My neighbour has a four year old 3.6 volt 850 milliamp/hr cordless telephone
handset battery which is used frequently and often for long periods; i.e.
talking continuously for several hours. Removed from the handset and with no
load the open circuit voltage of the three cell battery is 4.02 volts.

She feels battery is defective; I feel it is overused between charges!

Can anyone suggest please;
a) How long, continuously, can such a battery, when fully charged,
typically, operate the handset before requiring to be placed back onto the
main unit to be replenished?
b) What would be a typical or designed 'duty cycle' for a cordless phone.
i.e. what percentage of use away from the main unit versus placed on the
main unit for recharging?

It would seem that the designers must base the battery capacity of some sort
of average expectation of the amount of handset use away from the main unit.

Similarly; we recently mislaid our 900 mhz cordless handset, for nearly a
week. When found its battery was 'flat'. It took several days for the
battery to recharge to operate 'normally'.

Comments welcomed. TIA

"Terry" wrote in message
...
My neighbour has a four year old 3.6 volt 850 milliamp/hr cordless
telephone handset battery which is used frequently and often for
long periods; i.e. talking continuously for several hours. Removed
from the handset and with no load the open circuit voltage of the
three cell battery is 4.02 volts.

She feels battery is defective; I feel it is overused between
charges!

Can anyone suggest please;
a) How long, continuously, can such a battery, when fully charged,
typically, operate the handset before requiring to be placed back
onto the main unit to be replenished?
b) What would be a typical or designed 'duty cycle' for a cordless
phone. i.e. what percentage of use away from the main unit versus
placed on the main unit for recharging?

It would seem that the designers must base the battery capacity of
some sort of average expectation of the amount of handset use away
from the main unit.

Similarly; we recently mislaid our 900 mhz cordless handset, for
nearly a week. When found its battery was 'flat'. It took several
days for the battery to recharge to operate 'normally'.

Comments welcomed. TIA


Would that all questions were so simple.

A rechargeable battery, whether Ni-Cad or Ni-MH, can be recharged
typically 500 times, give or take a bit.

If the battery is four years old and it has been caned, as your
description indicates, it is likely well past its sell-by date and
needs replacing - they don't cost the earth, assuming you can still
get one!


--
Woody

harrogate2 at ntlworld dot com

On Wed, 30 Mar 2005 15:03:53 -0330, "Terry"
wrote:

My neighbour has a four year old 3.6 volt 850 milliamp/hr cordless telephone
handset battery which is used frequently and often for long periods; i.e.
talking continuously for several hours. Removed from the handset and with no
load the open circuit voltage of the three cell battery is 4.02 volts.

Four years of hard use & its time for a new battery! With a typical
lifetime of 500-1000 cycles (under very good operating conditions) &
figure maybe 250 discharges a year & you get a 2-4 year life.

She feels battery is defective;

If its got less talk time between recharges than it did when new, it
_is_ probably defective...

I feel it is overused between charges!

Its only overused if it is used after the batteries are discharged

If the built-in battery management if working correctly, using the
handset until it cuts off from low battery should not hurt in - BUT - it
should be promptly recharged. Actually nicads like being used &
generally give very good life. End-of-life is a gradual reduction in
capacity (as neighbor may have noticed).

Can anyone suggest please;
a) How long, continuously, can such a battery, when fully charged,
typically, operate the handset before requiring to be placed back onto the
main unit to be replenished?
b) What would be a typical or designed 'duty cycle' for a cordless phone.
i.e. what percentage of use away from the main unit versus placed on the
main unit for recharging?

It would seem that the designers must base the battery capacity of some sort
of average expectation of the amount of handset use away from the main unit.

Usually "the designers" spend a few extra $ to let the consumer know
these things & publish the document as an instruction manual, which the
consumer thinks is extra packing only to throw away...

Similarly; we recently mislaid our 900 mhz cordless handset, for nearly a
week. When found its battery was 'flat'. It took several days for the
battery to recharge to operate 'normally'.

If it really took "several days" to recharge something is probably
defective. 10-14 hours (overnight) is what I see most...

Comments welcomed. TIA


Get the information from the neighbors manual (hahaha) or look up the
model # on the web & d/l it.

I have found most phone manuals available on the manufactures web
site. Below is part of a pdf on a Sony 900MHz from ~1999. The handset
battery referred to as BP-T23 is: 3.6V, 600mAH (3 std. AA cells).

Quote from pdf...


Battery duration
A fully charged battery pack lasts for about:
Approx. 7 hours when you use the handset continuously
Approx. 6 days when the handset is in standby mode.


Notes:
The battery pack will gradually discharge over a long period of time,
even if not in use.

If you leave the battery pack in the handset without charging it, the
battery pack will be completely discharged.

It may require several times of charging to recover its full capacity.


To obtain the best performance from the battery :
Do not place the handset on the base unit after each call. The battery
works best if the handset is returned to the base unit after two or
three calls. However, do not leave the handset off the base unit for a
long period of time as this will completely discharge the battery pack.


When to purchase a new battery pack:

If the battery lasts only a few minutes even after 10 hours of
charging, the usable life of the battery has expired and needs
replacement.
Contact your local Sony authorized dealer or service center, and ask for
a Sony BP-T23 rechargeable battery pack.


Note : Battery life may vary depending on usage condition and ambient
temperature.


If you do not use the handset for a long period of time, remove the
battery pack after charging for more than 10 hours. This maintains
battery life.


Specifications - Handset
Power source
Rechargeable battery pack BP-T23
Battery charging time
Approx. 10 hours
Battery life
Standby: Approx. 6 days
Talk: Approx. 7 hours

These phones charge very slowly. It might be that she is leaving
it off the hook a greater percentage of the time than the system
can handle.

It is not unusual for NiCads in this kind of service to last a lot
longer than 4 years.

Best regards
mark

Kim Clay wrote:
On Wed, 30 Mar 2005 15:03:53 -0330, "Terry"
wrote:


My neighbour has a four year old 3.6 volt 850 milliamp/hr cordless telephone
handset battery which is used frequently and often for long periods; i.e.
talking continuously for several hours. Removed from the handset and with no
load the open circuit voltage of the three cell battery is 4.02 volts.


--
----------------------------------------------------------------------
Mark W. Lund, PhD ** Battery Chargers
CEO ** Bulk Cells and Custom Battery Packs
PowerStream Technology ** Custom Power Supplies
140 S. Mountainway Drive ** DC/DC Converters
Orem Utah 84058 ** Custom UPS
http://www.PowerStream.com ** Engineering, manufacturing, consulting

"Mark W. Lund, PhD" wrote in message
...
These phones charge very slowly. It might be that she is leaving
it off the hook a greater percentage of the time than the system
can handle.

It is not unusual for NiCads in this kind of service to last a lot
longer than 4 years.

Best regards
mark

Many thanks for the various comments. Terry.