LiIon batteries: What counts as a charge-discharge cycle?

LiIon batteries are said to have a finite number of charge-discharge cycles
built in to them. I've seen some claims that ANY application of charge,
regardless of the initial state of the battery, counts as one.

We were all taught to run our NiCd batteries down to near exhaustion before
charging them to avoid the dreaded "memory effect"; should we treat LiIons
the same way to avoid using up their cycles?

--
Bert Hyman St. Paul, MN (E-Mail Removed)

On 2010-03-24 00:07:34 +0100, Bert Hyman said:

> LiIon batteries are said to have a finite number of charge-discharge cycles
> built in to them. I've seen some claims that ANY application of charge,
> regardless of the initial state of the battery, counts as one.
>
> We were all taught to run our NiCd batteries down to near exhaustion before
> charging them to avoid the dreaded "memory effect"; should we treat LiIons
> the same way to avoid using up their cycles?

I would say no to this.
on my macbook pro, I can see when the cycles number changes
and it needs a certain amount of charge to do so
only charge a little doesnt increment the number of charges cycles.

--

Jean-Yves.

In news:(E-Mail Removed) John Fields
<(E-Mail Removed)> wrote:

> On 23 Mar 2010 23:07:34 GMT, Bert Hyman <(E-Mail Removed)> wrote:
>
>>LiIon batteries are said to have a finite number of charge-discharge
>>cycles built in to them.
>
> ---
> Said by whom?

The popular press.

>
> As far as I know, lithium ion cells have a finite number of
> charge-discharge cycles, but the number depends largely on how they're
> used and the environment in which they're used as opposed to an
> arbitrary number purposely "built" into them.
> ---
>
>
>>I've seen some claims that ANY application of charge,
>>regardless of the initial state of the battery, counts as one.
>
> ---
> Cite your source?

The all-knowing "they," as in "they said ..."

> ---
>
>>We were all taught to run our NiCd batteries down to near exhaustion
>>before charging them to avoid the dreaded "memory effect"; should we
>>treat LiIons the same way to avoid using up their cycles?
>
> ---
> No.
>
> Discharging LiIOns below a lower limit, like lead-acid batteries, can
> permanently damage them.
>
> http://www.google.com/#hl=en&source=...ery&rlz=1W1GFR
> C_en&aq=3&aqi=g10&aql=f&oq=Lithium+&gs_rfai=&fp=d5 3639546d3e9460



--
Bert Hyman St. Paul, MN (E-Mail Removed)

In article <Xns9D44B8640DEC1VeebleFetzer@216.250.188.140>,
Bert Hyman <(E-Mail Removed)> wrote:
>LiIon batteries are said to have a finite number of charge-discharge cycles
>built in to them. I've seen some claims that ANY application of charge,
>regardless of the initial state of the battery, counts as one.
>
>We were all taught to run our NiCd batteries down to near exhaustion before
>charging them to avoid the dreaded "memory effect"; should we treat LiIons
>the same way to avoid using up their cycles?

This does not directly answer your first question, but it is instructive
reading:

http://batteryuniversity.com/parttwo-34.htm

To answer your second question (and based on the above) deep discharge of
lithium-ion batteries (even within the safe limits usually enforced by
protection circuits built into commercial packs) shortens their useful life.