Question about cordless telephone

[[email protected]]

I have a cordless telephone with NiCd rechargeable battery.

I am wondering what the best strategy for prolonging the life of the
battery.

Should I always leave the phone in the cradle to recharge or will that
cause a memory effect. I seem to recall one manufacturer's
instructions recommending always having it in the cradle.

I would think being a NiCd (as opposed to NiMh) that I should run the
battery down before putting it back in cradle. Of course if I do that
then I am without a phone during recharging.

Thanx in advance for suggestions.



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[Aplin17]

Be careful not to reverse charge the batteries if you do leave it off charging.

 

[Lou]

Hi

Contrary to a popular belief, the "memory effect" doesn't affect the
life of a NiCd, quite the opposite in fact. What it does affect is
the useful charge, that is the charge effectively recoverable after a
full recharge. The memory effect results in a drop in the terminal
voltage after a fraction of the stored charge has been recovered,
making the remainder unusable by the electronic circuit it feeds. The
fact that some charge always remains in the elements protects them
against dendrite formation and element inversion, the two main
killers of batteries.
The small amplitude charge/discharge cycles are also influence
favourably the life expectancy. Also note that the memory is not a
permanent condition, and can be erased after some ch/dsch cycles.

If you want to use the full capacity of your battery, you must only
work in a regime of complete ch/dsch to avoid memory. It will however
affect the life because large amounts of electrode material is
transformed/displaced each cycle, and this material does not
necessarily land back where it originated, resulting in a progressive
deformation of the electrodes. There is also the danger of unequal
capacities among elements, with the risk of the weakest element being
reversed at the end of the discharge.

Thus, leaving your phone on its cradle might look like the safe
option, but it is not necessarily the case: some simplified chargers
continue supplying a much too large current after the battery has
been charged, resulting in a continued electrolysis exceeding the H2
recombination capacity of the cell, eventually causing its failure by
a lack of electrolyte (the cell "goes dry"). A symptom of this problem
is the battery pack getting warm after 12 h. charge.

Lou

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[[email protected]]

On 14 Dec 2004 08:26:36 -0600,

Hi

Contrary to a popular belief, the "memory effect" doesn't affect the
life of a NiCd, quite the opposite in fact. What it does affect is
the useful charge, that is the charge effectively recoverable after a
full recharge. The memory effect results in a drop in the terminal
voltage after a fraction of the stored charge has been recovered,
making the remainder unusable by the electronic circuit it feeds. The
fact that some charge always remains in the elements protects them
against dendrite formation and element inversion, the two main
killers of batteries.
The small amplitude charge/discharge cycles are also influence
favourably the life expectancy. Also note that the memory is not a
permanent condition, and can be erased after some ch/dsch cycles.

If you want to use the full capacity of your battery, you must only
work in a regime of complete ch/dsch to avoid memory. It will however
affect the life because large amounts of electrode material is
transformed/displaced each cycle, and this material does not
necessarily land back where it originated, resulting in a progressive
deformation of the electrodes. There is also the danger of unequal
capacities among elements, with the risk of the weakest element being
reversed at the end of the discharge.

Thus, leaving your phone on its cradle might look like the safe
option, but it is not necessarily the case: some simplified chargers
continue supplying a much too large current after the battery has
been charged, resulting in a continued electrolysis exceeding the H2
recombination capacity of the cell, eventually causing its failure by
a lack of electrolyte (the cell "goes dry"). A symptom of this problem
is the battery pack getting warm after 12 h. charge.

Lou

Thanx for such a detailed explanation. If the battery pack does not
get warm after twelve hour charge would this suggest that there is not
overcharging happening? Is there any other way to determine
overcharging??

It is interesting that one of my phones instructions say to leave
phone in cradle and the other says to let it discharge completely.
Both are NiCd btw.

If leaving the phone in the cradle too long is bad then when I go away
on vacation for a week or two, the best strategy would let the phone
just discharge.

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Posted at:
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-----------------------------------------------------
-----------------------------------------------------

A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

 

[Lou]

You can measure the residual current supplied by the cradle after a
full recharge: if it exceeds the capacity/20, it's probably unsafe.
Ideally, it ought to be in the region of C/40. It is not a good idea
to let the phone discharge completely: you risk element inversion;
the best solution in this case is to disconnect or remove the battery
from the phone.
Lou

*-----------------------*
Posted at:
www.GroupSrv.com
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