Re: [NTLK] Constantly charging NiMH batteries from BTI

From: Lallang_at_aol.com
Date: Thu Aug 30 2001 - 03:34:40 EDT


In a message dated 08/29/2001 21:21:54, James Elliott=20
<rootbeeraddict_at_yahoo.com> writes:

>I have the NiCad pack in my 120 which I leave in the cradle when not=20
>in use. Is this a bad thing? What is it that you are referring to?

In general, NiCd batteries exhibit a hysteresis or memory effect. What this=
=20
means is that if you don't discharge them totally before recharging them,=20
you'll begin to find that the battery life seems to get shorter and shorter.=
 =20
NiMH batteries don't exhibit this effect. But I don't know what other=20
problems might occur if I left it constantly charging. Hence my question.

Here is a reference URL: =20
http://library.cs.tuiasi.ro/miscellanea/ultimate-computer-buyer-guide/ch07/1=
05

-107.html

The relevant paragraphs from the above URL are extracted below: =20

The use of nickel metal-hydride batteries (Ni-MH), and nickel cadmium=20
(Ni-Cad) batteries is fairly widespread. Ni-MH batteries have a few advantag=
es
over Ni-Cad batteries. Nickel metal-hydride batteries are lighter in weight=20
than nickel cadmium batteries. Nickel metal-hydride (Ni-MH) batteries delive=
r
about 25 percent more power than nickel cadmium (Ni-Cad) of the same weight.=
=20
Ni-MH batteries are somewhat free of the problem known as Ni-Cad
memory (technically known as hysteresis). This is a problem that depresses a=
=20
battery=E2=80=99s ability to be fully recharged. For example, if you use a N=
i-Cad
battery and run it down for only 20 minutes a few times before recharging,=20
the battery will end up delivering only 20 minutes of power before going
dead. Fixing this requires the battery to be fully drained of power before=20
recharging, known as deep power cycling. It is recommended you deep power
cycle a Ni-Cad battery once every 90 days, and once every 30 days for Ni-MH=20
batteries. Ni-Cad and Ni-MH batteries have a lifetime recharge cycle of
100 to 500 charges, and each deep power cycling will take away one of these=20
cycles.=20

Going with the better Ni-MH batteries costs more, but if you depend on a=20
portable it is a small price to pay. In addition, Ni-MH batteries are a more
green product because they readily decompose and are non-toxic. Ni-Cad has=20
been declared a toxic substance because of the dangerous cadmium it
contains.

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