Archived from groups: comp.sys.laptops (
More info?)
Re:
Lithium bateries ... also have by far the
shortest life,
Nickel Cadmium batteries do not have (and never have) had a 'memory
effect'. This was something dreampt up by the marketing men trying to
persuade us to buy the much more expensive (at the time) Nickel
Metal-Hydride batteries.
Anyone on this board who has had any significant amount of experience
with both NiCad and Lithium batteries knows that both of those
statements are categorically wrong.
In fact, the "memory effect" was widely discussed decades ago, when
there was alternative to NiCad batteries.
Ye Electrik Fanne Clubbe wrote:
> "Barry Watzman" <WatzmanNOSPAM@neo.rr.com> wrote in message
> news:42765783.60604@neo.rr.com...
>
>>Compared to NiCad, Lithium batteries do not have the "memory effect",
>>and don't need to be fully chaged/discharged (which was related to the
>>memory effect). However, almost everyone advises to do a full charge,
>>then a nearly full discharge (but not below about 20%), then a recharge
>>on the first use of a new lithim battery. I don't have any experience
>>to either refute or support that, but it's a nearly universal
>>recommendation.
>>
>>There is certainly nothing wrong with cycling the battery (substantial
>>discharge & recharge), that is, indeed, the expected application. The
>>number of cycles is limited and finite, but moderately large (hundreds).
>>
>
>
> You can often find what to do. but not why to do it.
>
> The first time you use a Lithium battery, the advise is to discharge it
> until the monitor circuit cuts it off. This is not for the benefit of the
> battery itself, but to calibrate the charge monitor circuit. This should be
> repeated every few months.
>
> It makes no difference how far you discharge a lithium battery (as long as
> you don't overdo it). You strike 15-20% of its capacity for every 100
> charge/discharge cycles. To clarify: that's 100 charge and discharge where
> it's fully discharged every time. Or 200 cycles where it is only 50%
> discharged or any combination and permutation thereof.
>
> There is also a time penalty. Generally a battery loses 20% of its capacity
> for every year it is fully charged and stored at 25 Celcius. Lower
> temperatures (*NOT* below zero Celcius), it lasts longer. Lower charge, it
> lasts longer. If not used, they are best stored at 40% charge in a fridge.
>
> Although Lithium bateries offer the highest energy capacity for size and
> weight of any currently available technology, they also have by far the
> shortest life,
>
> Incidentally, Nickel Cadmium batteries do not have (and never have) had a
> 'memory effect'. This was something dreampt up by the marketing men trying
> to persuade us to buy the much more expensive (at the time) Nickel
> Metal-Hydride batteries. The ironic part is that Ni-MiH batteries do suffer
> from a phenomenon that appears to be similar to 'memory effect' called
> voltage depression. The belief in the memory effect is a symptom of an
> unrelated problem that occurs in little used Ni-Cd cells (Nickel whisker
> growth).
>
>