occasionally to make sure I didn't knock the adapter out of
>the wall. According to the on screen indicator I have not noticed less than
>100% charge after full charge is first reached.

        As you point out, the 701C (which I also now own) specifically
tells you NOT to run the batteries down all the way.

        I don't know *anything* about the technical details, but I do know
they can make NiMH batteries that do not exhbit this memory effect.  I
think the tradeoff is that the battery doesn't have as many charging cycles
in its lifetime (my Father used to work for a battery company, so he knows
more about this than I do).  Motorola uses this type of battery technology
on its 2-way radios (I don't know about its cellular phones), since these
are usually something that has to be constantly charged to capacity to get
maximum usage out of it, and that necessity overrides charge-cycle life.  I
presume IBM finally figured out the same thing when it made the 701 and
used that same type of technology for that model's batteries.

        The tradeoff, of course, is you'll have to buy a new battery more
often--but unless you were diligent in not recharging it too much in the
first place, you would have had to do that even sooner with the old
technology.


-----                                          ____________________________
Randy Whittle    whittle@usc.edu               |       WWW Home Page:     |
USC Graduate School of Business                |          http://         |
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